Microbiology Midterm Review

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Microbiology Midterm Review - Quiz

Practice test for the Microbiology Midterm.


Questions and Answers
  • 1. 

    Disease-causing microorganisms are called

    • A.

      Decomposers.

    • B.

      Procaryotes.

    • C.

      Pathogens.

    • D.

      Eucaryotes.

    • E.

      Fermenters.

    Correct Answer
    C. Pathogens.
    Explanation
    Disease-causing microorganisms are commonly referred to as pathogens. Pathogens are organisms such as bacteria, viruses, fungi, or parasites that can cause disease in their host. They can infect humans, animals, and plants, leading to various illnesses and health problems. The term "pathogens" is widely used in the field of microbiology and medicine to describe these harmful microorganisms.

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  • 2. 

    The microorganisms that do not have a nucleus in their cells are called

    • A.

      Decomposers.

    • B.

      Procaryotes.

    • C.

      Pathogens.

    • D.

      Eucaryotes.

    • E.

      Fermenters.

    Correct Answer
    B. Procaryotes.
    Explanation
    The correct answer is procaryotes. Prokaryotes are single-celled organisms that lack a nucleus and other membrane-bound organelles. They are characterized by their simple cell structure and include bacteria and archaea. Prokaryotes play important roles in various ecosystems, including as decomposers, pathogens, and fermenters. However, it is important to note that not all prokaryotes are decomposers, pathogens, or fermenters.

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  • 3. 

    When humans manipulate the genes of microorganisms the process is called

    • A.

      Bioremediation.

    • B.

      Genetic engineering.

    • C.

      Epidemiology.

    • D.

      Immunology.

    • E.

      Taxonomy.

    Correct Answer
    B. Genetic engineering.
    Explanation
    Genetic engineering refers to the process of manipulating the genes of microorganisms, typically through the introduction of foreign DNA or modification of existing DNA. This process allows scientists to alter the genetic makeup of microorganisms in order to produce desired traits or outcomes. Bioremediation, on the other hand, refers to the use of microorganisms to remove or neutralize pollutants from the environment. Epidemiology and immunology are fields of study related to the spread and control of diseases, while taxonomy is the classification and categorization of organisms.

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  • 4. 

    Which of the following is not considered a microorganism?

    • A.

      Mosquito

    • B.

      Protozoa

    • C.

      Bacteria

    • D.

      Viruses

    • E.

      Fungi

    Correct Answer
    A. Mosquito
    Explanation
    A mosquito is not considered a microorganism because it is a macroscopic organism that can be seen with the naked eye. Microorganisms, on the other hand, are microscopic organisms that can only be seen under a microscope. Protozoa, bacteria, viruses, and fungi are all examples of microorganisms as they are too small to be seen without magnification.

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  • 5. 

    Which of the following is a unique characteristic of viruses that distinguishes them from the other major groups of microorganisms?

    • A.

      Cause human disease

    • B.

      Lack a nucleus

    • C.

      Cannot be seen without a microscope

    • D.

      Contain genetic material

    • E.

      Lack cell structure

    Correct Answer
    E. Lack cell structure
    Explanation
    Viruses are unique from other major groups of microorganisms because they lack cell structure. Unlike bacteria, fungi, and protozoa, viruses are not composed of cells. Instead, they consist of genetic material (DNA or RNA) surrounded by a protein coat called a capsid. This lack of cell structure means that viruses cannot carry out any metabolic processes on their own and rely on host cells to replicate and cause diseases.

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  • 6. 

    Pasteur used swan-neck flasks in his experiments to prove that

    • A.

      Air had "vital forces" capable of spontaneous generation.

    • B.

      Microbial fermentation could be used to make wine.

    • C.

      Dust in air was a source of living microorganisms.

    • D.

      Microorganisms could cause disease.

    • E.

      Microorganisms could be grown in laboratory infusions.

    Correct Answer
    C. Dust in air was a source of living microorganisms.
    Explanation
    Pasteur used swan-neck flasks in his experiments to prove that dust in the air was a source of living microorganisms. The swan-neck flasks allowed air to enter the flask, but prevented dust particles from reaching the culture medium. By observing that the culture medium remained sterile as long as the flask remained intact, but became contaminated with microorganisms when the flask was tilted or broken, Pasteur demonstrated that the dust in the air was responsible for the contamination and the growth of microorganisms. This experiment refuted the theory of spontaneous generation and supported the concept of biogenesis.

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  • 7. 

    Spontaneous generation is the belief that

    • A.

      Germs cause infectious diseases.

    • B.

      Microbes are diverse and ubiquitous.

    • C.

      Microbes placed in an infusion can grow in it.

    • D.

      Aseptic techniques reduce microbes in medical settings.

    • E.

      Living things arise from nonliving matter.

    Correct Answer
    E. Living things arise from nonliving matter.
    Explanation
    The correct answer is "living things arise from nonliving matter." Spontaneous generation refers to the belief that living organisms can arise from nonliving materials. This theory was widely accepted until it was disproven by Louis Pasteur's experiments in the 19th century, which demonstrated that living organisms only come from pre-existing living organisms. This discovery laid the foundation for the modern understanding of microbiology and the concept of biogenesis.

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  • 8. 

    Koch's postulates are criteria used to establish that

    • A.

      Microbes are found on dust particles.

    • B.

      A specific microbe is the cause of a specific disease.

    • C.

      Life forms can only arise from preexisting life forms.

    • D.

      A specific microbe should be classified in a specific kingdom.

    • E.

      Microbes can be used to clean up toxic spills.

    Correct Answer
    B. A specific microbe is the cause of a specific disease.
    Explanation
    Koch's postulates are a set of criteria used to determine whether a specific microbe is the cause of a specific disease. These postulates include isolating the microbe from an infected individual, culturing it in a laboratory, infecting a healthy individual with the cultured microbe, and observing the same disease symptoms in the newly infected individual. If the microbe satisfies all of these criteria, it can be concluded that it is the causative agent of the disease. This helps in identifying and understanding the causes of various infectious diseases and developing appropriate treatments and preventive measures.

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  • 9. 

    Which of the following is a scientific name?

    • A.

      Bacteria

    • B.

      Protista

    • C.

      Species

    • D.

      Bacillus subtilis

    • E.

      Bacilli

    Correct Answer
    D. Bacillus subtilis
    Explanation
    Bacillus subtilis is a scientific name because it follows the binomial nomenclature system used in taxonomy. It consists of two parts: the genus name (Bacillus) and the specific epithet (subtilis). This naming convention helps to provide a standardized way of identifying and classifying organisms. In contrast, the other options (bacteria, Protista, species, bacilli) do not follow this format and are not considered scientific names.

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  • 10. 

    The study of evolutionary relationships among organisms is called

    • A.

      Biotechnology.

    • B.

      Genetics.

    • C.

      Recombinant DNA.

    • D.

      Phylogeny.

    • E.

      Taxonomy.

    Correct Answer
    D. Phylogeny.
    Explanation
    The study of evolutionary relationships among organisms is called phylogeny. Phylogeny involves analyzing and comparing genetic and physical characteristics of different species to determine their evolutionary history and how they are related to each other. It helps scientists understand the evolutionary patterns and processes that have shaped life on Earth. Biotechnology, genetics, and recombinant DNA are related fields but focus on different aspects of biology, while taxonomy is the science of classifying and naming organisms.

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  • 11. 

    A scientist collects grass clippings to find the source of an outbreak of tularemia is an example of working in the field of

    • A.

      Food microbiology.

    • B.

      Epidemiology.

    • C.

      Agricultural microbiology.

    • D.

      Genetic engineering.

    • E.

      Biotechnology.

    Correct Answer
    B. Epidemiology.
    Explanation
    The given scenario involves a scientist collecting grass clippings to investigate the source of an outbreak of tularemia. Epidemiology is the branch of science that studies the patterns, causes, and effects of diseases in populations. In this case, the scientist is trying to understand and control the spread of tularemia, which is a disease affecting a large number of individuals. Therefore, the correct answer is epidemiology.

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  • 12. 

    Helminths are

    • A.

      Bacteria.

    • B.

      Protozoa.

    • C.

      Molds.

    • D.

      Parasitic worms.

    • E.

      Infectious particles.

    Correct Answer
    D. Parasitic worms.
    Explanation
    Helminths are classified as parasitic worms. They are multicellular organisms that infect and live in the bodies of animals, including humans. Unlike bacteria, protozoa, molds, and infectious particles, helminths are specifically characterized as worms that cause parasitic infections.

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  • 13. 

    Organisms called parasites are

    • A.

      Always classified in the kingdom Monera.

    • B.

      Always harmful to their host.

    • C.

      The decomposers in ecosystems.

    • D.

      Always a virus.

    • E.

      Free-living.

    Correct Answer
    B. Always harmful to their host.
    Explanation
    Parasites are organisms that rely on a host organism for their survival and reproduction. They harm their host by feeding on their tissues, causing diseases, and sometimes even leading to the death of the host. Therefore, the statement "always harmful to their host" is a correct explanation for parasites.

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  • 14. 

    The surgeon who advocated using disinfectants on hands and in the air prior to surgery was

    • A.

      Joseph Lister.

    • B.

      Ignaz Semmelweis.

    • C.

      Robert Koch.

    • D.

      Louis Pasteur.

    • E.

      Antonie van Leeuwenhoek.

    Correct Answer
    A. Joseph Lister.
    Explanation
    Joseph Lister is the correct answer because he was a surgeon who promoted the use of disinfectants on hands and in the air before surgery. Lister is known as the pioneer of antiseptic surgery, as he introduced the concept of sterilizing surgical instruments and creating a clean operating environment to prevent infections. His work greatly contributed to the reduction of post-operative infections and improved patient outcomes in surgery.

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  • 15. 

    Which of the following are the main decomposers of the earth?

    • A.

      Bacteria and fungi

    • B.

      Bacteria and viruses

    • C.

      Algae and viruses

    • D.

      Protists and fungi

    • E.

      All organisms are decomposers

    Correct Answer
    A. Bacteria and fungi
    Explanation
    Bacteria and fungi are considered the main decomposers of the earth because they play a crucial role in breaking down organic matter and recycling nutrients in the ecosystem. Bacteria are responsible for breaking down complex organic compounds into simpler forms, while fungi specialize in decomposing dead plant and animal material. Together, they help in the decomposition process by releasing enzymes that break down organic matter, returning essential nutrients back to the soil for other organisms to utilize.

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  • 16. 

    Which of the following diseases is transmitted by mosquitoes?

    • A.

      Diarrheal diseases

    • B.

      Tuberculosis

    • C.

      Malaria

    • D.

      Septicemia

    • E.

      Influenza

    Correct Answer
    C. Malaria
    Explanation
    Malaria is transmitted by mosquitoes. Mosquitoes become infected with the malaria parasite by biting an infected person and then transmit the parasite to another person when they bite them. This disease is prevalent in tropical and subtropical regions where the Anopheles mosquito, the carrier of the parasite, is present. Malaria can cause high fever, chills, flu-like symptoms, and in severe cases, it can be life-threatening. Effective prevention measures include the use of mosquito nets, insect repellents, and antimalarial medications.

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  • 17. 

    All of the following are correct about prokaryotes except

    • A.

      They are smaller than eukaryotes.

    • B.

      They lack a nucleus.

    • C.

      They are less complex than eukaryotes.

    • D.

      They have organelles.

    • E.

      They are found nearly everywhere.

    Correct Answer
    D. They have organelles.
    Explanation
    Prokaryotes are single-celled organisms that lack a nucleus and membrane-bound organelles. They are generally smaller and less complex than eukaryotes. However, they are found nearly everywhere, in various environments such as soil, water, and even in extreme conditions like hot springs and deep-sea vents. The absence of organelles is a characteristic feature of prokaryotes, as they do not have structures like mitochondria or chloroplasts that are present in eukaryotic cells.

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  • 18. 

    Which of the following is the correct way to write the scientific name of this bacterium?

    • A.

      Staph Aureus

    • B.

      Staphylococcus Aureus

    • C.

      Staphylococcus aureus

    • D.

      Staphylococcus Aureus

    • E.

      S. Aureus

    Correct Answer
    C. Staphylococcus aureus
    Explanation
    The correct way to write the scientific name of this bacterium is "Staphylococcus aureus" because scientific names follow a specific format called binomial nomenclature, which includes the genus name (Staphylococcus) and the species name (aureus). The genus name is always capitalized and the species name is always written in lowercase.

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  • 19. 

    Which of the following diseases probably involves microbial infection?

    • A.

      Gastric ulcers

    • B.

      Female infertility

    • C.

      Coronary artery disease

    • D.

      Cervical cancer

    • E.

      All of the choices are correct.

    Correct Answer
    E. All of the choices are correct.
    Explanation
    All of the given diseases - gastric ulcers, female infertility, coronary artery disease, and cervical cancer - can potentially involve microbial infection. Microbes such as Helicobacter pylori have been linked to gastric ulcers, certain sexually transmitted infections can cause female infertility, some infections can contribute to the development of coronary artery disease, and certain strains of human papillomavirus (HPV) are known to cause cervical cancer. Therefore, all of the choices can be correct in terms of microbial involvement.

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  • 20. 

    The Five I's of studying microorganisms include all of the following except

    • A.

      Inoculation.

    • B.

      Incubation.

    • C.

      Infection.

    • D.

      Isolation.

    • E.

      Identification.

    Correct Answer
    C. Infection.
    Explanation
    The Five I's of studying microorganisms refer to the five essential steps involved in microbiological techniques: inoculation, incubation, isolation, identification, and inspection. Infection is not included in the Five I's because it is not a step in the process of studying microorganisms. Infection refers to the invasion and multiplication of pathogenic microorganisms in a host organism, which is a different concept compared to the techniques used in studying microorganisms in a laboratory setting.

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  • 21. 

    All of the following are examples of different types of microbiological media except

    • A.

      Broth.

    • B.

      Enriched.

    • C.

      Agar.

    • D.

      Petri dish.

    • E.

      Gelatin.

    Correct Answer
    D. Petri dish.
    Explanation
    The question is asking for an example of a microbiological media, which is a substance used to grow and cultivate microorganisms in a laboratory setting. Broth, enriched, agar, and gelatin are all examples of different types of microbiological media. However, a petri dish is not a type of media itself, but rather a container or dish used to hold the media. Therefore, the correct answer is petri dish.

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  • 22. 

    The term that refers to the purposeful addition of microorganisms into a laboratory nutrient medium is

    • A.

      Isolation.

    • B.

      Inoculation.

    • C.

      Immunization.

    • D.

      Infection.

    • E.

      Contamination.

    Correct Answer
    B. Inoculation.
    Explanation
    Inoculation refers to the purposeful addition of microorganisms into a laboratory nutrient medium. This process is done in order to study and culture specific microorganisms for various purposes such as identification, testing, or research. Isolation refers to the separation or purification of a specific microorganism from a mixed population, immunization refers to the process of inducing immunity against a specific pathogen, infection refers to the invasion and multiplication of microorganisms in a host organism, and contamination refers to the introduction of unwanted microorganisms into a sterile environment.

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  • 23. 

    Which of the following is essential for development of discrete, isolated colonies?

    • A.

      Broth medium

    • B.

      Differential medium

    • C.

      Selective medium

    • D.

      Solid medium

    • E.

      Assay medium

    Correct Answer
    D. Solid medium
    Explanation
    Solid medium is essential for the development of discrete, isolated colonies because it provides a solid surface for the bacteria to grow on. This allows individual bacterial cells to form colonies without mixing or spreading into each other. In contrast, broth medium is a liquid medium that does not provide a solid surface, making it difficult for colonies to form. Differential medium and selective medium are types of solid media that have specific components to differentiate between different types of bacteria or select for the growth of specific bacteria, but they are not necessary for the development of discrete, isolated colonies. Assay medium is a general term for a medium used for specific tests or assays and may or may not be solid.

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  • 24. 

    A microbiologist inoculates Staphylococcus aureus into a culture medium.  Following incubation, both Staphylococcus aureus and Staphylococcus epidermidis are determined to be growing in this culture.  What is the most likely explanation?

    • A.

      The microbiologist used too much inoculum.

    • B.

      The culture is contaminated.

    • C.

      The incubation temperature was incorrect.

    • D.

      The culture medium must be selective.

    • E.

      The culture medium must be differential.

    Correct Answer
    B. The culture is contaminated.
    Explanation
    The most likely explanation is that the culture is contaminated. This is because both Staphylococcus aureus and Staphylococcus epidermidis are growing in the culture, which suggests that there is an external source of contamination. If the microbiologist had used too much inoculum, only Staphylococcus aureus would have grown. If the incubation temperature was incorrect, it would affect the growth of both bacteria. If the culture medium was selective, only one type of bacteria would have grown. If the culture medium was differential, it would allow for the differentiation of different types of bacteria, but it would not explain the presence of both Staphylococcus aureus and Staphylococcus epidermidis.

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  • 25. 

    A microbiologist inoculates Staphylococcus epidermidis and Escherichia coli into a culture medium.  Following incubation, only the E. coli grows in the culture.  What is the most likely explanation?

    • A.

      The microbiologist used too much inoculum.

    • B.

      The culture is contaminated.

    • C.

      The incubation temperature was incorrect.

    • D.

      The culture medium must be selective.

    • E.

      The culture medium must be differential.

    Correct Answer
    D. The culture medium must be selective.
    Explanation
    The most likely explanation is that the culture medium used is selective, meaning it only allows the growth of specific types of bacteria. In this case, the medium is likely designed to support the growth of Escherichia coli but not Staphylococcus epidermidis. This is supported by the fact that only the E. coli grows in the culture while the other bacteria does not.

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  • 26. 

    Which method often results in colonies developing down throughout the agar and some colonies on the surface?

    • A.

      Streak plate.

    • B.

      Spread plate.

    • C.

      Pour plate.

    • D.

      All of the choices are correct.

    • E.

      None of the choices are correct.

    Correct Answer
    C. Pour plate.
    Explanation
    Pour plate is the correct answer because this method involves mixing the sample with melted agar before pouring it into a Petri dish. The colonies develop both throughout the agar and on the surface because the sample is evenly distributed throughout the medium. This allows for the growth of both aerobic and anaerobic bacteria, resulting in colonies developing in various locations within the agar.

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  • 27. 

    Which type of medium is able to distinguish different species or types of microorganisms based on an observable change in the colonies or in the medium?

    • A.

      Differential

    • B.

      Selective

    • C.

      Enumeration

    • D.

      Enriched

    • E.

      Reducing

    Correct Answer
    A. Differential
    Explanation
    Differential medium is able to distinguish different species or types of microorganisms based on an observable change in the colonies or in the medium. This type of medium contains specific nutrients or indicators that allow for the differentiation of microorganisms based on their ability to metabolize or produce certain compounds. By observing the changes in the colonies or the medium, scientists can identify and differentiate between different types of microorganisms.

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  • 28. 

    A microbiologist decides to use a nutrient medium that contains thioglycollic acid.  What type of microbe is she attempting to culture?

    • A.

      Fastidious

    • B.

      Gram positive

    • C.

      Anaerobe

    • D.

      Gram negative

    • E.

      Virus

    Correct Answer
    C. Anaerobe
    Explanation
    The microbiologist is attempting to culture anaerobic microorganisms. Thioglycollic acid is often added to nutrient media to create an anaerobic environment by removing oxygen. Anaerobes are microorganisms that can survive and grow in the absence of oxygen.

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  • 29. 

    Which of the following characteristics refers to the microscope's ability to show two separate entities as separate and distinct?

    • A.

      Resolving power

    • B.

      Magnification

    • C.

      Refraction

    • D.

      All of the choices are correct.

    • E.

      None of the choices are correct.

    Correct Answer
    A. Resolving power
    Explanation
    The resolving power of a microscope refers to its ability to show two separate entities as separate and distinct. It is a measure of the microscope's ability to distinguish fine details and separate closely spaced objects. A higher resolving power means that the microscope can produce a clearer and more detailed image, allowing for better visualization and analysis of the specimen. Magnification refers to the microscope's ability to enlarge the image, while refraction refers to the bending of light as it passes through different media.

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  • 30. 

    If a microbiologist is studying a specimen at a total magnification of 950X, what is the magnifying power of the objective lens is 10X?

    • A.

      100X

    • B.

      950X

    • C.

      85X

    • D.

      850X

    • E.

      95X

    Correct Answer
    E. 95X
    Explanation
    The magnifying power of a microscope is calculated by multiplying the magnification of the objective lens by the magnification of the eyepiece. In this case, the magnification of the objective lens is given as 10X. Since the total magnification is given as 950X, we can divide the total magnification by the magnification of the objective lens to find the magnification of the eyepiece. Therefore, the magnifying power of the eyepiece is 950X / 10X = 95X.

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  • 31. 

    The type of microscope in which you would see brightly illuminated specimens against a black background is

    • A.

      Bright-field.

    • B.

      Dark-field.

    • C.

      Phase-contrast.

    • D.

      Fluorescence.

    • E.

      Electron.

    Correct Answer
    B. Dark-field.
    Explanation
    In a dark-field microscope, the specimens are illuminated from the side, causing them to appear bright against a black background. This technique is particularly useful for observing transparent or unstained specimens, as it enhances contrast and allows for better visualization of fine details. Bright-field microscopy, on the other hand, illuminates the specimen from below, resulting in a bright background and darker specimen. Phase-contrast microscopy is used to visualize transparent specimens by exploiting differences in refractive index, while fluorescence microscopy uses fluorescent dyes to label specific structures or molecules. Electron microscopy uses a beam of electrons instead of light to visualize specimens at a much higher resolution.

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  • 32. 

    This microscope achieves the greatest resolution and highest magnification:

    • A.

      Bright-field

    • B.

      Dark-field

    • C.

      Phase-contrast

    • D.

      Fluorescence

    • E.

      Electron

    Correct Answer
    E. Electron
    Explanation
    The electron microscope achieves the greatest resolution and highest magnification among the given options. Unlike other microscopes that use light, the electron microscope uses a beam of electrons to illuminate the specimen. Since electrons have a much shorter wavelength than light, they can resolve smaller details, leading to higher resolution. Additionally, the electron microscope can achieve much higher magnification levels due to the shorter wavelength of electrons. Therefore, the electron microscope is the most suitable option for achieving the greatest resolution and highest magnification.

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  • 33. 

    Which is incorrect about chocolate agar?

    • A.

      It can be used to cultivate Neisseria.

    • B.

      It usually uses sheep blood that has been heated.

    • C.

      It has chocolate extract in it.

    • D.

      It is an enriched medium.

    • E.

      It is used to grow fastidious bacteria.

    Correct Answer
    C. It has chocolate extract in it.
    Explanation
    Chocolate agar does not contain chocolate extract. It is named "chocolate agar" because it has a dark brown color, similar to chocolate. The agar is made by adding lysed red blood cells to a nutrient agar base, which provides the necessary nutrients for bacterial growth. The red blood cells release factors that enhance the growth of fastidious bacteria, making it an enriched medium. It is commonly used to cultivate fastidious organisms, such as Haemophilus influenzae and Neisseria species.

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  • 34. 

    The specimen preparation that is best for viewing cell motility is

    • A.

      Hanging drop.

    • B.

      Fixed stained smear.

    • C.

      Gram stain.

    • D.

      Negative stain.

    • E.

      Flagellar stain.

    Correct Answer
    A. Hanging drop.
    Explanation
    The hanging drop method is the best specimen preparation technique for viewing cell motility because it allows for the observation of live, moving cells under a microscope. In this method, a drop of the specimen is suspended from a coverslip, creating a hanging drop. The coverslip is then inverted and placed on a slide, creating a sealed chamber. This technique maintains the humidity and prevents drying of the specimen, allowing cells to remain viable and exhibit their natural motility. Fixed stained smear, gram stain, negative stain, and flagellar stain are not specifically designed for observing cell motility.

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  • 35. 

    The primary purpose of staining cells on a microscope slide is to

    • A.

      Kill them.

    • B.

      Secure them to the slide.

    • C.

      Enlarge the cells.

    • D.

      Add contrast in order to see them better.

    • E.

      See motility.

    Correct Answer
    D. Add contrast in order to see them better.
    Explanation
    Staining cells on a microscope slide is done to add contrast in order to see them better. By using different dyes or stains, the cells can be highlighted and differentiated from their surroundings, making them easier to observe and study under a microscope. Staining enhances the visibility of cellular structures, such as organelles or specific cell components, allowing for a more detailed examination and analysis of the cells. This technique is commonly used in various scientific and medical fields to aid in the identification and characterization of cells.

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  • 36. 

    A microbiologist makes a fixed smear of bacterial cells and stains them with Loeffler's methylene blue.  All the cells appear blue under the oil lens.  This is an example of

    • A.

      Negative staining.

    • B.

      Using an acidic dye.

    • C.

      Simple staining.

    • D.

      Using the acid-fast stain.

    • E.

      Capsule staining.

    Correct Answer
    C. Simple staining.
    Explanation
    The given scenario describes a situation where all the bacterial cells appear blue after staining with Loeffler's methylene blue. This indicates that the stain is being taken up by all the cells and uniformly coloring them. In simple staining, a single dye is used to stain the cells, allowing for better visualization of their morphology and arrangement. Since all the cells appear blue, it suggests that the dye used in this case is basic, rather than acidic. Therefore, the correct answer is simple staining.

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  • 37. 

    Bacteria that require special growth factors and complex organic substances are called

    • A.

      Fastidious.

    • B.

      Pathogenic.

    • C.

      Harmless.

    • D.

      Anaerobic.

    • E.

      Aerobic.

    Correct Answer
    A. Fastidious.
    Explanation
    Fastidious bacteria are those that have specific and complex requirements for growth, such as the need for special growth factors and complex organic substances. These bacteria are unable to grow or reproduce without these specific conditions being met. Pathogenic bacteria, on the other hand, are capable of causing disease, while harmless bacteria do not cause harm to their host. Anaerobic bacteria can survive and grow without oxygen, whereas aerobic bacteria require oxygen for their growth. Therefore, the correct answer is fastidious, as it accurately describes bacteria with specific growth requirements.

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  • 38. 

    All of the following are correct about agar except

    • A.

      It is flexible.

    • B.

      It melts at the boiling point of water (100 degrees Celsius).

    • C.

      It is a source of nutrition for bacteria.

    • D.

      It solidifies below 42 degrees Celsius.

    • E.

      It is solid at room temperature.

    Correct Answer
    C. It is a source of nutrition for bacteria.
    Explanation
    Agar is a gelatinous substance that is commonly used in laboratories for various purposes, such as growing bacteria or fungi. It is not a source of nutrition for bacteria, as it does not provide any essential nutrients or energy sources. Agar is flexible, meaning it can be molded or shaped easily. It solidifies below 42 degrees Celsius and remains solid at room temperature. It does not melt at the boiling point of water (100 degrees Celsius), but rather it remains in its solid form.

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  • 39. 

    Spirochetes have a twisting and flexing locomotion due to appendages called

    • A.

      Flagella.

    • B.

      Cilia.

    • C.

      Fimbriae.

    • D.

      Periplasmic flagella (axial filaments).

    • E.

      Sex pili.

    Correct Answer
    D. Periplasmic flagella (axial filaments).
    Explanation
    Spirochetes have a unique twisting and flexing locomotion, which is achieved through the use of appendages called periplasmic flagella (axial filaments). These flagella are located within the periplasmic space, which is the space between the inner and outer membranes of the spirochete cell. The rotation of these flagella causes the spirochete to move in a corkscrew-like manner, allowing it to navigate through various environments. This distinguishes spirochetes from other microorganisms that may use different appendages such as flagella, cilia, fimbriae, or sex pili for locomotion.

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  • 40. 

    The transfer of genes during bacterial conjugation involves rigid, tubular appendages called

    • A.

      Flagella.

    • B.

      Cilia.

    • C.

      Fimbriae.

    • D.

      Periplasmic flagella (axial filaments).

    • E.

      Sex pili.

    Correct Answer
    E. Sex pili.
    Explanation
    Bacterial conjugation is a process in which genetic material is transferred between bacterial cells through direct contact. This transfer is facilitated by sex pili, which are rigid, tubular appendages on the surface of the bacterial cell. These sex pili allow the donor cell to attach to the recipient cell and transfer the genetic material, such as plasmids, from one cell to another. Therefore, sex pili are the correct answer for the given question.

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  • 41. 

    All bacterial cells have

    • A.

      A chromosome.

    • B.

      Fimbriae.

    • C.

      Endospores.

    • D.

      Capsules.

    • E.

      Flagella.

    Correct Answer
    A. A chromosome.
    Explanation
    All bacterial cells have a chromosome, which is a circular DNA molecule that contains the genetic information of the cell. This chromosome is essential for the survival and reproduction of the bacterium. Fimbriae, endospores, capsules, and flagella are also common features of bacterial cells, but not all bacterial cells have these structures.

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  • 42. 

    The term that refers to the presence of flagella all over the cell surface is

    • A.

      Amphitrichous.

    • B.

      Atrichous.

    • C.

      Lophotrichous.

    • D.

      Monotrichous.

    • E.

      Peritrichous.

    Correct Answer
    E. Peritrichous.
    Explanation
    Peritrichous refers to the presence of flagella all over the cell surface. This means that the flagella are distributed all around the cell, allowing the cell to move in multiple directions. Amphitrichous refers to having flagella at both ends of the cell, atrichous refers to the absence of flagella, lophotrichous refers to having multiple flagella at one end of the cell, and monotrichous refers to having a single flagellum at one end of the cell. Therefore, peritrichous is the correct answer as it accurately describes the presence of flagella all over the cell surface.

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  • 43. 

    A bacterial genus that has waxy mycolic acid in the cell walls is

    • A.

      Mycobacterium.

    • B.

      Mycoplasma.

    • C.

      Streptococcus.

    • D.

      Corynebacterium.

    • E.

      Salmonella.

    Correct Answer
    A. Mycobacterium.
    Explanation
    Mycobacterium is the correct answer because it is a bacterial genus known for having waxy mycolic acid in its cell walls. This unique feature gives Mycobacterium species their characteristic resistance to staining and their ability to cause diseases such as tuberculosis and leprosy. Mycoplasma, Streptococcus, Corynebacterium, and Salmonella are all bacterial genera that do not have waxy mycolic acid in their cell walls.

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  • 44. 

    Which is mismatched?

    • A.

      Ribosomes - protein synthesis

    • B.

      Inclusions - excess cell nutrients and materials

    • C.

      Plasmids - genes essential for growth and metabolism

    • D.

      Nucleoid - hereditary material

    • E.

      Cytoplasm - dense, gelatinous solution

    Correct Answer
    C. Plasmids - genes essential for growth and metabolism
    Explanation
    Plasmids are small, circular DNA molecules that can replicate independently of the chromosomal DNA. They often contain non-essential genes that provide advantages to the organism, such as antibiotic resistance. While plasmids can carry genes that contribute to growth and metabolism, they are not essential for these processes. The essential genes for growth and metabolism are typically found in the chromosomal DNA. Therefore, the statement that plasmids contain genes essential for growth and metabolism is incorrect.

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  • 45. 

    The function of bacterial endospores is

    • A.

      Convert gaseous nitrogen to a usable form for plants.

    • B.

      Reproduction and growth.

    • C.

      Protection of genetic material during harsh conditions.

    • D.

      Storage of excess cell materials.

    • E.

      Sites for photosynthesis.

    Correct Answer
    C. Protection of genetic material during harsh conditions.
    Explanation
    Bacterial endospores are specialized structures formed by certain bacteria as a survival mechanism during unfavorable conditions such as extreme temperatures, desiccation, or exposure to harmful chemicals. These endospores are highly resistant to these harsh conditions and protect the genetic material of the bacteria, allowing it to remain dormant until more favorable conditions arise. This ensures the survival of the bacteria and the preservation of its genetic information. Therefore, the function of bacterial endospores is the protection of genetic material during harsh conditions.

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  • 46. 

    Endospores are

    • A.

      Metabolically inactive.

    • B.

      Resistant to heat and chemical destruction.

    • C.

      Resistant to destruction by radiation.

    • D.

      Living structures.

    • E.

      All of the choices are correct.

    Correct Answer
    E. All of the choices are correct.
    Explanation
    The correct answer is that all of the choices are correct. Endospores are metabolically inactive, meaning they are in a dormant state and do not carry out any metabolic processes. They are also resistant to heat and chemical destruction, allowing them to survive in harsh conditions. Additionally, they are resistant to destruction by radiation. Therefore, all of the given statements accurately describe endospores.

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  • 47. 

    Which term is not used to describe bacterial cell shapes?

    • A.

      Coccus

    • B.

      Tetrad

    • C.

      Vibrio

    • D.

      Rod

    • E.

      Spirochete

    Correct Answer
    B. Tetrad
    Explanation
    The term "tetrad" is not used to describe bacterial cell shapes. A tetrad refers to a group of four bacterial cells that are arranged in a square or rectangular shape. The other terms listed - coccus, vibrio, rod, and spirochete - are all used to describe different shapes of bacterial cells.

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  • 48. 

    When a rod shaped bacteria is short and plump, it is called a

    • A.

      Spirochete.

    • B.

      Pleomorphic.

    • C.

      Vibrio.

    • D.

      Coccobacillus.

    • E.

      Spirillum.

    Correct Answer
    D. Coccobacillus.
    Explanation
    When a rod-shaped bacteria appears short and plump, it is referred to as a coccobacillus. This term is used to describe bacteria that have a shape similar to a coccus (spherical) but are slightly elongated like a bacillus (rod-shaped). Coccobacilli are often seen as oval or rounded rods, and they can appear singly or in pairs. They are typically shorter and wider than typical rod-shaped bacteria, giving them a more plump appearance. The term coccobacillus is commonly used to describe certain bacteria species, such as Haemophilus influenzae.

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  • 49. 

    What is the correct sequence for a Gram stain?

    • A.

      Gram's iodine, crystal violet, alcohol, safranin

    • B.

      Crystal violet, safranin, alcohol, Gram's iodine

    • C.

      Crystal violet, Gram's iodine, alcohol, safranin

    • D.

      Safranin, crystal violet, Gram's iodine, alcohol

    • E.

      Alcohol, crystal violet, safranin, Gram's iodine

    Correct Answer
    C. Crystal violet, Gram's iodine, alcohol, safranin
    Explanation
    The correct sequence for a Gram stain is crystal violet, Gram's iodine, alcohol, safranin. This sequence is important for differentiating between Gram-positive and Gram-negative bacteria. Crystal violet is the primary stain that stains both types of bacteria purple. Gram's iodine is the mordant that forms a complex with crystal violet, making it more difficult to wash out of Gram-positive bacteria. Alcohol is the decolorizer that removes the crystal violet-iodine complex from Gram-negative bacteria, leaving them colorless. Safranin is the counterstain that stains Gram-negative bacteria pink, allowing them to be differentiated from the purple Gram-positive bacteria.

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  • 50. 

    All of the following are correct about biofilms except

    • A.

      They are cooperative associations among several microbial groups.

    • B.

      They play an important role in recycling elements in the earth.

    • C.

      They can colonize medical devices.

    • D.

      An example could be the scum that builds up in toilet bowls.

    • E.

      They are harmless aggregations of microbes.

    Correct Answer
    E. They are harmless aggregations of microbes.
    Explanation
    Biofilms are not harmless aggregations of microbes. They are cooperative associations among several microbial groups that play an important role in recycling elements in the earth, can colonize medical devices, and can be exemplified by the scum that builds up in toilet bowls.

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