Micro Study Guide 2

A halophile is an organism that thrives in high salt concentrations. Therefore, it would grow best in salt lakes, where the salt concentration is high. Acid pools, fresh water ponds, hot geyser springs, and arid desert soil do not provide the high salt levels that a halophile requires for optimal growth.

If a culture starts with 1 cell and after 4 hours there are 64 cells, it means that each cell divides into 2 cells every hour. Therefore, in the first hour, there are 2 cells, in the second hour, there are 4 cells, in the third hour, there are 8 cells, and in the fourth hour, there are 16 cells. So, after 4 hours, there have been 4 generations of cell division. However, since the question asks for the total number of generations that have occurred, we need to include the initial generation, making the total 5 generations.

All of the choices are correct because microorganisms, like other organisms, have genomes that consist of chromosomes, plasmids, mitochondrial DNA, and chloroplast DNA. Chromosomes are the main genetic material found in the nucleus of cells, while plasmids are small, circular pieces of DNA that can replicate independently. Microorganisms, such as bacteria and fungi, also have mitochondria and chloroplasts, which have their own DNA. Therefore, all of these components can be found in the genomes of microorganisms.

The replication fork is the site where the old DNA strands separate and new DNA strands are synthesized during DNA replication. This is where the DNA helicase enzyme unwinds the double helix and separates the two strands. The newly synthesized DNA strands are then elongated by DNA polymerase using the existing strands as templates. The replication fork moves along the DNA molecule as replication progresses.

Guanine does not pair with uracil. Guanine pairs with cytosine through three hydrogen bonds, while adenine pairs with thymine through two hydrogen bonds. The pairing of nitrogenous bases is a fundamental aspect of DNA structure and is crucial for the encoding of genetic information.

Sarcinae refers to a cuboidal packet of cells. This term is used to describe a specific arrangement of bacteria, where the cells divide in three perpendicular planes, forming a cube-like structure. This arrangement is commonly observed in certain bacteria, such as the genus Sarcina. The cells within the packet are typically tightly packed together, creating a distinct appearance under a microscope. This arrangement is different from other options listed, such as cocci in pairs, coffee-bean shaped rods in pairs, or vibrios in threes.

Based on the information given, the culture is growing at the bottom of the tube. This suggests that the culture is growing in the absence of oxygen, as oxygen tends to accumulate at the top of the tube. Therefore, the culture must be anaerobic, meaning it can survive and grow in the absence of oxygen.

The E. coli that normally live in the human large intestines and produce vitamin K that the body uses would be best termed a mutualistic relationship. Mutualism refers to a symbiotic relationship where both organisms involved benefit from each other. In this case, the E. coli bacteria benefit by having a habitat to live in, while the human body benefits from the production of vitamin K. Therefore, both parties in this relationship are mutually dependent and gain advantages from each other's presence.

Peritrichous refers to the presence of flagella all over the cell surface. This means that the flagella are distributed uniformly around the cell, allowing for movement in any direction. This is in contrast to other terms such as monotrichous (single flagellum at one end), lophotrichous (multiple flagella at one end), amphitrichous (multiple flagella at both ends), and atrichous (no flagella).

The fact that there was moderate growth of the culture in both the candle jar (anaerobic condition) and the anaerobic jar suggests that the species can tolerate and grow in the absence of oxygen. However, the heavy growth of the culture on the incubator shelf indicates that it can also thrive in the presence of oxygen. Therefore, this species is a facultative anaerobe, which means it can switch between aerobic and anaerobic metabolism depending on the availability of oxygen.

A microaerophile is a type of organism that requires a small amount of oxygen to grow, but cannot tolerate normal atmospheric levels of oxygen. This means that it needs oxygen to survive, but too much oxygen can be harmful to its growth. Therefore, it is best suited to environments where oxygen levels are low, such as in an anaerobic jar.

The statement "it plays a role in cell motility" is incorrect because a slime layer does not contribute to cell motility. A slime layer is a type of glycocalyx that surrounds the cell and protects it from loss of water and nutrients. It also allows cells to participate in biofilms. However, it can be easily washed off the cell, unlike a capsule which is tightly attached to the cell surface.

All bacterial cells have a chromosome, which is a single circular DNA molecule that contains the genetic information necessary for the cell's survival and reproduction. The chromosome is located in the nucleoid region of the cell and is responsible for controlling the cell's activities and determining its characteristics. Unlike eukaryotic cells, bacterial cells do not have a nucleus, so the chromosome is not enclosed within a membrane. Instead, it is free-floating within the cytoplasm. The chromosome plays a crucial role in the cell's ability to carry out essential functions such as protein synthesis and cell division.

The term "psychrophile" could be used for this species because it is able to thrive and grow in cold temperatures, such as those found in a refrigerator. This is supported by the fact that there was abundant growth at refrigeration and no growth at higher temperatures of 37°C and 50°C.

Microorganisms require trace elements in small quantities for enzyme function and maintenance of protein structure. Trace elements are essential for various metabolic processes in microorganisms, as they serve as cofactors for enzymes. These elements, such as iron, copper, zinc, and manganese, play crucial roles in electron transfer reactions, DNA synthesis, and other cellular functions. Although required in small amounts, trace elements are indispensable for the growth and survival of microorganisms.

Metabolism refers to all the chemical reactions that occur within a cell. It includes both catabolic reactions (breakdown of molecules to release energy) and anabolic reactions (building up of molecules using energy). Redox reactions involve the transfer of electrons between molecules, while phosphorylation is the addition of a phosphate group to a molecule. Cellular respiration is a specific metabolic process that involves the breakdown of glucose to produce energy. Therefore, metabolism is the most appropriate term to encompass all the chemical reactions of the cell.

When bacteria living in a freshwater stream are moved to salty seawater, they would experience a hypertonic environment. In this situation, the concentration of solutes outside the bacterial cells is higher than inside the cells. As a result, water would move out of the cells through osmosis, causing them to shrink or shrivel. This is because water naturally moves from an area of lower solute concentration (inside the cells) to an area of higher solute concentration (outside the cells) in an attempt to equalize the concentration on both sides.

Archaea is the correct answer because they are known to thrive in extreme environments, such as hot acidic habitats. They have the ability to survive in conditions with low pH and high temperatures, making them well-suited for the described environment in the waste piles of coal mines. Gracillucates, Firmicutes, Actinobacteria, and Spirochaetes are not typically associated with extreme environments like this.

The DNA of microorganisms is made up of subunits called nucleotides. Nucleotides are the building blocks of DNA and consist of a sugar molecule, a phosphate group, and a nitrogenous base. They are arranged in a specific sequence to form the genetic code of an organism. This code contains the instructions for the synthesis of proteins and the functioning of the organism. Therefore, nucleotides play a crucial role in the structure and function of DNA in microorganisms.

In anaerobic respiration, organisms use alternative electron acceptors when oxygen is not available. Nitrate, sulfate, and nitrite are all common alternative electron acceptors in anaerobic respiration. However, oxygen cannot serve as a final electron acceptor in anaerobic respiration because the process specifically occurs in the absence of oxygen. Therefore, the correct answer is oxygen.

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A Gram-positive cell wall primarily consists of peptidoglycan, which provides structural support to the cell. It also contains small amounts of teichoic acid and lipoteichoic acid, which help in regulating the movement of ions and molecules across the cell wall. Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet stain during the Gram staining process, giving them a purple color. This is in contrast to Gram-negative bacteria, which have a thinner peptidoglycan layer and an outer membrane that does not retain the stain, resulting in a pink color. Therefore, the given characteristics of the cell wall indicate that it belongs to a Gram-positive bacterium.

The term phototroph refers to an organism that gets energy from sunlight. This means that the organism is able to convert sunlight into usable energy through a process called photosynthesis. It uses this energy to carry out its metabolic activities and sustain its life.

Peptidoglycan is a unique macromolecule found in bacterial cell walls. It provides structural support and protection to the bacterial cell. It forms a mesh-like structure, providing rigidity to the cell wall and preventing the cell from bursting under osmotic pressure. Peptidoglycan is composed of alternating sugar residues, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), cross-linked by short peptide chains. This unique composition is specific to bacterial cell walls and is not found in cell membranes, capsules, slime layers, or inclusions.

The outcome of the Gram stain is based on differences in the cell wall. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain and appears purple under the microscope. On the other hand, Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, which does not retain the stain and appears pink or red after counterstaining with safranin. Therefore, the cell wall composition is crucial in determining the outcome of the Gram stain.

All of the choices are correct because endospores are metabolically inactive, meaning they are in a dormant state and do not carry out any metabolic processes. They are resistant to heat and chemical destruction, allowing them to survive in extreme conditions. They are also resistant to destruction by radiation, making them highly durable. Despite being inactive, endospores are still living structures, albeit in a dormant state. Therefore, all of the given choices accurately describe the characteristics of endospores.

Macronutrients are essential nutrients that organisms need in large quantities for their cell structure and metabolism. They provide energy and are involved in various biological processes. In the context of microorganisms, macronutrients are crucial for their growth and survival. Therefore, microorganisms require large quantities of macronutrients for their cell structure and metabolism.

Transfer RNA (tRNA) molecules are responsible for carrying amino acids to the ribosomes during protein synthesis. Each tRNA molecule has a specific anticodon sequence that matches with the codon sequence on the messenger RNA (mRNA) molecule. This allows the tRNA to recognize and bind to the corresponding codon on the mRNA, bringing the correct amino acid to the growing protein chain. Therefore, tRNA is the correct answer for this question.

Bacterial endospores serve as a means of protecting the genetic material of the bacteria during harsh conditions. These conditions can include extreme temperatures, lack of nutrients, or exposure to harmful chemicals or radiation. The endospore is a dormant and highly resistant structure that forms inside the bacterial cell, encasing the DNA and other essential components. This protective mechanism allows the bacteria to survive in unfavorable environments until conditions become more favorable for growth and reproduction.

The correct answer is UAAGGCCU because in transcription, the DNA sequence is transcribed into mRNA by replacing each DNA base with its complementary RNA base. In this case, A is replaced with U, T is replaced with A, C is replaced with G, and G is replaced with C. Therefore, the mRNA transcript of the given DNA sequence ATTCCGGA would be UAAGGCCU.

A bacterial cell exhibiting chemotaxis probably has flagella. Chemotaxis is the movement of an organism in response to a chemical stimulus, and flagella are the whip-like appendages that bacteria use for movement. Therefore, it is likely that a bacterial cell exhibiting chemotaxis would have flagella to enable it to move towards or away from a particular chemical signal.

Mycobacterium is the correct answer because it is a bacterial genus that is known for having waxy mycolic acid in its cell walls. Mycolic acid helps to protect the bacteria from the host immune system and contributes to their ability to cause chronic infections. Mycobacterium includes several species, including the ones that cause tuberculosis and leprosy. Mycoplasma, Streptococcus, Corynebacterium, and Salmonella do not have waxy mycolic acid in their cell walls, making them incorrect answers.

In the cell, energy released by electrons is often used to phosphorylate ADP. This means that ADP (adenosine diphosphate) is converted into ATP (adenosine triphosphate) by adding a phosphate group. ATP is the primary energy currency of the cell and is used to power various cellular processes. Therefore, the energy released by electrons is utilized to generate ATP, which is essential for the cell's energy needs.

Enzymes are proteins that function as catalysts. Catalysts are substances that speed up chemical reactions without being consumed or permanently changed in the process. Enzymes facilitate biochemical reactions by lowering the activation energy required for the reaction to occur. They do so by binding to specific molecules, called substrates, and converting them into products. Enzymes play a crucial role in various biological processes, such as digestion, metabolism, and DNA replication. Therefore, the statement "proteins that function as catalysts" accurately describes the nature and function of enzymes.

The anticodon is the three nucleotide sequence on a tRNA molecule that is complementary to the codon on mRNA during translation. In this case, the codon for alanine is GCA. To find the anticodon, we need to determine the complementary sequence. The complementary bases for G, C, and A are C, G, and U respectively. Therefore, the anticodon for the codon GCA is CGU.

Bacterial endospores are resistant, dormant structures that certain bacteria produce as a survival mechanism under unfavorable conditions. Staphylococcus is a genus of bacteria that does not produce endospores. Sporosarcina, Bacillus, and Clostridium, on the other hand, are known to produce endospores. Therefore, the correct answer is Staphylococcus.

Fimbriae are short, numerous appendages found on the surface of some bacterial cells. They are used by the bacteria to adhere to surfaces, such as host tissues or other cells. Fimbriae are important for the bacteria to establish infections and colonize specific sites in the body. They can also play a role in biofilm formation, which is a protective matrix that bacteria can form on surfaces. Flagella, on the other hand, are long whip-like structures that bacteria use for movement. Cilia are similar to flagella but are found in eukaryotic cells. Periplasmic flagella are flagella that are located in the periplasmic space of certain bacteria.

Plasmids are circular DNA molecules that are separate from the chromosomal DNA in bacteria. They play a crucial role in modern genetic engineering techniques as they can be easily manipulated and transferred between different organisms. Plasmids are often used as vectors to introduce foreign DNA into host cells, allowing scientists to insert, delete, or modify specific genes. This ability to manipulate plasmids has revolutionized genetic engineering, enabling the production of genetically modified organisms and the development of new medical treatments and technologies.

If a cell's ribosomes are destroyed, it would directly result in the stoppage of protein synthesis. Ribosomes are responsible for protein synthesis in cells, and without them, the cell would not be able to produce proteins. Proteins are essential for various cellular functions, including structural support, enzymatic reactions, and cell signaling. Therefore, the destruction of ribosomes would immediately halt the production of proteins, leading to significant disruptions in cellular processes.

An intron is a sequence of bases on a gene that does not code for protein. It is a non-coding region that is transcribed into RNA but is later removed during the process of RNA splicing. In contrast, exons are the coding regions of a gene that are translated into protein. Promoters are DNA sequences that initiate transcription, operators are DNA sequences that control gene expression, and operons are clusters of genes that are transcribed together. Therefore, the correct answer is intron.

Lipopolysaccharide is a major component of the outer membrane of gram-negative bacteria. It plays a crucial role in protecting the bacteria from the host immune system and is responsible for many of the pathogenic properties of these bacteria. Gram-positive bacteria do not have an outer membrane and therefore do not contain lipopolysaccharide. Acid-fast bacteria, such as Mycobacterium tuberculosis, have a unique cell wall structure that includes mycolic acids, not lipopolysaccharide. Protoplasts are bacterial cells that have had their cell walls removed, so they also do not contain lipopolysaccharide.

Saprobes are organisms that obtain nutrients by feeding on dead organisms. They play a crucial role in decomposition and recycling of organic matter in ecosystems. Unlike parasites, which rely on living hosts, saprobes derive their nutrients from dead organic material. Autotrophs, on the other hand, are organisms that can produce their own food through photosynthesis or chemosynthesis. Lithoautotrophs are a specific type of autotrophs that obtain energy from inorganic compounds. Phototrophs are also autotrophs, but they obtain energy from sunlight through photosynthesis. Therefore, the correct answer for this question is saprobes.

Plasmids are small, circular pieces of DNA that are separate from the main bacterial chromosome. They often contain non-essential genes, such as those involved in antibiotic resistance or the ability to produce toxins. While plasmids can provide certain advantages to bacterial growth and metabolism, they are not essential for these processes. Therefore, the statement "plasmids - genes essential for growth and metabolism" is mismatched.

An organism with a temperature growth range of 45*C to 60*C would be called a thermophile. Thermophiles are organisms that thrive in high temperatures, typically above 45°C. They have adapted to survive and reproduce in extreme heat, which would be detrimental to most other organisms. Thermophiles are often found in hot springs, hydrothermal vents, and other geothermal environments.

The nitrogen base sequence of rRNA is an important indicator of evolutionary relatedness because it is highly conserved among different organisms. Over time, mutations can occur in the DNA sequence of an organism, including the rRNA genes. By comparing the nitrogen base sequences of rRNA from different organisms, scientists can determine how closely related they are. The more similar the sequences, the more closely related the organisms are believed to be. This method is widely used in phylogenetic studies to determine the evolutionary relationships between different species.

A heterotroph is an organism that must obtain organic compounds for its carbon needs. This means that it cannot use CO2 as its carbon source like autotrophs do. Instead, heterotrophs rely on consuming other organisms or organic matter to obtain the necessary carbon compounds for their survival and growth.

The lag phase of the bacterial growth curve refers to the initial period where newly inoculated cells are adapting to their new environment. During this phase, the cells are metabolizing and preparing for growth, but they are not actively multiplying. This phase is characterized by a slower rate of cell division as the bacteria adjust to the conditions of their new surroundings.

The stationary phase of the bacterial growth curve is the phase in which the rate of multiplication equals the rate of cell death. During this phase, the number of new cells being produced is balanced by the number of cells dying, resulting in no net increase in the population size. This phase occurs when the bacteria have depleted essential nutrients or when they have reached the carrying capacity of their environment.

Microorganisms that lack catalase or superoxide dismutase would struggle to survive in an environment with oxygen. Catalase and superoxide dismutase are enzymes that help break down harmful reactive oxygen species (ROS) produced during normal cellular metabolism. Without these enzymes, the microorganism would be unable to neutralize ROS, leading to oxidative stress and damage to cellular components. Oxygen is a major source of ROS, so an oxygen-rich environment would be particularly challenging for these microorganisms to survive in.

Biofilms 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 seen as the scum that builds up in toilet bowls. However, they are not harmless aggregations of microbes as they can cause infections and be resistant to antibiotics.