Microbiology Lab Exam #2

The statement is true because a substrate is indeed the molecule that an enzyme acts upon. Enzymes are biological catalysts that speed up chemical reactions by binding to specific molecules, known as substrates, and converting them into products. The enzyme's active site interacts with the substrate, facilitating the reaction and allowing it to occur more efficiently. Therefore, the term "substrate" accurately describes the molecule that an enzyme can act on.

Enrichment media are specifically designed to provide optimal conditions for the growth and multiplication of certain organisms. These media contain a rich supply of essential nutrients that support the metabolic needs of these organisms, allowing them to flourish. By creating an environment that is highly favorable for the growth of specific organisms, enrichment media facilitate their isolation and identification in laboratory settings. Therefore, it is correct to say that enrichment media contain nutrients that greatly encourage the growth of some organisms.

Mannitol salt agar is a type of agar that is commonly used in microbiology to culture and identify bacteria. It is both selective and differential because it contains a high concentration of salt, which inhibits the growth of most bacteria except for those that can tolerate salt. Additionally, it contains mannitol, a type of sugar that can be fermented by certain bacteria. The fermentation of mannitol leads to a change in the pH of the agar, causing it to turn yellow. This allows for the differentiation of bacteria based on their ability to ferment mannitol. Therefore, mannitol salt agar is both selective, as it only allows certain bacteria to grow, and differential, as it allows for the differentiation of bacteria based on their metabolic capabilities.

The efficiency of a disinfectant or antiseptic is influenced by several factors, including concentration, length of exposure, and environmental conditions. Concentration refers to the strength or amount of the disinfectant or antiseptic used, and a higher concentration is generally more effective. The length of exposure refers to the amount of time the disinfectant or antiseptic is in contact with the target surface or organism, with longer exposure times typically leading to better results. Environmental conditions, such as temperature and humidity, can also impact the effectiveness of the disinfectant or antiseptic. Therefore, all of these factors play a role in determining the efficiency of the disinfectant or antiseptic.

A color change from green to blue in the inoculated Simmons citrate agar indicates a positive test for citrate utilization. This means that the organism being tested is capable of using citrate as a carbon source for growth. The change in color is due to the production of alkaline byproducts during citrate metabolism, which causes the pH indicator in the agar to shift from green to blue. Therefore, the statement is true.

The oxidase enzyme is indeed crucial in the electron transport system during aerobic respiration. This enzyme helps in transferring electrons from the electron carriers to the final electron acceptor, which is oxygen in aerobic respiration. Without the oxidase enzyme, the electron transport chain would not be able to function properly, resulting in a disruption of ATP production through oxidative phosphorylation. Therefore, the statement is true.

Lipase is the correct answer because it is an enzyme that specifically breaks down fats into smaller units called fatty acids and glycerol. This process is known as lipolysis. Lipase is produced by the pancreas and is essential for the digestion and absorption of dietary fats in the small intestine. Without lipase, fats would not be properly broken down and absorbed, leading to digestive issues and nutrient deficiencies.

The measurement of antibiotic resistance is done by measuring the diameter around a disc, which is called the "zone of inhibition." This zone indicates the area where the antibiotic has prevented the growth of bacteria. The larger the zone of inhibition, the more effective the antibiotic is against the bacteria. This measurement is commonly used in laboratory testing to determine the susceptibility of bacteria to different antibiotics.

Bacteria obtain nutrients based on their genetics and the enzymes they can produce. This means that the specific nutrients a bacteria can utilize are determined by its genetic makeup and its ability to produce the necessary enzymes to break down and utilize those nutrients. Therefore, the statement is true.

The correct answer is catalase. Catalase is an enzyme that facilitates the decomposition of hydrogen peroxide into water and oxygen. In the given equation, 2 molecules of hydrogen peroxide (H2O2) react to form 2 molecules of water (H2O) and 1 molecule of oxygen (O2). Catalase speeds up this reaction by lowering the activation energy required for the decomposition of hydrogen peroxide.

The chills and fever symptoms of malaria are caused by the release of merozoites into the bloodstream. Merozoites are a stage in the life cycle of the malaria parasite, and when they are released, they invade red blood cells, leading to the characteristic symptoms of the disease. This is why the statement is true.

Staphylococcus aureus is a type of bacteria that is known to ferment mannitol. Fermentation is a metabolic process in which microorganisms convert sugars into acids, gases, or alcohol. Mannitol is a type of sugar alcohol that can be fermented by certain bacteria, including Staphylococcus aureus. This fermentation process can be used as a diagnostic test to identify and differentiate Staphylococcus aureus from other bacteria. Therefore, the statement that Staphylococcus aureus will ferment mannitol is true.

Proteolysis refers to the process of breaking down proteins into smaller peptides or individual amino acids. This process is essential for various biological functions such as digestion, cellular turnover, and regulation of protein activity. Therefore, the statement "proteolysis means digestion of protein" is true, as it accurately describes the process of protein breakdown.

The correct answer is "aspergillus." The other options, balantidium and ring stage, do not fit the context of the question, which asks for selecting the ones you like. Aspergillus is a genus of fungi, and it is possible that the question is referring to selecting favorite organisms or preferences in the field of microbiology.

The catalase test is particularly useful in distinguishing between streptococaceae and staphylococci. This test is based on the presence of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. Staphylococci produce catalase and will produce bubbles of oxygen when hydrogen peroxide is added to their colonies. On the other hand, streptococaceae do not produce catalase and will not produce bubbles. Therefore, the catalase test can be used to differentiate between these two groups of bacteria.

Amylase is the correct answer because it is an enzyme that specifically breaks down starch into smaller units. Starch is a complex carbohydrate made up of long chains of glucose molecules, and amylase helps to break these chains into smaller, more easily digestible units such as maltose and glucose. This process is important for the digestion of starch in the body, allowing it to be absorbed and used for energy. Decarboxylase, lipase, and proteinase are enzymes that have different functions and do not play a role in starch digestion.

Merozoites are a stage in the life cycle of the malaria parasite. They are formed in the liver and then released into the bloodstream, where they invade and multiply within red blood cells (erythrocytes). This process is a crucial step in the development and spread of malaria within the human body. Therefore, the statement that merozoites form in the liver and erythrocytes of humans infected with malaria is true.

Lactose fermentation is very useful in the identification of gram-negative rods because it helps to differentiate between different species of bacteria. Gram-negative rods that can ferment lactose produce acid as a byproduct, which lowers the pH of the medium. This change in pH can be detected using indicators such as phenol red, allowing for the identification of lactose-fermenting gram-negative rods. This characteristic is particularly important in clinical microbiology for identifying certain pathogenic bacteria, such as Escherichia coli, which is a common cause of urinary tract infections.

Neisseria sp is a type of bacteria that is commonly found in the throat and upper respiratory tract. This is supported by scientific research and studies that have identified Neisseria species in these areas of the body. Therefore, the statement that Neisseria sp can be found in the throat and upper respiratory tract is true.

In the malarial parasite, fertilization occurs in the lumen of the mosquito's gut. This means that when a mosquito infected with the malarial parasite bites a human, the parasite is transferred to the human's bloodstream. Inside the mosquito's gut, male and female gametes of the parasite fuse to form a zygote, which then develops into sporozoites. These sporozoites migrate to the mosquito's salivary glands and can be transmitted to another human when the mosquito bites again. Therefore, the statement "True" is correct.

A lactose non-fermenting gram-negative rod that produces a positive test for urea hydrolysis is most likely to be the genus Proteus. This is because Proteus species are known to be lactose non-fermenters and are capable of hydrolyzing urea, producing a positive result in the urea hydrolysis test. Therefore, the correct answer is True.

In the carbohydrate tests, phenol red broth base is used with the appropriate carb. If the indicator turns yellow, it indicates that acid is produced. This means that the carbohydrate has been fermented by the microorganism, resulting in the production of acidic byproducts.

The IMVic series is a set of tests used to identify enteric bacilli. These tests include Indole, Methyl Red, Voges-Proskauer, and Citrate utilization tests. By performing these tests, microbiologists can determine the presence of certain enzymes and metabolic pathways in the bacteria, which helps in identifying the specific species or group of enteric bacilli. Therefore, the statement "the IMVic series is a sense of tests used to identify enteric bacilli" is true.

Caseinase, also known as proteinase, is an enzyme that specifically breaks down milk protein, which is primarily composed of casein. This enzyme is capable of hydrolyzing the peptide bonds in casein, resulting in the breakdown of the milk protein into smaller peptides and amino acids. Gelatin, starch, and fats are not targeted by caseinase, and therefore, they are not affected by its action.

The statement is false because when E. coli acts as a pathogen, it is most often found in the gastrointestinal tract rather than the respiratory tract. E. coli is a common cause of foodborne illnesses and urinary tract infections, but it is not commonly associated with respiratory infections.

Barritts reagent is a commonly used chemical test to detect the presence of acetyl methyl carbinol (acetoin) in a culture. Acetyl methyl carbinol is a metabolic byproduct produced by certain bacteria during the fermentation process. When Barritts reagent is added to a culture, it reacts with acetyl methyl carbinol to produce a red color, indicating a positive result for its presence. Therefore, the statement "True" is correct, as adding Barritts reagent to a culture is indeed used to test for the presence of acetyl methyl carbinol.

The correct answer is rhizopus. Rhizopus is a type of fungus that is commonly found in soil and decaying organic matter. It is known for its ability to grow rapidly and produce spores, which can be dispersed by wind or water. Rhizopus is also used in various industrial processes, such as the production of enzymes and organic acids. In the context of the given options, rhizopus is the most relevant choice as both "ring stage" and "balantidium" do not match the characteristics or classification of rhizopus.

African sleeping sickness is caused by a protozoan. Protozoa are single-celled organisms that can cause various diseases in humans. In the case of African sleeping sickness, the protozoan responsible is called Trypanosoma brucei. This parasite is transmitted to humans through the bite of infected tsetse flies. Once inside the human body, the protozoan can invade the central nervous system, leading to symptoms such as fever, fatigue, and sleep disturbances. Therefore, the correct answer is protozoan.

The oxidase test helps to differentiate between the membranes of Pseudomonas and Neisseria genera. This test is based on the presence of the enzyme cytochrome c oxidase, which is found in the respiratory chain of these bacteria. Salmonella, on the other hand, does not possess this enzyme. Therefore, the correct answer is a & b, which refers to Pseudomonas and Neisseria.

The given statement is false. Staphylococcus epidermidis is actually a gram-positive pathogen. Gram-negative bacteria have a different cell wall structure compared to gram-positive bacteria, which can be distinguished by the Gram staining method. Staphylococcus epidermidis is a common bacterium found on the skin and mucous membranes, and it is known to cause infections, particularly in immunocompromised individuals or when medical devices are implanted.

The normal flora of the mouth or throat refers to the microorganisms that naturally reside in these areas without causing harm. Myobacterium tuberculosis, which causes tuberculosis, is not a part of the normal flora. Streptococcus mutants, lactobacillus acidophilus, and neisseria sap are all commonly found in the mouth or throat as part of the normal flora.

Penicillium is the correct answer because it is a genus of fungi that is commonly used in the production of antibiotics, including penicillin. Penicillium is known for its ability to inhibit the growth of certain bacteria, making it a valuable tool in medicine. The other options, rhizopus and plasmodium, are not directly related to antibiotic production and do not possess the same medical significance as penicillium.

The catalase test does not differentiate gram-negative rods. The catalase test is used to differentiate between bacteria that produce the enzyme catalase and those that do not. Catalase-positive bacteria can break down hydrogen peroxide into water and oxygen, while catalase-negative bacteria cannot. This test is not specific to gram-negative rods and can be used for a wide range of bacteria. Therefore, the statement that the catalase test differentiates gram-negative rods is false.

The correct answer is crytosporidium. The question is asking for the name of a slide, and out of the given options, crytosporidium is the only one that fits. The other options, plasmodium and aspergillis, do not match the question's prompt.

The statement in the question is incorrect. Intestinal pathogens in the family Enterobacteriaceae are actually gram-negative rods, not gram-positive rods. Enterobacteriaceae is a family of bacteria that includes well-known pathogens like Escherichia coli and Salmonella. These bacteria are characterized by their ability to ferment glucose and produce acid and gas. Additionally, they possess a lipopolysaccharide outer membrane, which is a characteristic feature of gram-negative bacteria. Therefore, the correct answer is false.

Beta hemolysis of red blood cells refers to the complete lysis or destruction of red blood cells. This means that the red blood cells are completely broken down, leading to the release of hemoglobin and a clear zone around the bacterial colony on a blood agar plate. This is in contrast to alpha hemolysis, which refers to partial lysis of red blood cells, and gamma hemolysis, which refers to no lysis of red blood cells. Therefore, the correct answer is "complete".

Entamoeba is the correct answer because it is one of the options given in the question. The question asks the respondent to select the ones they like, and out of the options provided, entamoeba is the one that the respondent likes.

Valley fever is not associated with Staphylococcus aureus. Staphylococcus aureus is a bacterium that can cause various infections, including boils, carbuncles, and impetigo. Valley fever, on the other hand, is a fungal infection caused by inhaling spores of the fungus Coccidioides species. It primarily affects the lungs and can cause symptoms such as fever, cough, and fatigue. Therefore, valley fever is unrelated to Staphylococcus aureus.

The coagulase test would best distinguish between Staphylococcus aureus and Staphylococcus epidermis. This test detects the presence of the coagulase enzyme, which is produced by S. aureus but not by S. epidermis. The coagulase enzyme causes the plasma in the test tube to clot, indicating a positive result for S. aureus. This test is important because S. aureus is a more pathogenic species compared to S. epidermis, and the ability to differentiate between them is crucial for appropriate treatment and infection control measures.

SIM (Sulfide Indole Motility) is the most suitable media for detecting H2S (hydrogen sulfide) production. SIM contains iron and sulfur compounds that react with H2S to produce a black precipitate, indicating the presence of H2S production. TSA (Tryptic Soy Agar), EMB (Eosin Methylene Blue Agar), and Sab-Dex (Sabouraud Dextrose Agar) are not specifically designed for detecting H2S production and may not provide accurate results.

A negative test for nitrite in the nitrate reduction test indicates that nitrate has remained unchanged. This means that there has been no conversion of nitrite to ammonia and free nitrogen.

Sab- Dex is the best medium suitable for the cultivation of a wide variety of fungal types. Sab- Dex is a selective medium that contains nutrients to support the growth of fungi and inhibitory agents to prevent the growth of bacteria. It is commonly used in clinical laboratories for the isolation and identification of dermatophytes and other pathogenic fungi. The medium's composition and inhibitory properties make it ideal for promoting fungal growth while suppressing the growth of unwanted contaminants.

Fungi best grow at temperatures ranging from 20 to 25 degrees Celsius. This temperature range provides the ideal conditions for fungal growth and reproduction. Temperatures below 20 degrees Celsius may slow down the growth of fungi, while temperatures above 25 degrees Celsius can inhibit their growth or even kill them. Therefore, the optimal temperature range of 20-25 degrees Celsius is crucial for the successful development and proliferation of fungi.

Plasmodium is the correct answer because it is a genus of parasitic protists that causes malaria in humans. The other options, trypanosoma and penicillium, do not cause malaria and are not related to the question.

In the malarial parasite life cycle, the definitive host refers to the organism in which the parasite reaches sexual maturity and reproduces. While humans can be infected by the malarial parasite and act as intermediate hosts, the definitive host for most species of the parasite is the female Anopheles mosquito. Therefore, the given statement that the definitive host in the malarial parasite life cycle is man is incorrect.

All of the above tests can effectively separate the hemolytic group A Streptococci aureus from group B through N. The bactitracin test is used to differentiate between group A and other beta-hemolytic streptococci. The camp test is used to identify group B Streptococci by detecting the presence of a hemolysin. The bile esculin test is used to differentiate group D Streptococci from other streptococci. The 6.5% NaCl medium is used to selectively isolate group D Streptococci from other streptococci. Therefore, all of these tests are effective in separating the different groups of streptococci.

A positive test for H2S production in the most media is not manifested as a cerise or magenta colored precipitate.

TSI agar and SIM medium are not solely used to detect H2S production. TSI agar is a differential medium used to detect the production of hydrogen sulfide (H2S), as well as the fermentation of sugars and the production of gas. SIM medium is also used to detect H2S production, but it is also used to detect motility and indole production. Therefore, the statement "TSI agar and SIM medium are used solely to detect H2S production" is false.

The given statement is false. Entamoeba histolytica is not a true fungus; it is actually a protozoan parasite that causes dysentery. Protozoa are single-celled eukaryotic organisms, while fungi are a separate group of eukaryotes that include organisms like mushrooms and yeasts. Therefore, the correct answer is false.