Microbio Lab Quiz 2

What is alpha hemolysis?

Partial hemolysis of blood cells due to hydrogen peroxide produced by the organism.

What is beta hemolysis?

Complete hemolysis of blood cells due to the action of cytotoxins such as streptolysin enzyme.

What does non-hemolytic (gamma) mean?

Organisms that do not cause destruction of blood cells.

What is the purpose of an EMB plate?

To select gram-negative bacteria and differentiate lactose fermenters from non-fermenters.

What is the first step in the lytic cycle of a bacteriophage?

Adsorption: the phage finds a specific receptor on the bacterial surface.

What happens during penetration in the lytic cycle?

The phage injects its DNA into the bacterial cell by punching a hole through the cell wall.

What occurs after the bacterial chromosome is degraded in the lytic cycle?

The viral DNA produces an enzyme that cuts the bacterial chromosome into pieces.

What is the role of endolysin in the lytic cycle?

It digests the cell wall from inside out, leading to the release of new phages.

What is a plaque assay used for?

To measure the concentration of bacteriophages by counting clear zones (plaques) on a plate.

What does a positive result in Simmon's Citrate Test indicate?

The organism can utilize citrate as a sole carbon source, turning the medium blue.

What does urease do?

It breaks down urea into carbon dioxide and ammonia, raising the pH and causing a color change.

What indicates a positive oxidase test?

A purple or pink color on the filter paper after applying the colony.

What does a bubbling reaction in a catalase test indicate?

The presence of catalase, which breaks down hydrogen peroxide into water and oxygen.

What is the purpose of the Kirby-Bauer antimicrobial sensitivity test?

To determine the susceptibility of bacteria to different antibiotics using a standardized method.

What does a large zone of inhibition in the Kirby-Bauer test indicate?

The bacteria are susceptible to the antibiotic.

What is the effect of UV light on microorganisms?

It kills microorganisms by producing pyrimidine dimers in DNA, impairing replication and gene expression.

What is the role of citrate permease?

It transports citrate into the cell for energy production in certain microorganisms.

What is the significance of phenol red in the urease test?

It acts as a pH indicator, turning yellow in acidic conditions and hot pink in basic conditions.

What does a green result in Simmon's Citrate Test indicate?

The organism cannot utilize citrate as a carbon source.

What is the dilution factor in serial dilution?

It represents the positive exponent indicating the concentration reduction step-by-step.

What does a yellow result in the urease test indicate?

The absence of urease activity, meaning the organism does not break down urea.

What is the purpose of using Mueller-Hinton Medium in antibiotic testing?

It provides a standardized environment for comparing results across different labs.

What is the expected result for a non-hemolytic organism in a throat culture?

No hemolysis observed around the bacterial growth.

What is the consequence of not having a suitable host for bacteriophages?

No phage replication can occur.

What is the significance of the clear zones in a plaque assay?

Each clear zone corresponds to one plaque-forming unit (PFU) of bacteriophage.

What is a limitation of UV light sterilization?

UV light can only be used for surface sterilization and cannot penetrate surfaces.

Why are endospores resistant to UV light?

Endospores are resistant structures that offer protection against radiation.

What type of DNA damage does UV light cause in vegetative cells?

UV light forms pyrimidine dimers in the DNA of vegetative cells.

What is an antiseptic?

An antiseptic is a product that destroys or inhibits the growth of microorganisms in or on living tissue.

Give an example of an antiseptic.

Iodine, silver nitrate, triclosan, or ethanol.

What is a disinfectant?

A disinfectant is a product that destroys or inhibits the growth of microorganisms on surfaces.

Give an example of a disinfectant.

Cresols (Lysol) or bleach.

What is an obligate aerobe?

An obligate aerobe requires oxygen for growth and cannot survive in environments without oxygen.

What is a microaerophile?

A microaerophile requires a limited amount of oxygen; excess oxygen inhibits their growth.

What is a facultative anaerobe?

A facultative anaerobe can grow in both aerobic and anaerobic environments, preferring oxygen when available.

What is an aerotolerant anaerobe?

An aerotolerant anaerobe does not use oxygen but can tolerate it and grow in aerobic environments.

What is an obligate anaerobe?

An obligate anaerobe cannot survive in the presence of oxygen and uses alternate electron acceptors for respiration.

What is the purpose of fluid thioglycollate (FTG) tubes?

FTG tubes are used to test for oxygen requirements in microorganisms.

What does resazurin indicate in FTG tubes?

Resazurin indicates the presence of oxygen; it turns red when oxygen is present.

What is the coagulase test used for?

The coagulase test differentiates Staphylococcus aureus from Staphylococcus epidermidis based on plasma clotting.

What indicates microbial contamination in water analysis?

The presence of indicator organisms like coliforms suggests contamination.

What is the significance of water analysis?

Water analysis is significant for public health protection and detection of unsafe drinking water.

What does MPN stand for in water analysis?

Most Probable Number, used as an indicator for water quality.

What is a benefit of using a wet-mount for visualizing organisms?

Wet-mount allows for no heat-fixation, keeping cells undistorted and enabling observation of cell movement.

What is a caveat of using a wet-mount?

Bacterial cells can be difficult to see when unstained.

How do you prepare a wet-mount slide?

Make a well with a wax circle, add water sample, and gently place a coverslip on top.

What happens to vegetative cells during UV exposure?

Extensive DNA damage occurs in exposed vegetative cells.

What occurs to endospores during UV exposure?

Endospores can germinate after UV exposure, leading to growth in the culture.

What is the NJ beach closure cutoff for Enterococci?

104 Enterococci per 100mL.