Micro Chap 6

What safety level is our microbiology lab?

BSL 2 and microbes are BSL 1

Why are obligate aerobes at a disadvantage?

Because oxygen is poorly soluble in the water of their environment.

6-7 Identify a way in which pathogens find it advantageous to form biofilms.

Because the biofilm is what allows the bacteria to be resistant to antibiotics. (Community survival)

Which biosafety level is appropriate for handling microbes that present a moderate risk of infection?

Bsl-2 Bsl2 lab workers are required to wear lab coats gloves and eye protection

Microbes that require many growth factors are grown in which media?

Chemically defined media

Which of the following statements regarding infections involving biofilms is FALSE? A Microbes in biofilms are more resistant to antimicrobials than are independent organisms. B It is estimated that nearly 70% of all infections are caused by biofilms. C The majority of hospital-acquired infections (nosocomial infections) are related to biofilms. D There is no way to prevent biofilms from developing on surfaces.

D There is no way to prevent biofilms from developing on surfaces. This is false. Antimicrobials can be applied to the surface of catheters and IV tubing to prevent biofilm development.

Which of the following is not a step in bacterial cell division?

Disappearance of nuclear envelope

What is an example of a facultative anaerobe?

E coli in the intestinal tract

In facultative anaerobes, where is there greater growth?

Greater growth in the presence of oxygen

Why does lactoferrin inhibit biofilm formation?

It binds to iron, making it unavailable for bacteria. Iron is used for surface motility and aggregation of biofilm so it is not formed,

6.2 Other than controlling acidity, what is an advantage of using phosphate salts as buffers in growth media?

It provides nutrients (phosphorous) and is non toxic

Intense activity preparing for population growth occurs in which phase of the bacterial growth curve?

Lag phase

During which phases of the bacterial growth curve are there no changes in the number of living cells?

Lag phase and stationary phase

During which phases of bacterial growth are there logarithmic changes in population growth?

Log phase and death phase

Which of the following phases of the bacterial growth curve is matched with the correct definition?

Log phase- the phase in which organisms are actively dividing and the generation time is constant This is the steep upward slope of the bacterial growth curve, where organisms are rapidly multiplying.

Which type of organism is responsible for most of the common spoilage and disease organisms?

Mesophiles

Microbes have very narrow optimum temperature ranges. Which of the following classifications of microbes are most likely to cause human disease, based on their temperature requirements?

Mesophiles The temperature range of mesophiles overlaps that of normal human body temperature, allowing the greatest growth.

Compare mold and yeast pH to bacteria pH

Molds and yeast grow over a greater pH range and at pH lower than bacteria (about pH 5 to 6)

How long does it take for the daughter cells to initiate or start the next round of replication?

No time is required -- they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right.

What is the difference between peroxidase and catalase?

Peroxidase oxidizes peroxide to water Catalase oxidizes peroxide to water AND oxygen

Which of the following statements accurately describes the culture medium necessary for growing an obligate anaerobe such as clostridium tetanus?

Reducing media are complex media containing chemicals such as thioglycate that combine with oxygen creating an anaerobic environment

Which process is best for the short-term storage of bacterial cultures?

Refrigeration Refrigeration is the best short-term storage method for microbes. Refrigeration slows down metabolic activity, but the microbes can be quickly revived when returned to optimum temperatures.

Which step of binary fission is the reason for genetically identical daughter cells?

Replication of the bacterial chromosome

In a standard growth curve, what phase represents when the number of cells growing and dying are about equal?

Stationary phase

How do we measure bacterial growth?

The amount of lactic acid produced

What enables the copied chromosomes to separate during binary fission?

The chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes.

Why is sugar added to fruit to make jams and jellies?

The high salt or sugar concentrations draw water out of any microbial cells that are present and thus prevent their growth.

6-1 Why are hyperthermophiles that grow at temperatures above 100°C seemingly limited to oceanic depths?

The immense pressure in the ocean depths prevents water from boiling even at temperatures well above 100°C.

What would happen if the septum did not form during binary fission?

The parent cell would now have two copies of the chromosome.

Why is it difficult to define psychrophile, mesophile, and thermophile?

Their temperatures for growth overlap (etc. psychrophile can grow in mesophile temp like 15-20C)

Why can't obligate anaerobes grow in oxygen?

They cannot produce peroxidase or catalase to breakdown peroxide product thus oxygen becomes toxic for them

What is not a direct measurement of microbial growth?

Turbidity-inidrect method of cloudiness thru a spectrophotometer

Which results when a single bacterium reproduces?

Two genetically identical daughter cells

What pathway does yeast and bacteria use when growing anaerobically?

Yeast use fermentation Bacteria use anaerobic respiration

An organism that has peroxidase and superoxidase dismutase but lacks catalase is most likely an

aerotolerant anaerobe can produce one enzyme and SOD, but can only partially neutralize

Assume you have inoculated 100 facultatively anaerobic cells onto nutrient agar and incubated the plate aerobically. You then inoculated 100 cells of the same species onto nutrient agar and incubated the second plate anaerobically. After incubation for 24 hours, you should have a. more colonies on the aerobic plate b. more colonies on the anaerobic plate c. the same number of colonies on both plates

although aerobic is faster, c. same number of colonies

Why is the prevention of biofilms important in a health care environment?

because biofilms are 1000 times more resistant to microbicides. -most nosocomial infections are prob. related to biofilms on medical catheters

Which of the following is not a characteristic of biofilms? a. antibiotic resistance b. hydrogel c. iron deficiency d. quorum sensing

c. iron deficiency

Bacteria that can grow in the presence or absence of oxygen (O2) are called __________.

facultative anaerobes Facultative anaerobes are able to use oxygen if it is present but also grow in the absence of oxygen, although with decreased efficiency.

The chemical requirements for microbial growth include carbon, nitrogen, phosphorus, and sulfur. Why do all cells need nitrogen?

for building amino acids, proteins, and nucleic acids Amino acids, proteins, and nucleic acids all include significant amounts of nitrogen.

A media that has a pH indicator and high salt concentration can likely ________ the growth of most bacteria

inhibit high salt takes water out of cell

For which of the following types of microbes would a microbiologist employ living host cells to support their growth?

obligate intracellular organisms, such as chlamydias, rickettsias, and viruses These organisms cannot grow on media but require living host cells when cultured.

Which of the following would NOT be used to culture aerobes? a. selective media b. reducing media c. enrichment media d. differential media e. complex media

reducing media reducing media removes oxygen for anaerobes

The term trace elements refers to

small mineral requirements

If 100 colonies are on a 1:1000 dilution plate, how many bacteria/mL were in the original shape?

100*1000= 100,000

Starting with three cells, how many cells would result from three rounds of replication?

24

Put the following steps of bacterial replication in the correct order, starting from a parent cell. 1. Cell elongation 2. Septum formation 3. Chromosome replication 4. Separation of daughter cells

3, 1, 2, 4

If you begin with six cells, how many cells would you have after three rounds of division?

48 cells

Which of the following temperatures would most likely kill a mesophile? a. -50C b. 0C c. 9 C d. 37 C e. 60 C

60 C

Which bacterium would theoretically be more likely to grow at refrigerator temperatures: a human intestinal pathogen or a soilborne plant pathogen?

A soilborne plant pathogen because it is more likely to survive in lower temps than a human intestinal pathogen (seen at about 37 C)

6.3 Why might primitive civilizations have used food preservation techniques that rely on osmotic pressure?

Adding high salt or sugar concentrations inhibits the growth of bacteria because in hypertonic solutions water will move out of the cell