Chapter 4 Question Microbiology

Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur may be considered: minor elements. major elements. acidic elements. neutral elements.

Differential media only allows certain bacteria to grow. True False

During which phase of the bacterial growth curve does the total number of viable cells decline? Stationary Lag Death Exponential

The simplest technique for isolating bacteria in growth media is referred to as the: streak-plate method. pour-plate method. serial dilution method. MPN method.

What would true about an organism called Bacillus fastidiosus? It could probably be grown on a minimal medium. It might be expected to depend on sunlight for energy. It might be expected to have a spherical shape. It might be expected to be very flexible in its growth requirements. It might be expected to be very strict in its growth requirements.

A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria,with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample? 10,000 320,000 100,000 64,000

Organisms that are indifferent to the presence of oxygen and do not use it are: obligate aerobes. aerotolerant anaerobes. facultative anaerobes. microaerophiles.

Organisms may derive energy from: sunlight AND metabolizing chemical compounds. temperature gradients AND pH gradients metabolizing chemical compounds AND temperature gradients. sunlight AND temperature gradients.

Bacteria on fish caught in the Arctic Ocean would: be freezophiles AND continue to grow while the fish is in the refrigerator. be mesophiles AND would not grow very well in the refrigerator. be psychrophiles AND would continue to grow while the fish is in the refrigerator. be mesophiles AND would continue to grow while the fish is in the refrigerator.

Organisms that use CO2 as their source of carbon are called: chemotrophs. autotrophs. organotrophs. heterotrophs.

Prokaryotes are the only organisms able to use atmospheric nitrogen as a nitrogen source. True False

There are five stages of growth in an open system of culture. True False

The enzymes that deal with toxic oxygen-containing molecules is/are: cytochrome oxidase AND glycolase. glycolase AND superoxide dismutase. superoxide dismutase AND catalase. catalase AND cytochrome oxidase. superoxide dismutase AND cytochrome oxidase.

The solidifying agent used most successfully in bacterial nutrient media is: peptone. agar. starch. gelatin.

During which phase of the bacterial growth curve does a bacterial population become much more resistant to harmful conditions? Late log phase Exponential phase Lag phase Stationary phase

You take absorbance readings on a spectrophotometer across a 6-hour culture of E. coli cells growing in tryptic soy broth (TSB). Your absorbance readings clearly indicate a lag phase, a log phase, and a stationary phase. You come back in and take readings at 8, 10, 12, 14, and 16 hours, but the absorbance number remains the same. Shouldn't it start coming down as the closed batch culture enters death phase? What's the most likely thing that is happening? It'll happen-E. coli just grows slowly, having a long generation time. We haven't gotten to the end of the stationary phase yet. Be patient! A spectrophotometer can measure absorbance as an indicator of cell number, but can't discriminate between a live cell and a dead one. The presence of dead cells keeps the absorbance high even into the death phase. Perhaps there's a big smudge of something on the tube that is blocking some of the light. This would lead to an elevated reading for every timepoint after the smudge was placed on the tube. Clearly, something is wrong with the spectrophotometer and it isn't measuring the correct values. Perhaps something is on the detector, making it register falsely high absorbance numbers.

The lag phase of the bacterial growth curve is marked by: metabolically active cells. vigorously dividing cells. dormant, metabolically inactive cells. a decrease in cell mass.

All the bacterial cells that result from the replication of a single original bacterial organism are said to be a: population. lag culture. pure culture.

Small organic molecules that must be provided to bacteria in order for them to grow are called: water. vitamins. minerals. growth factors.

Prokaryotic cells divide by a process known as: conjugation. binary fusion. binary fission. mitosis.

Products that limit pH changes are often incorporated into media and are referred to as: buffers. enzymes. acids. bases.

A physician sends a stool sample to your lab, and wants to know if there are lactose fermenting microbes in the sample. How might you determine if these microbes are present or not from this mixed-microbe specimen? Streak the sample for isolation on a blood agar plate (which contains lactose AND red blood cells that enrich the culture for iron). None of the above would work-there's no way to reliably determine this feature from the specimen given. Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present). Streak the sample for isolation on Thayer-Martin agar (which contains lactose and particular antibiotics for selectivity).

The scientist that contributed most to the development of pure culture techniques was: Edward Jenner. Alexander Fleming. Louis Pasteur. Robert Koch.

In nature, bacteria: often grow in close association with many other kinds of organisms. may remain in a prolonged exponential phase. frequently synthesize structures such as slime layers. may adhere to surfaces by means of pili and slime layers. All of the choices are correct.

During which phase of growth are bacteria most susceptible to antibiotics? Lag Exponential (log) Stationary Decline

A single bacterial cell may multiply to form a visible colony. True False

Which of the statements about biofilms is true? Biofilms are a peptidoglycan-encased community of microorganisms. may protect organisms against harmful chemicals. are a random mixture of bacteria. may significantly inhibit bioremediation efforts.