Exam 3

Question 1

In anoxygenic photosynthesis, which compound (or compounds) is (are) used by purple and green bacteria as a source of electrons for the reduction of CO2?

Answer 1

H2S

Question 2

In an ecological sense, the variety of photosynthetic pigments found among different groups of photosynthetic bacteria allows them to:

Answer 2

avoid direct competition by absorbing different wavelengths of light

Question 3

Spirochetes that are known human pathogens include:

Answer 3

Two or more are correct (vibrio cholera and borrelia burgdorferi)

Question 4

Rickettsias and chlamydias are two unrelated groups of bacteria that nevertheless share a unique characteristic. This characteristic is:

Answer 4

they are both obligate intracellular parasites of eukaryotes

Question 5

As discussed in lecture, which of the following bacteria are aerobic chemolithotrophs?

Answer 5

Nitrobacter

Question 6

What important soil process are these chemolithotrophic bacteria (nitrobacter) involved in?

Answer 6

nitrification

Question 7

The hypothesis has been proposed that magnetotactic bacteria sense the Earth’s magnetic field in order to:

Answer 7

swim in the direction of a microaerophilic environment

Question 8

What evidence suggests that cyanobacteria-like ancestors were present on the Earth as early as 3.5 billion years ago?

Answer 8

fossilized stromatolites

Question 9

Many of the magnetotactic bacteria are found among the:

Answer 9

spirilla

Question 10

In lecture, Hyphomicrobium was given as an example of a:

Answer 10

budding bacterium

Question 11

The currently accepted division of all living organisms on Earth into three domains is based on differences in what fundamental characteristic?

Answer 11

small-subunit ribosomal RNA sequences

Question 12

Current estimates are that _______ of the microorganisms in a typical environmental sample, such as soil or water, have been cultivated before in the laboratory.

Answer 12

less than 1%

Question 13

From your reading in the textbook, metagenomics refers to:

Answer 13

using modern genomic techniques to study entire microbial communities directly in their natural environments.

Question 14

From your reading in the textbook, enzymes that are used in the laboratory to recognize and cleave DNA molecules at very specific base sequences, often for the purpose of cloning, are called:

Answer 14

restriction endonucleases

Question 15

One general characteristic of gene transfer processes in bacteria is:

Answer 15

Gene transfer is always unidirectional (from donor to recipient)

Question 16

A mutation occurs in the lac operon of E. coli. You observe that the mutant is unable to bring lactose into the cell. Which gene(s) in the operon has (have) been mutated?

Answer 16

lacY

Question 17

E. coli normally synthesizes the enzyme B-galactosidase when the sugar lactose is present but not when it is absent. A strain of E.coli is isolated in the lab that always synthesizes B-galactosidase regardless of whether lactose is present or not. What is the most likely explanation for this isolate’s phenotype?

Answer 17

The strain carries a mutation in the gene encoding the lactose repressor that eliminates its ability to bind to the operator of the lactose operon.

Question 18

In general, plasmids are likely to encode any of the following functions except:

Answer 18

ribosome biosynthesis

Question 19

In the process of translation, the fidelity (accuracy) of polypeptide synthesis is primarily maintained by the complementary pairing of three-base nucleotide sequences in the:

Answer 19

messenger RNA and transfer RNA

Question 20

The movement of transfer RNA molecules through the ribosome is always in the direction:

Answer 20

A site»» P site&raquo_space;»> E site

Question 21

Methanogens are a group of archaea that are distinguished by their ability to carry out the following reaction:

Answer 21

4H2 + CO2&raquo_space;»> CH4 + 2H2O

Question 22

Microbiologist is called in when a salt pond suddenly develops a noticeable purple color. When she looks at a water sample under the light microscope, she observes a large number of unicellular organisms swimming around that are a few micrometers in length. Streaks on TSA plate, but nothing grows after incubation at 25 degrees C for several days. What is the most likely explanation for this negative result?

Answer 22

The organism is a halophilic archaeon and must be grown on a culture medium with a high (~25%) salt concentration.

Question 23

What is the phenotypic consequence of a single mutation?

Answer 23

A mutation may be beneficial or harmful, depending on whether it makes the organism better or worse adapted to survive and reproduce in its environment.

Question 24

You have isolated a bacterium from the sediment of a playa lake. It is a rod-shaped organism that is Gram-positive and is strictly anaerobic. Which one of the following genera does it belong to?

Answer 24

Clostridium

Question 25

What is the most appropriate way to confirm identification of Clostridium?

Answer 25

test for endospore formation

Question 26

When you have a sore throat and the doctor does a throat swab for culture on a blood agar plate, what is he/she looking for?

Answer 26

Beta hemolytic streptococci

Question 27

Geosmin, a chemical compound with an “earthy” odor , is produced by organisms in what bacterial genus?

Answer 27

Streptomyces

Question 28

Two human diseases caused by mycobacteria are:

Answer 28

tuberculosis and leprosy

Question 29

Fungi acquire nutrients by secreting extracellular enzymes that break down dead organic matter so that they can then take up the soluble nutrients. The reason they cannot ingest food particles directly is that they have a cell wall composed of:

Answer 29

Chitin

Question 30

The interwoven mass of vegetative filaments of a fungus is called a(an):

Answer 30

mycelium

Question 31

Some animal viruses are enveloped. Where are the genes located that encode the enzymes responsible for biosynthesis of the envelope lipids?

Answer 31

in the host cell’s chromosomes

Question 32

The _______of a virus protects its ________.

Answer 32

capsid; nucleic acid

Question 33

A bacterial chromosome contains bacteriophage DNA that is silent (not expressed) and is carried from one generation to the next. This phenomenon is known as:

Answer 33

lysogeny

Question 34

The two scientists who are credited with discovering the first bacterial viruses (aka bacteriophages) are:

Answer 34

Frederick Twort and Felix d’Herelle

Question 35

Which of the following statements accurately describes viral plaques?

Answer 35

Each plaque is presumed to arise from a single lytic virus particle.

Question 36

The most important factor that determines the host specificity of a viral infection is the:

Answer 36

presence of appropriate receptors on the surface of the host cell

Question 37

All of the following diseases are thought to be caused by prions except:

Answer 37

psittacosis (parrot fever) in birds

Question 38

“Virus” was originally a rather vague term used to describe any infectious agent that caused disease. Improvements in what technology in the late 1800’s led to our modern, more precise definition of a virus?

Answer 38

Filtration

Question 39

A bacterial virus that is composed of a head that contains the genetic material, a tail, endplate, and tail fibers is designated as a (an):

Answer 39

complex virus

Question 40

Transfer of DNA from one bacterium to another by means of a viral intermediate is:

Answer 40

Two or more are correct