Exam 3 Flashcards
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?
H2S
In an ecological sense, the variety of photosynthetic pigments found among different groups of photosynthetic bacteria allows them to:
avoid direct competition by absorbing different wavelengths of light
Spirochetes that are known human pathogens include:
Two or more are correct (vibrio cholera and borrelia burgdorferi)
Rickettsias and chlamydias are two unrelated groups of bacteria that nevertheless share a unique characteristic. This characteristic is:
they are both obligate intracellular parasites of eukaryotes
As discussed in lecture, which of the following bacteria are aerobic chemolithotrophs?
Nitrobacter
What important soil process are these chemolithotrophic bacteria (nitrobacter) involved in?
nitrification
The hypothesis has been proposed that magnetotactic bacteria sense the Earth’s magnetic field in order to:
swim in the direction of a microaerophilic environment
What evidence suggests that cyanobacteria-like ancestors were present on the Earth as early as 3.5 billion years ago?
fossilized stromatolites
Many of the magnetotactic bacteria are found among the:
spirilla
In lecture, Hyphomicrobium was given as an example of a:
budding bacterium
The currently accepted division of all living organisms on Earth into three domains is based on differences in what fundamental characteristic?
small-subunit ribosomal RNA sequences
Current estimates are that _______ of the microorganisms in a typical environmental sample, such as soil or water, have been cultivated before in the laboratory.
less than 1%
From your reading in the textbook, metagenomics refers to:
using modern genomic techniques to study entire microbial communities directly in their natural environments.
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:
restriction endonucleases
One general characteristic of gene transfer processes in bacteria is:
Gene transfer is always unidirectional (from donor to recipient)
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?
lacY
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?
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.
In general, plasmids are likely to encode any of the following functions except:
ribosome biosynthesis
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:
messenger RNA and transfer RNA
The movement of transfer RNA molecules through the ribosome is always in the direction:
A site»» P site»_space;»> E site
Methanogens are a group of archaea that are distinguished by their ability to carry out the following reaction:
4H2 + CO2»_space;»> CH4 + 2H2O
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?
The organism is a halophilic archaeon and must be grown on a culture medium with a high (~25%) salt concentration.
What is the phenotypic consequence of a single mutation?
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.
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?
Clostridium
What is the most appropriate way to confirm identification of Clostridium?
test for endospore formation
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?
Beta hemolytic streptococci
Geosmin, a chemical compound with an “earthy” odor , is produced by organisms in what bacterial genus?
Streptomyces
Two human diseases caused by mycobacteria are:
tuberculosis and leprosy
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:
Chitin
The interwoven mass of vegetative filaments of a fungus is called a(an):
mycelium
Some animal viruses are enveloped. Where are the genes located that encode the enzymes responsible for biosynthesis of the envelope lipids?
in the host cell’s chromosomes
The _______of a virus protects its ________.
capsid; nucleic acid
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:
lysogeny
The two scientists who are credited with discovering the first bacterial viruses (aka bacteriophages) are:
Frederick Twort and Felix d’Herelle
Which of the following statements accurately describes viral plaques?
Each plaque is presumed to arise from a single lytic virus particle.
The most important factor that determines the host specificity of a viral infection is the:
presence of appropriate receptors on the surface of the host cell
All of the following diseases are thought to be caused by prions except:
psittacosis (parrot fever) in birds
“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?
Filtration
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):
complex virus
Transfer of DNA from one bacterium to another by means of a viral intermediate is:
Two or more are correct
