All the bacteria cells that result from the replication of a single original bacterial organism are said to be a
pure culture
The scientist that contributed most to the development of pure culture techniques was
Robert Koch
The solidifying agent used most successfully in bacterial nutrient media is
agar
Prokaryotic cells divide by a process known as
binary fission
In nature, bacteria
often grow in close association with many other kinds of organisms
may remain in a prolonged exponential phase
frequently synthesize structure such as slime layers
may adhere to surfaces by means of pili and slime layers
ALL OF THE ABOVE IS CORRECT
Biofilms
are polysaccharide- encased community of microorganisms, may enhance bioremediation efforts AND may protect organisms against harmful chemicals
The simplest technique for isolating bacteria in growth media is referred to as the
streak plate method
Bacteria may be stored
on a slant in the refrigerator, frozen in glycerol solution AND lypophilized.
In the growth curve of a bacteria population, the bacteria are rapidly increasing in number in the
exponential (log) phase
During which phase of growth are bacteria most susceptible to antibiotics?
exponential log
When doing experiments with bacteria
the age of the bacteria is not important
During which phase of the bacteria growth curve does the total number of viable cells decline?
death
The lag phase of the bacterial growth curved is marked by
metabolically active cells
Late log phase of the bacterial growth curve
is marked by thee production of secondary metabolites
During which phase of the bacterial growth curve does a bacterial population become much more resistant to harmful conditions
late log phase
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 min sits for 3 hrs before finally being assayed. How many bacteria will then be presented within the sample?
320,000
A pure culture in exponential growth phase has a bacterial concentration of 6.4 * 10^8 cell/ml if the bacterium has a generation time of 1h, How long ago was the cell concentration 8.0*10^7 cells/ml?
3h
In a rapidly multiplying bacterial population, cell numbers increase
logarithmically
The speed of enzymatic reactions approximately doubles for each
10 degree Celsius rise in temp
Generally the proteins of thermophiles
resist denaturation
A hot tub (approx. 104 deg F or 40 deg C) would most likely contain
mesophiles
The optimal temp. for most human pathogens might be expected to range from
35-40 degree Celsius
Bacteria on fish caught in the Artic Ocean would
be psychrophiles AND continue to grow while the fish is in the refrigerator.
Mycobacterium leprae is typically found infecting the ears, toes and fingers of its host due to its
need for cooler temp
Organisms that require gaseous oxygen for metabolism are referred to as
obligate aerobes
Which of the following is/are obligate aerobes?
Micrococcus luteus
Organisms that are indifferent to the presence of oxygen and do not use it are
aerotolerant anaerobes
The enzymes that deal with toxic oxygen - containing molecules is/are
superoxide dismutase AND catalase
Shake tubes are used to determine the
oxygen requirements for bacterial growth
The optimum pH for growth of most species of bacteria is
pH 7
High concentrations of salt and sugar in foods
are useful in preserving the food AND tend to draw water out of a cell
Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur may be considered
major elements
Trace elements
include zinc, copper, and manganese AND may be needed for enzyme function.
Small organic molecules that must be provided to bacteria in order for them to grow are called
growth factors
The prefix photo-indicates that an organism will make use of ____ for energy purposes.
light
Organisms that use organic molecules as their source of carbon are called
heterotrophs
Organisms may derive energy from
sunlight AND metabolizing chemical compounds
Organism that use CO2 as their source of carbon are called
autotrophs
Chemoheterotrophs
use pre-formed organic molecules as a carbon source AND as an energy source
An organism called Bacillus fastidiosus
night be expected to be a very strict as to its growth requirements, would probably be grown on a chemically defined media AND might be expected to have a rod shape
Peptone
refers to a hydrolysate of proteins used in growth media
Medically important bacteria are often
grown on agar containing blood AND grown at 37 deg celsius
Products which limit pH changes are often incorporated into media and are referred to as
buffers
A medium that inhibits the growth of organisms other than the one being sought is termed a(n)
selective medium
MacConkey agar is
a selective and differential agar
Candle jars are usually used to
provide an atmosphere with CO2
In the cultivation of microaerophilic and anaerobic bacteria
atmospheric oxygen in a(n) candle/anaerobe jar is converted to water
Agar
has chemical and physical properties that make it almost ideal for solidifying media
Agar replaced gelatin as the gelling (solidifying) agent for media because
much fewer bacteria can break down agar than gelatin AND agar is solid at body temp
It is assumed that every colony observed on a streak plate arose from a single bacterium
True
In microbiology, growth usually refers to an increase in size of the bacterium
False
There are 5 stages of growth in an open system of culture.
False
Secondary metabolites may be antibiotics
True
A single bacterial cell may multiply to form a visible colony
True
Prokaryotes are the only organisms able to use atmospheric nitrogen as a nitrogen source
True
Freezing is an effective means of destroying bacteria
False
One would expect most strict anaerobic organisms to have superoxide dismutase.
False
Differential media only allows certain bacteria to grow
False
A microbe is discovered growing hear a deep sea thermal vent when researchers bring a sample up to the surface and try to grow it in a lab at room temp. in a normal incubator, they are unsuccessful. Why?
The pressure isnt the same at sea-level as it is on the ocean floor.
You are a microbiologist working for a pharmaceutical company and discover a new secreted metabolite that can serve as a medication. Your company asks you to oversee the production of the metabolite which of the following is something that is NOT important to consider if you need to grow 5,000 liter cultures of bacteria for the purpose of harvesting the metabolite they secrete.
The death rate of the bacteria after stationary phase is complete
You are working in a clinical laboratory in a hospital setting. You're handed a throat swab from a patient. You are told specifically that the physician is only interested in what Gram positive cells are present what might you do first to go about working towards this goal? Identification isnt the main goal here just a first step to work towards determining what Gram positive cells might be there...
Perform a Gram stain
A physician send a stool sample to your lab, and wants to know if there are lactose formenting 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 MacConkey agar plate (which contains lactose AND a pH indicator that turns pink when acid by products are present)
Your are in charge of water quality for your city's water treatment plant of the methods at your disposal, which will be the most efficient and cheapest method of determining the number of viable bacteria in the water coming out of your plant?
Using membrane filtration followed by placing the membrane in a growth medium for colony counts after incubation
You take absorbance readings on a spectrophotometer across a lehr 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 and take readings at 8,10,12,14+16hrs. but the absorbance number remains the same. Shouldnt it start coming down as the closed batch culture enters death phase? Whats the most likely thing that is happening?
when we establish a growth curve, we should actually plot the log of the number of viable cells vs. time. However, a spectrophotometer can only measure absorbance. Absorbance is NOT the same as the number of viable cells. Many of the cells in the tube are most likely dead, but the machine cant discriminate between a live cell and dead one. This keeps the absorbance high even into the death phase
