Chapter 9 Microbial Growth
chemostat
A ____________________ is a culture vessel fitted with an opening to add nutrients (feed) and an outlet to remove contents (effluent), effectively diluting toxic wastes and dead cells.
alkaliphile
A bacterium that thrives in a soda lake where the average pH is 10.5 can be classified as a(n) ________.
halophile
A bacterium that thrives in the Great Salt Lake but not in fresh water is probably a ________.
2nd
A division septum forms in the center of the cell. Which step is this in the binary fission (1st, 2nd, or 3rd) ?
Growth curve
A population displays a predictable pattern called a _______________
psychrotrophs
A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following? A. thermophiles B. acidophiles C. mesophiles D. psychrotrophs
Most probable number
A statistical estimate of the number of live cells in a liquid is usually done by ________.
ATP acid from fermentation
Active growth of a culture may be estimated indirectly by measuring the following products of cell metabolism: ________ or ________.
alkaliphiles
Bacteria isolated from Lake Natron, where the water pH is close to 10, are which of the following? A. alkaliphiles B. facultative anaerobes C. neutrophiles D. obligate anaerobes
mesophiles
Bacteria isolated from a hot tub at 39 °C are probably which of the following? A. thermophiles B. psychrotrophs C. mesophiles D. hyperthermophiles
barophiles
Bacteria isolated from the bottom of the ocean need high atmospheric pressures to survive. They are ________.
halotolerant
Bacteria living in salt marshes are most likely which of the following? A. acidophiles B. barophiles C. halotolerant D. thermophiles
Biofilm
Bacteria that are attached to a surface and form a 3-dimensional structure, held together by an extracellular polymeric substance is ??
acidophiles
Bacteria that grow in mine drainage at pH 1-2 are probably which of the following? A. alkaliphiles B. acidophiles C. neutrophiles D. obligate anaerobes
different sides of cell.
Binary Fission: Chromosome is replicated and new and old chromosomes move to _____________________
center of cell.
Binary Fission: FtsZ Protein band forms in ___________________
Z ring Plasma membrane
Binary Fission: FtsZ proteins assemble to form a ____________ that is anchored to the _______________.
1st
Binary fission in bacteria starts with the replication of DNA as the cell elongates. Which step is this in the binary fission (1st, 2nd, or 3rd) ?
Log Phase
Binary fission is occurring at maximum rate in what phase?
complex differential
Blood agar contains many unspecified nutrients, supports the growth of a large number of bacteria, and allows differentiation of bacteria according to hemolysis (breakdown of blood). The medium is ________ and ________.
3rd
Two daughter cells of similar size form and separate, each receiving a copy of the original chromosome. Which step is this in the binary fission (1st, 2nd, or 3rd) ?
Direct/total count
Used to estimate the total number of cells in a larger sample are??
optimum temperature pH oxygen
What are the physical requirements for the phases of growth?
Direct and indirect
What are two methods of bacterial count?
It forms a contractile ring at the septum.
What is the function of the Z ring in binary fission? A. It controls the replication of DNA. B. It forms a contractile ring at the septum. C. It separates the newly synthesized DNA molecules. D. It mediates the addition of new peptidoglycan subunits.
facultative anaerobe
What is this tube?
microaerophile
What is this tube?
obligate aerobe
What is this tube?
obligate anaerobe
What is tube number 2
Lag Phase
What phase are metabolically active and cell do NOT divide?
Septum
When _____________ is complete, cells are considered divided.
Cells are metabolically inactive at the base of a biofilm.
Which is a reason for antimicrobial resistance being higher in a biofilm than in free-floating bacterial cells? A. The EPS allows faster diffusion of chemicals in the biofilm. B. Cells are more metabolically active at the base of a biofilm. C. Cells are metabolically inactive at the base of a biofilm. D. The structure of a biofilm favors the survival of antibiotic resistant cells.
mountain lake with a water temperature of 12 °C
Which of the following environments would harbor psychrophiles? A. mountain lake with a water temperature of 12 °C B. contaminated plates left in a 35 °C incubator C. yogurt cultured at room temperature D. salt pond in the desert with a daytime temperature of 34 °C
the length of time it takes for a population of cells to double
Which of the following is the best definition of generation time in a bacterium? A. the length of time it takes to reach the log phase B. the length of time it takes for a population of cells to double C. the time it takes to reach stationary phase D. the length of time of the exponential phase
Lower water activity
Which of the following is the reason jams and dried meats often do not require refrigeration to prevent spoilage? A. low pH B. toxic alkaline chemicals C. naturally occurring antibiotics D. low water activity
total plate count
Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter? A. turbidity measurement B. total plate count C. dry weight measurement D. direct counting of bacteria on a calibrated slide under the microscope
They bind directly to DNA to activate transcription.
Which of the following statements about autoinducers is incorrect? A. They bind directly to DNA to activate transcription. B. They can activate the cell that secreted them. C. N-acylated homoserine lactones are autoinducers in gram-negative cells. D. Autoinducers may stimulate the production of virulence factors.
Log Phase
Which phase is best for research? A. Log B. Lag C. stationary D. death
Log Phase
Which phase is sensitive to antibiotics (pathogen) ?
Log Phase
Which phase is very sensitive to adverse conditions?
It is a capnophile.
Why do the instructions for the growth of Neisseria gonorrheae recommend a CO2-enriched atmosphere? A. It uses CO2 as a final electron acceptor in respiration. B. It is an obligate anaerobe. C. It is a capnophile. D. It fixes CO2 through photosynthesis.
Aerotolerant anaerobes
________________ are anaerobic bacteria that can grow in the presence of air. (Not shown in diagram.)
Serial dilution
________________ involves diluting a fixed volume of cells mixed with dilution solution using the previous dilution as an inoculum. The result is dilution of the original culture by an exponentially growing factor.
Direct method
count individual cells, More accurate, but takes a lot longer is what method?
thermophile
soil bacteria in temperate forest?
psychrophile
water heater set at 50 °C?
log phase
which phase do cells divide exponentially?
Fragmentation
Filamentous cyanobacteria often divide by which of the following? A. budding B. mitosis C. fragmentation D. formation of endospores
Turbidity
For this indirect method of estimating the growth of a culture, you measure ________ using a spectrophotometer.
exponential growth
Generation time grown pattern is termed as?
factor of 2
Generation time: Each new fission cycle or generation increases the population by a ______________
Cell synthesizes new cell components and increases in size The number of cells in the population increases
Growth takes place on two levels: which are?
Fastidious
Haemophilus influenzae must be grown on chocolate agar, which is blood agar treated with heat to release growth factors in the medium. H. influenzae is described as ________. A. an acidophile B. a thermophile C. an obligate anaerobe D. fastidious
1600
If a culture starts with 50 cells, how many cells will be present after five generations with no cell death? A. 200 B. 400 C. 1600 D. 3200
small peptitide
In Quorum sensing, g+ has what?
n-acetylated homoserine lactone
In Quorum sensing, g- has what?
spectrophotometer
In an indirect cell count: A _____________________ is commonly used to measure the turbidity of a bacterial cell suspension as an indirect measure of cell density.
logarithmic aerobic
In the Chemosta, the addition and removal of fluids is adjusted to maintain the culture in the _______________ phase of growth. If _________________ bacteria are grown, suitable oxygen levels are maintained.
Most probable number method
In the ____________________, sets of five lactose broth tubes are inoculated with three different volumes of pond water: 10 mL, 1 mL, and 0.1mL. Bacterial growth is assessed through a change in the color of the broth from red to yellow as lactose is fermented.
stationary phase
In what phase does toxic waste accumulates?
hydrothermal vent at the bottom of the ocean
In which environment are you most likely to encounter a hyperthermophile? A. hot tub B. warm ocean water in Florida C. hydrothermal vent at the bottom of the ocean D. human body
a hot vent at pH 1.5
In which environment are you most likely to encounter an acidophile? A. human blood at pH 7.2 B. a hot vent at pH 1.5 C. human intestine at pH 8.5 D. milk at pH 6.5
death phase
In which phase would you expect to observe the most endospores in a Bacillus cell culture? A. death phase B. lag phase C. log phase D. log, lag, and death phases would all have roughly the same number of endospores.
Lag Phase
New enzymes to use available nutrients are induced is what phase?
Stationary phase
Number of cell death = to the number of cells alive is what phase?
Culture Density
Number of cells per unit volume?
Death phase
Number of dying cells is higher than the number of cells dividing is what phase?
Stationary phase
Number of new cells equal to number of dying cells is what phase?
stationary phase
Pathogen and expressive of virulence factors is what phase?
an obligate aerobe
Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. It does not grow in the absence of oxygen. The bacterium is probably which of the following? A. an aerotolerant anaerobe B. an obligate aerobe C. an obligate anaerobe D. a facultative anaerobe
the density of the population
Quorum sensing is used by bacterial cells to determine which of the following? A. the size of the population B. the availability of nutrients C. the speed of water flow D. the density of the population
Colony-Forming Units per milliliter (CFU/mL)
Results of direct viable counts are expressed as
complex selective
Rogosa agar contains yeast extract. The pH is adjusted to 5.2 and discourages the growth of many microorganisms; however, all the colonies look similar. The medium is ________ and ________.
Divisome
Septum formation begins (____________ activates peptidoglycan formation).
halotolerant
Staphylococcus aureus can be grown on multipurpose growth medium or on mannitol salt agar that contains 7.5% NaCl. The bacterium is ________.
aerotolerant anaerobe
Streptococcus mutans is a major cause of cavities. It resides in the gum pockets, does not have catalase activity, and can be grown outside of an anaerobic chamber. The bacterium is probably which of the following? A. a facultative anaerobe B. an obligate aerobe C. an obligate anaerobe D. an aerotolerant anaerobe
Plate Count
The ________ method allows direct count of total cells growing on solid medium.
Z ring
The _____________ pinches the cell envelope to separate the cytoplasm of the new cells.
Generation or doubling time
The time required to produce two daughter cells from a parent through one round of binary fission (a complete fission cycle).
The organisms are obligate anaerobes.
An inoculated thioglycolate medium culture tube is clear throughout the tube except for dense growth at the bottom of the tube. What is your conclusion? A. The organisms are obligate anaerobes. B. The organisms are facultative anaerobes. C. The organisms are aerotolerant. D. The organisms are obligate aerobes.
The organisms are facultative anaerobes.
An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion? A. The organisms die in the presence of oxygen B. The organisms are facultative anaerobes. C. The organisms should be grown in an anaerobic chamber. D. The organisms are obligate aerobes.
10 to 12 minutes
Average generation time can be as short as ____________
20 to 60 minutes
Average generation time is ________________ under optimum conditions
Direct or total count
Counting the number of cells in a liquid culture (known volume) or colonies on a plate microscopically is ???
hemocytometer Petroff-Hausser counting chamber
Direct count of total cells can be performed using a ________ or a ________.
Petroff-Hausser Chamber
Direct or total count uses a special microscope slide (__________________) calibrated to accept a tiny sample that is spread over a premeasured grid.
Log phase
During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, be most effective? A. death phase B. lag phase C. log phase D. stationary phase
a selective medium, a differential medium, and a complex medium
EMB agar is a medium used in the identification and isolation of pathogenic bacteria. It contains digested meat proteins as a source of organic nutrients. Two indicator dyes, eosin and methylene blue, inhibit the growth of gram-positive bacteria and distinguish between lactose fermenting and nonlactose fermenting organisms. Lactose fermenters form metallic green or deep purple colonies, whereas the nonlactose fermenters form completely colorless colonies. EMB agar is an example of which of the following? A. a selective medium only B. a differential medium only C. a selective medium and a chemically defined medium D. a selective medium, a differential medium, and a complex medium
Bacterial Count
Estimating the number of bacterial cells in a sample
acidophile
Lactobacillus acidophilus grows best at pH 4.5. It is considered a(n) ________.
Optimum Growth pH
Most favorable pH for the growth of an organism ?
thioglycollate broth
The effect of oxygen is often determined using ________________, a special medium that contains a reducing agent (thioglycollate) that removes oxygen so that a gradient occurs within the tube.
Persister cells
The live cells in the death phase are called what?
Indirect methods
estimating the number of cells based on turbidity, in liquid or dry weight., Less accurate, but quick is what method?
Neutrophiles
grow best around neutral pH 6 and 8 ?
Acidotolerant
grow best at pH 7 but can also grow at lower pH ?
Acidophiles
grow best at pH < 7 ?
Alkaliphiles
grow best at pH > 7?
mesophile
human pathogen?