Microbial Nutrition and Growth Flashcards
What is carbon used for in organisms?
everything?
What is quorum sensing?
bacteria communicate with each other by secreting molecules. signals can lead to new genes being expressed.
Carbon source for photoautotrophs
CO2
What are superoxide free radicals?
an oxygen-based free radical
Which type of organisms are most likely to contaminate a brine (salt) solution found in pickles?
halophiles
Describe plate counts
count colonies on plate, colonies between 25-250
describe most probable number
best guess at cell number based on the fact that more dilutions are required for a denser culture. used for organisms that don’t grow well in solid media. Use different dilutions and dye indicators
lag phase
cells not actively dividing, adjusting to environment
What ingredient is added to make liquid media solid or semi-solid?
agar
Describe two methods for obtaining isolated colonies.
streak plates and pour plate
Describe binary fission. Describe how to calculate the number of cells after each round.
binary fission is the splitting of a bacterial cell. They split into two every time.
Define facultative anaerobes, where they are in the tube, and a species example
prefer O2 but can adapt to a lack of it
E.coli
define microaerophiles, where they are in the tube, and an example
prefer a low oxygen environment
campylobacter jejuni
What macromolecules require nitrogen?
amino acids, DNA, RNA, and proteins
Energy source for chemotrophs
organic and inorganic chemicals
What is a colony?
cluster of cells that can be seen with the naked eye and originated from 1 cell
Carbon source for chemoheterotrophs
organic chemicals
describe direct microscopic count
individual cells are counted using a special cell counter and adding a known volume of the inoculum
describe metabolic activity indirect measurement
production of a product or utilization of a substrate used to estimate cell number
define obligate anaerobes, where they are in the tube, and example
cannot live in the presence of O2
clostridium
Define obligate aerobes
need O2 to live
stationary phase
no net growth, # of cells dividing and dying are at equal rates
Which type of organisms are most likely to contaminate and grow in the refrigerator?
psychrotolerant
define capnophiles
thrive in a high level of CO2
What reaction does catalase catalyze?
coverts hydrogen peroxide into H2O and O2
Carbon source for chemoautotrophs
inorganic molecules, fix their own C
During which phase are bacteria most susceptible to antibacterial agents?
log phase
What temperature do pathogenic organisms grow best at?
37 C
describe dry weight measurment
used fo molds. cells are collected, dried, and then weighed
Define generation time.
time to split into 2 cells
Describe the range of temperature of growth for the following organism types:
a. thermophiles (including extreme)
b. mesophiles
c. psychrotolerants (psychrotrophs)
d. psychrophiles
a. thermophiles (including extreme)- 45-105 C
b. mesophiles- 15-45 C
c. psychrotolerants (psychrotrophs)- 0-40 C
d. psychrophiles- -5-20 C
What three enzymes are important for neutralizing superoxide free radicals? How do they function?
SOD- conversion of superoxide free radical and free H+ ions into hydrogen peroxide and oxygen
catalase- converts hydrogen peroxide to H2O+O2
peroxidase- converts hydrogen peroxide and H+ ions into H2O
describe turbidity (spectrophotometry/nephelometry)
cloudiness of the suspension is used to approximate the number of cells. Light is shone through the mixture and the percentage of light leaving the mixture determines the turbidity.
Describe two ways to cultivate anaerobes.
reducing media or anerobe jar
describe membrane filtration
cells in solution are poured through a membrane that catches the cells. Cells are transferred to media to be counted
What macromolecules require sulfur and phosphorus?
amino acids and DNA/RNA
define aerotolerant anaerobes, where they are in the tube, and an example
not killed by O2 but do not use it
streptococci
death/decline phase
cells die off due to waste or lack of space or nutrients
Carbon source for photoheterotrophs
organic chemicals
Which microbes have SOD, catalase, or peroxidase?
obligate anaerobes have SOD and catalase
facultative anaerobes have SOD and catalase
aertolerant anaerobes have SOD but no catalase
log phase
exponential growth, most sensitive to antimicrobial agents
Describe two ways to store bacterial cultures.
fridge, deep freeze, freeze-drying
How are biofilms different than their single species counter parts?
act differently
Which pH do pathogenic organisms grow best at?
6.5-7.5
What are some sources of nitrogen that bacteria use?
free amino acids, peptides, and proteins. Some use N2 gas
Energy source for phototrophs
light
How do high concentrations of salt and sugar affect cells?
plasmolysis, cell membrane pulls away from cell wall
How do differential and selective media differ? Can a medium be both selective and differential?
differential media- differentiates the growths by growing style (color changing)
selective media- only allows for certain microbes to grow
yes
Describe flow cytometry
single file flow of cells flow through a machine and light scatter is used to count them
Define inoculum and culture (note there are different ways to use the word culture: noun, verb, adjective).
inoculum- cultural medium that contains microbes
culture (noun)- the thing you are growing
culture (verb)- to culture a bacteria
How does defined media differ from complex media?
defined media everything is known quantities in the media
complex is a mixture of things and the exact quantities are not known
