CH7 Flashcards
Media containing some ingredients of unknown chemical composition are called __________ media.
complex
A growth medium that distinguishes among different groups of bacteria on the basis of colony appearance or changes is called a __________ medium.
differential
Organisms that grow well at 0°C and have optimum growth temperatures of 15°C or lower are called
psychrophiles
All fastidious microorganisms require what growth?
extra nutrients (such as vitamins and amino acids)
What reasons for the occurrence of a lag phase in a bacterial growth curve?
- The medium may be different from the previous growth medium so that the cells must synthesize new enzymes to use different nutrients.
- The cells may be old and depleted of ATP, essential cofactors, and ribosomes that must be synthesized before growth can begin.
- The organisms may have been injured and require time to recover.
Given a log phase bacterial culture with 1 x 10^6 cells per ml and a generation time of 30 minutes, how long does it take the culture to reach a density of 6.4 × 10^7 cells per ml?
3 hours
Microorganisms are most nearly uniform in terms of chemical and physiological properties during __________ phase.
exponential
Media in which all components and their concentration are known are called __________ media.
defined
For surface cultivation of microorganisms, a sulfated polymer called agar can be extracted from __________ and added to liquid media in order to cause it to solidify.
algae
Organisms that do not require oxygen for growth but grow better in its presence are called
facultative anaerobes.
The total number of viable microorganisms remains constant in stationary phase because
either there is a balance between cell division and cell death or there is a cessation of cell division even though the cells may remain metabolically active.
can be used to isolate pure cultures of bacteria from mixtures
streak plate, pour plate and spread plates
regarding tolerance of microbes to osmotic stress
cell walls help protect some organisms placed into hypotonic environments
Organisms that are damaged by the normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2–10% for growth are called
microaerophiles
Most microorganisms maintain their internal pH
near neutral (pH 7 or 7.5)
Organisms that require high levels of sodium chloride in order to grow are called __________ organisms.
halophilic
What method can be used to determine the number of viable microorganisms in a sample?
measuring colony forming units per ml
At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the log phase culture has a population of 65 million cells. The mean generation time is approximately
20 minutes.
Agar is an excellent solidifying agent for microbiological media because
- it is not degraded by most microorganisms.
- solid agar remains solid until the temperature is raised to 90°C, and liquid agar remains liquid if the temperature is lowered to 45°C.
Cells may enter stationary phase because of
- the depletion of an essential nutrient.
- the accumulation of toxic waste products.
- a lack of available oxygen.
What is considered a cardinal growth temperature?
minimum, maximum, and optimum temperature
A growth medium that favors the growth of some microorganisms but inhibits the growth of other microorganisms is a __________ medium.
selective
Organisms that grow near deep-sea volcanic vents are likely to be
thermophilic.
Organisms that grow in the mud under relatively non-turbulent bodies of water are likely to be
anaerobes.
Organisms that ignore oxygen and grow equally well in its presence or absence are called
aerotolerant.
budding and coenocytic growth
binary fission
environmental factors for microbial growth
- pH
- water and osmotic pressure
- oxygen
acid loving (0.1-5.4)
acidophiles
neutral loving (5.5-8.0)
neutrophiles
basic loving (8.0-11.5)
alkaliphiles
- most neutrophiles
- Lactobacillus, sulfer oxidizers, Bacillus
bacteria
prefer acidic pH’s
fungi and algae
- narrow ranges
- neutrophiles
protozoa
all metabolizing cells require
liquid water
- bacteria, algae, and fungi- have cell walls
- protozoa- contractile vacuoles
hypotonic enviornment
example of hypo- and hyper- tonic environments
hypo- tap water
hyper- skin, salt lakes
- plasmolysis
- tolerance
hypertonic environment
concrete compatible solutes
tolerance
example of osmotolerant
Staphylococcus sp (fungi)
require high salt in water
osmophiles/halophiles
- grow best below 20 degrees C
- fridge (slime on meat), oceans, Antarctic soils
- more on planet than any other phile
psychrophile
- medium loving temps (20-40 degrees C)
- optimum in humans is at 60 degree C
- human associated
mesophiles
- optimum above 65 degree C (40-70 degree C)
- hot water heater, early ones in hot springs and compost
thermophiles
- no eukaryotic above 60 degree C
- optimum above 100 degree C
- bottom of ocean in volcanic vents
- need to put in pressurized containers to view
hyperthermophiles (extremophiles)
how are MOs able to grow at 120 degree C?
pressure
grow over broad ranges of temps
eurythermal microbe
grow over narrow ranges of temps
stenothermal microbe
is oxygen soluble?
no
- need O2 to grow
- algae, most fungi, and protozoa
- aerobic respiration
- surface of media, shaking/bubbling
- hard to culture, MOs can easily infect
obligate aerobe
- grow better with O2 (aerobic respiration)
- can also grow with out O2 (anaerobic respiration)
- yield less energy and are slower than aerobic
facultative anaerobe
- ignore O2 (fermentation or anaerobic resp.)
- grow slowly
- Streptococcus sp and Lactobacillus sp
aerotolerant anaerobe
what are problems with aerotolerant anaerobes?
have a lot of growth factor requirements and difficult to grow in culture
- O2 is toxic
- killed by oxygen
- agar deep, thioglycollate, anaerobe jar
- important human associated anaerobe
- Clostridium sp an Bactericides sp
strict anaerobe
three ways to culture strict anaerobes
- agar deep (no O2 at bottom)
- thioglycollate (chemically binds O2)
- anaerobe jar (Gas Pak)
- most recently discovered
- require low O2 (2-10%); requires high CO2
- agar deep, candle jar
- Helicobactor pylori
microaerobe
explain how a microaerobe in candle jars
- sample with cork
- lit candle using up O2 and producing CO2
- at 5%, O2 candle will go out
- agar inverted petri plates in a closed jar
what are complex medias made of?
grind up yeasts for use of complexes
examples of solid and liquid medias
liquid- broth
solid- agar
- complex polysaccharide from marine algae
- solidify agent at low [ ] (1.5%)
- melts at 100 degree C, remains liquid to 40 degree C (can grow thermophiles)
- not broken down by most MOs
- expensive
agar
-contain ingredient (s) that inhibit growth of unwanted MOs
selective media
contents in selective media
- sugar/pH in Sabourouds agar/ PDA
- brilliant green dye- Salmonella
- specific antibodies to inhibit the unwanted
- different kind of MOs look/react differently on medium
- blood agar
differential media
describe blood agar in differential media
- 5% sheep blood
- rich for fastidious MOs (a lot of growth factor)
- different type of hemolysis (hemolozymes)
- can see different reactions
describe MacConkey’s selective and differential agar
- selective- bile salts and crystal violet inhibit gram + bacteria
- differential- lactose and pH indicator neutral red (MO’s that ferment lactose become pink/red)
enrichment media and procedures
- when MO of intrest is present in low proportions
- medium favors growth of MO of intrest, proportions in the mixture increases
- repeated transfers of 10 required
- plant/animal cells grown in specialized media
- viruses, parasitic bacteria such as Chamlydia, Rickettsia and some spirochetes
tissue/cell culture
- lower proportions of organisms
- dilute
- isolation
streak plate method
diluted sample will be spread on agar
spread plate method
what is the goal of streak plate and spread plate methods?
individual, isolated cells that will grow colonies
-used for isolation
-for counting
-mixing MO with cooled agar, then it solidifies
A- better seperations, colonies found through out medium
D- can allow microarofiles at bottom
-tiny colonies deep in agar
pour plate method
- agar slants with refrigeration (4 degree C)
- few weeks to months
short term storage of cultures
different ways for long term storage of cultures
- liquid nitrogen (-196 degree C)
- ultra freezer (-70 to 120 degree C) electricity can be a problem
- lyophilization (freeze drying) -best long term storage
- freeze under vacuum, dehydrate, seal
- no ice crystals because they destroy membranes
- preference if MO can handle it
lyophilization
reference for ID, study and patents
American Type Culture Collection ATCC
no change in number of living cells
lag phase
- exponential growth
- almost all cells are uniform, growing at optimum rate
- only lasts for a few hours
- binary fission
exponential (log) phase
- bacteria could have run out of living cells is constant
- accumulation of waste products
stationary phase
- log death rates
- dying at predicable death rate
death phase
number of viable MOs remain constant in the _____ and _____ phase of batch cultures growth curve
lag and stationary phases
- number of generations per hour
- E. coli (4.8 generations/hr)
- M. tuberculosis (.07 generations/hr)
k
growth rate
number of generations
n
- time interval for a cell to divide
- time for population to double
- E. coli (12.5 minutes)
- M. tuberculosis (14 hours)
g
generation time
what is on the x and y axis of batch culture growth curve (binary fission)
x- time
y- log number of viable cells
equation for growth rate
k= (# of cells start with - # of cells end with) / .3t
equation for generation time
g= 1/k
methods we can use to monitor growth
- microscopic count
- electric counter (coulter counter)
- turbidity (cloudiness)
- cell mass
- plate/colony count
- little/ no debris present
- living and dead cells counted (hard to distinguish)-D
- quick-A
- require skill
- motility of MO- D
microscopic count
- particle counts
- large MOs, little debris
- living and dead cells counted- D
- expensive- D
- easy to use, least skill requiring -A
- used for rbc’s
electric counter (coulter counter)
- related to cell [ ], calibrate first
- living an dead cells counted- D
- quick- A
- spectrophotometer
turbidity (cloudiness)
- liquid medium
- very high number or mass required (fungi)
- collect, wash, dry, weigh
- living and dead cells- D
cell mass
- living cells grow and form colonies
- time, expensive, clumps of cells
- appropriate mediums/conditions
- spread and pour plate methods
plate/ colony counts
