Exam 2 (Ch. 6 Microbial Growth) Flashcards
Growth (def.)
increase in number of cells
colonies
groups of cells that can be seen without a microscope
what does CFU stand for
colony forming units
another name for colony forming units is
colony
things needed for growing microbes (4 things)
- chemical needs for microbe must be determined-media (what do they eat)
- media is made and sterilized (autoclaved)
- microbe is inoculated into media
- inoculated media is placed in proper env’t (temp, pH, oxygen, light, etc.)
autoclave (def.)
heat under pressure for 20 min.
culture (def.)
microbe growing on the media
inoculate (def.)
process of adding/ introducing microbes to the media
incubate (def.)
the appropriate time and temp to grow the specific bacteria
enrichment culture (def.)
set of conditions such as temp, pH, salinity, light, nutrients, and oxygen that are tailored to requirements of desired microbe
pure culture (def.)
one type of microbe
mixed culture (def.)
2 or more types of microbes
how many zones are created to isolate pure colonies
four
zone one has the fewest _____ colonies and zone four has the most
isolated
zone four has the most______colonies
isolated
culture media (def.)
nutrient material made for the growth of microbes (food)
nutrient broth (def.)
liquid media
agar (def.) (3 things)
- solidifying agent
- liquid at 100 degrees C
- solid at 40 degrees C
complex media (def. and ex.)
media that uses substances where precise contents are unknown. ex: yeast extract, casein, beef extract, etc.)
chemically defined media (def.)
exat chemical composition is known
selective media (def. and ex.)
designed to encourage only growth of desired microbe,
ex: sabouraud agar pH of 5.6 to grow fungi
differential media (def. and ex.)
contains substances that allow different microbes to be identified growing on the same media, ex: S. aureus growing on MSA turns the agar from red to yellow when present
MSA tands for
mannitol salt agar
carbon (2 things)
- most abundant element
2. used to make carbs, proteins, lipids, and nucleic acids
name 4 organic compounds
carbs, proteins, lipids, nucleic acids
4 chemical requirements for growth
nitrogen, phosphorus, sulfur, trace elements
nitrogen (3 things)
- 2nd most abundant element
- used to make proteins and nucleic acids
- found in nature as ammonia, N2 gas, or nitrate
phosphorus
used to make DNA, RNA, ATP, and phospholipids
sulfur
used to make vitamins and amino acids
trace elements (def. and ex.)
needed in small amounts for enzymes to function, ex: Fe, Cu, Zn, Mg
aerobe (def.)
uses oxygen
anaerobe (def.)
doesn’t use oxygen
obligate aerobe (def. and ex.)
must have oxygen, ex: Micrococcus luteus
obligate anaerobe (def. and ex.)
dies in the presence of oxygen, ex: Clostridium tetani
facultative anaerobe (def. and ex.)
uses oxygen when present but can grow without it,
ex: E. coli
aerotolerant anaerobe (def. and ex.)
can survive in presence of oxygen but grows better without it, ex: Lactobacillus
cardinal temperatures (def.)
min., opt., and max. temperatures
minimum temperature (def.)
lowest temperature at which growth will occur
optimum temperature (def.)
temp at which growth is most rapid
maximum temperature (def.)
highest temp. at which growth will occur
psychrophile (5 things)
- cold-loving
- can grow at 0 degrees C
- opt. below 5-15 degrees C
- found in glaciers and deep in ocean
- ex: Polaromonas vacuolata
psychrotroph (2 things)
- optimum 20-30 degrees C
2. ex: Staphlococcus aureus (food spoiler)
mesophile (5 things)
- moderate temp. loving
- 25-40 degrees C
- most common
- found in animals, soil and water
- ex: E. coli
thermophile (4 things)
- heat loving
- opt. 50-60 degrees C
- found in volcanoes, hydrothermal vents and hot springs
- ex: Thermus aquaticus
acidophile (3 things)
- opt. pH below 6.5
- found in areas with sulfuric or hydrochloric acid (hot springs)
- ex: fungi, Helicobacter pylori, Lactobacillus
Helicobacter pylori
likes to live in your stomach and can cause ulcers
alkaliphiles (3 things)
- opt. pH above 8
- found in soda lakes
- ex: Bacillus alkalophilus
neutrophiles (2 things)
- opt. pH 7
2. most bacteria are in this category
halophiles (3 things)
- require high salt concentration
- found in Dead Sea or Great Salt Lake
- ex: Halococcus
growth requirements for most microbes (3 things)
- mesophiles
- pH (neutral) 7
- little salt
plate count (2 things)
- most common method
2. measures number of viable cells
serial dilution (explain)
bacteria are added to tubes at varying dilutions, poured into plates, allowed to grow
a plate with the highest dilution will have the _______ amount of bacteria (growth)
least
pour plate method (5 things)
- bacteria added to liquid agar
- mixture poured into empty plates
- agar solidifies, plate incubated
- colonies grow within and on surface of agar
- plates with 30-300 colonies are used to calculate original cell concentration
spread plate method (3 things)
- bacteria added to solid agar
- spread over surface of agar with sterile rod
- colonies only on surface of agar
direct microscopic count (def.)
look through a microscope and count the number of bacteria
Pros of direct microscopic count
no incubation time (fast) and cheap
Cons of direct microscopic count
dead cells are counted
2 types of plate counts
pour plate and spread plate
4 types of measurement for microbial growth
- plate count
- direct microscopic count
- turbidity
- most probable number
MPN stands for
most probable number
turbidity (4 things)
- more bacteria in liquid culture means more turbid (cloudy)
- beam of light passes through the test tube
- more bacteria, less light will pass through
- uses spectrophotometer
most probable number (MPN) (5 things)
- used when plate counts aren’t reliable
- estimates number of microbes in original sample using a serial dilution
- positive results seen by gas production
- a table estimates the number of microbes in original sample
- used in testing water purity
generation
1 cell dividing into 2
generation time
time it takes for the population size to double
growth curve (3 things)
- graph that plots growth of a population
- used to calculate generation time
- uses logarithmic scale
4 phases of growth, in order
lag phase, log or exponential phase, stationary phase, death phase
lag phase (2 things)
- period of adjustment
2. slow growth
log or exponential phase
population is doubling
stationary phase (2 things)
- equal number of cells dividing and dying
2. due to depletion of nutrients, accumulation of waste, drop in pH
death phase
cells are dying
2 ways of preserving bacterial cultures
flash-freezing and lyophilization
flash-freezing
pure culture of bacteria are quickly frozen at -50 to -95 degrees Celsius
lyophilization (4 things)
- pure culture is flash frozen
- vacuum is used to remove water
- result is powder residue
- bacteria revived by adding liquid media
