Quiz 6
Brewer anaerobic jar
*ANAEROBIC CULTURE METHOD* Contains a chemical packet used to produce CO2 and H2. *A methylene blue indicator strip turns white when O2 has been reduced. (or remains blue in the presence of oxygen)*
Thioglyoclate broth
*Used in reducing medium for ANAEROBIC CULTURE METHODS* Heated to drive off O2 and/or addition of agar to increase viscosity --> reduces diffusion of air into medium Sodium thioglycolate (HSCH2COONa) will combine with oxygen and deplete oxygen in culture medium.
What do obligate aerobes, facultative anaerobes, and aerotolerant anaerobes have in common
- presence of *superoxide dismutase (SOD)*
Psychotrophs
0-40 C, optimu temp is 20-30 C
Isotonic, hypotonic, hypertonic
1. Isotonic: same [solute] inside and outside cell = no net movement of water in/out of cell 2. Hypotonic: lower [solute] outside cell = movement of water in cell 3. Hypertonic: higher [solute] outside cell = movement of water out of cell = plasmolysis
Molds and yeasts grow between pH
5-6
Most bacteria grow between what pH
6.5-7.5 --> *neutrophiles*
Acidophiles grow in acidic environments and pH is
< 5.5
Acaliphiles pH
> 8.5
What is added in the growth medium during pH experiment?
Chemical buffers, a solution composed of an acid and its conjugate base that serves to moderate the pH of the solution.
How do you culture microaerophiles?
In a co2 jar
What is the final electron acceptor in anaerobic respiration?
Inorganic compounds other than o2
Why cant obligate anaerobes grow in presence of oxygen?
lack enzymes to neutralize harmful forms of oxygen
During which phase are cells growing the fastest?
log/exponential growth phase
The highest temp at which a species can grow
maximum growth temp
The lowest temp a species will grow
minimum growth temp
The temp a species grows the fastest
optimum growth temp
Living organisms obtain energy by ...
oxidizing substances (removing electrons)
What is the final electron acceptor in aerobic respiration?
oxygen
Anaerobic incubators/glove boxes
air evacuated from chamber and can be replaced with CO2 and nitrogen
Thermophiles
Heat-loving > 45 C, 50-60 C optimum growth
What happens if microaerophiles are exposed to normal atmospheric oxygen?
Produce amounts of toxic forms of oxygen
Aerotolerant anaerobes
cannot use oxygen but tolerate it well --> obtain energy ONLY by fermentation
facultative anaerobes
capable of living with or without oxygen, but grow generally better with oxygen --> if O is present, obtain energy via aerobic respiration --> If O is absent, use fermentation or anaerobic respiration e.g. E. coli MOST BACTERIA ARE THIS TYPE
At temperatures near the max growth temp, growth ______
ceases --> possibly due to denaturation of enzymes
Psychrophiles
cold-loving 0-20 C, optimum temp is 15 C
Reducing media
contain reagents that chemically combine with free oxygen, reducing the concentration of oxygen.
Osmosis
diffusion of water across a selectively permeable membrane from high water concentration to low water concentration
Obligate anaerobic bacteria
do not use oxygen (will die) --> lack catalase and accumulation of hydrogen peroxide is lethal --> obtain energy via anaerobic respiration or fermentation
The shorter the generation time, the ____ the growth
faster
Hyperthermophiles
grow at VERY HIGH temps > 80 C is optimum growth temp
Mesophiles
grow best at moderate temps 25-40 C *MOST BACTERIA ARE THIS*
Microaerophiles
grow best in an atmosphere with increased carbon dioxide (5% to 10%) and lower concentrations of oxygen (2-10%). --> obtain energy via aerboic respiration
Extreme or obligate halophiles *require* ____ osmotic pressure
high
Facultative halophiles tolerate _____ osmotic pressure
high
An increase in salt or sugar causes
hypertonic environment --> plasmolysis
Microbial growth
increase in NUMBER of cells (not cell size)
Obligate aerobic bacteria
require oxygen --> obtain energy via aerobic respiration
What are common indicators used in reducing media?
resaurzin (pink in presence of oxygen, white if absent) methylene blue (blue in presence of oxygen, colors if absent0
Generation/doubling time
time it takes for one cell to divide into two
