Lec 5 Flashcards
Growth of microorganisms reproducing by binary
fission can be plotted as the _____
logarithm of cell number versus the incubation time (Growth curve)
No immediate increase in cell mass or cell number (Cell is synthesizing
new components)
lag phase
_______
* Inoculum is from an old culture
* Inoculum is from a refrigerated source
* Inoculation into a chemically-different medium
LONG LAG PHASE
_________
* Young, vigorously growing exponential phase
culture is transferred to fresh medium of same
composition
SHORT LAG PHASE (or even absent)
WHAT PHASE?
Microorganisms are growing and dividing at the
maximal rate possible given their genetic potential,
nature of medium and conditions under which they
are growing
Rate of growth is constant
Microorganism doubling at regular intervals
The population is most uniform in terms of chemical
and physiological properties
Exponential/log phase
WHAT PHASE?
Population growth ceases and the growth
curve becomes horizontal (around 109
cells on the average)
Stationary phase
What phase?
Detrimental environmental changes like
nutrient depletion and build up of toxic
wastes lead to the decline in the number of
viable cells
Usually logarithmic (constant every hour)
death phase
- The time required for a microbial population to
double in number
GENERATION TIME
- The rate of microbial population growth
expressed in terms of the number of generations
per unit time
MEAN GROWTH RATE CONSTANT(k)
What type of measurement of cell number and cell mass
* Total Cell Count or Direct Microscopic Counts
* Viable Cell Count
* Membrane Filtration Method
DIRECT
What type of measurement of cell number and cell mass
- Biomass Determination
- Turbidity Measurements
- Most Probable Number
INDIRECT
- A culture system with constant
environmental conditions
maintained through continual
provision of nutrients and removal
of wastes
CONTINUOUS CULTURE
SYSTEM
- A continuous culture apparatus that
feeds medium into the culture vessel at
the same rate as medium containing
microorganisms is removed
CHEMOSTAT
- A continuous culture system
equipped with a photocell that
adjusts the flow of medium through
the culture vessel so as to
maintain a constant cell density or
turbidity
TURBIDOSTAT
- Solutes that are compatible with metabolism and
growth when at high intracellular concentrations - Example: Halobacterium (require high salt
concentration for normal activity)
COMPATIBLE SOLUTES
HIGH CONTENT OF UNSATURATED FATTY ACIDS
HELP MAINTAIN A SEMI-FLUID MEMBRANE STATE AT LOW
TEMPERATURE
PSYCHROPHILY
PROTEINS OR ENZYMES = INCREASED NUMBER OF SALT BRIDGES
(RESIST UNFOLDING IN THE AQUEOUS MILIEU)
THERMOPHILY
What type of Microbes based on temperature range?
- Small range
- Neisseria gonorrhea
STENOTHERMAL MICROBES
What type of Microbes based on temperature range?
- Wide range
- Enterococcus faecalis
EURYTHERMAL MICROBES
- Increased pressure does adversely affect them but not as
much as it does non-tolerant bacteria
BAROTOLERANT
- Grow more rapidly at high pressures
BAROPHILIC
