Module 4 pt. 3 Flashcards
essential ingredient of bacterial protoplasm
needed by actively metabolizing cells
Water
minimum pressure needed to be applied to a solution to prevent the flow of water across a semipermeable membrane
Osmotic pressure
organisms that can grow at relatively
high salt concentration (up to 10%)
salt-loving organisms; require relatively
high salt concentrations for growth (i.e. archea require
NaCl concentrations of 20 % or higher)
osmotolerant
halophiles
Classification of Halophiles
low halophiles – 1-6% NaCl
mild or moderate halophiles – 6-15% NaCl
extreme halophiles – 15-30% NaCl
pressure exerted by standing water, in proportion to its depth
doubles with every 10 meter increase in
depth
Hydrostatic Pressure
bacteria that live at high pressures
Beyond 10 MPa
52 MPa and 98C
piezophiles (barophiles)
Psychropiezophiles
Thermopiezophiles
Binary Fission (5)
- Replication of chromosome
- Cell grow in size (double)
- Septum formation
- Completion of septum with
formation of distinct walls - Cell separation
PS. Generation - interval for the formation of two cells / time required to give rise to 2 daughter cells
Calculating Generation times
N = No2^n
- N = final cell number
- N0 = initial cell number
- n = number of generations that have occurred
during the period of exponential growth
g = t/n
* g = generation time
* t = hours or minutes of exponential growth
n=3.3 (logNt-log No)
k = 0.693/g
4 phases of bacterial growth curve:
– Lag
– Log or Exponential
– Stationary
– Decline/Death phase
No significant or immediate increase
in cell numbers but there may be an increase in the
size of the cell.
◼ adaptation phase
Lag phase
cells
start dividing and their number increases
exponentially
◼ organisms divide at their most rapid rate
bacteria are more susceptible to antibiotics
Log phase
cell division decreases
due to depletion of nutrients & accumulation of
toxic products; inadequate oxygen supply; pH
change
▪ growth rate tapers off
Stationary phase
Population decreases due to the death of cells
cells undergo lysis or involution (assume a variety of unusual shapes)
Decline (Death) Phase
killing or complete elimination
of all viable microorganisms
sterilization
elimination or reduction of
pathogens from inanimate objects or
surfaces
disinfection
– reduction of microbial
populations to levels considered safe by
public health standards
sanitization
prevention of infection in living
tissues using chemicals
antisepsis
one of the most useful methods of microbial control
* reliable, safe, relatively fast, inexpensive
* use to sterilize or decrease microbial number
* moist heat or dry heat
HEAT
one of the most useful methods of microbial control
* reliable, safe, relatively fast, inexpensive
* use to sterilize or decrease microbial number
* moist heat or dry heat
time required to kill all bacteria
in a particular culture at a
specified temperature
thermal death point
thermal death time
- efficient penetrating properties
- destroys microorganisms by irreversibly coagulating their proteins
- boiling, pasteurization, pressurized steam
Moist heat
100ºC
* destroys most bacteria
and fungi, inactivates
some viruses
* kills vegetative cells and
eukaryotic spores within
10 minutes
Boiling
- use of brief heat treatment (moderately high temperature) to
reduce the number of spoilage organisms and kill pathogens
(Ex. Salmonella, Mycobacterium)
Pasteurization
62.8ºC for 30 minutes
72ºC, 15 seconds (flash method)
140ºC -150ºC (several seconds)
Low temperature holding (LTH)
high-temperature-short-time (HTST) method
ultra-high-temperature (UHT) method
- pressure cookers and autoclave
- heat water in an enclosed vessel that achieves
temperatures above 100ºC - 15 minutes, 15 psi, 121ºC (kills endospores and disrupts
viruses’ nucleic acids)
Pressurized Steam
