Chapter 4 Flashcards
(45 cards)
- Orderly increase in the sum of all the
components of an organism - Cell multiplication, increase in the number of
single bacteria making up population , “culture”
growth
the number of viable cells per unit volume of
culture
cell concentration
dry weight of cells per
unit volume of culture
biomass concentration
- Can be measured by cell concentration (the
number of viable cells per unit volume of
culture) - Biomass concentration (dry weight of cells per unit volume of culture)
Viable cell count
- Measured by photoelectric means
- Related to viable count using a standard curve
-A barely turbid suspension of Escherichia coli
contains about 107 cells per milliliter, and a
fairly turbid suspension contains about 108 cells per milliliter
turbidity
The Growth Rate Constant
Can be measured in grams of biomass producedper hour
Product of time (t)
Growth rate constant (k)
Biomass concentration (B)
Exponential growth
Increase in cell number, not cell size!
microbial growth
what are the physical requirements for growth: Temperature
minimum growth temperature, optimum growth temperature, maximum growth temperature
Five groups based on optimum growth
temperature
- Psychrophiles
- Psychrotrophs
- Mesophiles
- Thermophiles
- Hyperthermophiles
– period of little or no cell division and it
can last for 1 hour or several days
Lag
cells begin to divide and enter a period
of growth or logarithmic increase; cells are
most active metabolically
log
metabolic activities of
individual surviving cells slow; microbial death
balance the no. of new cells; period of
equilibrium
stationary
no. of death exceeds the no. of new
cells formed
death
- Death mean irreversible loss
If it fails to give rise to a colony
Depends on the medium
First hour after treatment are also critical in the determination of “killing.”
measurement of death
physical methods for bacterial control of microbial growth
sterilization
Disinfection
Pasteurization
aseptic technique
Some Common biocides used for Antisepsis, Disinfection, Preservation and other purposes
alcohols, aldehydes, Biguanides, Bisphenols, Halogen-releasing agent, heavy metal derivatives, organic acids, peroxygens, phenols and cresol, quaternary ammonium compounds, vapor phase
Strategies to Control Bacteria at the Environmental Level
Antibiotics as the gold standard of treatment
Prevent exposure to infectious agents
destroys or eliminate all forms of microbial life from an object or environment
sterilization
eliminates many or all pathogenic microorganisms, except bacterial spores from an object or an environment
disinfection
application of heat, for the purpose of killing or retarding the development of pathogenic bacteria
pasteurization
pathogenic organisms are reduced to safe levels on in animate object, reducing cross infection
sanitization
removal of organic or inorganic material from objects and surfaces, manually or mechanically using water with detergent or enzymatic product
cleaning
chemical or physical agent usually broad spectrum that inactivates microorganisms
biocide
- term to a property by which biocide is able to kill bacteria
- Killed organism can no longer reproduce even after being removed from contact with the agent
- causes lysis (dissolution) of the cells
bacteriocidal
