Unit III Flashcards
Two main categories of Growth Requirements
Physical and Chemical
Cold loving microbes
Psychrophiles
Lowest temperature at which species will grow
Minimum Growth Temperature
Moderate temperature loving microbes
Mesophiles
Heat loving microbes
Thermophiles
More common than psychrophiles; optimum growth temperature at 20-30°C
Psychotrophs
Bacteria growing near neutral pH 6.5-7.5
Neutrophiles
Bacteria tolerant of acidity;thrives on pH 1-5
Acidophiles
Process of contraction or shrinkahe of protoplasm and causes cell water loss
Plasmolysis
Requires high salt concentration for growth
Obligate Halophiles
Do not require high salt concentration, but are able to grow at salt concentration higher than normal e.g. 2%—a concentration that inhibits the growth of many other organisms
Facultative Halophiles
Half the dry weight of cell
Carbon
14% and 4% of the total dry weight
Nitrogen and Phosphorus respectively
Gets most of their carbon source from their energy sources
Chemoheterotrophs
Structural backbone of all living matter
Carbon
Essential for the synthesis of nucleic acids
Phosphorus
Microbes that use molecular Oxygen (O2)
Aerobes
Organisms that require oxygen to live
Obligate Aerobes
Aerobic bacteria that has developed the ability to continue growing in the absence of oxygen
Facultative aerobes
A toxic form of Oxygen that is a normal molecular Oxygen boosted into a higher energy state
Singlet Oxygen
Superoxide anions; formed in small amounts during normal respiration
Superoxide radicals
Are bacteria unable to use molecular Oxygen for energy-yielding reaction
Anaerobes
Fermentative anaerobes; cannot use oxygen for growth
Aerotoleranr anaerobes
used to synthesize sulfur-containing amino acids and vitamins such as thiamine and biotin.
Sulfur
are complex polymer containing many times its dry weight in water.
Hydrogels
thin slimy layer encasing baceria
Biofilms
ability of bacteria to communicate and coordinate behavior
Quorum sensing
nutrient material prepared for the growth of microorganisms in a laboratory
Culture medium
Microbes introduced into a culture medium to initiate growth.
Inoculum
microbes that grow and multiply in or on a culture medium
culture
type of culture medium whose exact chemical composition is known.
Chemically-defined media
A complex polysaccharide; used as solidifying agent for culture media in petri dishes, slants, and deeps
Agar
Usually reserved for laboratory experimental work, or for the growth of autotrophic bacteria.
Complex Media
shorter chains of amino acids
peptone
complex medium in liquid form
nutrient broth
type of growth media used to avoid anaerobes’ exposure to oxygen
reducing media/Special media
chemically combines with dissolved oxygen and deplete oxygen in the culture medium
Sodium thioglycolate
Aerobic Bacteria; grow better at high-CO2 concentrations
Capnophiles
additives suppress unwanted microbes and encourage desired microbes
Selective Medium
changed in a recognizable manner by some bacteria; Makes it easy to distinguish colonies of Different microbes
Differential Medium
Similar to selective media, but designed to increase the numbers of desired microbes to detectable levels. Encourages growth of the desired microbe
Enrichment Culture
culture containing only one species or strain
Pure culture
can be used for the short-term storage of bacterial cultures
Refrigeration
rapid cooling of pure culture in suspension liquid
Deep freezing
Freeze drying
Lyophilization
bacteria normally reproduce through
Binary Fission
time required for a cell to divide
generation time
Phase of Growth; period of little or no cell division.
The Lag
The phase of Growth; Cellular reproduction is most active during this period
The log
the growth rate slows as the bacteria approach the carrying capacity,
Stationary
the number of death exceeds the number of new cells formed
death phase
The most frequently used method of measuring bacterial populations
Plate counts
Method of choice for low counts
Filtration
statistical estimating technique is based on the fact that the greater the number of bacteria in a sample, the more dilution is needed to reduce the density to the point at which no bacteria are left to grow in the tubes in a dilution series.
Most probable number (MPN)
Microbes in a measured volume of a bacterial suspension are counted with the use of a specially designed slide (Petroff-Hausser Cell counter).
Direct Microscopic count
Microbial contamination
Sepsis
Absence of significant contamination
Asepsis
Acquired during the process of receiving healthcare
Nosocomial
Expected to destroy pathogens but do not achieve sterility
Antimicrobial chemicals
Antimicrobial chemical used on objects
Disinfectant
Antimicrobial chemicals used in living tissue
Antiseptic
Removal of all microbial life
Sterilization
Mechanical removal of microbes
Degerming
Reduces microbes to safe public health levels
Sanitization
Inhibits bacterial reproduction
Bacteriostatic
Kills bacteria
Bactericidal
Factors affecting the effectiveness of antimicrobial treatments
Number of microbes
Environmental influences
Time of exposure
Microbial Characteristics
lowest temperature at which all the microorganisms in a particular liquid suspension will be killed in 10 minutes
Thermal Death Point (TDP)
minimal length time for all bacteria in a particular liquid culture to be killed at a given temperature
Thermal Death Time (TDT)
D-value; is the time, in minutes, in which 90% of a population of bacteria at a given temperature.
Decimal reduction time (DRT)
kills microorganisms primarily by coagulating proteins (denaturation)
Moist Heat sterilization
preferred method of sterilization in health care environment
Autoclaving
at what temperature will organisms will be killed
15psi @ 121°C
