Intro to Bacteria 2 Flashcards
How do bacteria reproduce?
By asexual means, process called binary fission
What is binary fission?
Bacterial chromosome replicates to form 2 identical chromosomes
cell grows in size, wall and membrane grow inwards from middle of cell to form a septum
cell divides to form 2 identical daughter cells
Bacterial growth curve
tale 1 bacterial cell and add to culture medium, divides into two daughter cells, each divides into two, measure no. of cells over time to construct growth curve
What is the lag phase?
growth of individual cells but no increase in numbers
what is the log phase?
rapid cell growth and division, slope of line = growth rate of bacteria
what is the stationary phase?
nutrients are depleted and toxic products accumulate, rate of division equals rate of cell death
carbon source
autotroph - source carbon from atmospheric CO2
heterotrophs - source carbon from organic compounds
most pathogenic bacteria are heterotrophic
Nutrient requirements
macro - carbon, oxygen, hydrogen, iron, sulfur
micro - manganese, zinc, cobalt, molybdenum
What are growth factors?
factors that cannot be synthesized by the organism but are essential for growth
amino acids, purines/pyrimidines and vitamins
fastidious
require variety of growth factors
what is a culture medium
can be solid or liquid
grows, transports and stores microorganisms
What is agar?
sulfated polymer extracted from red algae
melts at 80 to 90, solidifies at 40 - 42
most m.o. cannot degrade it
Types of media
synthetic/defined
complex
selective
differential
what is a bacterial colony?
multiplication of a single bacterial cell following incubation
what is a pure culture?
a population of cells arising from a single cell
spread/streak technique
temperature requirements
thermophiles, greater than 45
psychrophiles/cryophiles, less than 10
mesophiles, 15 to 40
most pathogenic bacteria are mesophiles and grow best at body temp 37
pH requirements
acidophiles
alkaliphiles
neutrophiles
most pathogens are neutrophiles and grow best around pH 7
what are obligate aerobes?
cannot grow in absence of oxygen
what are obligate anaerobes
can only grow in the absence of oxygen
what are facultative anaerobes?
can grow in the presence or absence of oxygen and use it for respiration
what are microaerophiles?
can use oxygen but only at low oxygen density
what are aerotolerant organisms?
can grow in the presence of oxygen but do not use it for respiration
How to generate anaerobic conditions?
use of special reducing agents, remove air with vacuum pump
GasPak, water is added to chemicals in an envelope to generate h2 and co2
o2 combines with h2 to form water
What is quorum sensing?
phenomenon in which bacteria monitor their own population density through sending the levels of signal molecules
the concentration of signal molecules increases with the cell population until it reaches a critical level or quorum
bacteria then express quorum dependent genes, virulence factors
Measurement of cell mass, Turbidity
measured using a spectrophotometer, amount of light scattered directly related to biomass of cells present and indirectly related to cell number.
quantitative Polymerase Chain Reaction
measure genetic material of bacterial cell
Physical methods to control bacterial growth
heat
low tmep
filtration
radiation
What is disinfection?
aim to remove micro-organisms from environment
toxicity to host
anti-sepsis, remove micro-organisms from living tissue
Disinfection factors
spectrum of activity
efficacy
cost
environmental effect
toxicity
contact time
work in organic matter
work in temperature
Spaulding classification
bacterial endospores
myobacteria
non-enveloped, non-lipid
gram-negative bacteria
fungi
large non-enveloped viruses
gram-positive
enveloped-lipid viruses
Disinfection programme
most modern disinfectants are mixtures of different chemicals
re-introduction of animals
farm setting
on-going monitoring
