Microbial Growth
an increase in number of cells, not cell size
discrete colony
an aggregation of cells arising from a single parent cell
reproduction
what results in growth?
nutrients: chemical and energy requirements
1) Source of Carbon, Energy, and Electrons 2) Oxygen Requirements 3) Nitrogen Requirements 4) Other chemical requirements
Autotrophs
those using an inorganic source of carbon (Carbon dioxide)
Heterotrophs
those catabolizing reduced organic molecules (proteins, carbohydrates, amino acids, and fatty acids)
Chemotrophs
those that acquire energy from Redox reactions involving Inorganic and Organic chemicals
Phototrophs
those that use light as their energy source
Obligate Aerobes
must have oxygen to survive
Obligate Anaerobes
poisoned by oxygen and cannot tolerate it
Singlet Oxygen
molecular oxygen with electrons boosted to higher energy state (usually during Aerobic Metabolism)
Carotenoids
Phototrophic organisms have these to remove the excess energy of Singlet Oxygen
Superoxide free radicals
some form during incomplete reduction of Oxygen, during Electron Transport in Aerobes ,and during metabolism by Anaerobes in presence of Oxygen
Peroxide Anion
formed during reactions catalyzed by Superoxide Dismutase and other reaction
Hydroxyl radical
results from ionizing radiation and from incomplete reduction of Hydrogen Peroxide
Hydroxyl radical
The most reactive of the four toxic forms of oxygen
Hydroxyl radical
Not a threat to Aerobes due to actions of the enzymes Catalase and Peroxidase which prevent H2O2 from accumulating
Aerobes
undergo Aerobic Respiration
Anaerobes
do not use Aerobic Metabolism
Facultative Anaerobes
can maintain life via Fermentation or Anaerobic Respiration or by Aerobic respiration
Aerotolerant Anaerobes
do not use Aerobic Metabolism, but do have some enzymes that detoxify oxygen's poisonous forms, so can grow in its presence
Microaerophiles
Aerobes that require Oxygen levels from 2-10% and have a limited ability to detoxify Hydrogen Peroxide and Superoxide Radicals
Trace Elements
inorganic elements required in small amounts, usually enzyme cofactors
Growth Factors
organic chemicals that cannot be synthesized by certain organisms (Vitamins, Essential Amino Acids, Purines, Pyrimidines, Cholesterol, NADH, and Heme)
Temperature, pH, Osmotic Pressure
Physical requirements for growth
effect of temperature on proteins
can denature them at high temp.
effect of low temperature on lipid-containing membranes of cells and organelles
makes them rigid and fragile
effect of high temperature on lipid-containing membranes of cells and organelles
makes them too fluid and they cannot contain the cell or organelle any longer
optimum growth temperature
that at which growth rate is highest
categories of microbes based on temperature range
psychrophiles, mesophiles, thermophiles, and hyperthermophiles
psychrophiles
grow best at about 15 degrees celcius; can grow below 0 degrees celcius, but not much above 20 degrees celcius, cause food spoilage
mesophiles
those growing best between 20 degrees and 40 degrees celcius; the human pathogens are in this group
thermophiles
those that grow above 45 degrees celcius; occur in hot springs and compost piles
hyperthermophiles
Archaea growing about 80 degrees celcius and some above 100 degrees celcius
why organisms are sensitive to changes in acidity
because H+ and OH- interfere with H bonding in proteins and nucleic acids
Neutrophiles
microbes that grow best in a narrow range around neutral pH (6.5-7.5); includes most bacteria an protozoa
Acidophiles
those that grow best in acidic habitats; include other bacteria and fungi
alkalinophiles
microbes that live in alkaline soils and water up to pH 11.5
why microbes require water
to dissolve enzymes and nutrients require in metabolism; also because it is an important reactant in many metabolic reactions
endospores and cysts
what cease most metabolic activity in a dry environment for years?
hypotonic solutions
those with lower solute concentrations and higher water concentrations; cells placed in these solutions gain water; and if they lack a cell wall, may burst
hypertonic solutions
those with higher solute concentrations and lower water concentrations; cells placed in these solutions undergo CRENATION
Crenation
shriveling of cytoplasm; this effect helps preserve some foods
obligate halophiles
those that grow in up to 30% salt, require high osmotic pressure
facultative halophiles
those that do not require, but can tolerate high salt concentrations, tolerate high osmotic pressure
Barophiles
organisms that live under extreme pressure
Biofilms
microbial communities that form slime or hydrogels; organized, coordinated, functional community
Quorum Sensing
cell to cell chemical communication
Inoculum
sample of a microbe that is introduced into a Medium
Medium
collection of nutrients that may be liquid (broth) or solid (usually agar)
Environmental, Clinical, Stored
the three types of specimens from which the inoculum comes
Culture
act of cultivating microorganisms, or the microorganisms that are cultivated
Pure Cultures
contains only 1 species or strain
colony forming unit
a colony (CFU)
Aseptic technique
used to prevent contamination of sterile substances or objects
Streak Plates
isolation technique using a sterile loop or needle to spread inoculum across surface of solid medium to isolate CFUs, to isolate a pure culture
Pour Plates
isolation technique using a series of serial dilutions to separate CFUs, mixed with liquid agar which then solidifies
reducing media
contain ingredients that chemically combine with O2 and are heated to kill off O2, growth of obligate anaerobes
chemically Defined Media
those in which the exact chemical composition is known
Complex Media
nutrients including extracts from yeasts, meat, or plants
Selective Media
suppress growth of unwanted bacteria and encourage growth of desired microbes
Differential Media
make it easier to distinguse colonies of desired microbes from other colonies growing on the plate.
enrichment culture
designed to increase numbers of desired microbes at detectable levels
budding
reproduction process where a small initial outgrowth enlarges until its size approaches that of parent cell
refrigeration
used for short-term storage
deep-freezing
used for long-term storage; maintaining temperatures between -50 degrees celcius and -95 degrees celcius
Lyophilization
used for very long-term storage; freeze-drying- removing water from frozen culture using intense vacuum converting ice directly into a gas
Binary Fission
reproduction process in which a cell replicated its DNA, grows to twice its normal size, then divides in half, forming two new cells; with each division, the number of cels doubles, increasing by multiples of two
Generation time
time required for cell to grow and divide, population doubles
Growth Curve
graph of the number of organisms in growing population over time
Lag phase
time interval in which cells are very metabolically active (synthesizing enzymes), but not dividing; cell # is constant
Log Phase
time interval in which cells are rapidly growing and reproducing; population increases logarithmically; also when they're most susceptible to drugs
Stationary phase
interval when population is relatively constant, since # of new cells produced = # dying; population stabalizes, equilibrium
Death Phase
interval in which # of dying cells exceeds # of new cells formed; so there is a decline in overall # of cells
Viable Plate Counts
direct method of measuring microbial growth that determines the # of microbes in sampling by counting the # of colonies growing on the agar plate after being serially diluted and transferred to a plate either by spread method or pour plate method; count t
Filtration
direct method for measuring microbial growth where the number of microbes in a liquid sample is determined by trapping organisms on a fine membrane filter; transferring it to solid culture medium, allowing colonies to grow and counting them
pH of bacteria
pH of 6.5 to 7.5
pH of molds and yeasts
pH of 5 to 6
plasmolysis
hypertonic environment, increase in salt or sugar
chemoheterotroph
use organic carbon sources
chemoautotroph
use CO2
phosphorus
in DNA, RNA, ATP and membranes
sulfur
in amino acids
nitrogen
in amino acids and proteins
carbon
structural organic molecule, energy source
sterile
no living microbes
agar
complex polysaccharide, liquifies at 100 celcius, solidifies at 40 celcius.
capnophiles
require high CO2 conditions
biosafety level 1
no special precautions
biosafety level 2
lab coat, gloves, eye protection
biosafety level 3
biosafety cabinets to prevent airborne transmission
biosafety level 4
sealed negative pressure, exhaust air filtered twice
colony
a population of cells arising from a single cell or spore or from a group of attached cells
serial dilutions
original inoculum is diluted several times to ensure colony counts within range
spread plate method
inoculum spread on agar plate and spread uniformly with glass rod
turbidity
as bacteria multipy within a medium, the medium becomes cloudy with cells, measure with a spectrophotometer.