describe the growth patterns of macrobes and microbes?
- macrobe growth= increase in size
- microbe growth= increase in cell number via binary fission (bacteria, protists, algae) or budding (yeast)
why do microbes have such diverse habitats?
- -they are small
- -they need small amounts of nutrients
- -they have diverse metabolisms
- -they can tolerate a wide variety of physical conditions
what are the basic nutrients that all organisms need to survive?
carbon, energy, and electrons/hydrogen ions
what are the 4 groups of microbes, based on how they retain their carbon (nutrition) and energy.
photoautotrophs- get energy from light and carbon from the environment
chemoautotrophs- get energy from chemicals and energy from the environment
photoheterotrophs- get energy from light and carbon from organic compounds
chemoheterotrophs- get energy and carbon from organic compounds
What are the 4 physical requirements for microbial growth?
Temperature, PH, and Osmotic Pressure, and hydrostatic pressure
Explain why temperature is important for microbial growth
what are the microbes with various temp preferences?
- temp plays an important role because it affects the 3D structure or biological molecules. Microbes have minimum, optimum, and maximum growth temperatures.
- -cold causes slow growth
- -optimal is maximum growth
- -maximal causes denaturation to occur
psychrophiles (cold lovers): 0-15 degrees C
mesophiles (most pathogens): 20-40 degrees C, optimal is 37 degrees
thermophiles (warm lovers): 45-110 degrees C
Explain why PH is important for microbial growth.
what are the microbes with various ph preferences?
H+ and OH- interfere with the hydrogen bonding of proteins and nucleic acids. A PH that the microbe doesn't like can destroy tertiary and quaternary protein structures and nucleic acid structures.
Acidophiles (acid-lovers): PH 0.1-5.4
Neutrophiles: PH 5.4-8.0 (most human pathogens)
Alkaliphiles (base-lovers): PH 7-11.7
Why is water important in microbe growth?
most microbes need water to dissolve enzymes and nutrients for metabolism. cells will eventually die without water although endospores and cysts can last a long time without it.
water also effects osmotic and hydrostatic pressure
why is Osmotic pressure important for microbial growth? what are the types of osmotic pressure?
it determines the amount of pressure put on the cell's membrane due to the dissolved substances in the solution
- hyperosmotic (hypertonic) environment- the substances are on the outside of the cell and cause the cell to shrink due to water loss=plasmalysis
- *used in food preservation
- *halophiles can live in extreme salty
hypoosmotic (hypotonic) environment- substances are on the inside of the cell so the cell takes up water=turgid. this is for cells with cell walls. if the cell doesn't have cell walls, then the cell bursts.
why is hydrostatic pressure important for microbial growth?
bacteria can survive to a depth of 7000m. Barophiles actually require pressure to keep their tertiary structure.
for each 10m of depth, water pressure increases by 1 atm pressure
what are the essential elements?
CHONPS, trace elements (Zn, Mn, Ng, etc), and vitamins/growth factors
function of essential element Carbon
Carbon acts as an energy source an is a building block for cells (carbohydrates, etc)
function of essential element Nitrogen
nitrogen is used in amino acids, purines and pyrimidines
*nitrogen fixation- cyanobacteria and rhizobium can reduce N2 into NH3 which is an essential process to fertilize soil
importance of essential element oxygen
in aerobic microbes (obligate aerobes), oxygen is the final electron acceptor of the electron transport chain. However, superoxide radials and peroxide anions of oxygen are also toxic. these toxic forms of oxygen cause cell damage and damage to lipids and proteins
name and explain the 5 types of microbes classified by their oxygen requirements.
Aerobes- metabolize aerobically; obligate require O2
Anaerobes- metabolize anaerobically; obligate are poisoned by O2
Facultative anaerobes- can metabolize aerobically and anaerobically
Aerotolerant anaerobes- metabolize anaerobically; can detoxify oxygen' poisonous forms
Microaerophiles- require oxygen levels from 2-10%; have a limited ability to deto
function of essential element Sulfur
sulfur is for cysteine, methionine and coenzymes
function of essential element phosphate
needed for nucleic acids, ATP, and phospholipids
what are the 3 types of microbe relationships? explain.
antagonistic- one organism harms or kills the other
synergistic- both organisms cooperate to reap better benefits than if they were living alone (they are able to live separately)
symbiotic- they live in close nutritional and/or physical contact and are interdependent on each other. they do not live apart.
what are biofilms?
complex relationships between organisms. they microbes operate differently as a group than they would independently.
what is quorum sensing
bacteria respond to signals from each other and with new behaviors
what are the 6 types of general culture media?
what methods would you use to preserve a culture?
refridgeration: 4 degrees C
deep freezing: -70 degrees C
lyophilization (freeze drying)
what is the mechanism that microbes grow? what is their growth pattern?
- they grow by binary fission=the cell duplicates itself by splitting into two daughter cells.
- *growth is logarithmic
- *their generation time is the time is takes the cells to double in number (20 minutes to us is 20 hours to them, for example)
- *all cells do not divide at the same time=non-synchronous, but they do all stay in the same growth phase
what are the phases of microbial growth? explain.
log phase- growth at exponential rate (meaning, 2, 4, 8, 18, etc). this phase has a finite number because as bacterial increase in number, nutrients and depleted and waste accumulates. the limiting factor is the rate of energy production from ATP
stationary phase- this is the leveling out phase. nutrition is limited, wastes may be at toxic levels, there isn't enough O2 and PH isn't at its optimal level.
death/decline phase- too much waste, and not enough nutrition, cells begin to die.
what are the 5 direct methods of counting microbial growth?
Viable plate counts
Most probable number
what are the indirect methods of measuring microbial growth?
- turbidity- measuring with a spectrophotometer
- (the metabolic products or the dry weight)