Microbial Growth Environments Flashcards
what are extremophiles?
organisms that grow under harsh conditions that would kill most other organisms
what are common influential environmental conditions?
changing solute concentrations, pH, temperature, oxygen concentration, pressure
what conditions do most microbes prefer?
neutral environment conditions (osmolarity, temp, pH, and pressure)
what are the most common mechanisms used by extremophiles?
synthesized specialized enzymes and proteins, altering of genomic material, altering membrane composition, opening/closing channels or similar mechanism to acquire or remove substances to balance the intracellular environment
what is the typical outcome of osmotic concentrations on most microbes?
depending on osmolarity, there will be an influx of water in or out of the cell, causing it to burst or to shrink
how do microbes adapt to changes in osmotic concentration?
trigger channels in the membranes to ope which allows solute to leave or increase their internal osmotic concentration
what is the typical outcome of pH changes on most microbes?
cytoplasmic pH becomes acidic or alkaline, causes cell death
how do microbes adapt to pH changes?
utilize mechanisms that maintain a neutral pH such as exchange of protons, synthesizing special proteins, or producing waste products to balance the environmental pH
why are microbes so sensitive to temperature change?
microbes cannot regulate their internal temperature and their enzymes do not function well outside of their optimal range
how do microbes adapt to temperature changes?
utilize means to stabilize proteins and membranes
what is the typical outcome of oxygen concentration changes on most microbes?
organisms can be strict to facultative aerobes or anaerobes
O2 is toxic to strict anaerobes, so they must find other ways to make energy. strict aerobes are not fit for oxygen poor environments, so they will die without it
how do obligate anaerobes adapt when there is oxygen present?
they will sometimes associate with facultative anaerobes who will remove any oxygen from the environments
they also utilize enzymes that scavenge and neutralize reactive oxygen byproducts
what pressure are all microbes always at?
1 atm
what microbes need adaption mechanisms for pressure changes?
extremophiles
what are the four main types of extremophiles?
halophiles, acidophilus, thermophiles, and obligate anaerobes/aerobes
what happens when cells are in a hypotonic solution?
water enters the cell which causes it to swell and burst
what happens when cells are in a hypertonic solution?
water leaves the cell, causing membrane shrinkage from the cell wall
how do microbes reduce osmotic concentration of their cytoplasm in hypotonic solutions?
mechanosensitive channels in the plasma membrane
what are halophiles?
microbes that grow optimally in the presence of NaCl or other salts at a concentration above about 0.2 M
what makes a halophile extreme?
require salt concentrations between 3 and 6.2 M
their cell wall, proteins, and plasma membrane require high salt to maintain stability and activity
what are bacteria and protists classified as in regards to pH preference?
neutrophiles
what conditions do fungi prefer (pH)?
more acidic environments, between 4-6
what are most archaea classified as (pH)?
acidophiles (pH of 0-5)
what is the acidic tolerance response?
microbes pump protons out of the cell
some synthesize acid and heat shock proteins that protect main proteins
how do many microbes change the pH of their habitats?
by producing acidic or basic waste products
what are the 3 distinct cardinal growth temperatures?
minimal, maximal, and optimal
what is the temperature range for psychrophiles?
0-20 degrees C
what is the temperature range for psychrotrophs?
0-35 degrees C
what is the temperature range of mesophiles?
20-45 degrees C
what is the temperature range for thermophiles?
55-85 degrees C
what is the temperature range for hyperthermophiles?
85-113 degrees C
how do thermophiles adapt to high temperatures?
they have more chaperone proteins and H bonding in proteins
they have more saturated, branched and higher MW lipids
they have ether linkages in the archaeal membranes
what are barotolerant microbes?
adversely affected by increased pressure, but no as severely as non tolerant organisms
what are barophilic (peizophillic) microbes?
microbes that require or grow more rapidly in the presence of increased pressure
can change membrane fatty acids to adapt to high pressures
what gas has the higher impact on microbial growth? O2 or CO2?
O2
what are the three categories that microbes fall into in regards to oxygen concentration?
those that use oxygen and detoxify it
those that can neither use nor detoxify oxygen
those that do not use oxygen but can detoxify it
what is a singlet oxygen?
an extremely reactive molecule that can damage and destroy a cell by the oxidation of membrane lipids
what are the other 3 toxic byproducts of microbial oxygen processing?
superoxide ions, hydrogen peroxide, and hydroxyl radicals
what enzyme converts superoxide ions into hydrogen peroxide?
superoxide dismutase
what enzyme converts hydrogen peroxide into water and oxygen?
catalase
what are aerobes?
microbes that can use gaseous oxygen in their metabolism and posses the enzymes needed to process toxic oxygen products
what are some examples of obligate aerobes?
most fungi, protozoa, and many bacteria such as Bacillus and mycobacterium tuberculosis
what are microaerophiles?
microbes harmed by normal atmospheric concentrations of oxygen but require a small amount of it for metabolism
what are facultative anaerobes?
microbes that do not require oxygen for metabolism but use it when present
what are some example of facultative anaerobes?
many gram negative intestinal bacteria, staphylococci
what is the difference between anaerobes and obligate anaerobes?
anaerobes lack the metabolic enzyme systems for using oxygen is respiration, but obligate anaerobes also lack the enzymes for processing toxic oxygen and die in its presence
what are some examples of obligate anaerobes?
many oral bacteria, intestinal bacteria
what are aerotolerant anaerobes?
microbes that do not utilize oxygen but can survive and grow to a limited extent in its presence
why are aerotolerant anaerobes not harmed by oxygen?
they possess alternate mechanisms for breaking down peroxides and superoxides
what are some examples of aerotolerant anaerobes?
certain lactobacilli and streptococci, clostridial species
what are the characteristics of natural microbial growth environments?
complex and constantly changing
expose a microorganism to overlapping gradients of nutrients and environmental factors
contain both micro- and macroorganisms
what types of envrionments do most microbes inhabit?
oligotrophic environments
what are some of the ways in which microbes have evolved to respond to starvation and environmental stresses?
morphological changes such as endospores
entering the stationary phase of growth curve
using cellular components as nutrients
numerous genes and proteins that help
viable but not cultural state
what is quorum sensing?
the bacterial cell to cell communication process
how does quorum sensing work?
requires an autoinducer
controls genes that direct activities that are beneficial when performed in synchrony
produces small proteins that increase in level as microbes replicate and convert a microbe to a competent state
DNA uptake occurs and encourages horizontal gene transfer
what are some things that are controlled by quorum sensing?
bioluminescence, sporulation, competence, antibiotic formation, biofilm formation, and virulence factor secretion
how do most microbes grow?
attached to surfaces, or sessile, rather than free floating
what are free floating microbes called?
planktonic
what is a biofilm?
attached microbes that form a complex, slime enclosed community
where can biofilms form??
on any conditioned surface
what are the five steps of biofilm formation?
- reversible attachment of planktonic cells
- first colonizers become irreversibly attached
- growth and cell division
- production of EPS and formation of water channels
- attachment of secondary colonizers and dispersion of microbes to new sites
what is heterogeneity?
differences in metabolic activity and locations of microbes
how do interactions occur between organisms attached in biofilms?
exchanges take place metabolically through DNA uptake and communication
