Chapter 3: Microbial Growth Flashcards
physical requirements
temperature, pH, osmotic pressure
chemical requirements
carbon, nitrogen, sulfur, phosphorous, oxygen, trace elements, organic growth factors
psychrophiles
cold loving
psychrotrophs
grow betweeen o and 20-30 degrees C
cause food spoilage
mesophiles
moderate temperature loving
thermophiles
heat loving, optimum growth 50-60 degrees C
hyperthermophiles
optimum growth above 80 degrees C
hydrothermal vents
most bacteria grow between pH of
6.5 and 7.5
molds and yeasts grow between pH of
5 and 6
acidophiles grow in pH of
acid pH
hypertonic environment
more solute outside cells
plasmolysis
cell shrinking due to high osmotic pressure
extreme/obligate halophiles require high
osmotic pressure (high salt)
facultative halophiles tolerate
high osmotic pressure
why is carbon required
backbone of organic molecule
why is nitrogen required
component of proteins, DNA, RNA, ATP
why is sulfur required
in amino acids, thiamine, biotin
why is phosphorous required
used in DNA, RNA, ATP; found in cell mambranes
why are trace elements required
inorganic elements required in small amounts usually as enzyme cofactors
what trace elements are needed
iron, copper, molybdenum, zinc
obligate aerobes
need oxygen
facultative anaerobes
grow via fermentation or anaerobic respiration without oxygen
obligate aerobes
unable to use oxygen and harmed by it
aerotolerant anaerobes
tolerate but cannot use oxygen
microaerophiles
require oxygen concentration lower than air (21%)
bacteria from lowest to highest in terms of oxygen
obligate aerobes, aerotolerant annaerobes, microaerophiles, facultative anaerobes, obligate anaerobes
organic growth factors
organic compounds obtained from environment
types of organic growth factors
vitamins, amino acids, purines, pyrimidines (vitamins are inorganic)
biofilms
microbial communities that form slime of hydrogels that adhere to surfaces
bacteria communicate cell to cell via
quorum sensing
benefits to biofilms
share nutrients to increase growth and reproduction, shelter bacteria from harmful environment, 1000x resistance to microbicide
culture medium
nutrients prepared for microbial growth, most common is agar
sterile
no living microbes
inoculum
introduction of microbes into a medium using sterile pipet, loop, or swab
culture
microbes growing in or on a culture medium
agar
complex polysaccharide used as solidifying agent for culture media for petri plates
chemically defined media
exact chemical composition is known used to grow fastidious organisms which require many growth factors
complex media
extracts and digests of yeasts, meats, and plants, chemical composition varies batch to batch
difference betweeen nutrient broth and nutrient agar
broth is liquid, agar is solid
reducing media
used for cultivation of anerobic bacteria
reducing media contains
sodium thioglycolate that combine O2 to deplete it - heated to drive oxygen off
capnophiles
microbes require high CO2 conditions; create CO2 packet using candle jar
BSL 1
no special precuations, basic teaching lab
BSL 2
lab coat, gloves, eye protection
BSL 3
biosafety cabinets to prevent airborne transmission
BSL 4
seals, negativee pressure, hot zone - fully suited, air tube filtered through HEPA filters
what is special about HEPA filters
can filter viral particles
selective media
contains inhibitors to suppress unwanted microbes to grow pure cultures
differential media
allows distinguishing of colonies of different microbes on same plate
enrichment culture
encourages growth of desired microbe by increasing very small numers of desired organism to detectable levels - usually a liquid
pure culture
contains one speciess or strain
colony
10-100 million cells arising from a single cell
CFU
colony forming unnit
streak plate method
used to isolate pure cultures
deep-freezing
-50 to -95 degrees C to preserve microbes
lyophilization (freeze drying)
-54 to -72 degrees C and dehydrated in a vacuum to preserve microbes
bacterial growth
increase in number of cells, NOT cell size
binary fission
one splits into two; cell elongates, DNA replicates, cell wall/membrane constrict, cross-wall forms, cell separates
other methods of microbial reproduction
budding, conidiospores (actinomycetes - fungus), fragmentation of filaments
exponential growth
2 ^(# of generations) growth curves represented logarithmically
phases of microbial growth graph
lag, log, stationary, death
lag phase
no significant increase in population growth
log phase
exponential growth
stationary
reproduction equals death
death phase
population decreases
population dynamics important to study
infectious disease, food preservation, industrial processes (ethanol)
direct measurements
plate fount, filtration, most probable number, direct microscopic count
plate count
count colonies, original inoculum must go through serial dilution
plate counts occur on
agar via pour plate mehtod or spread plate method
filtration
solution passses through filter that collects bacteria; placed on petri dish and allowed to grow
most probablt number
multiple tube test, count positive tubes, compare to statisticle table
5 tubes per set, 3 sets, dilutions of 10mL, 1mL, and 0.1mL
direct microscopic count
volume of bacterial suspension placed on slide, acerage # of bacteria per viewing field calculated
direct microscopic count uses what type of cell counter
Petroff-Hausser
numer bacter/mL =
cells counted / volume area counted
turbidity
measuring cloudiness with spectrophotometer
metabolic activity and turbiditiy
amount of metabolic product is proportional to # of bacteria
dry weight
bacteria are filtered, dried, and weight - used for filamentous organisms
antibiotic resistance forces us to
change way we view disease and treat patients
evolution of resistance
mutation
mechanisms of resistance
conjugation, transductions, transformation
development of resistant population
resistant cells are not killed off, continue to divide resulting in completely resistant population
mutation and evolutionary pressure cause
rapid increase resistance to antibiotics
how does modern technology/sociology relate to resistance
travelers carry resistant bacteria, spreads quickly
large cities with poor sanitation
how is food a source of infection that can develop resistance
food prepared outside of home; contamination unnoticed until outbreak occurs - hard to trace origin of infection
example of resistance in food
E. coli O157 in spinach and lettuce
as foodborne infection increase
use of antibiotics increase - resistance increases
immunocompromised people
HIV, organ transplant recipients - increase use of antibiotics - increased resistance
emerginc disease
not seen before
remerging disease
caused by organisms resistant to treatment (Ebola)
clinical success of antibiotics led to
increasing efforts to discover new antibiotics
modification of existing drugs
develop broader range drugs
plasmids containing gene for resistance can
integrate into chromosome
resistance island
resistance genes can accumulate and are stably maintained
resistance can be shared cell to cell via
conjugation w/ sex pillus
microorganisms producing antibiotic substances hace autoprotective mechanisms
transmembrane proteins pump out freshly produced antibiotic so it does not accumulate
genes that code for pumps closely linked to genes that code for antibiotics meaning
close on chromosome, cannot be separated during crossover; activated/deactivated together
how to be resistant to antibiotics
inactivation of antibiotic
efflux pumping of antibiotic (pumping out)
modification of antibiotic target
alteration of metabolic pathway
inactivation of antibiotic
enzymatic breakdown of antibiotic molecule
B-lactamase
secrete into bacterial periplasmic space, attacks antibiotics as it approaches its target
how may forms of B-lactamase
more than 190
efflux is what type of transport
active - requires ATP
efflux proteins found in
plasma membrane - gram negativee
efflux keeps antibiotic levels
below lethal level
genes that code for efflux located on
plasmid or transposon (jumping gene)
some bacteria reduce permeability to keep antibiotic out by
turn of production of porin and other channel membran proteins - must slow metabolic activity
reduced production of porin seen in resistance to
streptomycin, tetracycline, sulfa drugss (penicillin, etc.)
modification of target to escape antibiotic activity
can change structure of target but still must be functional
MRSA and PBP protein
alteration of metabolic pathway
drugs competitively inhibit metabolic pathway, bacteria can overcome this by using different pathway
how much of S. aureaus genome codes for resistance
7%
bacillus subtilis
nonpathogenic bacteria, does not code for resistance
cephalosporins
broad range drugs - lead to rise of resistance
clostridium difficile
superinfection pathogen - very resistant to antibiotics; establish in intestinal tract, my be dormant or chronic illness
