Bacterial Growth & Genetics Flashcards
capnophilic
require carbon dioxide concentrations greater than those in room air for optimal growth
facultative anaerobe
organism that can grow with or without oxygen
fastidious nutrition
need by the cell for numerous essential nutrients
fermentation
anaerobic ATP generating process in which organic substrates are oxidized incompletely to form acids or alcohol
generation time
time needed by a cel to form two daughter cells from a mother cel
lag phase
phase of cell metabolism in which cells are preparing for cell biosynthesis and growth
microaerophile
a cell that requires low oxygen levels for growth
pasteurization
when milk (products) are exposed to certain temperatures for a certain amount of time to destroy (potentially) pathogenic non-spore bacteria transmissible by these products
deletion mutant
mutation, loss of gene portion
diploid/haploid
2N/1N
growth, in terms of bacteria
means multiplication (increase in number, not size)
bacteria energy is produced via
oxidation reduction of various substrates (proteins/carbs) and breakdown of protein products found in growth medium
aerobes
SOD and catalase
anaerobes
neither SOD nor catalase
facultative anaerobes
SOD and catalase
microaerophilic
oxygen tolerant, SOD, no catalase
autotrophs
bacteria that derive energy from the oxidation of inorganic substrates or from sunlight if photosynthetic (energy used to fix and convert CO2 into bacterial mass)
heterotrophs
all bacteria of medical importance, require one or more organic carbon components as energy sources and for biosynthetic precursors
siderophores
Fe chelating substances that compete with the host for Fe
growth factor requirements
when a bacteria requires exogenour sources of aa, B vitamins and/or nucleic acid constituents, are determined with the use of chemically defined media
psychrophiles
0 to 25 dgrs C, optimum 10-15 dgrs C
mesophiles
most human infections, 15 to 45 dgrs C, optimum 30-37 dgrs C
thermophiles
35 to 70 dgrs C, optimum ~55 dgrs C
in the absence of oxygen
everything but aerobes will use metabolic intermediates as the terminal electron acceptor
fermentation
anaerobic utilization of carbohydrates, distinguished by end product
homolactic acid fermentation
simplest pathway
catalase
break, 2h2o2 –> 2h2o + o2
SOD
make, so2- + 2H+ –> h2o2 +o2
CO2
atmospheric component required by most bacteria
ideal pH
6-7.4
ideal osmotic pressure
physiological saline (ability to live at high pressures is important for isolation)
binary fission
2 identical daughter cells barring spontaneous mutation
in a colony
all bacteria derived from a single progenitor, and are therefore clonal
solid media
is liquid media with agar
liquid media
employed due to ease and accuracy in isolation
indirect measurements of growth
change in turbidity, bacterial dry weight, bacterial nitrogen
direct measurement of growth
total/viable counting techniques, hemocytometer,
viable/plate count
depends on plating suitable dilutions of a sample to ensure that the counting is possible
cell max
maxes out before cell number
lag phase
inoculum adaptation, little to no increase in numbers, cells become more metabolically active, cells increase in mass
duration of lag phase
depends on inoculum size and metabolic state and suitability of the environment
log phase
rapid increase in numbers until a max log rate is achieved; growth parameters (including number) are increasing at the same rate
cells in log phase
are large, rich in ribosomes and active metabolically, sensitive to bactericidal antibiotics
stationary phase
nutrient depletion, metabolic products accumulating, growth slows until viable concentration becomes constant (dynamic)
cells in stationary phase
are smaller, less metabolically active, and more resistant to toxic agents
death or decline phase
rapid decrease in cell number, not well understood
small cells are found in
lag, stationary, and death phases
medium cells are found in
acceleration, deceleration,
cellular activity and size in log phase
very high, steady state, large
changes in protein synthesis
controlled by RNA polymerase sigma factors
all methods of bacteria killing are
TIME DEPENDENT, minimal effective time required
temperature
moist more effective (autoclave); fridge/freezer temperatures prevent growth, but do not kill
autoclave
15lbs. 15 minutes
oven sterilization
2 hours, 160-180 degrees
radiation
UV (DNA sensitivity, little penetration power), ionization (effective but expensive)
four physical methods of bacteria genocide
temperature, radiation, filtration, asepsis
more convenient filter
cellulose ester type, used when there is a propensity to denature at high temperatures
asepsis
maintain sterility (wrapping)
chemical methods to stop bacterial growth
alcohols, detergents, phenols, helogens, heavy metals, h2o2, formaldehyde, glutaraldehyde, ethylene oxide
formaldehyde, glutaraldehyde, ethylene oxide
alkylating agents (oxide in gaseous form)
shigella
quickly developed resistance to sulfa drugs
genetic code
non overlapping and redundant
mutation
any heritable change or alteration in DNA that is mutated
alleles
different forms of the same gene
haploid
bacteria, do not have to worry about recessive phenotypes
merodiploid state
when a second copy or a specific gene on a plasmid is introduced into a bacteria (semi-diploid –> two copies of only one gene)
diploid bacteria
only found for a certain time during cell division
types of mutation
point, frameshift mutation
reversion/supression
come on, after a nonsense mutation
missense
different aa
frame shift mutations
usually result in the formation of a truncated or shortened abnormal protein product, does not change codons prior to the mutation
induced mutation
external stimuli – chemical, physical, site-directed mutagens
composite transposon
consists of a host gene flanked by an insertion sequence
episome
a plasmid that can integrate itself into the chromosome of a host organism
insertion sequence
transposon gene flanked by special DNA sequences necessary for movement
lysogeny
when bacterial and viral genomes replicate synchronously in a virus-infected bacterium; results in viral genome integration into the bacterial genomes
lysogenic bacteriophage
bacterial virus with a toxin encoding genome that integrates into the host genomes
plasmids
autonomously replication DNA molecules found in bacteria. transferred from cell to cell, control their own ‘copy number’, HAVE LINEAR VERSIONS
replicons
any form of DNA that includes all elements necessary for replication, includes plasmids, chromosomal DNA, bacteriophages. not transposons
transduction
introduction of foreign genes into a cell via a virus vector
generalized transduction
any one host gene has an equal chance of being transduced
specialized transduction
only the host gene adjacent to the phage DNA attachment site is transduced
bacteria can evolve faster by
acquiring exogenous DNA and subsequently generating a new set of phenotypes
recombinations is used to
adapt/speed up evolution, change genome order, aids in DNA repair of large chromosomal breaks
four types of recombination
homologous, illegitimate, site-specific, insertion sequences and transposons
rec A
homologous recombination, large region
sequence specific enzymes
site-specific (small region), insertions sequences and transposons (very small region)
incorporation of circular (plasmid) vs. linear DNA
one vs. two crossovers
excised DNA
usually lost, but can persist as a plasmid if it contains a replicon
site specific recombination involving a plasmid or phage
results in a net increase in chromosomal DNA
transposition requires
site specific recombinase called a transposase (usually contains all the necessary genes for transposition)
transposons (overview)
30-1000bp, variations in complexity, inverted repeats at both ends, often carry antibiotic resistance
pathogenicity islands are introduced
via site specific enzymes
path islands..
occupy large chromosomal regions and are found in pathogenic strains with virulent genes and mobility genes, varied G+C content, flanked, associated with tRNA, and unstable
transformation
introduction of ‘naked’ DNA, sensitive to DNAase
smooth strep pneumoniae
virulent mice killers!
naturally competent bacteria (transformation)
strep pneum, h. influenzae, n. meningitidis
natural (genetic) transformation
requires homologous recombination to form a stable recombinant gene
induced transformation
bacteria are manipulated via high salt concentrations or electroporation. important for molecular biology and recombinant DNA technology
conjugation is
almost exclusively mediated by plasmids
conjugative plasmids
have the F factor and are low in copy number
4 types of conjugation
regular, Hfr, nonconjugative plasmid mobilization, conjugative transposons
Hfr chromosome transfer
high frequency recombination: integration via site specific recombination (into chromosomal replicon, can still conjugate)
hfr can
excise again to form an F plasmid again, incorrect excision results in a F’ element; or it can conjugate into a recipient F cell DIRECTLY FROM THE CHROMOSOME <– used to map genomes in the past
mobilizable plasmids
do not have transfer genes, but do have oriT (origin of transfer), transfer factors come from a helper plasmid cell (increases the probability of plasmid conjugation)
self transfer
movement of a COPY of the transposon and chromosomal integration
mobilization can
occur with a co-resident plasmid
conjugative transposon can either
donate its machinery to the plasmid or can insert into the plasmid
R plasmids
resistance plasmids
many bacterial pathogens
require large plasmids for their virulence
plasmid mediated virulence factors
antibiotic resistance genes, colonization factors (CFA), toxins, virulence, invasions, secretion
transduction
a phage carrying chromosomal DNA from an infected donor to a newly infected recipient cell. requires a specific bacteriophage or virus to mediate exchange
lysed bacteria on a agar plate
results in a cleared zone or ‘plaque’
simple and complex phage
filamentous; T4 (consist of nucleic acid and protein)
phage infection is initiated by
binding to specific receptors on the surface of the bacteria (conjugation pili, flagella, teichoic acid)
transducing particles
not lytic and used to inject recombinant DNA into a new host without its eventual lysis (do not possess own genetic material)
transduction can be prevented
by removing phage particles from culture supernatant
lysogenic phase
integration of prophage into bacterial chromosome in order to form a lysogen, triggered to lytic cycle via external stress
lysogen is
immune from a second or superinfection with another similar phage
temperate phase λ
first phage used to study lysogeny and immunity, can do specialized transduction (few specific donor genes)
stress leads to
specific bacterial protease that degrades repressor molecules resulting in prophage release and eventually lytic death
specialized transduction
rare recombinants formed during excision of the prophage upon stress that contain a small region of chromosome adjacent to prophage attachment site
phage conversion examples are
v. cholera:entero/choleratoxin; c. botulinum:botox; s. pyogenes:pyrogenic exotoxins
phage conversion is
transduction that leads to conversion of a non-pathogenic bacteria into a pathogenic one; common method for obtaining virulence genes
