Bacteria Flashcards
what 3 divisions can bacteria be split into according to their nutritional requirements?
simple needs
complex needs
unknown needs
what do bacteria with simple needs require?
only basic needs (e.g. glucose, phosphate, sulphate) as they can make complex substances themselves
what do bacteria with complex needs require?
growth factors and other substances (e.g. amino acids/nucleotides) as they cannot create these on there own
what are bacteria with complex needs also known as?
fastidious bacteria
can bacteria with unknown needs survive outside the host?
no - cannot be grown in a lab
what are the pH requirements of most bacteria?
neutral or slightly alkaline
what is bacteria’s optimum temperature?
varies between bacteria depending on their target host. Those that live in mammals have an optimum temperature of 35-37 degrees
how do strictly (obligate) aerobic bacteria respire?
use O2 at all times
how do microaerophillic bacteria respire?
in limited oxygen (e.g. 5%) and can be killed by high oxygen concentrations
how do facultatively anaerobic bacteria respire?
can grow without o2 but do not need to. Are metabolically flexible
how do strictly anaerobic bacteria respire?
without oxygen
what can the respiration style of a bacteria tell us about their location in the body?
how reliant they are on air can illustrate if they function best in the intestine (low or no o2) or elsewhere where o2 is higher
what 2 byproducts are there of respiration and metabolism in bacteria?
hydrogen peroxide and superoxide radical
what is hydrogen peroxide taken up by?
catalase
what is superoxide radical taken up by?
superoxide dismutase
do anaerobic bacteria produce hydrogen peroxide and superoxide radical?
no
how do strictaerobic bacteria acquire energy?
aerobic respiration
how do microaerophillic bacteria acquire energy?
aerobic respiration
how do facultative anaerobic bacteria acquire energy?
aerobic respiration
anaerobic respiration
fermentation
how do strict anaerobic bacteria acquire energy?
anaerobic respiration
fermentation
do strict aerobic bacteria have a detox system?
yes - catalase and superoxide dismutase
do microaerophillic bacteria have a detox system?
yes - only superoxide dismutase
do facultative anaerobic bacteria have a detox system?
yes - catalase and superoxide dismutase
do strict anaerobic bacteria have a detox system?
no
what are barriers on a bacterial cell to nutrient uptake?
outer membrane and plasma membrane
what are not barriers on a bacterial cell to nutrient uptake?
capsule and peptidoglycan
what are the 3 mechanisms for nutrient uptake?
passive diffusion
active diffusion
active transport
what are the by products of fermentation?
acids, CO2, hydrogen, alcohols
what does fermentation produce?
ATP
NADH2
NADPH2
what are the products of respiration?
CO2, ATP, NADH2 and NADPH2
what is the terminal electron acceptor for aerobic respiration?
oxygen
what are the terminal electron acceptors for anaerobic respiration?
nitrogen
sulfates
carbon dioxide
what are the types of media used to grow bacteria in labs?
nutritionally simple
enriched (non-specific)
selective
differential
what is the benefit of selective media over other types?
can inhibit or suppress other bacteria and enrich wanted bacteria
what does differential media allow for?
viewing visual differences in bacterial colonies
describe the bacterial growth curve in a closed sytem
lag - log - stationary - death
what happens during the lag phase of bacterial growth?
bacteria adapts to environment (e.g. selects enzymes that work best at host temperature and pH)
what happens during the log phase of bacterial growth?
bacteria multiply exponentially
what happens during the stationary phase of bacterial growth?
a factor inhibits further bacterial growth so number remain steady
what happens during the death phase of bacterial growth?
bacteria either poison themselves or starve
how can doubling times vary between bacteria?
some can double every 20 minutes (E. Coli) others may take 24 hours (Mycobacterium bovis/TB)
what does the slow doubling time of TB mean for testing?
very difficult to find an effective test for
what is the value of studying bacteria?
identify it
learn how it may be killed (e.g. infection control)
vaccine production
what does the morphology of bacteria describe?
its gross structure and shape
what are the 4 main bacteria shapes?
coccus
bacillus
coccobacillus
pleomorphic
what are the 9 main parts of a bacterial cell?
mesosome nucleoid ribosome inclusion bodies capsule surface proteins cell wall plasma membrane flagellum
what is in the nucleoid of bacterial cells?
area of DNA
what is the function of the mesosome?
holds proteins in one place
what makes up the protoplast of a cell?
plasma membrane, cytoplasm and contents
what are hopanoids used for in the bacterial plasma membrane?
stabilising the membrane
describe the features of a gram positive cell wall
plasma membrane on the inside, peptideoglycan layer on the outside which can close gaps within itself if the bacteria is in a dry area
where are gram positive cells often found?
outside the body (in dry areas)
describe the features of a gram negative cell wall
two plasma membranes with a peptidoglycan layer in the centre. On the external plasma membrane there are lipopolysaccarides which contain antigens that keep immune cells away from the sensitive plasma membrane
what are glycocalyx?
capsules/slime layers outside the cell wall which interfere with immune response
what are flagella used for?
movement
what are fimbriae (pili) used for?
used to stick to surfaces
what are gram stain tests able to tell us?
the environment which the tested bacteria prefer
what colour will a negative gram stain show?
purple
what colour will a positive gram stain show?
pink
where is bacterial DNA found?
nuclear region
how many chromosomes do bacteria have?
1
what shape are chromosomes in bacteria?
circular/double stranded and super coiled
what are plasmids made up of?
extra-chromosomal circular DNA
what is the function of plasmids?
auxillary genes, give the bacteria extra functions
what types of plasmid are there?
resistance virulence colicin fertility degradative
what does variation of bacteria affect?
virulence
resistance to host defences
resistance to treatments
how does mutation affect variation?
affect resident genome
how does recombination affect variation?
relies on new DNA gained by taking up plasmoids
when is variation retained?
were it causes and increase in fitness
what is the name of bacteria which is free living in the environment?
saprophytes
what is the name of the bacteria which live on/in animals?
parasites
what are the 3 types of parasitic bacteria?
symbiotic
commensal
pathogenic
what happens in a host parasite relationship with symbiotic bacteria?
bacteria and host gain (e.g. cellulase producing bacteria in the rumen)
what happens in a host parasite relationship with commensal bacteria?
bacteria gain but cause no harm
what happens in a host parasite relationship with pathogenic bacteria?
bacteria gain and cause harm
what are the 2 types of pathogenic bacteria?
obligate and facultative
how do facultative pathogenic bacteria cause infection?
normally harmless but with altered host conditions some have the facility to be pathogenic given this changed opportunity
what are the 2 sources of infection by bacteria?
environment/other hosts
animals own commensal flora
what is bacterial infection by environment/other hosts called?
exogenous infection
what is bacterial infection by animals own commensal flora called?
endogenous infection
what are the 3 opportunities for facultative pathogens?
new body site
altered body site
reduced defences
what are examples of facultative infection caused by new body site?
e.coli - harmless in the gut but during surgery can be released into peritoneal cavity causing peritonitis
staph aureus - harmless in the nose but can lead to abscess if introduced through skin or septicemia if introduced into blood stream
what are examples of opportunities for facultative infection caused by altered body site?
temperature
pH
commensal flora change
what two things can cause alteration in commensal flora leading to growth of facultative bacteria?
antibiotic use - can wipe out all bacteria leaving those that are resistant room to grow
rapid nutritional change - alter commensal gut flora
what are examples of opportunities for facultative infection caused by reduced defences?
extremes of age malnutrition immunosuppressants primary infection stress
what are examples of stress that could lead to facultative infection caused by reduced defences?
transport crowding temperature extremes wounding trauma birth fatigue feed changes (e.g. weaning)
