L2 bacteria nutrition Flashcards by Kate Edens

what are the two types of culture media

defined

complex

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what does a define culture media mean

chemically pure
know the exact composition and all components
SPECIFIC chemicals: amino acids, vitamins and specific sugars
ingredients added individually

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Define a complex culture media

not chemically pure
don’t know the exact composition
complex nutrient sources : glucose, beef and yeast extract, peptones

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what kind of media are specialised medias

complex

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what are the five types of specialised media

transport
enriched 
enrichment broth
selective
differential

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define a transport media

maintains all organisms without cell division
used for transporting from patient to lab
minimal growth nutrients only buffers and salts

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define enriched media

“generally encouraging”
general nutrient supplements, serum or yeast extract
for the fastidious organisms (fussy)
harvest as many microbes from unknown situation

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define enrichment broth

“specifically encouraging”
promotes the growth of one organism (competitive advantage)
holds rest in lag phase
Increases the number to DETECTABLE levels

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define enrichment broth

“specifically encouraging”
promotes the growth of one organism (competitive advantage)
holds rest in lag phase
Increases the number to DETECTABLE levels

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define selective media

“specifically inhibiting”
isolation and identification of specific microbes
general nutrients plus specific chemicals that inhibit specific microbes
mannitol salt agar : selective for staphylococci

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define differential media

preliminary identification of pathogens
changes colour due to biochemical reaction
mannitol salt agar: S.aurues ferments the mannitol carb resulting in an acid which changes the agar plate colour

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mannitol salt agar fermentation process (products)

Mannitol-> D-fructose -> D-fructose-6-phosphate -> pyruvic acid -> organic acid

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mannitol salt agar fermentation process (enzymes/reactions)

Mannitol dehydrogenase

fructokinase

glycolysis

fermentation

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what type of media are blood agar plates

enriched

differential

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How are blood agar considered
enriched?

differential?

they contain lots of nutrients for general encouragement of growth

they change colour due to bacterial enzymes causing haemolysis of the red blood cells

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what colouring shows alpha haemolysis on blood agar

green discolouration

what colouring shows beta haemolysis on blood agar

completely clear

what colouring shows gamma haemolysis on blood agar

non-haemolytic

what are the stages of theoretical bacteria growth in a batch culture

lag 
exponential
stationary
death/decline
long term stationary phase

what occurs during the long term stationary phase

genetically distinct bacteria are reproducing, the ones best able to use the nutrients

bacteria growth equation

initial number x 2 ^ n

n = number of generations

what kind of bacteria is E.coli
oxygen sensitivity?
where is it commonly found
role in normal microbiome
media requirements

gram-negative rod
facultative anaerobic
lower intestine of warm blooded animals
food diegestion and Vitamin K2 production (blood clotting)
not reliant on media as it produces all 20 EAA

what is the name for an open system

continous culture

how do continuous cultures work?

keeps microbes in exponential or stationary phase by supplying the bacteria with fresh nutrients and removing the toxins
the rate of growth is relative to the ingrediants

what are continuous cultures used for?

when by-products of the bacteria need to be harvested

what is the name of the equipment used for making a continuous culture

chemostat

what are primary metabolites and when are they produced?

they are intermediate or end products of chemical reactions used for the growth of microbes -amino acids/ nucleotides produced during log/exponential phase

what are secondary metabolites used for and when are they produced?

not essential for growth accumulate in stationary phase -antibiotics

what ways can the population density be determined

direct: microscopic observation direct: turbidity viable: plate count

what does microscopic observation involve?

sample put onto a slide | using a counting chamber on the slide the cells are viewed and counted directly

what does using the turbidity to measure the pop. density involve

creating a standard curve of turbidity of the bacteria you are wanting to count using a spectrometer to measure the turbidity of your sample comparing your sample to the graph

what does a plate count involve

the sample is diluted and spread onto a plate each cell gives rise to a colony colonies are counted

why are direct methods advantageous

they are fast

what are the disadvantages to direct methods of pop. density counts

they count both dead and alive cells

advantages to viable cell counts

only counts alive cells, so it is more accurate

disadvantages to viable cell counts

takes a long time | colonies show after 18-24 hours of incubation

how is hektoen agar both differential and selective media

selective: contains bile salts that only some gram negative bacteria can grow in (E.coli) differential: contains acid fuchsin and bromothymol blue which are pH indicators, so when the lactose, sucrose and salicin (carbs) are fermented it changes colour due to the acid production