microlab bacterial isolation

describe salmonella

genus of rod shaped, gram negative bacterium

where is salmonella usually found

in digestive tract of animals

what condition comes from the common cause of food poisoning

salmonellosis

genus of salmonella does it belong to

escherichia

enteric bacteria means

adapted to grow in the gut of their host

what is the optimal growth temperature of salmonella and echerichia

37 C

at what temperature is salmonella bacterial growth halted but not killed off

4 C

storing food in the refrigerator prevents what

any potential salmonella bacteria from accumulating

before consumption food should be heated to what temperature for how long

75C for 10 mins

what biosafety level must be used when working with salmonella

BSL 2

all work with salmonella should be done in

designated workspace

what is salmonellosis

an infection triggered by salmonella bacteria

what usually kills ingested salmonella

stomach acidity

stomach acidity sometimes cannot kill some strains of salmonella, this is because

resistance

upon dying salmonella strains release

endotoxins

endotoxins of salmonella being released leads to

inflammation, manifesting as diarrhea, vomiting, cramps, and fever

what is the duration of salmonellosis infection

4-7days

severe cases of salmonella necessitate

hospitalization and fluid replacement

salmonella entering the bloodstream causes

sepsis

who are at risk of salmonella poisoning

vulnerable populations, infants, seniors, and immunocompromised individuals

how much salmonella causes are estimated per year

93.8 million

what is a growing concern for public health

reduced genetic diversity due to modern poultry farming practices

culturing techniques efficiently identify

bacterial strains based on growth requirements

the salmonella shigella agar (SSA) medium restricts

certain gram-positive strains growth

SSA permits what bacterial growth

specific gram-negative strains

SSA contains

peptone, lactose, and essential micro-nutrients

bile salts and brilliant green dye act as the

selective agents

pH indicator of SSA turn red when pH drops below

6.8

why does the pH dictator turn red

when lactose fermentation by Escherichia coli

what does salmonella use as a carbon source and does not ferment __

peptone; sugar

to aid identification SSA contains

ferric acid and sodium thiosulfate

most salmonella strains produce

hydrogen sulfide

when hydrogen sulfide is produced the medium turns

black

shigella lacks enzymes needed for

sulfur reduction

since shigella lacks enzymes needed for sulfur reduction what happens

it maintains its original color

define growth

an increase in the number of cells in a population

define generation time

the interval it takes for a population to double in size, either from a bacteria to two or from 500,000 to a million

what are some environmental conditions that affect the growth of microorganisms

temperature

pH level

water availability

oxygen

nutrient composition

pressure

radiation

what must be suitable in order to achieve an efficient growth of microorganisms

nutrient content and environmental conditions

what is used to grow microorganisms in the lab (nutrient solution)

culture medium/broth

to identify a bacterial species individual strains have to be

grown separately, staring from a single cell

what is the most commonly used method to isolate strains originating from a single cell

streaking

all streaking methods share a common prinicple

spreading a large number of cells over an agar plate in a sequential manner until they are well separated

why is each streak numbered and colored

to indicate the order of application

colonies after incubation and streaking consist of

genetically identical clones originating from single cells

isolated colonies with less competition for nutrients tent to grow

larger than those in close proximity

isolated colonies offer an opportunity to establish

pure cultures, genetically identical bacterial population, and in-depth study in liquid or solid media

laboratory doors and windows are kept closed to prevent

air currents and surface microorganism becoming airborne

wire loop and glass spreader are sterilized before and after use with

Bunsen burner

all work is performed close to

the bunsen burner flame

describe the logarithmic scale

a nonlinear scale that is used when measurements differ by several orders of magnitude

what are common uses for a logarithmic scale

earthquake strength, sound loudness, light intensity, growth curves, and pH of solutions