exp 10: human microbiota

Streptococci

the mucous membranes of the mouth and intestines of humans harbor

Strep throat, scarlet fever, pneumonia, meningitis, impetigo

pathogenic streptococci can cause

Meningitis

an infection of the lining around the brain and spinal cord

Fastidious organisms

require enriched media and controlled atmosphere in order to grow

Blood agar

good for growing streptococci

Hemolysin

proteins that damage animal cells and cause cause the to lyse, virulence factor

Nonhemolytic organisms

do not cause hemolysis on blood agar

Gamma hemolysis

used to describe this lack of hemolysis

Alpha hemolysis

incomplete lysis of red blood cells and is seen as a partial clearing of the red blood cells and a gray-ish darkening of the agar around the color of bacteria

hemoglobin

iron-containing molecule in red blood cells that carry oxygen

Methemoglobin

develops from hemoglobin, causes gray clearings

Viridians streptococci

alpha hemolytic streptococci that are normally present in the mouth and upper respiratory tract of humans

Beta hemolysis

causes complete destruction of red blood cells and is seen as a clearing around a colony

Streptokinase

virulence factor products by pathogenic streptococci, dissolves fibrin clots; used to dissolve blood clots

Facultative aerobe

grows in the presence or absence of oxygen

Microaerophilic metabolism

prefer increased CO2 and reduced oxygen

Obligate anaerobes

can only grow in the absence of oxygen

Candle jar

CO2 incubator, used for optimum growth of hemolysin, incubated at 37 C, the flame goes out as oxygen consumed

Microaerophilic

human streptococci metabolism

Dextran

polymer of glucose produced by streptococcus mutans, helps sick to the teeth

Dental plaque

biofilm of dextran and bacteria

Caries

tooth decay

Snyder’s test agar

used to indicate the relative number of lactobacilli in saliva; inhibits the growth of must bacteria

Bormocresol green

pH indicator in the medium for snyder’s test, becomes blue-green at pH 4.8, becomes yellow when the pH drops and lactic acid is present

Lactobacilli

species of bacteria that metabolize sugars to produce lactic acid

Coagulase

causes plasma to clot and is produced by staph aureus, can cause disease

Mannitol salt agar (MSA)

developed for isolating starch from food samples, 7.5% NaCL

Mannitol

make the MSA a differential medium, fermented by different species which causes color change

Plasma

the liquid portion of anticoagulated blood and contains the clotting factors

Fibrinogen

clotting factor, present in plasma as a soluble protein

Commensalism

relationship where one population benefits and one is unaffected

E coli and bacteroides

example of a commensalistic relationship

skin, nose, and throat

where species of staph can be found in humans

staphylococci

gram-positive, catalase-positive cocci

streptococci

gram-positive, catalase-negative cocci

mutualism

both populations benfit from association