Metabolic Diversity

• Two fundamental nutritional needs:1.Acquiring chemical energy in the form of ATP– Pump ions, move cargo, undergo chemical

reactions in the cell

2.Obtaining carbon– Used to synthesize fatty acids, DNA, RNA, and

other molecules

Culturing Techniques

• Researchers use specific compounds and substrates in the culture medium and observe what grows!

• MacConkey agar– Isolates enteric, Gram-negative, bacteria based on

their ability to ferment lactose

SIM Test

• S = Sulfur reduction

• I = Indole production– Kovac’s reagent

• M = Motility

Simmons Citrate Test

• Tests the ability of certain organisms to utilize citrate as a carbon source.

• pH indicator = Bromthymol blue– pH > 7.5 turns royal blue– Neutral pH green (just like uninoculated media)

Christensen Urea Test

• Some bacteria utilize urea, which results in the formation of ammonia.– Alkaline• Produces a red-pink/red-violet color

– A negative reaction will have no color change and the agar medium will remain pale yellow.

Identifying Specific Bacteria

Bacteria Genus

Sulfur Indole Lactose Citrate Urease

Escherichia - + + - -Edwardsiella + + - - +/-Salmonella + - +/- + -Enterobacter - - + + +

Water Quality Index

• Fecal coliform measurements:1. Multiple-Tube Fermentation

– Most Probable Number (MPN)

2. Membrane Filtration– Measures both Total Coliform and E. coli

Membrane Filtration using mColiblue