Most human pathogens are mesophiles.

Optimum temperature means enzymatic reactions are also at its maximum rate.

Facultative aerobes lack the superoxide dismutase.

Obligate aerobes have the enzyme catalase.

Extreme acidophiles and alkaliphiles maintain cytoplasmic pH values nearer to neutrality

Carotenoids protect cells from UV radiation and oxidative damage.

The oxidase test determines the presence of cytochrome C oxidase. A positive result shows the formation of pink to purple color.

In the absence of NaCl, halophiles can also grow when KCl, MgCl2 or CaCl2 are present.

Salt and sugar concentration is also a function of water availability.

Alkaliphiles produce enzymes that are added to laundry detergents to remove protein and fat stains from clothes.

Psychrotrophs are common spoilage microorganisms in chocolates, jams, and dried fish.

A hyperthermophile can produce Taq polymerase which is used to automate the repetitive steps in the polymerase chain reaction.

Acidophiles thrive in marine volcanic vents, metal ores, and coal mines.

Mesophiles are responsible for spoilage of stored raw meat, vegetables, and pasteurized milk.