Environmental Microbiology of Aquatic and Waste Systems

54 4 Taxonomy, Physiology, and Ecology of Aquatic Microorganisms

In microbiology, the catalase test is used to differenti­

ate between staphylococci and micrococci, which are

catalase­positive, from streptococci and enterococci,

which are catalase­negative

Optochin: Optochin (ethyl hydrocuprein hydro­

chloride) is used for the presumptive identification

of Streptococcus pneumoniae, which is optochin

sensitive, from Streptococcus viridans which is

resistant. Bacteria that are optochin sensitive will

not continue to grow (i.e., Streptococcus pneumo­

niae will die), while bacteria that are not optochin

sensitive will be unaffected (i.e., Streptococcus

viridans will survive).

Oxidase: An oxidase is any enzyme that catalyzes an

oxidation/reduction reaction involving molecular oxy­

gen (O 2 ) as the electron acceptor. In these reactions,

oxygen is reduced to water (H 2 O) or hydrogen perox­

ide (H 2 O 2 ). The oxidases are a subclass of the oxi­

doreductases. In microbiology, the oxidase test is used

as a phenotypic character for the identification of bac­

terial strains; it determines whether a given bacterium

produces cytochrome oxidases (and therefore utilizes

oxygen with an electron transfer chain) (see Fig. 4.7a).

7. Serology
   Bacterial species and serotypes can be identified by
   specific antigen/antibody reactions. Antigens are
   substances that induce the production of antibodies
   in an animal body. Bacteria and bacterial components

2H O 22 →2H O + O 2 2

Grampositivecocci

Catalase

+

Staphylococcus/

Micrococcus

−

Streptococcus

Oxidase

+

Staphylococcus Micrococcus

+

Coagulase

−

−

− +

Staphaureus

Hemolysis

Betahemolysis Alphahemolysis

Clumps

Cocciin

Chains

Cocciin

Note: The special enzymes used in the classification of Gram positive cocci are indicated in blue

Key: = Negative for the property in question = Positive for the property in question

Staphepidermidis

Fig. 4.7a The use of Special Enzymes secreted by some Gram positive cocci in their Classification