Environmental Engineering Reference
In-Depth Information
supply. Bacteria that need complex carbon compounds are heterotrophs .
Heterotrophs use a vast range of carbon sources, including fatty acids, alco-
hols, sugars, and other organic substances. Heterotrophic bacteria are wide-
spread in nature and include all those species that cause disease in humans,
other animals, and plants.
Classification
Classifying bacteria and other microbes is complicated because of the enor-
mous variety of microorganisms that differ widely in their metabolic and
structural properties. Some microorganisms are plant like, others are ani-
mal like, and still others are totally different from all other forms of life.
As an example of the classification process, let's consider microorganisms
in terms of their activities: Bacteria can be classified as aerobic , anaerobic , or
facultative . Aerobic bacteria must have oxygen to live. At the other extreme,
that same oxygen would be toxic to an anaerobe (bacteria that live without
oxygen). Facultative bacteria are capable of growth under aerobic or anaero-
bic conditions.
Because bacteria have so many forms, their proper classification or identi-
fication requires a systematic application of procedures to grow, isolate, and
identify the individual varieties. These procedures are highly specialized
and technical. Ultimately, bacteria are characterized based on observation
and experience. Fortunately, certain classification criteria have been estab-
lished to help in the sorting process (Singleton, 1992):
1. Shape
2. Size and structure
3. Chemical activities
4. Types of nutrients needed
5. Form of energy used
6. Physical conditions needed for growth
7. Ability to cause disease (pathogenic or nonpathogenic)
8. Staining behavior (Gram stain)
Based on these criteria and on observation and experience, it is possible to
identify bacteria from descriptions published in the latest Bergey's Manual of
Determinative Bacteriology .
Fecal Coliform bacteria: indicator Organisms
Fecal coliform are bacteria that live in the digestive tract of warm-blooded ani-
mals. They are excreted in the solid waste of humans and other mammals.
Fecal coliform generally enter the water in the following ways:
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