Nutiritional and Biochemical Characteristics of Bacteria

Nutiritional and Biochemical Characteristics of Bacteria

	Nutritional and Biochemical Characteristics of Bacteria - Bacteria vary in their nutritional requirements. Some, such as E. coli grow on simple synthetic media while others such as lactobacilli are fastidious and need specialized growth media. The range of conditions that support the growth of bacteria vary. For example, autotrophs are capable of synthesizing their entire requirements from simple inorganic compounds while heterotrophs such as lactobacilli, fail to grow in media unless one or more of the vitamins are present.
The ability or inability of an organism to grow on a medium containing a selective inhibitory factor (such as low pH, bile salts, antibiotics etc.) can also be a differentiating characteristics. The growth and multiplication of bacteria is the consequence of active metabolism and this is a reflection of the ability to utilise certain substrates, presence or absence of specific enzymes and the production of specific end products
These characteristics are therefore important in the identification of bacteria. The most commonly used biochemical tests include ability to utilize various sugars, production of acid and/or gas when grown in sugar media ( Which can be detected by a change in the colour of an indicator), ability to produce indole,H2s etc. When grown on an appropriate test medium are used for identification. The presence of certain enzymes such as catalase, gelatinase, urease, lecthinase or lipase are frequently used in identification of bacteria. More elaborate procedures for analysis special techniques such as chromatography, electrophoresis or spectroscopy.
Based on their relation to and requirement of oxygen, bacteria may be classified as strictly aerobic or anaerobic, microaeropholic and facultative. The obligate aerobic organisms such as the Azotobacter grow well only in the presence of oxygen while strict anaerobes such as clostridia grow only in the total absence of oxygen The lactobacilli on the other hand, vary from micro aerophilic to anaerobic. Facultative anaerobic organisms such as E. coli can grow both in the presence or absence of oxygen. Bacteria may also be classified based on their optimal temperature for growth, as mesophiles (20-45°C),psychrophiles (O°C), and thermophiles (55°C and above.)

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