Bacteria

Actinobacteria

Metabolism

Bacteria show a wide variety of different metabolisms and can accordingly be classified into primary nutritional groups. Heterotrophs depend on an organic source of carbon, while autotrophs are able to synthesize organic compounds from carbon dioxide and water. Autotrophs that obtain energy by oxidizing chemical compounds are called chemotrophs, and those that obtain their energy from light, via photosynthesis, are called phototrophs. There are many variations on this terminology such as chemoautotrophs and photosynthetic autotrophs and so on. In addition, bacteria are distinguished based on the source of reducing equivalents they are using. Those using inorganic compounds (e. g. water, hydrogen, sulfide or ammonia) for this purpose are called lithotrophs and others needing organic compounds (e. g. sugars or organic acids) and are called organotrophs. The metabolic modes of energy metabolism (phototrophy or chemotrophy), reducing equivalent sources (lithotrophy or organotrophy) and carbon sources (autotrophy or heterotrophy) can be combined differently in any single microorganism, and even shifting between different modes frequently occurs in many species.

Related Topics:
Metabolism - Primary nutritional groups - Heterotroph - Autotroph - Chemotroph - Photosynthesis - Phototroph - Inorganic - Lithotroph - Organotroph

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The photolithoautotrophs include the cyanobacteria, which are some of the oldest organisms known from the fossil record and probably played an important role in creating the Earth's oxygen atmosphere. They apparently pioneered the use of water as (lithotrophic) electron source and were the first to use the photosynthetic water splitting apparatus. Other photosynthetic bacteria use different electron sources and therefore do not produce oxygen. These anoxygenic phototrophs fall into four phylogenetic groups: the green sulfur bacteria, green non-sulfur bacteria, purple bacteria, and heliobacteria.

Related Topics:
Cyanobacteria - Oxygen - Water splitting - Green sulfur bacteria - Green non-sulfur bacteria - Purple bacteria - Heliobacteria

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Other nutritional requirements include nitrogen, sulfur, phosphorus, vitamins and metallic elements such as sodium, potassium, calcium, magnesium, manganese, iron, zinc, cobalt, copper and nickel for normal growth. For some species, additional trace elements such as selenium, tungsten, vanadium or boron are needed.

Related Topics:
Nitrogen - Sulfur - Phosphorus - Vitamin - Metallic element - Sodium - Potassium - Calcium - Magnesium - Manganese - Iron - Zinc - Cobalt - Copper - Nickel - Selenium - Tungsten - Vanadium - Boron

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Based on their response to oxygen, most bacteria can be placed into one of three groups: Some bacteria can grow only in the presence of oxygen and are called aerobes; others can grow only in the absence of oxygen and are called anaerobes; and some can grow in the presence or absence of oxygen and are called facultative anaerobes. Bacteria that do not utilize oxygen for respiration but still grow in its presence are called aerotolerant. Bacteria also thrive in environments that are considered extreme for mankind. These organisms are called extremophiles. Some bacteria inhabit hot springs and are called thermophiles; others inhabit highly saltine lakes and are called halophiles; yet others inhabit acidic or alkaline environments and are called and alkaliphiles, respectively; and still others inhabit alpine glaciers and are called psychrophiles.

Related Topics:
Aerobe - Anaerobe - Facultative anaerobe - Aerotolerant - Extremophile - Thermophile - Halophile - Acid - Alkaline - Alkaliphile - Psychrophile

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