Bacterial Nutrition
The minimum requirements for growth of bacteria include water, a
source of carbon, a source of nitrogen, and certain inorganic salts. These are
required for synthesis of proteins, enzymes, etc. For example,
o Nitrogen is required for
synthesis of proteins, DNA, RNA, and ATP.
o Sulfur is required for
certain amino acids and vitamins, and phosphorous is required for nucleic
acids, ATP, and phospholipids.
o In addition, inorganic ions,
such as potassium, sodium, iron, magnesium, calcium, and chloride are required
to facilitate enzymatic catalysis and to maintain chemical gradients across the
cell membrane.
Some bacteria grow in a variety of simple media. E. coli and other members of the family
Enterobacteriaceae are examples of bacteria that can grow in a variety of
simple media contain-ing the inorganic salts and with a source of energy, the
simplest being glucose. The inorganic salts in the media provide major essential
elements of carbon, hydrogen, oxygen, nitrogen, phos-phate, and sulfur. These
chemicals are usually present in the media and are not added specifically.
Some bacteria, such as H.
influenzae and other related bacteria, on other hand, are very fastidious
and have certain growth requirements. They require certain amino acids,
vitamins, and other growth factors that are supplied by adding yeast extract
and meat digests to the media. They also require addition of blood or serum for
their growth.
Certain lower forms of bacteria even fail to grow in cell-free
culture media and require living cells for their growth.
T. pallidumand M. lepraeare two pathogenic bacteria thatcannot grow in any
artificial culture media, but can only be cultured when inoculated into living
animals.
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