Habitat of Streptococcus

  1. All the Streptococcus species are the intracellular parasites of mucosal membranes and, for some species tooth surfaces of humans and several animals.
  2. Most of them are commensals normal flora on mucosal membranes of the upper respiratory tract, and some colonize the intestinal and genital tract of humans and animals.

Morphology of Streptococcus

  1. They are spherical or ovoid in shape but some species may develop rod-like cells depending on the growth conditions.
  2. Individual cells are typically 0.5-1.0 X 1.0-2.0 um.
  3. They are arranged in pairs or chains of upto 50 cells or more.
  4. Larger chains are formed in liquid than in solid media.
  5. They stain readily with ordinary dyes. They are Gram-positive but may become Gram-negative in ageing culture when the bacteria die.
  6. They are not motile in conventional sense, although a twitching motility associated with polar fimbriae has been described for S. sanguis isolates.
  7. They are non-sporing.
  8. Most strains of group A and group C possess capsules composed of hyaluronic acid, while members of group B and group D show polysaccharide capsules.
Streptococcus

Streptococcus pyogenes

Streptococcus pyogenes bacteria at 900x magnification


Streptococcus anginosus

Streptococcus anginosus

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