Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. They are cocci, meaning that they are shaped like spheres or circles. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name from Greek στρεπτος streptos, meaning easily bent or twisted, like a chain (twisted chain). Contrast this with staphylococci, which divide along multiple axes and generate grape-like clusters of cells. Streptococci are oxidase and catalase-negative, and many are facultative anaerobes.
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| Genus: | Streptococcus Rosenbach, 1884
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S. agalactiae | |
Streptococcus Media
Alpha-hemolytic S. viridans (right) and beta-hemolytic S. pyogenes (left) streptococci growing on blood agar
Example of a workup algorithm of possible bacterial infection in cases with no specifically requested targets (non-bacteria, mycobacteria etc.), with most common situations and agents seen in a New England setting. Main Streptococcus groups are included as "Strep." at bottom left.
Phylogenetic tree of Streptococcus species, based on data from PATRIC. 16S groups are indicated by brackets and their key members are highlighted in red.
A conceptual diagram of Streptococcus subclade taxonomy based on phylogenetic trees and the conserved signature indels (CSIs) that are specifically shared by groups of streptococci. The number of CSIs identified for each group is shown.
Common and species-specific genes among Streptococcus sanguinis, S. mutans, and S. pneumoniae. Modified after Xu et al. (2007)
