Written By: Ehsan Jahandarpour

Streptococcus is a genus of coccus (spherical) Gram-positive bacteria belonging to the phylum Firmicutes and the Lactobacillales (lactic acid bacteria) order. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name—from Greek στρεπτός 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. Most streptococci are oxidase- and catalase-negative, and many are facultative anaerobes. In 1984, many organisms formerly considered Streptococcus were separated out into the genera Enterococcus and Lactococcus. Currently, over 50 species are recognised in this genus.