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.