Staphylococcus aureus is a major human pathogen. Many of these species produce carotenoid pigments, which color their colonies yellow or orange. They ferment sugars, producing lactic acid as an end product. also inhabit human skin, but they are facultative anaerobes. are obligate aerobes that inhabit human skin. The various gram-positive cocci differ physiologically and by habitat. Species of Staphylococcus have no regular plane of division. resemble a string of beads because division always occurs in the same plane. Sarcina cells, for example, are arranged in cubical pockets because cell division alternates regularly among the three perpendicular planes. These arrangements reflect patterns of cell division and that cells stick together. Members of some genera are identifiable by the way cells are attached to one another: in pockets, in chains, or grape-like clusters. All are spherical or nearly so, but they vary considerably in size. The gram-positive cocci are a large group of bacteria with similar morphology. While living in their host organism, cocci can be pathogenic (e.g., streptococcus), commensal, or symbiotic. The cell wall structure for cocci may vary between gram-positive (thick peptidoglycan layers) and gram-negative (thin peptidoglycan layers). Ĭocci is an English loanword of a modern or Neo-Latin noun, which in turn stems from the Greek masculine noun κόκκος ( cóccos) meaning 'berry'. In contrast to many bacilli-shaped bacteria, most cocci bacteria do not have flagella and are non-motile. Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division. Coccus refers to the shape of the bacteria, and can contain multiple genera, such as staphylococci or streptococci. Bacteria are categorized based on their shapes into three classes: cocci (spherical-shaped), bacillus (rod-shaped) and spiral ( of which there are two types: spirillum and spirochete).
A coccus (plural cocci) is any bacterium or archaeon that has a spherical, ovoid, or generally round shape.
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