General Microbiology - Schlegel H. 1987

Prokaryotes. Systematic Review
Gram-Positive Cocci (Group 14)

Broadly speaking, the Gram-positive cocci among lactic acid Bacteria include genera such as Streptococcus, Leuconostoc, and Pediococcus (Section 8.2). They derive their energy through Fermentation, lack hemin pigments (Cytochromes) with few exceptions, and are microaerotolerant. In contrast, there are the aerobic and facultatively anaerobic genera Micrococcus and Staphylococcus, as well as the obligately anaerobic genera Sarcina, Peptococcus, Peptostreptococcus, and Ruminococcus.

The genus Micrococcus comprises pigmented bacteria whose yellow and orange colonies frequently appear on Petri dishes exposed to dusty air (Section 2.2.8). Because they form Cell packets (tetrads), they were formerly classified under the genus Sarcina. Currently, Sarcina lutea, S. flava, S. aurantiaca, and other species are grouped into the species Micrococcus luteus. This also includes Micrococcus lysodeikticus, a species named by A. Fleming for its marked sensitivity to Lysozyme. Micrococcus is an obligate aerobe and is characterized by a high GC content (66–72%).

¹ According to modern Classification, this also includes Rhodocyclus, Rhodobacter, and Rhodopina. — Editor's note.

The generic name Staphylococcus derives from the microscopic appearance of its Cells, which cluster like grapes (staphyli) (see Fig. 2.6); this cellular arrangement results from their irregular division in multiple planes. Representatives of this genus are facultative anaerobes; they synthesize cytochromes only under aerobic conditions and are relatively resistant to desiccation. S. aureus is pathogenic due to its toxins and exoenzymes, causing suppuration. Other strains produce enterotoxins when growing on unrefrigerated food products, thereby causing food poisoning.

Sarcina ventriculi (see Fig. 2.33) is a microaerotolerant bacterium easily isolated from soil, though it is also found in gastric contents during gastrointestinal disorders. This bacterium is notable for its large size (cell diameter of 4 µm), the aggregation of cells into large packets (exceeding 64 cells bound together by Cellulose), a wide tolerance to pH fluctuations (growing at pH values from 0.9 to 9.8), and The ability to form endospores.