Selenomonas species are strict anerobes usually found in cattle rumen. Kidney shaped cells bear flagella on concave side causing a flipping motility. You need special equipment to grow them in a carbon dioxide atmosphere. Exposure to air kills them. Streptococcus species require many growth factors and have fermentative metabolism producing mainly lactic acid.
Cells are round or ovoid in pairs or chains and most are non-motile.
Some species are pathogenic, but others are important in food processing such as milk fermenations. Streptomyces form filaments and might be mistaken for fungi but the cell wall does not contain cellulose which is present in the cell walls of fungi. Streptomyces form chains of aerial spores at the ends of filaments. Many species produce important antibiotics. Usually isolated from soil and decomposing leaves which often have the odor of Streptmyces cultures.