Definition of retain. transitive verb. 1a : to keep in possession or useb : to keep in one's pay or service; specifically : to employ by paying a retainerc : to keep in mind or memory : remember.
However, some gram- positive bacteria may also have capsules. Examples for gram-negative bacteria with capsules: Escherichia â¦coli, Klebsiella pneumoniae, Salmonella. Examples for gram-positive bacteria with capsules : Bacillus megaterium, Streptococcus pyogenes, Sterptococcus pneumoniae.
However, some Gram-positive bacteria may also have a capsule: 1  Bacillus megaterium for example, synthesizes a capsule composed of polypeptide and polysaccharides. 2  Streptococcus pyogenes synthesizes a hyaluronic acid capsule. 3  Streptococcus pneumoniae has at least 91 different capsular serotypes.