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.
Above: a section through a single-celled rod-shaped bacterium. Shown in purple is the tough capsule or cell wall of the. bacterium (this is a type of bacterium known as Gram positive, but there are other structural types with different wall. arrangements). This capsule protects the bacterium.