Bacterial genome consists of single molecule of double stranded DNA arranged in a circular form. Besides nuclear apparatus, bacteria may have extra chromosomal genetic material named as plasmids. Plasmids do not play any role in the normal function of the bacterial cell but may confer certain additional properties(Eg. Virulence, drug resistance) which may facilitate survival and propagation of the micro- organism.
Cellular element external to the cell envelope
Glycocalyx (capsule and slime layer)
Capsule is gel firmly adherent to cell envelope. Slime is gel easily washed off from cell envelope. All bacteria have at least a thin slime layer. Capsule is composed of polysaccharide and protein(D-Glutamate of Bacillus anthracis)
Features of capsule
Usually weakly antigenic.
Not necessary for viability.
Protects from phagocytosis.
Capsulated strains are invariably non-motile.
Visualized by negative staining and capsule staining.
Detected by quellung phenomenon.