General characteristic features of Bacteria

Bacteria share a consistent set of general features. They are prokaryotic, so they lack a nuclear membrane and any membrane-bound organelles. Their genetic material is not enclosed in a nucleus but sits free in the cytoplasm as a structure called the nucleoid, genophore or 'incipient nucleus'. Their cell wall is chemically built from polysaccharides and proteins. Most bacteria lack chlorophyll and are therefore heterotrophic (e.g. Vibrio cholerae), though some are autotrophic and carry bacteriochlorophyll instead (e.g. Chromatium). They reproduce vegetatively by binary fission and, under stress, by forming endospores, and they generate genetic variation not through true sex but through recombination achieved via conjugation, transformation and transduction. Bacterial cells also vary a great deal in outward shape (coccus/spherical, bacillus/rod, spirillum/spiral, vibrio/comma-shaped, and clustered forms like diplococcus, streptococcus, staphylococcus, tetracoccus and sarcina) and in how their flagella ar …