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more about bacteria's structure.
Gram positive and Gram negative bacteria have similar internal, but very different external structures. The cytoplasm of the bacterial cell contains the DNA chromosome, the mRNA, ribosomes, proteins, and metabolites). Unlike eukaryotes, the bacterial chromosome is a single, double-stranded circle that is contained not in a nucleus but in a discrete area known as the nucleoid. Histones are not required to maintain the conformation of the DNA, and the DNA does not form nucleosomes. Plasmids, which are smaller, circular, extrachromosomal DNAs, may also be present. Plasmids are most commonly found in Gram negative bacteria, and although not usually essential for cellular survival, they often provide a selective advantage: many confer resistance to one or more antibiotics.
A Gram positive bacterium has a thick layer of peptidoglycan . A Gram negative bacterium has a thin peptidoglycan layer and an outer membrane .


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