Index >>Prokaryotes Microbes >> Spheroplasts

These cells without cell walls have been designated as stable L-forms. L-forms can be selected by, cultivation of bacteria on an osmotically buffered penicillin containing medium. L-forms are, therefore, bacteria in which the primer for peptidoglycan has either been eliminated or modified by penicillin treatment. L-form can be obtained from both Gram positive and Gram negtive bacteria. Stable L-forms obtained from animal and man are different from mycoplasmas

Recent genetic studies have shown that L-forms are different from mycoplasma. For example, DNA base composition of Mycoplasma species ranges from 23 to 36 (39-41 in M. pneumoniae) mole per cent GC. whereas most other bacteria and the L-forms usually have higher per cent GC content (63-64 mole per cent GC). L-forms are formed in Mycobacterium tuberculosis. Streptococcus and othe S. Some bacteria undergo spontaneous mutation to loss of cell walls. For example, if DAP is witheld from the medium, which is osmotically protective, the bacteria grow without a cell wall  i.e. they are L-forms of the bacteria.