L-form bacteria

Some strains of bacteria lack cell wall. They are called L-form bacteria or L-phase bacteria or cell wall deficient bacteria. A German microbiologist Emmy Klieneberger-Nobel, working at Lister institute in London, had first isolated them and named them L-form, after her institute name. They are generated from the bacterial species that usually have the cell walls like Escherichia coli and Bacillus subtilis. L-form can be generated from the cell wall containing bacteria by treating them with lysozyme (an enzyme that digests cell wall) or by inhibiting the peptidoglycan synthesis with antibiotics. The morphology of L-form differs from the strain from which they are derived and they are generally spheres or spheroids in shape. For example, the L-form of Bacillus subtilis appears round in shape. 

Note: Mycoplasma differs from L-form. Both of them lacks the cell wall but later are derived from the cell wall containing bacteria.