Surface ultrastructure of the heteromorphic cells of Nostoc muscorum CALU 304 in a mixed culture with the Rauwolfia callus tissue

The ultrastructure of the heteromorphic cells (HMCs) of the cyanobacterium Nostoc muscorum CALU 304 grown in pure culture, monoculture, and a mixed cu lture with the Rauwolfia callus tissue was studied. The comparative analysi s of the cell surface of HMCs, the frequency of the generation of cell form s with defective cell walls (DCWFs), including protoplasts and spheroplasts , and the peculiarities of their ultrastructure under different growth cond itions showed that, in the early terms of mixed incubation, the callus tiss ue acts to preserve the existing cyanobacterial DCWFs, but begins to promot e their formation in the later incubation terms. DCWFs exhibited an integri ty of their protoplasm and were metabolically active. It is suggested that structural alterations in the rigid layer of the cell wall may be due to th e activation of the murolytic enzymes of cyanobacteria and the profound rea rrangement of their peptidoglycan metabolism caused by the Rauwolfia metabo lites diffused through the medium. These metabolites may also interfere wit h the functioning of the universal cell division protein of bacteria, FtsZ. In general, the Rauwolfia callus tissue promoted the unbalanced growth of the cyanobacterium N. muscorum CALU 304 and favored its viability in the mi xed culture. The long-term mixed cultivation substantially augmented the pr obability of the formation of L-forms of N. muscorum CALU 304.