A STUDY OF LIFE CYCLE FEATURES OF THREE STRAINS OF CYANOBACTERIA NOSTOC CF. PUNCTIFORME VAUCH

Abstract

The article presents the study of the life cycle of three strains (Pk20j, Ch55 and Sv31j) of filamentous nitrogen-fixing cyanobacteria Nostoccf. punctiforme Vauch. The wide distribution, high adaptation potential, tolerance to the artificial cultivation conditions, high growth rates and peculiar features of physiological and biochemical processes (propensity for oxygenate photosynthesis, nitrogen fixation, etc.) make these microorganisms a convenient biotechnological object of research. Although Nostoc cf. punctiforme can find use in various fields of biotechnology, its life cycle is still poorly understood. The methods of the study were the pendent drop method and the microscope observation of bacterial cultures inoculated into fresh Gromov’s medium No. 6. It was found that all the strains of cyanobacteria passed through several stages of development: the formation of hormogonia (status oscillatorioideus orsecondary hormogonia, day 2), the germination of hormogonia (statusoscillatorioideus, statuscylindrospermoideus and status anabaenoideus,days 2-5), the transition from filaments to colonies (status angulato-flexuosus, days 5-17), and the formation of colonies (status punctiforme, from day14 to more than a month; statussphaericus, status stratosus). The time of development in the laboratory heterogeneous population increases by 2-3 days as compared with the development of isolated hormogonia. The reproduction by secondary hormogonia can begin at any stage of the life cycle. Also, the three strains demonstrated different patterns of heterocyst formation. The obtained results indicate that cultivation conditions affect the life cycle of cyanobacteria and strains, isolated from different habitats, have intraspecific variability.