Structural, functional and molecular basis of cyanophage-cyanobacterial interactions and its significance

Abstract

The cyanophages are double-stranded deoxyribonucleic acid (ds-DNA) viruses, infecting cyanobacteria which are the first oxygenic photosynthesizers and significant nitrogen fixers of the biosphere. The evolutionary findings of the cyanophages do not truly reflect their actual time of origin. They show extreme diversification in morphology, habitat, host range and molecular attributes. They infect and establish an association with the cyanobacterial cells through one of the two modes of multiplication, that is, lytic or lysogenic type which might be dependent upon the environmental signals, such as nutritional status, the presence of any pathogenic condition and the relative concentration of either the control of repressor's operator/clear 1 (Cro/CI) protein that embody the bistable genetic switched regulators that are responsible to a large extent for the functioning of any of the above cycle. Various environmental factors that affect the stability and sustenance of the phages were meticulously reviewed. Genetic exchange and gene shuffling might be responsible for the enormous structural, functional, ecological and molecular diversity of the cyanophages. The cyanophages maintain the ecological equilibrium by keeping the nutrient cycling and microbial diversity at an appropriate level. Therefore, this review covers all the known, lesser acknowledged facets related to phage biology and clearly emphasizes the need for advanced molecular studies on the cyanophage-cyanobacterial association.