Responses of antioxidants for resilience to temporal variations in the cyanobacterium Microcystis aeruginosa
Minu Kesheri, Swarna Kanchan, Rajeshwar P. Sinha
Abstract
The responses of antioxidants and photosynthetic pigments to temporal variations in the bloom- forming cyanobacterium Microcystis aeruginosa dominating the eutrophic pond were investigated. Native-PAGE of superoxide dismutase (SOD) enzyme profile elucidated that while isoform number 1 identified as Fe-SOD showed its recurrent presence in all the three seasons, isoform 2 identified as Fe-SOD and isoform 3 as Mn-SOD were observed only in rainy season. However, densitometry analyses illustrated specific seasonal variations in the intensity of Fe-SOD isoform 1, with its intensity being the highest in winter season followed by rainy and summer seasons respectively. Interestingly, native-PAGE enzyme profile depicted the presence of three isoforms of catalase enzyme during rainy season while it was absent during winter and summer seasons. Correlogram elucidated that antioxidative enzymes SOD and catalase were positively correlated to phycocyanin while they remained negatively correlated to other polar and non-polar solvent soluble photosynthetic pigments. Good quality 3D models of Fe-SOD and Mn-SOD in Microcystis aeruginosa were generated by homology modeling. All metal binding positions were highly conserved and protein-protein interactions were also observed. The phylogenetic tree revealed that Microcystis sp. T1-4 is closest evolutionary homolog of Fe-SOD and Mn-SOD in Microcystis aeruginosa. Principal component analyses illustrated that enzymatic and non-enzymatic antioxidants contribute jointly and specifically to combat oxidative stress, may serve as biomarker of environmental cues and may be exploited for further biotechnological applications.