title: Impacts of varying light regimes on phycobiliproteins of Nostoc sp. HKAR-2 and Nostoc sp. HKAR-11 isolated from diverse habitats.
abstract: The adaptability of cyanobacteria in diverse habitats is an important factor to withstand harsh conditions. In the present investigation, the impacts of photosynthetically active radiation (PAR; 400-700 nm), ultraviolet-B (UV-B; 280-315 nm), and PAR + UV-B radiations on two cyanobacteria viz., Nostoc sp. HKAR-2 and Nostoc sp. HKAR-11 inhabiting diverse habitats such as hot springs and rice fields, respectively, were studied. Cell viability was about 14 % in Nostoc sp. HKAR-2 and <10 % in Nostoc sp. HKAR-11 after 48 h of UV-B exposure. PAR had negligible negative impact on the survival of both cyanobacteria. The continuous exposure of UV-B and PAR + UV-B showed rapid uncoupling, bleaching, fragmentation, and degradation in both phycocyanin (C-PC) and phycoerythrin (C-PE) subunits of phycobiliproteins (PBPs). Remarkable bleaching effect of C-PE and C-PC was not only observed with UV-B or PAR + UV-B radiation, but longer period (24-48 h) of exposure with PAR alone also showed noticeable negative impact. The C-PE and C-PC subunits of the rice field isolate Nostoc sp. HKAR-11 were severely damaged in comparison to the hot spring isolate Nostoc sp. HKAR-2 with rapid wavelength shifting toward shorter wavelengths denoting the bleaching of both the accessory light harvesting pigments. The results indicate that PBPs of the hot spring isolate Nostoc sp. HKAR-2 were more stable under various light regimes in comparison to the rice field isolate Nostoc sp. HKAR-11 that could serve as a good source of valuable pigments to be used in various biomedical and biotechnological applications.
authors.affiliation: Laboratory of Photobiology and Molecular Microbiology, Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi, 221005, India.
authors.forename: Vinod K
authors.initials: VK
authors.lastname: Kannaujiya
authors.affiliation: Laboratory of Photobiology and Molecular Microbiology, Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi, 221005, India. r.p.sinha@gmx.net.
authors.forename: Rajeshwar P
authors.initials: RP
authors.lastname: Sinha
mesh_terms: D017753:Ecosystem; D045482:Hot Springs / Q000382:microbiology; D050296:Microbial Viability / Q000528:radiation effects; D046937:Nostoc / Q000145:classification / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D017440:Photoperiod; D010788:Photosynthesis / Q000528:radiation effects*; D052979:Phycobiliproteins / Q000378:metabolism*; D045524:Phycobilisomes / Q000378:metabolism / Q000528:radiation effects*; D010798:Phycocyanin / Q000378:metabolism; D010799:Phycoerythrin / Q000378:metabolism; D011489:Protein Denaturation; D055550:Protein Stability; D012988:Soil Microbiology; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014466:Ultraviolet Rays; D014871:Water Microbiology
chemical_list: D052979:Phycobiliproteins; D045524:Phycobilisomes; D010798:Phycocyanin; D010799:Phycoerythrin
keywords: Absorption; Cyanobacteria; Fluorescence; Phycocyanin; Phycoerythrin