Occurrence and induction of a ultraviolet‐absorbing substance in the cyanobacterium Fischerella muscicola TISTR8215

The filamentous cyanobacterium Fischerella muscicola TISTR8215 was tested for the presence of ultraviolet (UV)‐absorbing mycosporine‐like amino acids (MAAs) and their induction by UV radiation. Reverse‐phase high performance liquid chromatographic coupled with photodiode‐array detection studies revealed the presence of a MAA having an absorption maximum at 332 nm and a retention time of around 16.1 min. Based on absorption maximum, the compound was designated as M‐332. This is the first report for the occurrence of a MAA and its inducibility as influenced by UV radiation in Fischerella strains studied so far. Photosynthetically active radiation (PAR) had no significant impact on MAA induction. PAR + UV‐A radiation significantly induced the synthesis of M‐332; however, PAR + UV‐A + UV‐B radiation conferred highest impact on MAA synthesis. The cultures exposed to alternate light and dark conditions showed the induction of M‐332 synthesis mostly during the light period in contrast to the decreased levels of M‐322 during the dark period suggesting a circadian induction of its synthesis. Overall results indicate that F. muscicola may protect itself from deleterious short wavelength UV radiation by synthesizing the photoprotective compounds particularly during summer time in its natural brightly‐lit habitats.