Biochemical and spectroscopic characterization of the cyanobacterium Lyngbya sp. inhabiting mango (Mangifera indica) trees: presence of an ultraviolet-absorbing pigment, scytonemin.
Sinha R. P., Klisch M., Akhouri Vaishampayan, Häder D. P.
Author Affiliation: Institut für Botanik und Pharmazeutische Biologie, Friedrich-Alexander-Universität, Staudtstr. 5, D-91058 Erlangen, Germany.
Acta Protozoologica 38 : 291-298
Abstract : Dried, yellow-brown, leathery mats of a cyanobacterium were collected from the bark of mango (Mangifera indica) trees and characterized by biochemical and spectroscopic methods. Based on morphological characteristics, the strain was identified as Lyngbya sp., a filamentous and non-heterocystous cyanobacterium belonging to the order Oscillatoriales. The sheath of Lyngbya sp. was typically colored by a yellow-brown, UV-absorbing pigment, scytonemin. The phycobiliproteins from Lyngbya sp. were separated into six vividly colored fractions by sucrose density gradient ultracentrifugation. SDS-PAGE analyses of the fractions revealed the presence of ? and ? subunits of phycocyanin (around 20 kDa) and phycoerythrin (around 22 kDa). In addition, the mostly non-pigmented rod and rod-core (molecular masses between 24 and 45 kDa) and core-membrane (molecular masses around 66 kDa) linker polypeptides were also detected on SDS-PAGE. Spectroscopic analyses of the fractions also confirmed the presence of phycobiliproteins viz., phycoerythrin (560 nm), phycocyanin (620 nm) and allophycocyanin (650 nm). HPLC analysis of the samples revealed the existence of UV-absorbing/screening pigment, scytonemin, with an absorption maximum at 386 nm in the UV-A (315-400 nm) range. In addition, the purified scytonemin also absorbed significantly in the UV-B (280-315 nm) and UV-C (100-280 nm) regions with peaks at 300, 278, 252 and 212 nm. The presence of mycosporines could not be detected.