Materials and methodsOrganisms and

Materials and methods
Organisms and growth conditions The four cyanobacteria
used in the study were collected from Meghalaya, India.
N. muscorum and A. variabilis were isolated from the water
collected from rice fields of Mawlai, Shillong, the nonheterocystous
filamentous Plectonema boryanum was isolated
from North-Eastern Hill University campus, Shillong, and
the branched heterocystous filamentous M. laminosus was
isolated from the hot spring at Jakrem, Meghalaya. These
(except M. laminosus) were grown in BG-110 in culture room
at 25±2 °C, pH 7.4, and in continuous light at a photon
fluence rate of 50 μmol photons m−2 s
−1 (Rippka et al.
1979). Batch cultures were maintained in culture room as
controls. M. laminosus was maintained at 45±2 °C inside a
B.O.D. incubator with all other conditions similar to the ones
used for the rest of the cyanobacteria.