Impact of pH on growth and survival of wild type , MHR (multiple herbicide resistant) and various class of salt/osmotolerant strains of diazotrophic cyanobacterium Anabaena variabilis
Nandita Singh* and Surendra Singh**
*Chhattisgarh Environment conservation Board Raipur-495677 (India) **Department of Biological Sciences, Rani Durgavati University, Jabalpur-482001 (India)
ABSTRACT
Cyanobacteria,an ubiquitous group of soil micro-organism, specially in flooded rice fields. The rice field ecosystem provides a favourable environment for the growth of cyanobacteria. In rice paddy fields, they contribute to soil fertilization by supplying nitrogen derived from atmospheric nitrogen fixation. Soil pH also has a selective effect on the distribution and predominance of algae. Although pH specific cyanobacteria growing at pH as low as 3.8 and high as 9.5 are not rare. Most of them have a wide pH range showing good growth at 6.5 – 8.5. The pH of natural habitats is known to vary from 1 to 11 and the organisms growing there are expected to have evolved mechanisms of pH homeostasis to overcome the adversity of external pH on their growth and survival. Our results indicate that pH of 6.0 and 12.0 proved lethal for wild type, MHR(multiple herbicide resistant) and salt/osmotolerant strains, whereas at pH 7.0 gradual increase in growth was observed. On the basis of all parameters it can be concluded that the sensitivity of wild type and MHR (multiple herbicide resistant) strains of Anabaena variabilis towards acidic and alkaline pH is higher as compared to other salt/osmotolerant strains, which promotes their application as biofertilizer where the soil is acidic and alkaline.