System analysis of salt and osmotic stress induced proteins in Nostoc muscorum and Bradyrhizobium japonicum.

In this study the proteome response of the two diazotrophic organism's viz. Nostoc muscorum and Bradyrhizobium japonicum exposed to salt (NaCl) and osmotic (sucrose) stresses was compared. Out of the total over expressed proteins; we have selected only three over expressed proteins viz. GroEL chaperonin, nitrogenase Mo-Fe protein and argininosuccinate synthase for further analysis, and then we analyzed the amino acid frequencies of all the three over expressed proteins. That led to the conclusion that amino acids e.g. alanine, glycine and valine that were energetically cheaper to produce were showing higher frequencies. This study would help in tracing the phylogenetic relationship between protein families.

Carbon dioxide regulation of autotrophy and diazotrophy in the nitrogen-fixing cyanobacterium Nostoc muscorum.

To understand how carbon and nitrogen metabolism are regulated in diazotrophically and non-diazotrophically grown cultures of the cyanobacterium Nostoc muscorum, we investigated the role of bicarbonate (HCO3⁻) in regulating diazotrophy and autotrophy. Results showed that HCO3⁻ concentration up to 12 mol m⁻³ enhanced growth, specific growth rate, photosynthetic pigments, photosynthetic O2 evolution and nitrogenase activity under diazotrophic growth conditions. The co-existence of different nitrogen sources in the growth medium further accelerate the examined parameters in the order of NO3⁻