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⁻<NO₂⁻<NH₄⁺<proline. Further, we examined the Ca⁺⁺-dependent ATPase activity and cytochrome c oxidase activity in the presence of graded concentration of HCO₃⁻ under diazotrophically grown and non-diazotrophically grown cultures. The activity of these enzymes was higher in the cells grown under elevated HCO₃⁻ concentration. The Ca⁺⁺-dependent ATPase activity was higher than that of cytochrome c oxidase, when NAPH was supplied as the electron donor. This finding suggested that photosynthetic generation of ATP utilized NADPH as an electron donor and cytochrome c oxidase activity is independent of NADPH.
Division of Microbiology, Department of Botany, Government Motilal Science College, Bhopal 462003, Madhya Pradesh, India. Electronic address: santoshbhargava@hotmail.com.
Santosh
S
Bhargava
Shweta
S
Chouhan
Vipin
V
Kaithwas
Rakesh
R
Maithil
D052818:Autotrophic Processes; D001639:Bicarbonates / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D045304:Cytochromes c / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D050502:Nostoc muscorum / Q000254:growth & development / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis; D010860:Pigments, Biological / Q000378:metabolism
D001639:Bicarbonates; D010860:Pigments, Biological; D002734:Chlorophyll; D002245:Carbon Dioxide; D045304:Cytochromes c; D009591:Nitrogenase; D000252:Calcium-Transporting ATPases; D009584:Nitrogen; D010100:Oxygen; D000077194:Chlorophyll A
Autotrophy; Cyanobacteria; Diazotrophy; Nostoc muscorum