Division of Microbiology, Department of Botany, Government Motilal Science College, Bhopal 462003, Madhya Pradesh, India.
Ecotoxicol Environ Saf. 2013 Dec;98:345-51. doi: 10.1016/j.ecoenv.2013.09.004. Epub 2013 Sep 25.
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.
为了了解蓝藻念珠藻在固氮和非固氮培养条件下碳氮代谢是如何被调控的，我们研究了碳酸氢盐（HCO₃⁻）在调控固氮和自养中的作用。结果表明，HCO₃⁻浓度高达 12 mol m⁻³可促进固氮生长条件下的生长、比生长速率、光合色素、光合 O₂ 释放和固氮酶活性。生长培养基中存在不同氮源的共存进一步按 NO₃⁻<NO₂⁻<NH₄⁺<脯氨酸的顺序加速了所检测参数的增长。此外，我们还研究了在固氮和非固氮培养条件下，HCO₃⁻浓度逐渐增加时，Ca⁺⁺依赖性 ATP 酶活性和细胞色素 c 氧化酶活性。在高浓度 HCO₃⁻下生长的细胞中，这些酶的活性更高。当以 NAPH 作为电子供体时，Ca⁺⁺依赖性 ATP 酶活性高于细胞色素 c 氧化酶活性。这一发现表明，光合生成的 ATP 利用 NADPH 作为电子供体，而细胞色素 c 氧化酶的活性不依赖于 NADPH。
