Li H, Sherman D M, Bao S, Sherman L A
Purdue University, Department of Biological Sciences, Lilly Hall, West Lafayette, IN 47907, USA.
Arch Microbiol. 2001 Jul;176(1-2):9-18. doi: 10.1007/s002030100281.
The temporal and spatial accumulation of cyanophycin was studied in two unicellular strains of cyanobacteria, the diazotrophic Cyanothece sp. strain ATCC 51142 and the non-diazotrophic Synechocystis sp. strain PCC 6803. Biochemistry and electron microscopy were used to monitor the dynamics of cyanophycin accumulation under nitrogen-sufficient and nitrogen-deficient conditions. In Cyanothece sp. ATCC 51142 grown under 12 h light/12 h dark nitrogen-fixing conditions, cyanophycin was temporally regulated relative to nitrogenase activity and accumulated in granules after nitrogenase activity commenced. Cyanophycin granules reached a maximum after the peak of nitrogenase activity and eventually were utilized completely. Knock-out mutants were constructed in Synechocystis sp. PCC 6803 cphA and cphB genes to analyze the function of these genes and cyanophycin accumulation under nitrogen-deficient growth conditions. The mutants grew under such conditions, but needed to degrade phycobilisomes as a nitrogen reserve. Granules could be seen in some wild-type cells after treatment with chloramphenicol, but were never found in Delta cphA and Delta cphB mutants. These results led to the conclusion that cyanophycin is temporally and spatially regulated in nitrogen-fixing strains such as Cyanothece sp. ATCC 51142 and represents a key nitrogen reserve in these organisms. However, cyanophycin appeared to play a less important role in the non-diazotrophic unicellular strains and phycobilisomes appeared to be the main nitrogen reserve.
在两种单细胞蓝细菌菌株中研究了藻青素的时空积累情况，这两种菌株分别是固氮的蓝囊藻属（Cyanothece sp.）菌株ATCC 51142和非固氮的聚球藻属（Synechocystis sp.）菌株PCC 6803。利用生物化学和电子显微镜技术监测在氮充足和氮缺乏条件下藻青素积累的动态变化。在12小时光照/12小时黑暗的固氮条件下生长的蓝囊藻属ATCC 51142中，藻青素相对于固氮酶活性进行时间调控，并在固氮酶活性开始后在颗粒中积累。藻青素颗粒在固氮酶活性达到峰值后达到最大值，最终被完全利用。在聚球藻属PCC 6803的cphA和cphB基因中构建了敲除突变体，以分析这些基因的功能以及在氮缺乏生长条件下藻青素的积累情况。这些突变体在这种条件下生长，但需要降解藻胆体作为氮储备。用氯霉素处理后，在一些野生型细胞中可以看到颗粒，但在ΔcphA和ΔcphB突变体中从未发现。这些结果得出结论，藻青素在诸如蓝囊藻属ATCC 51142这样的固氮菌株中受到时间和空间调控，并且是这些生物体中的关键氮储备。然而，藻青素在非固氮单细胞菌株中似乎发挥的作用较小，藻胆体似乎是主要的氮储备。
