Fuszard Matthew A, Wright Phillip C, Biggs Catherine A
ChELSI Institute, Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK.
Aquat Biosyst. 2012 Mar 19;8(1):7. doi: 10.1186/2046-9063-8-7.
The well-lit surface waters of oligotrophic gyres significantly contribute to global primary production. Marine cyanobacteria of the genus Prochlorococcus are a major fraction of photosynthetic organisms within these areas. Labile phosphate is considered a limiting nutrient in some oligotrophic regions such as the Caribbean Sea, and as such it is crucial to understand the physiological response of primary producers such as Prochlorococcus to fluctuations in the availability of this critical nutrient.
Prochlorococcus strains representing both high light (HL) (MIT9312) and low light (LL) (NATL2A and SS120) ecotypes were grown identically in phosphate depleted media (10 μM Pi). The three strains displayed marked differences in cellular protein expression, as determined by high throughput large scale quantitative proteomic analysis. The only strain to demonstrate a significantly different growth rate under reduced phosphate conditions was MIT9312. Additionally, there was a significant increase in phosphate-related proteins such as PhoE (> 15 fold increase) and a depression of the Rubisco protein RbcL abundance in this strain, whereas there appeared to be no significant change within the LL strain SS120.
This differential response between ecotypes highlights the relative importance of phosphate availability to each strain and from these results we draw the conclusion that the expression of phosphate acquisition mechanisms are activated at strain specific phosphate concentrations.
贫营养环流中光照良好的表层水对全球初级生产有显著贡献。原绿球藻属的海洋蓝细菌是这些区域光合生物的主要组成部分。在一些贫营养区域，如加勒比海，不稳定磷酸盐被认为是一种限制性营养物质，因此了解原绿球藻等初级生产者对这种关键营养物质可利用性波动的生理反应至关重要。
代表高光（HL）（MIT9312）和低光（LL）（NATL2A和SS120）生态型的原绿球藻菌株在磷酸盐耗尽的培养基（10 μM Pi）中以相同方式培养。通过高通量大规模定量蛋白质组学分析确定，这三种菌株在细胞蛋白质表达上表现出显著差异。在磷酸盐减少条件下，唯一显示出显著不同生长速率的菌株是MIT9312。此外，该菌株中磷酸盐相关蛋白如PhoE显著增加（增加超过15倍），而核酮糖-1,5-二磷酸羧化酶蛋白RbcL丰度降低，而LL菌株SS120内似乎没有显著变化。
生态型之间的这种差异反应突出了磷酸盐可利用性对每个菌株的相对重要性，从这些结果我们得出结论，磷酸盐获取机制的表达在菌株特异性磷酸盐浓度下被激活。
