Ilikchyan Irina N, McKay Robert Michael L, Kutovaya Olga A, Condon Rob, Bullerjahn George S
Department of Biological Sciences, Bowling Green State University Bowling Green, OH, USA.
Front Microbiol. 2010 Dec 14;1:135. doi: 10.3389/fmicb.2010.00135. eCollection 2010.
In phosphorus-limited marine environments, picocyanobacteria (Synechococcus and Prochlorococcus spp.) can hydrolyze naturally occurring phosphonates as a P source. Utilization of 2-aminoethylphosphonate (2-AEP) is dependent on expression of the phn genes, encoding functions required for uptake, and C-P bond cleavage. Prior work has indicated that expression of picocyanobacterial phnD, encoding the phosphonate binding protein of the phosphonate ABC transporter, is a proxy for the assimilation of phosphonates in natural assemblages of Synechococcus spp. and Prochlorococcus spp (Ilikchyan et al., 2009). In this study, we expand this work to assess seasonal phnD expression in the Sargasso Sea. By RT-PCR, our data confirm that phnD expression is constitutive for the Prochlorococcus spp. detected, but in Synechococcus spp. phnD transcription follows patterns of phosphorus availability in the mixed layer. Specifically, our data suggest that phnD is repressed in the spring when P is bioavailable following deep winter mixing. In the fall, phnD expression follows a depth-dependent pattern reflecting depleted P at the surface following summertime drawdown, and elevated P at depth.
在磷限制的海洋环境中，聚球蓝细菌（聚球藻属和原绿球藻属）可以将天然存在的膦酸盐水解为磷源。2-氨基乙基膦酸盐（2-AEP）的利用取决于phn基因的表达，这些基因编码摄取和碳-磷键裂解所需的功能。先前的研究表明，聚球蓝细菌phnD的表达（编码膦酸盐ABC转运蛋白的膦酸盐结合蛋白）可作为聚球藻属和原绿球藻属自然群落中膦酸盐同化作用的一个指标（伊利克奇扬等人，2009年）。在本研究中，我们扩展了这项工作，以评估马尾藻海中phnD的季节性表达。通过逆转录聚合酶链反应（RT-PCR），我们的数据证实，对于检测到的原绿球藻属，phnD的表达是组成型的，但在聚球藻属中，phnD的转录遵循混合层中磷的可利用模式。具体而言，我们的数据表明，在深冬混合后春季磷可生物利用时，phnD受到抑制。在秋季，phnD的表达遵循深度依赖模式，反映了夏季消耗后表层磷的耗尽以及深层磷的升高。
