Popendorf Kimberly J, Duhamel Solange
Lamont-Doherty Earth Observatory, Division of Biology and Paleo Environment, Columbia University, Palisades, NY, 10964, USA.
Environ Microbiol. 2015 Oct;17(10):3992-4006. doi: 10.1111/1462-2920.12932. Epub 2015 Jul 30.
Microbial uptake of dissolved phosphorus (P) is an important lever in controlling both microbial production and the fate and cycling of marine P. We investigated the relative role of heterotrophic bacteria and phytoplankton in P cycling by measuring the P uptake rates of individual microbial groups (heterotrophic bacteria and the phytoplankton groups Synechococcus, Prochlorococcus and picoeukaryotic phytoplankton) in the P-depleted Gulf of Mexico. Phosphorus uptake rates were measured using incubations with radiolabelled phosphate and adenosine triphosphate coupled with cell sorting flow cytometry. We found that heterotrophic bacteria were the dominant consumers of P on both a biomass basis and a population basis. Biovolume normalized heterotrophic bacteria P uptake rate per cell (amol P μm(-3) h(-1)) was roughly an order of magnitude greater than phytoplankton uptake rates, and heterotrophic bacteria were responsible for generally greater than 50% of total picoplankton P uptake. We hypothesized that this variation in uptake rates reflects variation in cellular P allocation strategies, and found that, indeed, the fraction of cellular P uptake utilized for phospholipid production was significantly higher in heterotrophic bacteria compared with cyanobacterial phytoplankton. These findings indicate that heterotrophic bacteria have a uniquely P-oriented physiology and play a dominant role in cycling dissolved P.
微生物对溶解态磷（P）的摄取是控制微生物生产以及海洋磷的归宿和循环的一个重要因素。我们通过测量墨西哥湾贫磷区域中各个微生物类群（异养细菌以及浮游植物类群聚球藻、原绿球藻和微微型真核浮游植物）的磷摄取率，研究了异养细菌和浮游植物在磷循环中的相对作用。磷摄取率通过用放射性标记的磷酸盐和三磷酸腺苷进行培养并结合细胞分选流式细胞术来测量。我们发现，无论是基于生物量还是基于种群数量，异养细菌都是磷的主要消费者。以生物体积归一化的异养细菌每细胞磷摄取率（amol P μm(-3) h(-1)）大约比浮游植物摄取率高一个数量级，并且异养细菌通常占微微型浮游生物总磷摄取量的50%以上。我们推测这种摄取率的差异反映了细胞磷分配策略的差异，并且发现，实际上，与蓝藻浮游植物相比，异养细菌用于磷脂生产的细胞磷摄取比例显著更高。这些发现表明，异养细菌具有独特的以磷为导向的生理学特性，并且在溶解态磷的循环中起主导作用。
