Who are the ubiquitous, biomass-significant red fluorescent picoplanktonic cells in temperate and polar surface oceans?

该提案的目的是确定包含大型浮游细菌的额外红色荧光组的细胞，并确定其代谢潜力。我们建议测试的假设，这些红色荧光细胞是有氧无氧光合浮游细菌（AAP）含有细菌叶绿素。以往的研究表明，AAP缺乏自养无机碳同化途径，不能光自养，依靠异养为他们的大部分细胞能量。然而，我们的临时测量的3 H-亮氨酸和35 S-甲硫氨酸的吸收由红色荧光细胞表明，这两种氨基酸的吸收率由这些细胞，虽然高于聚球藻光合蓝藻的吸收率，是大大低于平均异养浮游细菌细胞的氨基酸吸收率。因此，红色荧光细胞可能会收集光，以光化学氧化有机分子，以维持其在光温带和极地海洋中相当大的普遍存在的人口。该项目建议：（一）通过流式细胞术从大型浮游细菌的额外红色荧光组中分选出细菌遗传学上的附属细胞;（二）设计和测试用于鉴定流式分选细胞的特异性寡核苷酸探针;检查流式分选细胞中细菌叶绿素基因的存在;（三）检查红色荧光组系统发育组成的纬度变化。为了实现上述目标，我们将重点对在大西洋收集的样本进行分子分析，这些微生物是第一次观察到的。我们的最终目标是解释它们在海洋生态系统中的生态作用。

The aim of the proposal is to identify the cells comprising the extra red fluorescence group of large bacterioplankton and to ascertain their metabolic potential. We propose to test a hypothesis that these red fluorescent cells are aerobic anoxygenic phototrophic bacterioplankton (AAPs) containing bacteriochlorophylls. Previous studies show that AAPs lack autotrophic inorganic carbon assimilation pathways and are incapable of photoautotrophy, relying on heterotrophy for the majority of their cellular energetics. However, our provisional measurements of 3H-leucine and 35S-methionine uptake by the red fluorescent cells suggested that the uptake rates of both amino acids by these cells, although being higher than the uptake rates by Synechococcus phototrophic cyanobacteria, are considerably lower than the amino acid uptake rates by mean heterotrophic bacterioplankton cells. Therefore, the red fluorescent cells probably harvest light to photochemically oxidise organic molecules in order to sustain their sizeable ubiquitous population in the photic temperate and polar ocean. The project proposes (i) to phylogenetically affiliate cells, flow cytometrically sorted from the extra red fluorescence group of large bacterioplankton; (ii) to design and test specific oligonucleotide probes for identification of flow sorted cells; to examine the presence of bacteriochlorophyll genes in flow sorted cells; (iii) to examine latitudinal variations in phylogenetic composition of the red fluorescence group. In order to meet the above objectives we will focus on molecular analysis of samples collected in the Atlantic Ocean, where these microorganisms were first observed. Our ultimate goal is to explain their ecological role in oceanic ecosystems.