PDF(Pubmed)
Abstract：
One of the most hostile marine habitats on Earth is the surface of the South Pacific Gyre (SPG), characterized by high solar radiation, extreme nutrient depletion, and low productivity. During the SO-245 \"UltraPac\" cruise through the center of the ultra-oligotrophic SPG, the marine alphaproteobacterial group AEGEAN169 was detected by fluorescence in situ hybridization at relative abundances up to 6% of the total microbial community in the uppermost water layer, with two distinct populations (Candidatus Nemonibacter and Ca. Indicimonas). The high frequency of dividing cells combined with high transcript levels suggests that both clades may be highly metabolically active. Comparative metagenomic and metatranscriptomic analyses of AEGEAN169 revealed that they encoded subtle but distinct metabolic adaptions to this extreme environment in comparison to their competitors SAR11, SAR86, SAR116, and Prochlorococcus. Both AEGEAN169 clades had the highest percentage of transporters per predicted proteins (9.5% and 10.6%, respectively). In particular, the high expression of ABC transporters in combination with proteorhodopsins and the catabolic pathways detected suggest a potential scavenging lifestyle for both AEGEAN169 clades. Although both AEGEAN169 clades may share the genomic potential to utilize phosphonates as a phosphorus source, they differ in their metabolic pathways for carbon and nitrogen. Ca. Nemonibacter potentially use glycine-betaine, whereas Ca. Indicimonas may catabolize urea, creatine, and fucose. In conclusion, the different potential metabolic strategies of both clades suggest that both are well adapted to thrive resource-limited conditions and compete well with other dominant microbial clades in the uppermost layers of SPG surface waters.
摘要：
地球上最敌对的海洋栖息地之一是南太平洋环流（SPG）的表面，具有高太阳辐射的特点，营养极度枯竭和生产力低下。在SO-245“UltraPac”巡航通过超贫营养SPG中心期间，通过荧光原位杂交检测到海洋α-蛋白质细菌组AEGEAN169，其相对丰度高达最上层水层总微生物群落的6%，具有两个不同的种群（念珠菌Nemonibacter和Ca。Indimonas).分裂细胞的高频率与高转录水平相结合，这表明这两种进化枝可能具有高度代谢活性。AEGEAN169的比较宏基因组和代谢组学分析显示，与竞争对手SAR11，SAR86，SAR116和Prochloroccocus相比，它们对这种极端环境编码了微妙但独特的代谢适应。两种AEGEAN169进化枝每个预测蛋白的转运蛋白百分比最高（9.5％和10.6％，分别)。特别是,ABC转运蛋白与蛋白视紫红质的高表达和分解代谢途径的检测，建议两种AEGEAN169进化枝的潜在清除生活方式。尽管两个AEGEAN169进化枝可能共享利用膦酸盐作为磷源的基因组潜力，它们的碳和氮代谢途径不同。Ca.Nemonibacter可能使用甘氨酸甜菜碱，而Ca。氨单胞菌可能会分解尿素，肌酸,和狗娘养的。总之,两种进化枝的不同潜在代谢策略表明，两者都很好地适应了资源有限的条件，并与SPG地表水最上层的其他优势微生物进化枝竞争良好。
