Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America.
Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
PLoS One. 2020 Aug 27;15(8):e0234839. doi: 10.1371/journal.pone.0234839. eCollection 2020.
Distinct lineages of Gammaproteobacteria clade Woeseiales are globally distributed in marine sediments, based on metagenomic and 16S rRNA gene analysis. Yet little is known about why they are dominant or their ecological role in Arctic fjord sediments, where glacial retreat is rapidly imposing change. This study combined 16S rRNA gene analysis, metagenome-assembled genomes (MAGs), and genome-resolved metatranscriptomics uncovered the in situ abundance and transcriptional activity of Woeseiales with burial in four shallow sediment sites of Kongsfjorden and Van Keulenfjorden of Svalbard (79°N). We present five novel Woeseiales MAGs and show transcriptional evidence for metabolic plasticity during burial, including sulfur oxidation with reverse dissimilatory sulfite reductase (dsrAB) down to 4 cm depth and nitrite reduction down to 6 cm depth. A single stress protein, spore protein SP21 (hspA), had a tenfold higher mRNA abundance than any other transcript, and was a hundredfold higher on average than other transcripts. At three out of the four sites, SP21 transcript abundance increased with depth, while total mRNA abundance and richness decreased, indicating a shift in investment from metabolism and other cellular processes to build-up of spore protein SP21. The SP21 gene in MAGs was often flanked by genes involved in membrane-associated stress response. The ability of Woeseiales to shift from sulfur oxidation to nitrite reduction with burial into marine sediments with decreasing access to overlying oxic bottom waters, as well as enter into a dormant state dominated by SP21, may account for its ubiquity and high abundance in marine sediments worldwide, including those of the rapidly shifting Arctic.
基于宏基因组和 16S rRNA 基因分析，变形菌门 Woeseiales 分支的不同谱系在全球海洋沉积物中分布广泛。然而，人们对它们为何占优势，以及在冰川退缩导致迅速变化的北极峡湾沉积物中它们的生态作用知之甚少。本研究结合 16S rRNA 基因分析、宏基因组组装基因组（MAG）和基因组解析宏转录组学，在斯瓦尔巴特群岛 Kongsfjorden 和 Van Keulenfjorden 的四个浅层沉积物位点，揭示了 Woeseiales 在埋藏过程中的原位丰度和转录活性。我们提出了五个新的 Woeseiales MAG，并展示了埋藏过程中代谢可塑性的转录证据，包括通过反向异化亚硫酸盐还原酶（dsrAB）氧化硫，直至 4 厘米深度，以及亚硝酸盐还原，直至 6 厘米深度。一种单一的应激蛋白，孢子蛋白 SP21（hspA），其 mRNA 丰度比任何其他转录本高十倍，平均比其他转录本高一百倍。在四个地点中的三个地点，SP21 转录本丰度随深度增加而增加，而总 mRNA 丰度和丰富度下降，表明代谢和其他细胞过程的投资向孢子蛋白 SP21 的积累转移。MAG 中的 SP21 基因通常被参与膜相关应激反应的基因包围。Woeseiales 能够从硫氧化转变为硝酸盐还原，随着埋藏进入海洋沉积物，与上覆含氧底层水的接触减少，并进入以 SP21 为主导的休眠状态，这可能解释了其在全球海洋沉积物中的普遍存在和高丰度，包括在快速变化的北极地区。
