Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chilegrid.7870.8, Santiago, Chile.
Department of Oceanography, Universidad de Concepción, Concepción, Chile.
mSphere. 2021 Aug 25;6(4):e0052521. doi: 10.1128/mSphere.00525-21. Epub 2021 Aug 18.
Microbial proton-pumping rhodopsins are considered the simplest strategy among phototrophs to conserve energy from light. Proteorhodopsins are the most studied rhodopsins thus far because of their ubiquitous presence in the ocean, except in Antarctica, where they remain understudied. We analyzed proteorhodopsin abundance and transcriptional activity in the Western Antarctic coastal seawaters. Combining quantitative PCR (qPCR) and metagenomics, the relative abundance of proteorhodopsin-bearing bacteria accounted on average for 17, 3.5, and 29.7% of the bacterial community in Chile Bay (South Shetland Islands) during 2014, 2016, and 2017 summer-autumn, respectively. The abundance of proteorhodopsin-bearing bacteria changed in relation to environmental conditions such as chlorophyll and temperature. , , and were the main bacteria that transcribed the proteorhodopsin gene during day and night. Although green light-absorbing proteorhodopsin genes were more abundant than blue-absorbing ones, the latter were transcribed more intensely, resulting in >50% of the proteorhodopsin transcripts during the day and night. were the most abundant proteorhodopsin-bearing bacteria in the metagenomes; however, and were more represented in the metatranscriptomes, with qPCR quantification suggesting the dominance of the active SAR11 clade. Our results show that proteorhodopsin-bearing bacteria are prevalent in Antarctic coastal waters in late austral summer and early autumn, and their ecological relevance needs to be elucidated to better understand how sunlight energy is used in this marine ecosystem. Proteorhodopsin-bearing microorganisms in the Southern Ocean have been overlooked since their discovery in 2000. The present study identify taxonomy and quantify the relative abundance of proteorhodopsin-bearing bacteria and proteorhodopsin gene transcription in the West Antarctic Peninsula's coastal waters. This information is crucial to understand better how sunlight enters this marine environment through alternative ways unrelated to chlorophyll-based strategies. The relative abundance of proteorhodopsin-bearing bacteria seems to be related to environmental parameters (e.g., chlorophyll , temperature) that change yearly at the coastal water of the West Antarctic Peninsula during the austral late summers and early autumns. Proteorhodopsin-bearing bacteria from Antarctic coastal waters are potentially able to exploit both the green and blue spectrum of sunlight and are a prevalent group during the summer in this polar environment.
微生物质子泵感红发光蛋白被认为是光合生物中从光中储存能量的最简单策略。目前为止，研究最多的是变形菌视紫红质，因为它们在海洋中无处不在，除了南极洲，那里的研究仍然很少。我们分析了西南极沿海海水中的视紫红质的丰度和转录活性。结合定量 PCR(qPCR)和宏基因组学，2014 年、2016 年和 2017 年夏秋季，在智利湾(南设得兰群岛)，携带视紫红质的细菌相对丰度分别占细菌群落的 17%、3.5%和 29.7%。携带视紫红质的细菌的丰度随叶绿素和温度等环境条件的变化而变化。在白天和黑夜， 、 和 是转录视紫红质基因的主要细菌。虽然绿光吸收的视紫红质基因比蓝光吸收的更丰富，但后者的转录强度更高，导致白天和黑夜的视紫红质转录物超过 50%。在宏基因组中， 是携带视紫红质的最丰富的细菌;然而，在宏转录组中， 和 更具代表性，qPCR 定量表明活跃的 SAR11 分支的优势。我们的结果表明，视紫红质细菌在南极沿海水域的晚夏初秋很常见，需要阐明它们的生态相关性，以更好地了解阳光能量如何在这个海洋生态系统中被利用。自 2000 年发现以来，南大洋的含视紫红质微生物一直被忽视。本研究确定了南极半岛西部沿海水域携带视紫红质的微生物的分类，并量化了携带视紫红质的细菌的相对丰度和视紫红质基因的转录。这些信息对于更好地理解阳光如何通过与叶绿素无关的替代途径进入这个海洋环境至关重要。携带视紫红质的细菌的相对丰度似乎与环境参数(如叶绿素、温度)有关，这些参数在南极半岛西部沿海水域每年的夏末初秋都会发生变化。南极沿海水域的含视紫红质细菌有可能利用绿光和蓝光光谱，并且在这个极地环境的夏季是一个普遍存在的群体。
