Ferrieux Mathilde, Dufour Louison, Doré Hugo, Ratin Morgane, Guéneuguès Audrey, Chasselin Léo, Marie Dominique, Rigaut-Jalabert Fabienne, Le Gall Florence, Sciandra Théo, Monier Garance, Hoebeke Mark, Corre Erwan, Xia Xiaomin, Liu Hongbin, Scanlan David J, Partensky Frédéric, Garczarek Laurence
Sorbonne Université, CNRS, UMR 7144 Adaptation and Diversity in the Marine Environment (AD2M), Station Biologique de Roscoff (SBR), Roscoff, France.
Sorbonne Université, CNRS, UMR 7621 Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique de Banyuls/mer, Banyuls, France.
Front Microbiol. 2022 May 9;13:893413. doi: 10.3389/fmicb.2022.893413. eCollection 2022.
Marine cyanobacteria are ubiquitous in the ocean, a feature likely related to their extensive genetic diversity. Amongst the major lineages, clades I and IV preferentially thrive in temperate and cold, nutrient-rich waters, whilst clades II and III prefer warm, nitrogen or phosphorus-depleted waters. The existence of such cold (I/IV) and warm (II/III) thermotypes is corroborated by physiological characterization of representative strains. A fifth clade, CRD1, was recently shown to dominate the community in iron-depleted areas of the world ocean and to encompass three distinct ecologically significant taxonomic units (ESTUs CRD1A-C) occupying different thermal niches, suggesting that distinct thermotypes could also occur within this clade. Here, using comparative thermophysiology of strains representative of these three CRD1 ESTUs we show that the CRD1A strain MITS9220 is a warm thermotype, the CRD1B strain BIOS-U3-1 a cold temperate thermotype, and the CRD1C strain BIOS-E4-1 a warm temperate stenotherm. Curiously, the CRD1B thermotype lacks traits and/or genomic features typical of cold thermotypes. In contrast, we found specific physiological traits of the CRD1 strains compared to their clade I, II, III, and IV counterparts, including a lower growth rate and photosystem II maximal quantum yield at most temperatures and a higher turnover rate of the D1 protein. Together, our data suggests that the CRD1 clade prioritizes adaptation to low-iron conditions over temperature adaptation, even though the occurrence of several CRD1 thermotypes likely explains why the CRD1 clade as a whole occupies most iron-limited waters.
海洋蓝细菌在海洋中无处不在，这一特征可能与其广泛的遗传多样性有关。在主要谱系中，第一和第四进化枝优先在温带和寒冷、营养丰富的水域中生长，而第二和第三进化枝则偏好温暖、氮或磷含量低的水域。代表性菌株的生理特征证实了这种冷型（第一/第四）和暖型（第二/第三）的存在。最近发现，第五进化枝CRD1在世界海洋缺铁区域的群落中占主导地位，包含三个不同的具有生态意义的分类单元（ESTUs CRD1A - C），它们占据不同的热生态位，这表明在这个进化枝中也可能存在不同的热型。在这里，通过对代表这三个CRD1 ESTUs的菌株进行比较热生理学研究，我们发现CRD1A菌株MITS9220是暖型，CRD1B菌株BIOS - U3 - 1是冷温带型，CRD1C菌株BIOS - E4 - 1是暖温带窄温型。奇怪的是，CRD1B热型缺乏典型冷型的特征和/或基因组特征。相比之下，我们发现CRD1菌株与其第一、第二、第三和第四进化枝对应菌株相比具有特定的生理特征，包括在大多数温度下较低的生长速率和光系统II最大量子产率，以及D1蛋白较高的周转率。总之，我们的数据表明，CRD1进化枝在适应低温条件之前优先适应低铁条件，尽管几种CRD1热型的出现可能解释了为什么CRD1进化枝作为一个整体占据了大多数铁限制水域。
