Cyanobacteria thrive in diverse environments. However, questions remain about possible growth limitations in ancient environmental conditions. As a single genus, the Thermosynechococcus are cosmopolitan and live in chemically diverse habitats. To understand the genetic basis for this, we compared the protein coding component of Thermosynechococcus genomes. Supplementing the known genetic diversity of Thermosynechococcus, we report draft metagenome-assembled genomes of two Thermosynechococcus recovered from ferrous carbonate hot springs in Japan. We find that as a genus, Thermosynechococcus is genomically conserved, having a small pan-genome with few accessory genes per individual strain as well as few genes that are unique to the genus. Furthermore, by comparing orthologous protein groups, including an analysis of genes encoding proteins with an iron related function (uptake, storage or utilization), no clear differences in genetic content, or adaptive mechanisms could be detected between genus members, despite the range of environments they inhabit. Overall, our results highlight a seemingly innate ability for Thermosynechococcus to inhabit diverse habitats without having undergone substantial genomic adaptation to accommodate this. The finding of Thermosynechococcus in both hot and high iron environments without adaptation recognizable from the perspective of the proteome has implications for understanding the basis of thermophily within this clade, and also for understanding the possible genetic basis for high iron tolerance in cyanobacteria on early Earth. The conserved core genome may be indicative of an allopatric lifestyle-or reduced genetic complexity of hot spring habitats relative to other environments.

中文翻译：

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Thermosynechococcus属：广泛的环境分布，但高度保守的基因组核心。

蓝藻在不同的环境中茁壮成长。然而，关于古代环境条件下可能的生长限制的问题仍然存在。作为一个属，热聚球藻是世界性的，生活在化学性质多样的栖息地。为了了解其遗传基础，我们比较了热联球菌基因组的蛋白质编码成分。补充已知的热聚球藻的遗传多样性，我们报告了从日本碳酸亚铁温泉中回收的两种热聚球藻的宏基因组组装基因组草案。我们发现，作为一个属，热聚球藻在基因组上是保守的，它有一个小的泛基因组，每个菌株的辅助基因很少，并且该属独有的基因很少。此外，通过比较直系同源蛋白质组，包括对编码具有铁相关功能（摄取、储存或利用）的蛋白质的基因进行分析，尽管它们居住的环境范围不同，但在属成员之间没有检测到遗传内容或适应性机制的明显差异。总体而言，我们的结果突出了热聚球藻看似与生俱来的能力，即在没有经过大量基因组适应以适应不同栖息地的情况下。从蛋白质组的角度来看，在高温和高铁环境中发现热联球菌，但没有可识别的适应性，这对于理解该进化枝内嗜热的基础以及理解地球早期蓝藻高铁耐受性的可能遗传基础具有重要意义。