The <i>Thermosynechococcus</i> Genus: Wide Environmental Distribution, but a Highly Conserved Genomic Core

Abstract

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.

Diversity and Co-Occurrence Patterns of Fungal and Bacterial Communities from Alkaline Sediments and Water of Julong High-Altitude Hot Springs at Tianchi Volcano, Northeast China

“…The Julong hot springs are enriched with heavy metals, such as Fe and Mn. The fungal genus Plectosphaerella and the bacterial genus Thermosynechococcus have been reported to possess Mn-oxidizing [69] and iron-adapting abilities [70], respectively. The significant difference in these two genera in Pond A and Pond B may be caused by discrepant metal concentrations.…”

Comparative analysis reveals distinctive genomic features of Taiwan hot-spring cyanobacterium Thermosynechococcus sp. TA-1

“…Thermophilic cyanobacteria grow photosynthetically and are often the primary producers in non-acidic hot springs ( Ward et al, 2012 ). The underlying mechanisms of how thermophilic cyanobacteria adapt to diverse ecological niches and various stressful conditions of hot springs are still not fully understood ( Chen et al, 2021 ; Prondzinsky et al, 2021 ). The information would be valuable for developing feasible solutions to mitigate the impacts of global warming ( Matos et al, 2021 ).…”

“…Among thermophilic cyanobacteria, the genus Thermosynechococcus dominates the microbial mats in Asian non-acidic hot springs in the temperature range of about 50–65°C ( Liao et al, 2006 ; Everroad et al, 2012 ; Tang et al, 2018 ; Patel et al, 2019 ; Prondzinsky et al, 2021 ). The genome sequences of several representative Thermosynechococcus strains have been determined and analyzed.…”

“…Thermosynechococcus genomes typically have smaller sizes and higher GC content than most mesophilic cyanobacteria ( Larsson et al, 2011 ; Alcorta et al, 2020 ; Prondzinsky et al, 2021 ). Recently, a study found that Thermosynechococcus strains have a highly conserved genome core, and no clear genetic differences or adaptive mechanisms could be detected when comparing strains isolated from hot springs with different environmental factors ( Prondzinsky et al, 2021 ).…”

“…Thermosynechococcus genomes typically have smaller sizes and higher GC content than most mesophilic cyanobacteria ( Larsson et al, 2011 ; Alcorta et al, 2020 ; Prondzinsky et al, 2021 ). Recently, a study found that Thermosynechococcus strains have a highly conserved genome core, and no clear genetic differences or adaptive mechanisms could be detected when comparing strains isolated from hot springs with different environmental factors ( Prondzinsky et al, 2021 ). This observation contrasts with a study of Synechococcus phylogenetic lineage A/B strains from a hot spring in Yellowstone National Park, which identified genetic differentiation between high- and low-light adapted strains ( Becraft et al, 2015 ; Olsen et al, 2015 ).…”