Unveiling viral identity and their association with thermophilic hosts of phototrophic mats

Desvelando la identidad viral y su asociación con hospederos termófilos de tapetes fototróficos

Extreme environments represent ideal natural models to understand the principles of microbial ecology. We investigated the identity and biogeography of viruses and their interactions with the microbial communities in hydrothermal systems through meta-omics. The mining of viral sequences from cellular metagenomes and metatranscriptomes, shown that a large fraction of the active viral communities in neutral pH hot springs phototrophic mats are predominantly composed of Caudovirus such as cyanophages, which are infecting and potentially controlling relevant communities for the biogeochemical cycles. Metagenomic assembly lead to the recovery of the first T7-like thermophilic cyanophage (CHP58), that was associated with the cyanobacteria Fischerella spp. by CRISPR spacers. Additionally, we found marked differences in the number of CRISPR loci and spacers diversity in Fischerella, as well as Single Nucleotide Variants (SNVs) in the TC-CHP58 proto-spacers at different temperatures, which reinforce the theory of a coevolution between natural viral populations and their cyanobacterial hosts.
Metagenome Assembled Genomes (MAGs), as well as natural and mitomycin C induced viral communities from thermophilic phototrophic mats were interrogated for the presence of integrated temperate viruses. Our results suggest that most active and dominant bacterial taxa such as Fischerella, have as main predators the most abundant lytic viral populations. Meanwhile spontaneously or mitomycin C induced lysogenic viruses were associated to Proteobacteria and Firmicutes phyla, respectively.
Finally, a viral biogeographic pattern was observed for all existing viral metagenomes of hot springs, according to major ecological drivers (here, pH and temperature) by analysis of protein, gene and genome sequences. Protein sharing network of the global thermophilic viral communities showed high modularity, suggesting the gene flow restriction between hot springs and a high local richness, mostly due to the existence of specific virus-host pairs that are locally structured influenced by the environmental conditions that primarily affect the structure of the host community.

All these sponsored by: FONDECYT 1105171, 1190998 (CONICYT, Chile); FONDAP 15110009 – Center for Climate and Resilience Research (CR)2 (CONICYT, Chile).