journals.asm.org
Parasitic connections: a patescibacterial epibiont, its methylotrophic gammaproteobacterial host, and their phages | mBio
Patescibacteriota are ultra-small bacteria with reduced genomes that rely on symbiotic interactions with other prokaryotes; however, their host specificity and associated viral parasites remain poorly characterized due to limited cultured representatives. By combining targeted cultivation with genomic and microscopy analyses, we reveal previously unrecognized host lineages and expand the known viral diversity infecting this major, but still poorly known, bacterial phylum. We describe Strigamonas methylophilicida, a new patescibacterial species of the family Absconditicoccaceae that grows as an epibiont on various methylotrophic Gammaproteobacteria. This expands the host range for this family, previously found to infect only photosynthetic partners. Using enrichment cultures and metagenomics, we retrieved complete genomes of novel phages infecting S. methylophilicida and its methylotrophic hosts, including one phage that uses a modified genetic code matching that of the patescibacterium, which shows a specific viral adaptation to infect Absconditicoccaceae hosts. Our findings reveal a previously unrecognized patescibacteria-methylotrophs-phages tripartite interaction in freshwater environments, highlight the adaptations of patescibacterial phages, and shed light on the complex ecology and evolution of host-parasite-phage dynamics in understudied bacterial lineages.
