Polyphyletic origins and lineage-specific expansion of chemosensory systems in phylum Actinomycetota

Across 693 Actinomycetota genomes, only 6.9% encode complete chemosensory system clusters, restricted to a subset of lineages, while most genomes lack them.

• Why it matters: The evolutionary pattern of chemosensory systems in Actinomycetota is unclear, despite their ecological versatility and the role of signal transduction in environmental sensing.
• What they did: Using comparative genomics across 693 high-quality genomes, the study mapped CSS and two-component systems, analyzed CheA homolog phylogeny, and tracked lineage-specific CSS retention, simplification (F1 or F5), and expansion (F5, F8, F9, and ACF).
• The result: CheA homologs show polyphyletic distribution, and CSS-deficient classes are linked to enriched hybrid kinases, implying mosaic acquisition/diversification/loss and TCS-driven regulatory compensation in non-motile lineages.

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