A new Serratia taxon found in a trombidiform mite shows genomic evidence of host adaptation but is phylogenetically distinct from Serratia symbiotica

A putatively new Serratia taxon in the trombidiform mite Halotydeus destructor shows host-adaptation genomic signatures yet remains phylogenetically distinct from Serratia symbiotica.

• Why it matters: The shift from free-living bacteria to host-adapted symbionts usually leaves strong genomic traces, but this transition within Serratia has been documented only for aphid-associated S. symbiotica.
• What they did: Using metagenomic approaches, the study assembled and compared genomes from the new Serratia sp. in H. destructor against free-living Serratia species and S. symbiotica, focusing on genome size, transposase fraction, chromosomal rearrangements, and functional gene content.
• The result: The new Serratia sp. has reduced genome size and coding capacity, elevated transposase fraction, and chromosomal rearrangements relative to free-living Serratia, but its genome reduction pattern differs from S. symbiotica, and its gene profile is distinct; screening also suggests infections are common across H. destructor in its invasive Australian range.

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