Abstract
<jats:p>Background Human head lice (Pediculus humanus capitis de Geer) are known to harbor diverse maternally inherited bacterial symbionts. These endosymbiotic bacteria may contribute to insecticide degradation, potentially helping lice withstand particular environmental pressures. Using next-generation sequencing (NGS), this study investigated the bacterial symbionts present in wild head-louse populations and characterized their phylogenetic relationships in mutant and permethrin-susceptible strains. Methods Head lice specimens were collected from 10 locations across Fars Province, Iran. Following DNA extraction, the samples were analyzed using polymerase chain reaction (PCR), and the resulting amplicons were sequenced to detect mutations in specimens from each location. Lice were then classified according to the presence or absence of mutations and subjected to NGS to characterize the symbiotic bacterial communities in mutant and putatively permethrin-susceptible strains. Results Mutant strains were detected at only three sampling stations. Bioinformatic analysis of the nucleic acid sequences revealed three exons and two introns, with an expected amplicon length of 582 bp. NGS analysis showed that Candidatus Riesia pediculicola (Arsenophonus), belonging to the phylum Proteobacteria, was the predominant bacterial genus. Actinobacteria and Firmicutes were the second- and third-most abundant phyla, respectively. Most of the remaining 25 bacterial taxa were associated with the mutant strain. Additionally, two previously unreported bacterial genera were deposited in GenBank. Conclusions The distinct distribution of Arsenophonus species between susceptible and mutant head-lice strains, along with the greater abundance of Escherichia, Shigella, Lawsonella, and Megamonas in mutant strains, highlights the need for advanced metagenomic analyses to determine how these endosymbionts may help their hosts withstand specific environmental disturbances.</jats:p>