Publications

4368

ABSTRACT Five draft genome sequences of ‘ Candidatus Liberibacter solanacearum’ haplotype E from five different Bactericera trigonica vector insects sampled in France are reported. Each genome has a size of about 1.20 Mbp, a G + C content of 35% and approximately 1,000 predicted coding DNA sequences.

Abstract Rickettsia species, which constitute obligate intracellular bacteria adapted to a host-dependent lifestyle, have traditionally been classified into four phylogenetic groups. However, the available genomes are biased toward the Typhus and Spotted Fever groups, with early-diverging Ancestral group (AG) lineages being underrepresented. Here, we isolated six Candidatus Rickettsia mendelii strains from Ixodes turdus ticks in Japan. We obtained their whole-genome sequences, including one closed genome, and found that they form a distinct lineage in the AG and have the smallest genome among the known rickettsial species. Gene tree-aware reconstruction of evolutionary events using amalgamated likelihood estimation revealed that the last common ancestor of Rickettsia had a smaller gene family size than modern species do, and Ca . R. mendelii retains the most similar genomic content to this ancestral state. Various patterns of gene gain and loss among Rickettsia lineages were also suggested, highlighting their divergent evolutionary trajectories. These findings increase our understanding of Rickettsia genome evolution.

ABSTRACT Candidatus Saccharimonadia is a class‐level lineage of ultrasmall bacteria within the phylum Minisyncoccota (formerly Candidate Phyla Radiation or Ca . Patescibacteria), commonly found in activated sludge processes treating municipal wastewater. In this study, we aimed to elucidate the metabolic potential of Ca . Saccharimonadia by using shotgun metagenomic sequencing combined with a filtration‐based size‐fractionation approach for activated sludge from five wastewater treatment plants. A total of 65 high‐quality metagenomic bins were recovered, belonging to four orders and 19 families of Ca . Saccharimonadia, including previously unreported lineages in activated sludge. These bins had small genomes (approximately 0.46–1.73 Mbp) with limited metabolic capabilities, indicating dependency on other microorganisms. Notably, the order Ca . Saccharimonadales retained a type IV secretion system and effector gene cluster for parasitic interactions with the hosts, suggesting that Ca . Saccharimonadales bacteria may exhibit a parasitic lifestyle. Co‐occurrence network analysis showed that members of the order Ca . Saccharimonadales were significantly correlated with multiple lineages, including Actinobacteriota , for which a parasitic relationship has been previously demonstrated. Our results shed light on the potential ecophysiology of the diverse members of Ca . Saccharimonadia, providing a comprehensive understanding of Ca . Saccharimonadia in activated sludge.