ena-STUDY-UNIVERSITY OF LIVERPOOL-16-07-2021-14:33:18:096-273
Large-scale comparative genomics unravels great genomic diversity across the Rickettsia and Ca. Megaira genera and identifies Torix group as an evolutionarily distinct clade.
Rickettsia are intracellular bacteria that were originally described as arthropod borne pathogens. Over time Rickettsia have emerged as a diverse group of often non-pathogenic symbionts of invertebrates and microeukaryotes. However, our understanding of Rickettsia evolution is inhibited by sparse genomic data for symbiotic strains and the sister genus, Ca. Megaira. We present the first closed genome of Ca. Megaira from an alga (Mesostigma viride) and for two Torix Rickettsia from a midge (Culicoides impunctatus) and bed bug (Cimex lectularius). In addition, we constructed draft genomes for Ca. Megaira from another alga (Carteria cerasiformis), Transitional Rickettsia from a tsetse fly (Glossina morsitans submorsitans), and Torix Rickettsia from a spider mite (Bryobia graminum). We further assemble 22 draft rickettsial genomes extracted from arthropod genome sequencing projects, including the first draft genome for the Rhyzobius and Meloidae Rickettsia, 1 Adalia, 4 Transitional, 1 Spotted Fever, 7 Torix and 7 Belli group genomes. We used new and existing genomes for Rickettsia to estimate the phylogeny and metabolic potential of the different Rickettsia groups and reveal transitions in genomic properties. These data reveal that the Torix clade is unique amongst currently described Rickettsia, with highly distinct and diverse accessory genomes. We identify three subclades within the torix group, contrasting with the two subclades previously identified. Further, the torix clade share an intact pentose phosphate pathway with Ca. Megaira, that is not observed in other Rickettsia. Considering the distinctness and diversity of torix group Rickettsia, we propose that the group be named as Candidatus Tisiphia torix. Their commonness necessitates onward research to understand the biological and physiological bases of Ca. Tisiphia – host interactions.
Rickettsia are intracellular bacteria that were originally described as arthropod borne pathogens. Over time Rickettsia have emerged as a diverse group of often non-pathogenic symbionts of invertebrates and microeukaryotes. However, our understanding of Rickettsia evolution is inhibited by sparse genomic data for symbiotic strains and the sister genus, Ca. Megaira. We present the first closed genome of Ca. Megaira from an alga (Mesostigma viride) and for two Torix Rickettsia from a midge (Culicoides impunctatus) and bed bug (Cimex lectularius). In addition, we constructed draft genomes for Ca. Megaira from another alga (Carteria cerasiformis), Transitional Rickettsia from a tsetse fly (Glossina morsitans submorsitans), and Torix Rickettsia from a spider mite (Bryobia graminum). We further assemble 22 draft rickettsial genomes extracted from arthropod genome sequencing projects, including the first draft genome for the Rhyzobius and Meloidae Rickettsia, 1 Adalia, 4 Transitional, 1 Spotted Fever, 7 Torix and 7 Belli group genomes. We used new and existing genomes for Rickettsia to estimate the phylogeny and metabolic potential of the different Rickettsia groups and reveal transitions in genomic properties. These data reveal that the Torix clade is unique amongst currently described Rickettsia, with highly distinct and diverse accessory genomes. We identify three subclades within the torix group, contrasting with the two subclades previously identified. Further, the torix clade share an intact pentose phosphate pathway with Ca. Megaira, that is not observed in other Rickettsia. Considering the distinctness and diversity of torix group Rickettsia, we propose that the group be named as Candidatus Tisiphia torix. Their commonness necessitates onward research to understand the biological and physiological bases of Ca. Tisiphia – host interactions.