Carnimonas bestiolae sp. nov. and Cernens ardua gen. nov., sp. nov.: new halotolerant bacteria from the invasive solitary bee Megachile sculpturalis

Fifteen isolates from gut samples of the invasive solitary bee Megachile sculpturalis remained unidentified after matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis. Phylogenomic and overall genome relatedness indices analyses of five representative isolates demonstrated that 14 isolates represented a novel Carnimonas species for which we propose the name Carnimonas bestiolae sp. nov., with LMG 33810^T as the type strain. A single isolate represented a distinct lineage within the Halomonadaceae family with the genera Carnimonas and Halotalea as nearest neighbor taxa and is classified as Cernens ardua gen. nov., sp. nov., with LMG 33818^T as the type strain. Comparative genomic analysis and physiological characterization revealed functional differences between C. bestiolae, Ce. ardua and established Carnimonas and Halotalea species in central metabolism, fatty acid metabolism, and osmoregulatory pathways, the latter being consistent with adaptation to a saline environment. A reanalysis of previously published insect microbiome studies in which Carnimonas was reported, revealed 16S rRNA amplicon sequence variants with >99 % identity to C. bestiolae LMG 33810^T 16S rRNA in gut samples of Megachile sculpturalis, Anthidium florentinum, and the psyllid Leptynoptera sulfurea. In contrast, 16S rRNA amplicon sequence variants corresponding to Ce. ardua were rarely detected and only at low relative abundances, suggesting a transient association with the insect gut.