The genus Carnimonas belongs to the Halomonadaceae, a family of bacteria well-known for its ability to tolerate saline environments (de la Haba et al., 2014). To date, only a single species, Carnimonas nigrificans, isolated from cured meat products has been described and validly-named (Garriga et al., 1998). Carnimonas bacteria, or their DNA, were subsequently detected in other food products including Shuidouchi, a traditional fermented soybean product (Chen et al., 2019), table olives (Lopez-Garcia et al., 2021), pickled cucumbers (Liang et al., 2021), Daqu (a fermentation starter for Baijiu, a Chinese liquor) (Fan et al., 2019), and in the root endophyte compartment of foxtail millet (Setaria italica) (Chaluvadi and Bennetzen, 2018).

There is also an increasing number of reports of Carnimonas in insect samples. These bacteria have been detected in bee bread of honey bees (Anderson et al., 2013) and in Varroa destructor mites from winter beehive debris (Hubert et al., 2015); in bee bread, honey, and the gut of stingless bees (Basharat et al., 2023; Liu et al., 2023; Tang et al., 2021); in pupae, larvae, and adults of the small carpenter bee Ceratina calcarata (Nguyen and Rehan, 2022, Nguyen and Rehan, 2023); in Aedes aegypti and Culex quinquefasciatus mosquitoes (Ramos-Nino et al., 2020), and in various psyllids (Nakabachi et al., 2022). Moreover, Carnimonas was reported as core gut symbiont of Vespa simillima and Vespa mandarinia hornets (Suenami et al., 2019), as well as in the larval stage of the fruit fly Ceratitis capitata (Bel Mokhtar et al., 2022). Additionally, the gut microbiota of obligate necrophagous stingless bee species were dominated by Carnimonas and other bacteria from the Halomonadaceae family, such as Halotalea, Kushneria, and Zymobacter (Maccaro et al., 2024).

We earlier reported Carnimonas amplicon sequence variants in Megachile sculpturalis and Anthidium florentinum gut samples (Tuerlings et al., 2023). The former is the giant resin bee and is native to East Asia but has ranged extensively into North America and Europe. This solitary bee is a pollinator that forages on a large variety of flowering plants, and its generalist foraging behavior likely contributes to its success in invaded regions. However, introduced bees can have a negative impact on local ecosystems, by competing for floral resources and nest sites with native species and by facilitating the transmission of foreign pathogens (Quaranta et al., 2014). A. florentinum, another solitary bee of the family Megachilidae, is primarily distributed throughout the Mediterranean regions of Eurasia and also exhibits a generalized behavior to floral foraging (Fortunato et al., 2014). In the present study, we report the isolation of novel Carnimonas-like bacteria from M. sculpturalis gut samples and performed a physiological and comparative genomic analysis to assess the taxonomy and functional potential of these bacteria.