Communications Biology

Abstract Citrus greening disease, caused by ‘Candidatus Liberibacter asiaticus’, severely impacts citrus production worldwide. The development of sustainable control strategies for this disease is restricted by the unavailability of the bacterium in pure culture. Herein, the metabolic profile of the waxworm larvae, Galleria mellonella, was compared to that of Diaphorina citri, the vector of ‘Ca. L. asiaticus’. Our findings showed that G. mellonella larvae possess the nutritional needs to host ‘Ca. L. asiaticus’, supporting its short-term persistence, and responds to infection with a visible immune reaction by producing melanin upon bacterial invasion. The inoculated larvae exhibit detectable bacterial titers for up to four days when inoculated with infected citrus phloem sap or D. citri haemolymph, after which bacterial titers decline, and infected larvae show reduced survival compared to mock-treated and ‘Ca. L. asiaticus’-free controls. Metabolic profiling of G. mellonella, D. citri, and honeybees (Apis mellifera) reveals distinct chemical compositions in their haemolymph. G. mellonella contains higher levels of amino acids, organic acids, nucleotides, and sugar-nucleotides, providing essential nutrients for ‘Ca. L. asiaticus’, while D. citri is enriched in monosaccharides and sugar-alcohols. Citric acid was detected exclusively in the haemolymph of G. mellonella. These findings suggest G. mellonella as a convenient model that can transiently host ‘Ca. L. asiaticus’ for short-term use, which would facilitate high-throughput screening of antimicrobial compounds against ‘Ca. L. asiaticus’, as well as exploring host-pathogen interactions. This model could accelerate the development of effective treatments against citrus greening and inform broader strategies for managing vector-borne plant diseases.

AbstractThe continental bedrock contains groundwater-bearing fractures that are home to microbial populations that are vital in mediating the Earth’s biogeochemical cycles. However, their diversity is poorly understood due to the difficulty of obtaining samples from this environment. Here, a groundwater-bearing fracture at 975 m depth was isolated by employing packers in order to characterize the microbial community via metagenomes combined with prokaryotic and eukaryotic marker genes (16S and 18S ribosomal RNA gene). Genome-resolved analyses revealed a community dominated by sulfate-reducing Bacillota, predominantly represented by Candidatus Desulforudis audaxviator and with Wood-Ljungdahl as the most prevalent pathway for inorganic carbon fixation. Moreover, the eukaryotic community had a considerable diversity and was comprised of mainly flatworms, chlorophytes, crustaceans, ochrophytes, and fungi. These findings support the important role of the Bacillota, with the sulfate reducer Candidatus Desulforudis audaxviator as its main representative, as primary producers in the often energy-limited groundwaters of the continental subsurface.

AbstractGlyphosate is widely used as a herbicide, but recent studies begin to reveal its detrimental side effects on animals by targeting the shikimate pathway of associated gut microorganisms. However, its impact on nutritional endosymbionts in insects remains poorly understood. Here, we sequenced the tiny, shikimate pathway encoding symbiont genome of the sawtoothed grain beetleOryzaephilus surinamensis. Decreased titers of the aromatic amino acid tyrosine in symbiont-depleted beetles underscore the symbionts’ ability to synthesize prephenate as the precursor for host tyrosine synthesis and its importance for cuticle sclerotization and melanization. Glyphosate exposure inhibited symbiont establishment during host development and abolished the mutualistic benefit on cuticle synthesis in adults, which could be partially rescued by dietary tyrosine supplementation. Furthermore, phylogenetic analyses indicate that the shikimate pathways of many nutritional endosymbionts likewise contain a glyphosate sensitive 5-enolpyruvylshikimate-3-phosphate synthase. These findings highlight the importance of symbiont-mediated tyrosine supplementation for cuticle biosynthesis in insects, but also paint an alarming scenario regarding the use of glyphosate in light of recent declines in insect populations.