Newton, I. L. | bioRxiv Science

bioRxiv2023

Wolbachia is a nutritional symbiont

The intracellular bacterium Wolbachia is a common symbiont of many arthropods and nematodes, well studied for its impacts on host reproductive biology. However, its broad success as a vertically transmitted infection cannot be attributed to manipulations of host reproduction alone. Using the Drosophila melanogaster model and their natively associated Wolbachia strain "wMel", we show that Wolbachia infection supports fly development and buffers against nutritional stress. Wolbachia infection across several fly genotypes and a range of nutrient conditions resulted in reduced pupal mortality, increased adult emergence, and larger size. We determined that the exogenous supplementation of pyrimidines partially rescued developmental phenotypes in the Wolbachia-free flies, and that Wolbachia titers were responsive to reduced gene expression of the flys de novo pyrimidine synthesis pathway. In parallel, transcriptomic and metabolomic analyses indicated that Wolbachia impacts larval biology far beyond pyrimidine metabolism. Wolbachia-infected larvae had strong signatures of shifts in glutathione and mitochondrial metabolism, plus significant changes in the expression of key developmental regulators including Notch, the insulin receptor (lnR), and the juvenile hormone receptor Methoprene-tolerant (Met). We propose that Wolbachia acts as a beneficial symbiont to support fly development and enhance host fitness, especially during periods of nutrient stress. SIGNIFICANCEWolbachia is a bacterial symbiont of arthropods and nematodes, well described for its manipulations of arthropod reproduction. However, many have theorized there must be more to this symbiosis, even in well-studied Wolbachia-host relationships such as with Drosophila. Reproductive impacts alone cannot explain the success and ubiquity of this bacterium. Here, we use Drosophila melanogaster and their native Wolbachia infections to show that Wolbachia supports fly development and significantly buffers flies against nutritional stress. These developmental advantages might help explain the ubiquity of Wolbachia infections.

developmental biology↗

bioRxiv2022

A honey bee symbiont buffers larvae against nutritional stress through lysine supplementation

Honey bees, the worlds most significant agricultural pollinator, have suffered dramatic losses in the last few decades (1,2). These losses are largely due to the synergistic effects of multiple stressors, the most pervasive of which is limited nutrition (3-5). The effects of poor nutrition are most damaging in the developing larvae of honey bees, who mature into workers unable to meet the needs of their colony (6-8). It is therefore essential that we better understand the nutritional landscape experienced by honey bee larvae. In this study, we characterize the metabolic capabilities of a honey bee larvae-associated bacterium, Bombella apis (formerly Parasaccharibacter apium), and its effects on the nutritional resilience of larvae. We found that B. apis is the only bacterium associated with larvae that can withstand the antimicrobial larval diet. Further, we found that B. apis can synthesize all essential amino acids and significantly alters the amino acid content of synthetic larval diet, largely by increasing the essential amino acid lysine. Analyses of gene gain/loss across the phylogeny suggest that two distinct cationic amino acid transporters were gained by B. apis ancestors, and the transporter LysE is conserved across all sequenced strains of B. apis. This result suggests that amino acid export is a key feature conserved within the Bombella clade. Finally, we tested the impact of B. apis on developing honey bee larvae subjected to nutritional stress and found that larvae supplemented with B. apis are bolstered against mass reduction despite limited nutrition. Together, these data suggest an important role of B. apis as a nutritional mutualist of honey bee larvae.

microbiology↗