Predictive Genomic Analyses Inform the Basis for Vitamin Metabolism and Provisioning in Bacteria-Arthropod Endosymbioses

Abstract

The requirement of vitamins for core metabolic processes creates a unique set of pressures for arthropods subsisting on nutrient-limited diets. While endosymbiotic bacteria carried by arthropods have been widely implicated in vitamin provisioning, the underlying molecular mechanisms are not well understood. To address this issue, standardized predictive assessment of vitamin metabolism was performed in 50 endosymbionts of insects and arachnids. The results predicted that arthropod endosymbionts overall have little capacity for complete de novo biosynthesis of conventional or active vitamin forms. Partial biosynthesis pathways were commonly predicted, suggesting a substantial role in vitamin provisioning. Neither taxonomic relationships between host and symbiont, nor the mode of host-symbiont interaction were clear predictors of endosymbiont vitamin pathway capacity. Endosymbiont genome size and the synthetic capacity of nonsymbiont taxonomic relatives were more reliable predictors. We developed a new software application that also predicted that last-step conversion of intermediates into active vitamin forms may contribute further to vitamin biosynthesis by endosymbionts. Most instances of predicted vitamin conversion were paralleled by predictions of vitamin use. This is consistent with achievement of provisioning in some cases through upregulation of pathways that were retained for endosymbiont benefit. The predicted absence of other enzyme classes further suggests a baseline of vitamin requirement by the majority of endosymbionts, as well as some instances of putative mutualism. Adaptation of this workflow to analysis of other organisms and metabolic pathways will provide new routes for considering the molecular basis for symbiosis on a comprehensive scale.

Coxiella-Like Endosymbiont of Rhipicephalus sanguineus Is Required for Physiological Processes During Ontogeny

“…A general consistency among endosymbionts of obligate blood-feeders is their tendency to retain their B vitamins and co-factor synthesis pathways regardless of massive genomic erosion (Manzano-Marín et al, 2015). These micronutrients are suggested to be produced for the symbiont themselves (Serbus et al, 2017) and for their hosts (e.g., Hosokawa et al, 2010;Duron et al, 2018). CLE genomes differ considerably in completeness of B vitamin synthesis pathways (Tsementzi et al, 2018), and nutritional complementation evidence is not yet available for hard ticks.…”

Quantitative methods for assessing local and bodywide contributions to Wolbachia titer in maternal germline cells of Drosophila

“…However, due to re-use of dissection equipment, it is possible that trace amounts of Wolbachia DNA detected in uninfected samples by 16S rRNA gene profiling represent basal contamination of dissecting equipment. Furthermore, neither Spiroplasma , nor Buchnera, nor dozens of other known insect endosymbionts [12] were identified by the ovary microbiome analyses. This confirms that punctate nucleoids observed in Wolbachia- infected D. melanogaster ovary tissues represent Wolbachia, and can be analyzed with confidence in that regard.…”

“…The extent to which colonization mechanisms are shared between pathogenic and non-pathogenic bacteria is also unclear. Bacterial endosymbionts are carried by diverse host taxa, with dozens having been identified in insects alone [12]. Endosymbiotic Wolbachia bacteria are carried by approximately 50% of all insect species, as well as some mites, crustaceans and filarial nematodes [13–16].…”

Changes in Aphid Host Plant Diet Influence the Small-RNA Expression Profiles of Its Obligate Nutritional Symbiont,Buchnera

“…Insects, like many other animals, cannot synthesize B vitamins de novo , and so they obtain these necessary micronutrients from their diet or their association with various microorganisms (50). Within aphids, Buchnera possesses several genes for the biotin (B 7 ), folic acid (B 9 ), pantothenate (B 5 ), pyridoxine (B 6 ) riboflavin (B 2 ), and thiamine (B 1 ) biosynthesis pathways (13, 51). Vitamin B 6 is an important bacterial and eukaryotic cofactor, especially in amino acid metabolism (52, 53), and neither Buchnera nor A.…”