Grandeur Alliances: Symbiont Metabolic Integration and Obligate Arthropod Hematophagy

Abstract

Several arthropod taxa live exclusively on vertebrate blood. This food source lacks essential metabolites required for the maintenance of metabolic homeostasis, and as such, these arthropods have formed symbioses with nutrient-supplementing microbes that facilitate their host’s ‘hematophagous’ feeding ecology. Herein we highlight metabolic contributions of bacterial symbionts that reside within tsetse flies, bed bugs, lice, reduviid bugs and ticks, with specific emphasis on B vitamin and cofactor biosynthesis. Importantly, these arthropods can transmit pathogens of medical and veterinary relevance and/or cause infestations that induce psychological and dermatological distress. Microbial metabolites, and the biochemical pathways that generate them, can serve as specific targets of novel control mechanisms aimed at disrupting the metabolism of hematophagous arthropods, thus combatting pest invasion and vector-borne pathogen transmission.

A snapshot of the microbiome of Amblyomma tuberculatum ticks infesting the gopher tortoise, an endangered species

“…At the same time, however, Rickettsial endosymbiont from Ixodes pacificus and Ixodes scapularis appear to help its host in de novo biosynthesis of folic acid required for growth and development (Hunter et al, 2015; Kurtti et al, 2015). The necessity of symbiont for nutritional supplemental has been described in many hematophagus arthropods including ticks (Rio et al, 2016). In an interesting study, Rickettsia -infected whiteflies developed high survival rates and faster, higher fecundity when compared to whiteflies lacking Rickettsia infection, suggesting the potential role of these endosymbionts in the survival in particular genetic line (Cass et al, 2016; Himler et al, 2011).…”

Comparison of closely related, uncultivated Coxiella tick endosymbiont population genomes reveals clues about the mechanisms of symbiosis

“…Evidence for host-symbiont interactions that are based on proline metabolism are found in tsetse flies and in a trypanosome. In tsetse flies, removal of its essential symbiont, Wigglesworthia glossinidae, leads to hypoprolinemia due to the symbiont involvement in the pathway of proline metabolism, and ultimately decreased fecundity (Michalkova et al, 2014;Rio et al, 2016). In the trypanosomatid Crithidia deanei, proline was shown to be a growth promoter (as for tick cell culture), and the incorporation of proline was higher in cells bearing an endosymbiont (Galvez Rojas et al, 2008).…”

“…Multiple arthropod taxa feed exclusively on vertebrate blood, a highly restricted diet which lacks essential nutrients and metabolites, particularly B vitamin and various cofactor precursors (Duarte et al, 1999). Thus, blood feeding arthropods typically form close associations with nutrient-providing endosymbiotic bacteria that often become essential and even irreplaceable for their hosts fitness and reproduction (i.e., obligate symbionts) (Zientz et al, 2004;Manzano-Marín et al, 2015;Rio et al, 2016). For example, tsetse flies (Diptera: Glossinidae) rely on their obligate endosymbionts Wigglesworthia spp.…”

“…Similarly, the Wolbachia obligate symbiotic bacteria of bed bugs (Cimex lectularius) (Hosokawa et al, 2010), the gamma proteobacterial symbionts of lice (Sasaki-Fukatsu et al, 2006) or the Coxiella-like endosymbionts (CLE) of ticks (Smith et al, 2015) are required for survival and/or reproduction of their hosts, presumably as essential nutrient provisioning partners. Other proposed roles for arthropod symbionts include their involvement in waste degradation and protection against biotic and abiotic stress factors (Douglas, 2015;Rio et al, 2016). Since several of those arthropods are responsible for transmitting pathogens into their vertebrate hosts through blood feeding, their metabolic interdependencies with their bacterial symbionts might provide crucial information for developing vector control strategies and eliminating vector-borne pathogens (Zindel et al, 2011;Leitner et al, 2015).…”

Band‐aids for Buchnera and B vitamins for all

“…; Rio et al . ). This feature may serve as a pre‐adaptation, repeatedly sending bacteria down the path towards specialization and obligacy in hosts encountering scarce quantities of dietary riboflavin or in those obtaining ever‐lessening quantities from their mutation‐hampered symbionts (Fig.…”