Gut Microbiota in Nymph and Adults of the Giant Mesquite Bug (Thasus neocalifornicus) (Heteroptera: Coreidae) Is Dominated byBurkholderiaAcquiredDe NovoEvery Generation

Abstract

The coreid bug Thasus neocalifornicus Brailovsky and Barrera, commonly known as the giant mesquite bug, is a ubiquitous insect of the southwestern United States. Both nymphs and adults are often found aggregated on mesquite trees (Prosopis spp.: Fabaceae) feeding on seedpods and plant sap. We characterized the indigenous bacterial populations of nymphs and adults of this species by using molecular and phylogenetic techniques and culturing methods. Results show that this insect's bacterial gut community has a limited diversity dominated by Burkholderia associates. Phylogenetic analysis by using 16s rRNA sequences suggests that these β-Proteobacteria are closely related to those symbionts obtained from other heteropteran midgut microbial communities but not to Burkholderia symbionts associated with other insect orders. These bacteria were absent from the eggs and were not found in all younger nymphs, suggesting that they are acquired after the insects have hatched. Rearing experiments of nymphs with potentially Burkholderia contaminated soil suggested that if this symbiont is not acquired, giant mesquite bugs experience higher mortality. Egg, whole-body DNA extractions of younger nymphs, and midgut DNA extractions of fifth-instar nymphs and adults also revealed the presence of α-Proteobacteria from the Wolbachia genus. However, this bacterium was also present in reproductive organs of adults, indicating that this symbiont is not specific to the gut.

Wolbachia-Free Heteropterans Do Not Produce Defensive Chemicals or Alarm Pheromones

“…These compounds have been found in many other heteropterans (Aldrich 1988), and bioassays using model predators have confirmed that, as in other heteropterans, they confer defensive protection to nymphs, while in adults they function as alarm pheromones (Prudic et al 2008). Past work in this system using diagnostic PCR, revealed that Wolbachia infects several organs of this bug, including their scent glands (Olivier-Espejel et al 2011). Since (E)-2-hexenal and 4-oxo-(E)-2-hexenal are strong antibacterial substances (Noge et al 2012a), the presence of bacteria in these organs was intriguing.…”

“…In situ Hybridization Nymph DGAs were dissected and fixed with Carnoy's solution (ethanol:chloroform:acetic acid = 6:3:1 (vol/vol)) for 6 d and then treated for 7 d with 6 % H 2 O 2 in 80 % ethanol following the procedure described in Olivier-Espejel et al (2011). The universal probe Eub338 targeting bacterial 16S rRNA labeled with cyanine dye (5′-/5Cy3/ GCTGCCTCCCGTAG GAGT-3′) and a Wolbachia specific probe labeled with Cy5 (5′-/ Cy5 / AACCGACCCTATCCCTTCG-3′) were used to detect the bacteria.…”

“…Heteropterans have symbiotic associations with microorganisms that may be quite old (Kikuchi and Fukatsu 2003;Kikuchi et al 2005Kikuchi et al , 2011Olivier-Espejel et al 2011). Although several groups of bacteria are involved (Kuechler et al 2012), some of the microorganisms that often infect heteropterans are the Beta-proteobacteria Burkholderia and intracellular Alpha-proteobacteria from the order Rickettsiales such as Wolbachia and Rickettsia (Kikuchi et al 2007;Matsuura et al 2012).…”

Leaf-Footed Bugs (Coreidae)

“…However, Burkholderia bacterial symbionts are not acquired from the eggs in Thasus neocalifornicus Brailovsky & Barrera and must be acquired de novo, presumably from the soil, by the early instars (Olivier-Espejel et al 2011 ).…”

“…Nymphal descriptions and host plant associations for several species in Mexico are given by Brailovsky et al ( 1995 ) and components of the scent fl uid have been identifi ed for nymphs of one Mexican species (Noge et al 2012 ). The biology of the North American species, Thasus neocalifornicus Brailovsky & Barrera, has been thoroughly investigated, including the chemistry of the scent glands (Prudic et al 2008 ) and the gut biota (Olivier-Espejel et al 2011 ). Mozena obtusa Uhler has been extensively studied in Texas as a potential biological control agent for mesquite in Australia and South Africa (Cuda and DeLoach 1998 ).…”