The composition of hindgut microbiota of Periplaneta japonica in the presence of thelastomatid parasitic nematodes

Abstract

Thelastomatid nematodes (Nematoda: Oxyurida: Thelastomatoidea) are obligatory parasites that occur naturally in the hindgut of arthropods. Their origin and impact in the host is still unknown. Previous studies showed that the presence of thelastomatid nematodes in the gut of cockroaches (Periplaneta fuliginosa and P. americana) could influence the composition of their hindgut microflora. Through a metagenomic approach (S rRNA V-V sequencing), we have characterized the hindgut microbiome of P. japonica in the presence of thelastomatid nematodes (L, natural parasitic nematode Protrellus sp. present as a natural infection condition; and L, non-native parasitic nematode Leidynema appendiculatum present as an artificial infection condition). The hindgut microbiome of P. japonica in both conditions were mainly composed of Bacteroidetes, Firmicutes and Proteobacteria. Moreover, the natural and artificial infection by thelastomatid nematodes lead to shifts in the relative abundance of these main resident f lora as seen in P. americana. The OTUs percentage of Bacteroidetes and Proteobacteria were higher in P. japonica infected with Protrellus sp. (L) than in P. japonica infected by L. appendiculatum (L), while OTUs from Firmicutes phylum was higher in L than in L. This study fosters a detailed investigation in the role played by these animal parasites in their host insect. Nematol. Res. (),-(). Periplaneta japonica, the Japanese cockroach or Yamato cockroach, is a domiciliary pest originated from Japan, affecting other Asian countries (China and southeastern Russia) and recently found in New York (USA) (Evangelista et al.,). Adapted to northern climates, P. japonica is capable of surviving under freezing cond it ion s t h roug h t he st r ateg ic select ion of microhabitats and by displaying freeze tolerance (Tanaka et al., ; Mullins,). Recently, we discovered that P. japonica is naturally infected by thelastomatid parasitic nematodes from genus Protrellus and is capable of being artificially infected by the broad host range nematode, Leidynema appendiculatum (Ozawa and Hasegawa,). These thelastomatid nematodes are not pathogenic parasites for the cockroaches, still their function in the biology of the insect is unknown (Ozawa et al., ; Ozawa et al., ; Sriwati et al.,). Cockroaches are interesting insect models to study multi-trophic interactions due to their long-term evolution and resilience (Mullins,). As key-elements of insect's lifestyle, microbial communities (in particular gut residents) are involved in a wide range of functions (i.e. colonization and resistance to parasites and/or pathogens, diet breakdown, nutrient recycling and production of pheromones and/or kairomones) (Engel and Moran,). The diversity of these communities is host-dependent, mainly determined by its habitat, diet, developmental stage and phylogeny (Yun et al.,). Recently, the gut microbiome of Periplaneta fuliginosa and P. americana were investigated considering the presence of these nematodes (Vicente et al.,). The authors suggested that the presence of thelastomatid nematodes could influence the composition of hindgut microf lora, which was more biodiverse than the communities of non-infected hindgut and with major shifts in the relative abundance of the most representative taxa Bacteroidetes, Firmicutes and Proteobacteria (Vicente et al.,). Following our previous findings, here we briefly report, for the first time, the composition of the hindgut microbiome of the Japanese cockroach P. japonica in the presence of t hela stomat id nematodes u si ng a metagenomic approach. MATERIALS AND METHODS Periplaneta japonica Miyoshi (artificially infected with L. appendiculatum) and P. japonica Akita (naturally infected with Protrellus sp.) strains have been maintained in the Hasegawa Laboratory (Chubu University, Japan) since, respectively, and , under the conditions described in Vicente et al. (). Three adult males from each cockroach strain (n = ; average size:. . mm) were dissected to obtain the whole gut system. Hindgut sections were separated, carefully washed with sterile .M PBS (phosphate-buffered saline) pH., and stored at-ºC until further usage. The procedures for total DNA extraction from hindgut, PCR confirmation of