The impact of captivity conditions on gut microbial community associated with the southern green stinkbug (Nezara viridula).

MEDINA, VIRGINIA; SARDOY, PEDRO M.; PAGANO, EDUARDO A.; MIYAZAKI, SILVIA S.

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiología General; 2012

Sociedad Argentina de Microbiología General

Southern green stinkbug (Nezara viridula) is one of the most relevant pests of soybean crops, which feeds on the seeds in spite of their strong defenses against herbivory. We propose that the microbial community in the gut of stinkbugs may have a role in helping digestion and tolerance of chemical defenses of soybeans, such as protease inhibitors that decrease insect performance. The aim of this study was to describe the microbial communities present in the gut of adult southern green stinkbugs collected from their natural environment, and the effect of captivity on bacterial communities. Fifty percent of the insects collected from soybean crops and neighboring areas were dissected, and the rest were held for rearing with artificial diet and dissected 15 days later. Insect dissections were carried out under sterile conditions, and gut bacterias were analyzed using culturing and non-culturing techinques. Cell counts and isolations, and 16S ribosomal sequencing were performed and communities and pure cultures were analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA). In addition, proteolytic activities of pure bacterial cultures were assayed. In insects collected in their natural environment a transient flora with varying total bacterial count (from103 to 106 CFU/mg) was found, mainly proteolytic spore-forming rods identified as Bacillus pumilus, typical flora of host plants and soil, and Gram – of the Enterobacteriaceae family. On the other hand, the stinkbugs in captivity were less variable in bacterial counting (106 CFU/mg),  two enterobacteria of the genus Klebsiella sp. and Serratia marcescens were isolated and identified. Occasionally, Enterococcus faecium and Bacillus sp were also found in captivity. In addition, the CFU/mg of the entomopathogen Serratia marcescens seems to be associated with insect stress generated by the captivity conditions and was reduced with the addition of 125 mg/l of streptomycin into the drinking water. ARISA profiles of the microbiome of the stinkbugs fed in captivity showed lower diversity, 3 to 4 OTUs (Operational Taxonomic Unit) compared to 6 to 8 OTUs found in those insects collected from soybean cultivars. The biodiversity of the microbiome of the bugs in their natural environment is more complex than in captivity conditions. These changes in biodiversity should be taken into account for studies of  microbial communities impact on insects