Screening of antibiotics to alter the Plutella xylostella L (Plutellidae: Lepidoptera) gut microbial diversity

The diamondback moth, Plutella xylostella L (Plutellidae: Lepidoptera) is the most important pest of cruciferous crops in wide areas of the world. Larvae of P xylostella have rich microbial communities inhabiting in the gut and those bacteria contribute to the fitness. In the present investigations the effect of five different concentrations of eight antibiotics on gut bacterial diversity of P xylostella was studied. Bacterial culture (ISO-1) from gut homogenates was subjected to antibiotic screening tests. Cefixime (5 mg/ml) was the most effective antibiotic with the greatest inhibition zone (25 mm). The antibiotics were screened against the larvae of the insect. Higher mortality and reduced growth of larvae were recorded in case of larvae feeding on cefixime-treated leaves as compared to other treatments. Cefixime-exposed P xylostella was continuously reared in laboratory. Species diversity was significantly reduced in cefixime-exposed population. The cfu/ml of gut suspension was also reduced in cefixime-exposed population of the insect. The results indicated that bacterial symbionts play a crucial role in the successful development of the host.