Effects of Xenorhabdus and Photorhabdus bacterial metabolites on the ovipositional activity of Aedes albopictus

Abstract

Viral diseases like yellow fever, dengue, zika have an alarming impact on public health affecting millions of people around the globe. These diseases can be transmitted by Aedes albopictus – a species originally endemic to South Asia but now widely distributed in several countries outside Asia. Xenorhabdus and Photorhabdus spp., are enteric Gram-negative bacterial symbionts of insect-preying nematodes and are known to produce an array of natural products (NP) with various activities including larvicidal activity. This study demonstrated that supernatants of different Xenorhabdus and Photorhabdus bacteria effectively deterred Ae. albopictus mosquito oviposition in a concentration dependent manner. Xenorhabdus cabanillasii displayed deterrent effects at 50-5% concentrations with oviposition activity index values ranging between -0.87 and -0.35, whereas the index values for X. nematophila were between -0.82 and -0.52 at concentrations of 50-10%. The other bacteria (X. szentirmaii, X. doucetiae, and P. kayaii) were effective at concentrations ≥20%. Using promoter exchange mutants of selected biosynthetic gene clusters in a Δhfq background generated by the easyPACId approach, fabclavine from X. szentirmaii was identified as the bioactive compound with evident deterrent effects. Such compounds with deterrence effects could be useful in mosquito control programs as preventing breeding site in specific habitats can greatly influence mosquito species establishment, population densities, and dispersion in conducive areas.