Bacteria associated with Parthenium hysterophorus root exudate influence olfactory oviposition responses of Anopheles gambiae

Abstract

Introduction: Previously, we documented that the malaria vector Anopheles gambiae responds to volatile emissions from the root exudate water of the invasive plant, Parthenium hysterophorus. However, the origin of the volatiles remains to be investigated. Here, we isolated bacteria from the root exudate water of the plant, test the influence of their volatiles in gravid An. gambiae oviposition, and examined relationships between volatile profiles and oviposition.

Methods: Bacteria from root exudate water of P. hysterophorus were isolated using culture on Luria Bertani medium and identified by sequencing the 16S rRNA gene. Cultures of individual isolates were evaluated for egg laying response by gravid An. gambiae and number of eggs laid compared using generalized linear models relative to those in crude bacteria-mixture. Headspace volatile emissions of the bacterial isolates were analyzed by gas chromatography coupled to mass spectrometry (GC-MS) and relationships between volatile organic compound (VOC) profiles and gravid mosquito oviposition examined using Random Forest Analysis. Proximate analysis was performed to assess the difference in volatile chemistry among the different isolates.