THE MIDGUT BACTERIAL-FLORA OF WILD AEDES-TRISERIATUS, CULEX-PIPIENS, AND PSOROPHORA-COLUMBIAE MOSQUITOS

The midgut bacterial flora of wild-caught Aedes triseriatus, Culex pip iens, and Psorophora columbiae mosquitoes was investigated. Dissected midgut contents were examined using quantitative aerobic bacterial cul tures. Individual colonies (n = 134) were subcultured and identified t o species. Midgut bacterial counts changed dramatically during mosquit o development. A 280-1,100-fold decrease in the bacterial population o ccurred between the larval stage and pupal emergence, whereas a subseq uent 70-16,000-fold increase occurred after blood-feeding. Bacterial i dentifications revealed a complex flora with up to nine genera identif ied during any stage of development. Species most frequently isolated were Serratia marcescens, Klebsiella ozonae, Pseudomonas aeruginosa, a nd Enterobacter agglomerans. The presence of genetically well-characte rized bacteria in the midgut flora of mosquitoes may provide a means o f expressing novel genetic products in vector species.