Pseudomonas mendocina Isolated from Anopheles Midguts has a Greater Potential to Build Thick Biofilms than Serratia marcescens.

Malaria remains the most prevalent vector-borne disease. Manipulating the Anopheles midgut microbiota offers a promising malaria control strategy. Biofilm-forming Pseudomonas spp. may reduce Plasmodium infection in Anopheles mosquitoes because bacterial biofilms at the midgut epithelium may restrict the ookinete movement; therefore, it has a potential application as a malaria transmission blocking tool. Thus, the present study focuses on the characterization of the biofilm-forming potential of bacteria isolated from Anopheles midguts, with an emphasis on Pseudomonas and Serratia species. Bacteria were isolated, identified via 16S rDNA sequencing, and analyzed for antibiotic susceptibility and biofilm production. Isolates of interest were subjected to whole genome sequencing, and we focused our study on two distinct isolates (Serratia marcescens As_A1-C1 and Pseudomonas mendocina Ag_C1). The capacity of the isolates to form biofilms was evaluated by microbiological and biophysical tools, including quantification of biofilm maximum height using confocal microscopy. The various techniques allowed us to observe that S. marcescens As_A1-C1 formed poorly structured biofilms. In contrast, P. mendocina Ag_C1 produced highly thick and heterogeneous biofilms, which were more pronounced on complex culture media mimicking midgut conditions. Also, whole genome sequencing of S. marcescens and P. mendocina isolates revealed the carriage of relevant biofilm-related genes. Overall, our results highlight that the isolated P. mendocina has the potential to act as a tool for the development of new malaria control strategies.