Genomic, Physiologic, and Symbiotic Characterization of Serratia marcescens Strains Isolated from the Mosquito Anopheles stephensi

Strains of , originally isolated from the gut lumen of adult female mosquitoes, established persistent infection at high rates in adult whether fed to larvae or in the sugar meal to adults. By contrast, the congener originating from had lower infection in , suggesting co-adaptation of strains in different species of host mosquitoes. Coinfection at high infection rate in adult resulted after feeding and in the sugar meal, but when fed together to larvae, infection rates with were much higher than were in adult , suggesting a suppression effect of coinfection across life stages. A primary isolate of was resistant to all tested antibiotics, showed high survival in the mosquito gut, and produced alpha-hemolysins which contributed to lysis of erythrocytes ingested with the blood meal. Genomes of two primary isolates from , designated ano1 and ano2, were sequenced and compared to other symbionts associated with insects, nematodes and plants. ano1 and ano2 had predicted virulence factors possibly involved in attacking parasites and/or causing opportunistic infection in mosquito hosts. ano1 and ano2 possessed multiple mechanisms for antagonism against other microorganisms, including production of bacteriocins and multi-antibiotic resistance determinants. These genes contributing to potential anti-malaria activity including serralysins, hemolysins and chitinases are only found in some species. It is interesting that genome sequences in ano1 and ano2 are distinctly different from those in sp. Ag1 and Ag2 which were isolated from . Compared to sp. Ag1 and Ag2, ano1 and ano2 have more rRNAs and many important genes involved in commensal and anti-parasite traits.