AUTHOR=Chen Shicheng , Blom Jochen , Walker Edward D. 

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

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01483

DOI=10.3389/fmicb.2017.01483

ISSN=1664-302X

ABSTRACT=<p>Strains of <italic>Serratia marcescens</italic>, originally isolated from the gut lumen of adult female <italic>Anopheles stephensi</italic> mosquitoes, established persistent infection at high rates in adult <italic>A. stephensi</italic> whether fed to larvae or in the sugar meal to adults. By contrast, the congener <italic>S. fonticola</italic> originating from <italic>Aedes triseriatus</italic> had lower infection in <italic>A. stephensi</italic>, suggesting co-adaptation of <italic>Serratia</italic> strains in different species of host mosquitoes. Coinfection at high infection rate in adult <italic>A. stephensi</italic> resulted after feeding <italic>S. marcescens</italic> and <italic>Elizabethkingia anophelis</italic> in the sugar meal, but when fed together to larvae, infection rates with <italic>E. anophelis</italic> were much higher than were <italic>S. marcescens</italic> in adult <italic>A. stephensi</italic>, suggesting a suppression effect of coinfection across life stages. A primary isolate of <italic>S. marcescens</italic> 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 <italic>A. stephensi</italic>, designated <italic>S. marcescens</italic> ano1 and ano2, were sequenced and compared to other <italic>Serratia</italic> symbionts associated with insects, nematodes and plants. <italic>Serratia marcescens</italic> ano1 and ano2 had predicted virulence factors possibly involved in attacking parasites and/or causing opportunistic infection in mosquito hosts. <italic>S. marcescens</italic> 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 <italic>Serratia</italic> species. It is interesting that genome sequences in <italic>S. marcescens</italic> ano1 and ano2 are distinctly different from those in <italic>Serratia</italic> sp. Ag1 and Ag2 which were isolated from <italic>Anopheles gambiae</italic>. Compared to <italic>Serratia</italic> sp. Ag1 and Ag2, <italic>S. marcescens</italic> ano1 and ano2 have more rRNAs and many important genes involved in commensal and anti-parasite traits.</p>