title: Bacterial population dynamics in three anopheline species: the impact on Plasmodium sporogonic development.
abstract: The functional role of bacteria in the midgut of adult mosquitoes is unknown. In this study, we examined the population dynamics of midgut bacteria of laboratory reared Anopheles stephensi, An. gambiae, and An. albimanus. Mosquito midguts were dissected under sterile conditions and examined for the presence of bacteria using standard microbiologic techniques. Ninety percent and 73% (n = 30) of newly emerged An. gambiae and An. stephensi, respectively, harbored bacteria. In contrast, only 17% (n = 23) of An. albimanus harbored any bacteria. The bacterial population increased 11-40-fold in the presence of a blood meal, but then decreased to pre-blood meal levels in 3-5 days. Pseudomonas cepacia, Enterobacter agglomerans, and Flavobacterium spp. were found in all three anopheline species. Midgut bacteria were acquired both transtadially and through the sugar meal. Transtadial transmission was demonstrated by successfully passaging Escherichia coli HS5 from the larval to the adult stage. However, midgut bacteria were acquired more efficiently through the sugar meal than through transtadial passage. An increase in midgut bacterial counts after mosquitoes were exposed to a bacteria/sugar suspension significantly reduced oocyst infection rates and densities in Plasmodium falciparum-infected mosquito cohorts. Since bacteria occur naturally in wild mosquitoes, it may be possible to modify anopheline vector competence using introduced or indigenous bacteria.
authors.affiliation: Department of Microbiology, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Pumpuni
authors.forename: J
authors.initials: J
authors.lastname: Demaio
authors.forename: M
authors.initials: M
authors.lastname: Kent
authors.forename: J R
authors.initials: JR
authors.lastname: Davis
authors.forename: J C
authors.initials: JC
authors.lastname: Beier
mesh_terms: D000818:Animals; D000852:Anopheles / Q000382:microbiology*; D001419:Bacteria / Q000302:isolation & purification*; D018407:Bacterial Physiological Phenomena; D005260:Female; D007303:Insect Vectors / Q000382:microbiology*; D010963:Plasmodium falciparum / Q000254:growth & development*