Characterising the native midgut bacteria from main African malaria vector species, Anopheles arabiensis and An. funestus

Abstract

Malaria predominantly affects the African continent. The dominant African malaria vectors include mosquito species from the Anopheles gambiae complex and the Anopheles funestus group. Mosquito midgut microbiota play essential roles in physiology and disease transmission. Thus, if common bacteria exist amongst vector species, this could be exploited for malaria control. Accordingly, this study characterised the native midgut bacteria of Anopheles arabiensis (member of An. gambiae complex) and Anopheles funestus (member of An. funestus group). Additionally, field-collected mosquitoes are routinely preserved and transported to a laboratory for analysis and thus far, it is unknown if midgut bacteria can be identified from preserved Anopheles. Therefore, this study also investigated if midgut bacteria could be identified after mosquito preservation. Midgut bacteria were identified using culture-dependent (midgut dissections, culturomics, MALDI-TOF MS) and culture-independent techniques (midgut dissections, bacterial DNA extraction, next generation sequencing). Bacteria were identified from colonised mosquitoes that were fresh (non-preserved) and preserved on silica desiccant or in RNAlater™ solution. Bacteria were also characterised from field-collected An. arabiensis from KwaZulu-Natal and Mpumalanga. Results show that midgut bacteria can be characterised from preserved Anopheles samples. Aeromonas hydrophila, Elizabethkingia anophelis, Enterobacter cloacae, Herbaspirillum huttiense, Pseudomonas grimontii, Psychrobacter species, Raoultella ornithinolytica, Serratia oryzae, and Staphylococcus epidermidis were bacteria isolated from both vectors. Of these, S. epidermidis was also identified in field-collected An. arabiensis, making this a promising bacterium for future studies investigating the use of mosquito midgut bacteria for disease control. Overall, this study characterised the common midgut bacteria between An. arabiensis and An. funestus and discovered that midgut bacteria could be identified from preserved Anopheles.