Antibiotic Treatment in Anopheles coluzzii Affects Carbon and Nitrogen Metabolism

Abstract

The mosquito microbiota reduces the vector competence of Anopheles to Plasmodium and affects host fitness; it is therefore considered as a potential target to reduce malaria transmission. While immune induction, secretion of antimicrobials and metabolic competition are three typical mechanisms of microbiota-mediated protection against invasive pathogens in mammals, the involvement of metabolic competition or mutualism in mosquito-microbiota and microbiota-Plasmodium interactions has not been investigated. Here, we describe a metabolome analysis of the midgut of Anopheles coluzzii provided with a sugar-meal or a non-infectious blood-meal, under conventional or antibiotic-treated conditions. We observed that the antibiotic treatment affects the tricarboxylic acid cycle and nitrogen metabolism, notably resulting in decreased abundance of free amino acids. Linking our results with published data, we identified pathways which may participate in microbiota-Plasmodium interactions via metabolic interactions or immune modulation and thus would be interesting candidates for future functional studies.

Production of germ-free mosquitoes via transient colonisation allows stage-specific investigation of host–microbiota interactions

“…The production of a relevant negative control for the study of the adult mosquito microbiota has long been a technical issue, which was either solved by allowing normal development and treating emerging mosquitoes with antibiotics or by producing stunted germ-free mosquitoes 7 , 9 . However, antibiotic treatments are known to reduce bacterial load and modify microbiota composition rather than produce germ-free mosquitoes 23 , and toxic effects of antibiotics on the host cannot be ruled out 14 . Moreover, several pieces of evidence underline the requirement for standardised conditions during development due to carryover effects of the larval environment from larvae to adults.…”

“…The current gold standard to avoid any carry-over effect is the use of antibiotics at adult emergence after conventional larval rearing. However, antibiotics may have off-target effects (notably on mitochondria) and do not fully sterilise mosquitoes 14 . In the past, several studies proposed rearing protocols of germ-free larvae 15 , 16 , which could not be reproduced in recent experiments 9 .…”

Production of germ-free mosquitoes via transient colonisation allows stage-specific investigation of host-microbiota interactions

“…The production of a relevant negative control for the study of the adult mosquito microbiota has long been a technical issue, which was either solved by allowing normal development and treating emerging mosquitoes with antibiotics or by producing stunted germ-free mosquitoes 7,9 . However, antibiotic treatments are known to reduce bacterial load and modify microbiota composition rather than produce germ-free mosquitoes 23 , and toxic effects of antibiotics on the host cannot be ruled out 14 . Moreover, several pieces of evidence underline the requirement for standardised conditions during development due to carry over effects of the larval environment from larvae to adults.…”

“…The current gold standard to avoid any carry-over effect is the use of antibiotics at adult emergence after conventional larval rearing. However, antibiotics may have off-target effects (notably on mitochondria) and do not fully sterilize mosquitoes 14 . In the past, several studies proposed rearing protocols of germ-free larvae 15,16 , which could not be reproduced in recent experiments 9 .…”

The Axenic and Gnotobiotic Mosquito: Emerging Models for Microbiome Host Interactions

“…Using this approach, several groups have reported that the microbiome plays a role in modulating gut immunity thereby effecting susceptibility to viral and parasitic pathogens ( Xi et al, 2008 ; Dong et al, 2009 ; Kalappa et al, 2018 ; Wu et al, 2019 ). Similarly, antibiotic clearance of the microbiota has demonstrated a role for the microbiome in mosquito metabolism and sensitivity to insecticides ( Xiao et al, 2017 ; Barnard et al, 2019 ; Chabanol et al, 2020 ). These studies, like the presence/absence studies used in axenic models, offer generalizable insights into the effects of the microbiota on host phenotypes.…”