In vitro tolerance and biotransformation of temephos and deltamethrin by gut bacteria Chryseobacterium gleum and Cedecea neteri isolated from Aedes aegypti.
Abstract
The progressive loss of insecticide susceptibility in Aedes aegypti compromises the control of this arbovirus vector. The mosquito gut microbiota may modulate susceptibility and contribute to insecticide degradation. This study evaluated the in vitro tolerance of gut bacteria isolated from Ae. aegypti populations exposed to temephos and deltamethrin in Caquetá (Colombia) and their capacity to transform these insecticides. Growth and growth kinetics were assessed in minimal medium in the presence of commercial insecticide formulations. Biotransformation was investigated by ultra-high-performance liquid chromatography-positive electrospray ionization-Orbitrap high-resolution mass spectrometry (UHPLC-(+)ESI-Orbitrap/HRMS) and gas chromatography-mass spectrometry (GC-MS), which allowed the tentative identification of metabolites, whereas the reduction of the parent compounds was estimated from chromatographic peak areas relative to abiotic controls. All strains grew in Luria-Bertani medium, but only three showed consistent growth in M9 minimal medium with the insecticides. Although Enterobacter asburiae P2D2C1 was also analyzed by GC-MS with deltamethrin, its profiles did not allow a reliable characterization of products; the final characterization therefore focused on Chryseobacterium gleum P31D2 (temephos) and Cedecea neteri P2HD2 (deltamethrin). After 72 h, C. gleum P31D2 reduced the temephos signal by 76.05% relative to the abiotic control, and five metabolites were tentatively identified, including 4,4'-thiodiphenol, 4,4'-sulfinyldiphenol, and temephos sulfoxide. C. neteri P2HD2 reduced the relative abundance of deltamethrin by 75.39% over 24 h versus 8.52% in the abiotic control (net biotransformation, 66.87%), and four metabolites were tentatively identified, including 3-phenoxybenzaldehyde and 3-phenoxyphenylacetonitrile. Hypothetical metabolic pathways are proposed. These in vitro findings provide a basis for future studies on the role of gut bacteria in insecticide biotransformation.
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