Discovery of Antimicrobial Lipodepsipeptides Produced by a Serratia sp. within Mosquito Microbiomes

Abstract

The Anopheles mosquito that harbors the Plasmodium parasite contains a microbiota that can influence both the vector and the parasite. In recent years, insect-associated microbes have highlighted the untapped potential of exploiting interspecies interactions to discover bioactive compounds. In this study, we report the discovery of nonribosomal lipodepsipeptides that are produced by a Serratia sp. within the midgut and salivary glands of Anopheles stephensi mosquitoes. The lipodepsipeptides, stephensiolides A-K, have antibiotic activity and facilitate bacterial surface motility. Bioinformatic analyses indicate that the stephensiolides are ubiquitous in nature and are likely important for Serratia spp. colonization within mosquitoes, humans, and other ecological niches. Our results demonstrate the usefulness of probing insect-microbiome interactions, enhance our understanding of the chemical ecology within Anopheles mosquitoes, and provide a secondary-metabolite scaffold for further investigate of this complex relationship.

Identification of Antimicrobial Compounds from Sandwithia guyanensis-Associated Endophyte Using Molecular Network Approach

“…Compound 1 showed a molecular ion peak [M+H] + at m/z 670.4401 (calculated for 670.4386, ∆m = +2.2 ppm) in the ESI-HRMS spectrum, consistent with the molecular formula of C 33 H 59 N 5 O 9 . Analysis of 1D and 2D NMR spectra of compound 1 indicated the presence of five amino acids: threonine, valine, isoleucine and two serine residues and the presence of long alkyl chain, leading to its identification as a stephensiolide I analogue upon comparison with existing literature (Figure 3) [19,20]. The MS/MS spectrum of compound 1 confirmed the previous annotated structure through the detection of immonium ions and the classical peptide sequencing.…”

“…The proposed structures of the isolated molecules can be used to propagate the annotation to other connected MS/MS spectra. By comparison with literature data, the non-isolated molecules could be identified as stephensiolides A, B and E [19,20] ( Figure 2B). The absolute configuration of these identified and isolated compounds could not be confirmed.…”

“…Hence, it is for the first time that these compounds are isolated from a fungus. They had been described so far only once, from a bacterium associated with mosquitoes' metabolites from the Serretia genus [19,20]. This is the reason for the absence of these uncommon compounds in the available MS/MS databases.…”

“…The HMBC correlations 1 H-13 C between protons 1 with C-2 and C-3 as well as the correlations of H-5 and H-6 with C-3 and C-4 permitted to fix the double bond at position at C-5-C-6 of the acyl chain ( Figures S30-S33). Unfortunately, the coupling constants are not observable for the double bond protons and therefore, the configuration of the latter could not be determined [19].…”

“…The isolated compounds were identified as stephensiolides I (1), D (2), G (3), C (4) and stephensiolide F (5) by comparison with spectroscopic data from available literature ( Figure 3) [19,20]. The proposed structures of the isolated molecules can be used to propagate the annotation to other connected MS/MS spectra.…”