Imaging mass spectrometry and MS/MS molecular networking reveals chemical interactions among cuticular bacteria and pathogenic fungi associated with fungus-growing ants

Abstract

The fungus-growing ant-microbe symbiosis is an ideal system to study chemistry-based microbial interactions due to the wealth of microbial interactions described, and the lack of information on the molecules involved therein. In this study, we employed a combination of MALDI imaging mass spectrometry (MALDI-IMS) and MS/MS molecular networking to study chemistry-based microbial interactions in this system. MALDI IMS was used to visualize the distribution of antimicrobials at the inhibition zone between bacteria associated to the ant Acromyrmex echinatior and the fungal pathogen Escovopsis sp. MS/MS molecular networking was used for the dereplication of compounds found at the inhibition zones. We identified the antibiotics actinomycins D, X2 and X0β, produced by the bacterium Streptomyces CBR38; and the macrolides elaiophylin, efomycin A and efomycin G, produced by the bacterium Streptomyces CBR53.These metabolites were found at the inhibition zones using MALDI IMS and were identified using MS/MS molecular networking. Additionally, three shearinines D, F, and J produced by the fungal pathogen Escovopsis TZ49 were detected. This is the first report of elaiophylins, actinomycin X0β and shearinines in the fungus-growing ant symbiotic system. These results suggest a secondary prophylactic use of these antibiotics by A. echinatior because of their permanent production by the bacteria.

Secondary Metabolites from Escovopsis weberi and Their Role in Attacking the Garden Fungus of Leaf‐Cutting Ants

“…The finding of shearinines is in line with Boya et al., who recently observed shearinines D, F, and J in a co‐cultivation experiment with mutualistic Streptomyces symbionts of Acromyrmex echinatior leaf‐cutting ants against E. weberi TZ49 . Also, genome mining using antismash revealed that the E. weberi genome comprises genes involved in indole terpenoid biosynthesis fitting to the formation of shearinines.…”

“…Several shearinines have been recently identified as secondary metabolites from E. weberi . However, we observed additional prominent peaks 1 and 2 in the LC‐DAD‐ESI‐MS profile that turned out to be novel shearinine derivatives.…”

“…However, until now, no other secondary metabolites from E. weberi have been identified and it has not been established which compounds from E. weberi contribute to overpower the mutualistic fungus of leaf‐cutting ants . Here, we present the isolation and identification of secondary metabolites from E. weberi and evaluate their biological function, in particular their impact on L. gongylophorus and A. octospinosus leaf‐cutting ants.…”

“…In a co‐cultivation study of E. weberi with microbial symbionts of leaf‐cutting ants Férnandez‐Marín et al. discovered that E. weberi produces several shearinines …”

The Role of Soil Microbes in Promoting Plant Growth

“…The families of nitrogen-fixing bacteria (NFB) consist of more than one hundred of prokaryotes (Semenov et al, 2016). Generally, the symbiotic relationship between NFB and its host belongs to one-to-many relationship (Boya P et al, 2017). The initial product of assimilation with carbon dioxide is malic acid or aspartic acid in symbiotic NFB related to C4 plants, which the fixation efficiency was higher than that in C3 plant with the 3-phosphoglyceric acid.…”