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Arginine-derived polyketides are ubiquitous signals shaping cross-kingdom microbial interactions

ABSTRACT: Microbial consortia consist of a multitude of prokaryotic and eukaryotic microorganisms. Their interaction is critical for the functioning of ecosystems. Until now, there is limited knowledge about the communication signals determining the interaction between bacteria and fungi and how they influence microbial consortia. Here, we discovered that bacterial low molecular weight arginine-derived polyketides trigger the production of distinct natural products in fungi. These compounds are produced by actinomycetes found on all continents except Antarctica and are characterized by an arginine-derived positively charged group linked to a linear or cyclic polyene moiety. Producer bacteria can be readily isolated from soil as well as fungi that decode the signal and respond with the biosynthesis of natural products. Both arginine-derived polyketides and the compounds produced by fungi in response shape microbial interactions.

INSTRUMENT(S): Q Exactive Plus

ORGANISM(S): Streptomyces Iranensis

SUBMITTER: Thomas Krüger

LAB HEAD: Axel A. Brakhage

PROVIDER: PXD033242 | Pride | 2023-06-16

REPOSITORIES: Pride

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Project description:Mucormycosis is a life-threatening disease especially in immunocompromised patients that was caused my mucoralean fungi. The rate of mortality is tremendously increased in the last decades due to the lack of appropriate diagnostic tools, insufficient knowledge about the immune response toward the mucormycosis and unavailability of specific antifungal drugs. Several species of mucoralean fungi cause mucormycosis such as Lichtheimia, Rhizopus, and Mucor. Lichtheimia species ranks the second and third cause of mucormycosis in Europe and the USA, respectively. In this study, we investigated the receptors present on the surface of immune cells that bind to the spores of Lichtheimia. We focus on two strains of L. corymbifera (FSU:9682 and FSU:10164) using resting and heat-killed spores. Additionally, we choose alveolar macrophages (MH-S) to carry out our experiment. MH-S is the first line of defense in the lung and the major component in the innate immune system. MH-S surface proteins were biotinylated and incubated with Lichtheimia spores. The surface proteins and putative binding partners were enriched by streptavidin. LC-MS/MS analysis showed that several proteins are highly expressed in presence of Lichtheimia spores, of which the heat shock protein family A (HSPA8) was one of the most abundant proteins. FACS analysis and immunofluorescence examination confirmed that HSPA8 is highly abundant on the surface of the MH-S, but not on the surface of Lichtheimia spores. Moreover, our study showed that the intensity of HSPA8 on the surface of MH-S depends on the multiplicity of infection (MOI). Additionally, the blocking with anti-HSPA8 antibody reduced the capability of MH-S to engulf the Lichtheimia spores, but not Aspergillus fumigatus spores. This confirms that HSPA8 is specific to Lichtheimia. THis is the first study addressing the determination of surface receptors of alveolar macrophages that in the context of Mucoralean fungi.

Project description:Aspergillus species are a leading cause of invasive fungal infections. As resistance to first-line therapy involving triazole antifungal agents is rising, second-line therapy with echinocandins is expanding. Resistance to echinocandins is well-established to result from amino acid substitutions in the echinocandin drug target β-(1,3)-D-glucan synthase encoded by the fks1 gene. Recently, we identified several high MIC clinical isolates of A. fumigatus from patients failing echinocandin therapy that did not contain any mutation in the fks1 gene, indicating that echinocandin resistance in these isolates results from an undefined mechanism. To explore possible new mechanisms of resistance, we used a lab-derived strain, RG101, with a nearly identical susceptibility phenotype, as a model system. This strain does not contain fks1 mutations but showed prominent resistance to the echinocandin class drug caspofungin (CAS), while remaining sensitive to other echinocandins, azoles and polyenes. Glucan synthase isolated from RG101 was fully sensitive to drug. Yet, exposure to CAS during its growth yielded a modified enzyme that was insensitive (4-log orders) in kinetic inhibition assays to CAS, as well as other echinocandins. This induction of cross-resistance by CAS was also observed in clinical isolates. To determine the nature of a presumptive posttranslational modification (PTM) of the enzyme, we analyzed whole enzyme PTMs, including the known hot-spot regions, for methylation, acetylation and phosphorylation. While we did not identify any PTMs linked to resistance, analysis of the lipid microenvironment of CAS-induced resistant enzyme revealed a prominent increase in the abundance of dihydrosphingosine (DhSph) and phytosphingosine (PhSph). Exogenous addition of DhSph and PhSph to sensitive enzyme in in vitro kinetic inhibition assays recapitulated the CAS insensitivity of the cellular-derived enzyme. To further examine induction of drug-induced resistance, we used an in vitro assay to demonstrate that CAS, but not other echinocandin class drugs, prominently induced the production of mitochondrial-derived Reactive Oxygen Species (ROS) in A. fumigatus. RNASeq evaluation of whole cells confirmed a ROS signature in cells treated with CAS. Dampening the formation of ROS by antimycin A or thiourea eliminated the induction of drug resistance by CAS. We conclude that CAS-induced formation of ROS promotes a cellular stress response that alters the composition of plasma membrane lipids surrounding glucan synthase, changing its enzymatic properties to make it insensitive to echinocandins. This stress-induced response constitutes a novel mechanism of echinocandin resistance in Aspergillus, with implications for drug resistance and/or tolerance mechanisms in other fungal pathogens.

			Action	DRS
	LFQ.fasta	Fasta
	LFQ.mgf	Mgf
	LFQ.msf	Msf
	LFQ.pdResult	Other
	LFQ.pep.xml	Pepxml

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Arginine-derived polyketides are ubiquitous signals shaping cross-kingdom microbial interactions

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