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Mangotoxin production was first described in Pseudomonas syringae pv. syringae strains. A phenotypic characterization of 94 P. syringae strains was carried out to determine the genetic evolution of the mangotoxin biosynthetic operon (mbo). We designed a PCR primer pair specific for the mbo operon to examine its distribution within the P. syringae complex. These primers amplified a 692-bp DNA fragment from 52 mangotoxin-producing strains and from 7 non-mangotoxin-producing strains that harbor the mbo operon, whereas 35 non-mangotoxin-producing strains did not yield any amplification. This, together with the analysis of draft genomes, allowed the identification of the mbo operon in five pathovars (pathovars aptata, avellanae, japonica, pisi, and syringae), all of which belong to genomospecies 1, suggesting a limited distribution of the mbo genes in the P. syringae complex. Phylogenetic analyses using partial sequences from housekeeping genes differentiated three groups within genomospecies 1. All of the strains containing the mbo operon clustered in groups I and II, whereas those lacking the operon clustered in group III; however, the relative branching order of these three groups is dependent on the genes used to construct the phylogeny. The mbo operon maintains synteny and is inserted in the same genomic location, with high sequence conservation around the insertion point, for all the strains in groups I and II. These data support the idea that the mbo operon was acquired horizontally and only once by the ancestor of groups I and II from genomospecies 1 within the P. syringae complex. [ABSTRACT FROM AUTHOR]

Ancient environmental samples, including permafrost soils and frozen animal remains, represent an archive with microbial communities that have barely been explored. This yet unexplored microbial world is a genetic resource that may provide us with new evolutionary insights into recent genomic changes, as well as novel metabolic pathways and chemistry. Here, we describe Actinomycetota Micromonospora, Oerskovia, Saccharopolyspora, Sanguibacter and Streptomyces species were successfully revived and their genome sequences resolved. Surprisingly, the genomes of these bacteria from an ancient source show a large phylogenetic distance to known strains and harbour many novel biosynthetic gene clusters that may well represent uncharacterised biosynthetic potential. Metabolic profiles of the strains display the production of known molecules like antimycin, conglobatin and macrotetrolides, but the majority of the mass features could not be dereplicated. Our work provides insights into Actinomycetota isolated from an ancient source, yielding unexplored genomic information that is not yet present in current databases. [ABSTRACT FROM AUTHOR]

Background: Plants rely on their root microbiome as the first line of defense against soil-borne fungal pathogens. The abundance and activities of beneficial root microbial taxa at the time prior to and during fungal infection are key to their protective success. If and how invading fungal root pathogens can disrupt microbiome assembly and gene expression is still largely unknown. Here, we investigated the impact of the fungal pathogen Fusarium oxysporum (fox) on the assembly of rhizosphere and endosphere microbiomes of a fox-susceptible and fox-resistant common bean cultivar. Results: Integration of 16S-amplicon, shotgun metagenome as well as metatranscriptome sequencing with community ecology analysis showed that fox infections significantly changed the composition and gene expression of the root microbiome in a cultivar-dependent manner. More specifically, fox infection led to increased microbial diversity, network complexity, and a higher proportion of the genera Flavobacterium, Bacillus, and Dyadobacter in the rhizosphere of the fox-resistant cultivar compared to the fox-susceptible cultivar. In the endosphere, root infection also led to changes in community assembly, with a higher abundance of the genera Sinorhizobium and Ensifer in the fox-resistant cultivar. Metagenome and metatranscriptome analyses further revealed the enrichment of terpene biosynthesis genes with a potential role in pathogen suppression in the fox-resistant cultivar upon fungal pathogen invasion. Conclusion: Collectively, these results revealed a cultivar-dependent enrichment of specific bacterial genera and the activation of putative disease-suppressive functions in the rhizosphere and endosphere microbiome of common bean under siege. [ABSTRACT FROM AUTHOR]

Actinobacteria are a rich source of bioactive molecules, and genome sequencing has shown that the vast majority of their biosynthetic potential has yet to be explored. However, many of their biosynthetic gene clusters (BGCs) are poorly expressed in the laboratory, which prevents discovery of their cognate natural products. To exploit their full biosynthetic potential, better understanding of the signals that promote the expression of BGCs is needed. Here, we show that the human stress hormone epinephrine (adrenaline) elicits siderophore production by Actinobacteria. Catechol was established as the likely eliciting moiety, since similar responses were seen for catechol and for the catechol-containing molecules dopamine and catechin but not for related molecules. Exploration of the catechol-responsive strain Streptomyces sp. MBT84 using mass spectral networking revealed elicitation of a BGC that produces the angucycline glycosides aquayamycin, urdamycinone B and galtamycin C. Heterologous expression of the catechol-cleaving enzymes catechol 1,2-dioxygenase or catechol 2,3-dioxygenase counteracted the eliciting effect of catechol. Thus, our work identifies the ubiquitous catechol moiety as a novel elicitor of the expression of BGCs for specialized metabolites. The biosynthetic gene clusters of Actinobacteria are poorly expressed in the laboratory, necessitating a better understanding of the signals that promote their expression in order to exploit their full biosynthetic potential. Here, the authors show that the stress hormone epinephrine elicits the expression of biosynthetic gene clusters and influences the metabolism of Streptomyces, with the catechol moiety proving key to this response. [ABSTRACT FROM AUTHOR]

We describe the genetic organization of a copper-resistant plasmid containing copG and cusCBA genes in the plant pathogen Pseudomonas syrrngae. Chromosomal variants of czcCBA and a plasmid variant of cusCBA were present in different P. syringae pathovar strains. Transformation of the copper-sensitive Pseudomonas syringae pv. syringae FF5 strain with copG or cusCBA conferred copper resistance, and quantitative real-time PCR (qRT-PCR) experiments confirmed their induction by copper. [ABSTRACT FROM AUTHOR]