RESUMEN
The compound 2,4-diacetylphloroglucinol (DAPG) is a broad-spectrum antibiotic that is primarily produced by Pseudomonas spp. DAPG plays an important role in the biocontrol disease suppressing activity of Pseudomonas spp. In the current study, we report the discovery of the DAPG biosynthetic cluster in strains of Chromobacterium vaccinii isolated from Brazilian aquatic environments and the distribution of the biosynthetic cluster in the Chromobacterium genus. Phylogenetic analysis of the phlD protein suggests the biosynthetic cluster probably entered the genus of Chromobacterium after a horizontal gene transfer event with a member of the Pseudomonas fluorescens group. We were able to detect trace amounts of DAPG in wild type cultures and confirm the function of the cluster with heterologous expression in Escherichia coli. In addition, we identified and verified the presence of other secondary metabolites in these strains. We also confirmed the ability of C. vaccinii strains to produce bioactive pigment violacein and bioactive cyclic depsipeptide FR900359. Both compounds have been reported to have antimicrobial and insecticidal activities. These compounds suggest strains of C. vaccinii should be further explored for their potential as biocontrol agents.
Asunto(s)
Antibacterianos , Chromobacterium , Chromobacterium/genética , Filogenia , Antibacterianos/farmacología , Brasil , Escherichia coli , PseudomonasRESUMEN
Bacillus subtilis RC 218 was originally isolated from wheat anthers as a potential antagonist of Fusarium graminearum, the causal agent of Fusarium head blight (FHB). It was demonstrated to have antagonist activity against the plant pathogen under in vitro and greenhouse assays. The current study extends characterizing B. subtilis RC 218 with a field study and genome sequencing. The field study demonstrated that B. subtilis RC 218 could reduce disease severity and the associated mycotoxin (deoxynivalenol) accumulation, under field conditions. The genome sequencing allowed us to accurately determine the taxonomy of the strain using a phylogenomic approach, which places it in the Bacillus velezensis clade. In addition, the draft genome allowed us to use bioinformatics to mine the genome for potential metabolites. The genome mining allowed us to identify 9 active secondary metabolites conserved by all B. velezensis strains and one additional secondary metabolite, the lantibiotic ericin, which is unique to this strain. This study represents the first confirmed production of ericin by a B. velezensis strain. The genome also allowed us to do a comparative genomics with its closest relatives and compare the secondary metabolite production of the publically available B. velezensis genomes. The results showed that the diversity in secondary metabolites of strains in the B. velezensis clade is driven by strains making different antibacterials.
Asunto(s)
Antibiosis , Bacillus/fisiología , Agentes de Control Biológico , Fusarium/fisiología , Enfermedades de las Plantas/microbiología , Tricotecenos/metabolismo , Triticum/metabolismo , Triticum/microbiología , Bacillus/clasificación , Genoma Bacteriano , Genómica/métodos , Metaboloma , Metabolómica/métodos , Filogenia , Metabolismo SecundarioRESUMEN
The GH10 endo-xylanase from Thermoascus aurantiacus CBMAI 756 (XynA) is industrially attractive due to its considerable thermostability and high specific activity. Considering the possibility of a further improvement in thermostability, eleven mutants were created in the present study via site-directed mutagenesis using XynA as a template. XynA and its mutants were successfully overexpressed in Escherichia coli Rosetta-gami DE3 and purified, exhibiting maximum xylanolytic activity at pH 5 and 65°C. Three of the eleven mutants, Q158R, H209N, and N257D, demonstrated increased thermostability relative to the wild type at 70°C and 75°C.Q158R and N257D were stable in the pH range 5.0-10.0, while WT and H209N were stable from pH 8-10. CD analysis demonstrated that the WT and the three mutant enzymes were expressed in a folded form. H209N was the most thermostable mutant, showing a Tm of 71.3°C. Molecular dynamics modeling analyses suggest that the increase in H209N thermostability may beattributed to a higher number of short helices and salt bridges, which displayed a positive charge in the catalytic core, stabilizing its tertiary structure.