The Novel Lipopeptide Poaeamide of the Endophyte Pseudomonas poae RE*1-1-14 Is Involved in Pathogen Suppression and Root Colonization.

Endophytic Pseudomonas poae strain RE*1-1-14 was originally isolated from internal root tissue of sugar beet plants and shown to suppress growth of the fungal pathogen Rhizoctonia solani both in vitro and in the field. To identify genes involved in its biocontrol activity, RE*1-1-14 random mutagenesis and sequencing led to the identification of a nonribosomal peptide synthetase (NRPS) gene cluster predicted to encode a lipopeptide (LP) with a 10-amino-acid peptide moiety. The two unlinked gene clusters consisted of three NRPS genes, designated poaA (cluster 1) and poaB and poaC (cluster 2), spanning approximately 33.7 kb. In silico analysis followed by chemical analyses revealed that the encoded LP, designated poaeamide, is a structurally new member of the orfamide family. Poaeamide inhibited mycelial growth of R. solani and different oomycetes, including Phytophthora capsici, P. infestans, and Pythium ultimum. The novel LP was shown to be essential for swarming motility of strain RE*1-1-14 and had an impact on root colonization of sugar beet seedlings The poaeamide-deficient mutant colonized the rhizosphere and upper plant cortex at higher densities and with more scattered colonization patterns than the wild type. Collectively, these results indicate that Pseudomonas poae RE*1-1-14 produces a structurally new LP that is relevant for its antagonistic activity against soilborne plant pathogens and for colonization of sugar beet roots.

Structure elucidation and biosynthetic locus of trinickiabactin from the plant pathogenic bacterium Trinickia caryophylli.

Within the framework of our effort to discover new bioactive metabolites from Gram-negative bacteria, trinickiabactin (1) was isolated from the plant pathogenic strain Trinickia caryophylli DSM 50341. Whole genome sequencing allowed the identification of its biosynthetic gene cluster. The structure of 1 bears a rare diazeniumdiolate ligand system and was elucidated by a combination of NMR- and MS-spectroscopic techniques and bioinformatics. Trinickiabactin was found to be antibacterial toward several Gram-negative bacteria (MIC values ranged from 3.5 to 34.0 µg ml-1).

Draft Genome Sequence of Micromonospora sp. Strain MW-13, a Bacterial Strain with Antibacterial Properties and Plant Growth Promotion Potential Isolated from the Rhizosphere of Wheat in Iran.

Strain MW13 exhibited broad-spectrum antibacterial activity toward Gram-positive and Gram-negative pathogens. The 7.1-Mb draft genome gives insight into the complete secondary metabolite production capacity and reveals genes putatively responsible for its antibacterial activity, as well as genes which contribute to plant growth promotion.

Draft Genome Sequence of the Extensively Drug-Resistant Pseudomonas aeruginosa Clinical Isolate TUEPA7472.

Pseudomonas aeruginosa TUEPA7472 is extensively drug resistant (XDR) and is a representative Gram-negative rod that is multiresistant toward 4 classes of clinically relevant antibiotics (4MRGN). The 6.8-Mb draft genome sequence of this strain provides insight into these resistance mechanisms and the potential of the strain to produce virulence factors.

The contribution of genome mining strategies to the understanding of active principles of PGPR strains.

Pathogenic microorganisms and insects affecting plant health are a major and chronic threat to food production and the ecosystem worldwide. As agricultural production has intensified over the years, the use of agrochemicals has in turn increased. However, this extensive usage has had several detrimental effects, with a pervasive environmental impact and the emergence of pathogen resistance. In addition, there is an increasing tendency among consumers to give preference to pesticide-free food products. Biological control, through the employment of plant growth-promoting rhizobacteria (PGPR), is therefore considered a possible route to the reduction, even the elimination, of the use of agrochemicals. PGPR exert their beneficial influence by a multitude of mechanisms, often involving antibiotics and proteins, to defend the host plant against pathogens. To date, these key metabolites have been uncovered only by systematic investigation or by serendipity; their discovery has nevertheless been propelled by the genomic revolution of recent years, as increasing numbers of genomic studies have been integrated into this field, facilitating a holistic view of this topic and the rapid identification of ecologically important metabolites. This review surveys the highlights and advances of genome-driven compound and protein discovery in the field of bacterial PGPR strains, and aims to advocate for the benefits of this strategy.

Methods for the comprehensive structural elucidation of constitution and stereochemistry of lipopeptides.

A panel of methods of general suitability for complete structural elucidation of the stereochemistry of cyclopeptides, depsipeptides and lipopeptides is presented and described in detail. The suitability of the proposed methods was exemplified on the lipopeptide poaeamide from Pseudomonas poae. Amino acid configurations have been assigned by direct LC enantiomer separation with Chiralpak ZWIX(+) and were confirmed by GC enantiomer separation on Chirasil L-Val. 3-Hydroxydecanoic acid absolute configuration was analyzed on Chiralpak ZWIX(+) and confirmed by injection on ZWIX(-) which showed opposite elution order. Plenty of d-amino acids have been found in this lipopeptide. It contained in total 5 Leu residues of which one had d-configuration. The position of the d-Leu in the peptide sequence was determined by pepsin and chemical digestions in combination with isolation of diagnostic peptide-fragments and subsequent identification of absolute configurations of the Leu residues. This allowed pinpointing the position of the d-amino acid. The complementarity of the peptide retention profiles on Chiralpak ZWIX column as compared to both RPLC and HILIC suggests its great utility as an alternative peptide separation tool.