Genomic analysis and temperature-dependent transcriptome profiles of the rhizosphere originating strain Pseudomonas aeruginosa M18

<p>Abstract</p> <p>Background</p> <p>Our previously published reports have described an effective biocontrol agent named <it>Pseudomonas </it>sp. M18 as its 16S rDNA sequence and several regulator genes share homologous sequences with those of <it>P. aeruginosa</it>, but there are several unusual phenotypic features. This study aims to explore its strain specific genomic features and gene expression patterns at different temperatures.</p> <p>Results</p> <p>The complete M18 genome is composed of a single chromosome of 6,327,754 base pairs containing 5684 open reading frames. Seven genomic islands, including two novel prophages and five specific non-phage islands were identified besides the conserved <it>P. aeruginosa </it>core genome. Each prophage contains a putative chitinase coding gene, and the prophage II contains a <it>capB </it>gene encoding a putative cold stress protein. The non-phage genomic islands contain genes responsible for pyoluteorin biosynthesis, environmental substance degradation and type I and III restriction-modification systems. Compared with other <it>P. aeruginosa </it>strains, the fewest number (3) of insertion sequences and the most number (3) of clustered regularly interspaced short palindromic repeats in M18 genome may contribute to the relative genome stability. Although the M18 genome is most closely related to that of <it>P. aeruginosa </it>strain LESB58, the strain M18 is more susceptible to several antimicrobial agents and easier to be erased in a mouse acute lung infection model than the strain LESB58. The whole M18 transcriptomic analysis indicated that 10.6% of the expressed genes are temperature-dependent, with 22 genes up-regulated at 28°C in three non-phage genomic islands and one prophage but none at 37°C.</p> <p>Conclusions</p> <p>The <it>P. aeruginosa </it>strain M18 has evolved its specific genomic structures and temperature dependent expression patterns to meet the requirement of its fitness and competitiveness under selective pressures imposed on the strain in rhizosphere niche.</p

Some chemical and physical characteristics of pantomycin, and antiobiotic isolated from Streptomyces hygroscopicus.

The production, isolation, and some structural studies of an antifungal, antibacterial, and antiviral substance from cultures of Streptomyces hygroscopicus are described. This material, designated pantomycin, appears to be a polypeptide antibiotic with inclusion of fatty acids and carbohydrate residues. Amino acid analysis of pantomycin acid hydrolysates indicates that it contains threonine, serine, proline, glycine, alanine, valine, alloisoleucine, and an as-yet-unidentified amino acid which appears to be different from types encountered in proteinaceous materials. In addition to the aforementioned compounds, the antibiotic was shown to contain alpha-aminobutyric acid after hydrogenation. Analysis of ether extracts of the hydrolysate mixture indicated the presence of several fatty aicds; myristic, isotridecanoic, lauric, and undecylic acids. The amino and fatty acid composition of pantomycin is similar to the known antibiotic stendomycin. Pantomycin appears to also have at least one carbohydrate-like residue incorporated into its structure. The presence of carbohydrate was indicated by periodic acid-Schiff base staining of electrophoretic patterns as well as positive color formation in the phenol-sulfuric and Molisch tests, but the carbohydrate did not appear to be either a hexose or a pentose. The antibiotic, which appears to be dissociated in alcoholic solution, forms stable aggregates under aqueous conditons

Isolation and Characterization of Metabolites from<i>Pseudomonas syringae</i>-strain 3366 and their Phytotoxicity Against Certain Weed and Crop Species

Phytotoxic effects of metabolites from a naturally occurring rhizobacterial isolate,Pseudomonas syringaestrain 3366, were determined on downy brome and ‘Hill 81’ winter wheat, along with 10 other weed and crop species. Centrifuged supernatant and concentrated ethyl acetate extracts from aerobic shake cultures of strain 3366 suppressed germination of seeds and reduced root and shoot growth in agar diffusion assays, soil assays, and under field conditions. Generally, root growth was inhibited more than shoot growth. Strain 3366 metabolites applied in soil inhibited all species tested. Crude ethyl acetate extracts in soil inhibited downy brome at concentrations that had little effect on winter wheat. Inhibitory activity was greater in Palouse silt loam (pH 5.8, 3.6% organic matter) than in Shano silt loam (pH 9.0, 0.8% organic matter). Activity of extracted metabolites decreased rapidly in wet soil but remained high in dry soil. Active metabolites were isolated and purified from the ethyl acetate extract using column chromatography, thin-layer chromatography, and crystallization. Chemical analysis revealed the presence of phenazine-1-carboxylic acid, 2-amino phenoxazone, and 2-amino phenol. Activity of these metabolites against downy brome was confirmed in agar assays. Phenazine-1-carboxylic acid, the major identifiable metabolite present in ethyl acetate extracts (20% by weight), inhibited downy brome root growth by 99% at concentrations of 5.7 mg L−1. Production of these metabolites in field soil by live bacteria of strain 3366 was confirmed with thin-layer chromatography.</jats:p