Pseudomonas putida strain PCL1445 was isolated from roots of plants, grown on a site polluted with polycyclic aromatic hydrocarbons. PCL1445 produces biosurfactant activity at the end of the exponential growth phase. High-performance liquid chromatography (HPLC) analysis of supernatant extracts of PCL1445 showed two peaks with surface-tension reducing activity, tentatively assigned as biosurfactants putisolvin I and putisolvin II and was followed by structural analyses. A transposon mutant of PCL1445, strain PCL1436, which lacks the two surface-active peaks appeared to be mutated in an open reading frame (ORF) with amino acid homology to various lipopeptide synthetases. Structural analyses of the two biosurfactants of PCL1445 revealed that both are novel cyclic lipodepsipeptides with a hexanoic lipid chain connected to the N-terminus of a 12-amino-acid peptide moiety, in which the C-terminal carboxylic acid group forms an ester with the hydroxyl side-chain of Ser9. The difference between the two structures is located in the second amino acid from the C-terminus, being valine for putisolvin I, and leucine/isoleucine for putisolvin II. We show that these novel compounds lower the surface tension and influence the biofilm development on polyvinyl chloride (PVC). Biofilm formation of the bio-synthetic mutant PCL1436 was strongly increased containing more cells, which formed aggregates earlier as compared with wild-type PCL1445 biofilms. Using purified putisolvin I and II it was shown that biofilm formation of different Pseudomonas strains was inhibited and most interestingly, that both putisolvins are also able to break down existing Pseudomonas biofilms.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2958.2003.03751.x

Characterization of two Pseudomonas putida lipopeptide biosurfactants, putisolvin I and II, which inhibit biofilm formation and break down existing biofilms

Pseudomonas fluorescens DR54 showed antagonistic properties against plant pathogenic Pythium ultimum and Rhizoctonia solani both in vitro and in planta. Antifungal activity was extractable from spent growth media, and fractionation by semi-preparative HPLC resulted in isolation of an active compound, which was identified as a new bacterial cyclic lipodepsipeptide, viscosinamide, using 1D and 2D 1H-, 13C-NMR and mass spectrometry. The new antibiotic has biosurfactant properties but differs from the known biosurfactant, viscosin, by containing glutamine rather than glutamate at the amino acid position 2 (AA2). No viscosin production was observed, however, when Ps. fluorescens DR54 was cultured in media enriched with glutamate. In vitro tests showed that purified viscosinamide also reduced fungal growth and aerial mycelium development of both P. ultimum and R. solani. Viscosinamide production by Ps. fluorescens DR54 was tightly coupled to cell proliferation in the batch cultures, as the viscosinamide produced per cell mass unit approached a constant value. In batch cultures with variable initial C, N or P nutrient levels, there were no indications of elevated viscosinamide production during starvation or maintenance of the cultures in stationary phase. Analysis of cellular fractions and spent growth media showed that a major fraction of the viscosinamide produced remained bound to the cell membrane of Ps. fluorescens DR54. The isolation, determination of structure and production characteristics of the new compound with both biosurfactant and antibiotic properties have promising perspectives for the application of Ps. fluorescens DR54 in biological control.

Viscosinamide, a new cyclic depsipeptide with surfactant and antifungal properties produced by Pseudomonas fluorescens DR54.

Peptidic natural products (PNPs) are widely used compounds that include many antibiotics and a variety of other bioactive peptides Although recent breakthroughs in PNP discovery raised the challenge of developing new algorithms for their analysis, identification of PNPs via database search of tandem mass spectra remains an open problem To address this problem, natural product researchers use dereplication strategies that identify known PNPs and lead to the discovery of new ones, even in cases when the reference spectra are not present in existing spectral libraries DEREPLICATOR is a new dereplication algorithm that enables high-throughput PNP identification and that is compatible with large-scale mass-spectrometry-based screening platforms for natural product discovery After searching nearly one hundred million tandem mass spectra in the Global Natural Products Social (GNPS) molecular networking infrastructure, DEREPLICATOR identified an order of magnitude more PNPs (and their new variants) than any previous dereplication efforts

/pdf/dereplication-of-peptidic-natural-products-through-database-47szs9ltm1.pdf

Dereplication of peptidic natural products through database search of mass spectra

Agaricus bisporus browning: a review

Pseudomonas tolaasii is a bacterium endemic to the compost beds where common mushroom (Agaricus bisporus) is cultivated. Under some environmental conditions still not well-determined, but influenced by temperature and relative humidity, the bacterium can become pathogenic and provoke the brown blotch disease. This review describes the interaction between P. tolaasii and A. bisporus that results in the appearance of brown spots on the mushroom caps, typical symptoms of the disease. Firstly, P. tolaasii is studied, the changes in pathogenicity are explained, the compounds that provoke the damage are enumerated as well as various experimental methods to identify the pathogenic form of the bacteria. Secondly, mechanisms involved in the formation of the brown colour on the A. bisporus caps upon infection are briefly mentioned, taking into account the enzymes that catalyse the reaction, their mechanism, substrates and reaction products. Afterwards, a detailed description of the infection process is presented step by step, starting by the chemotactical attraction, fixation, secretion of the toxins, membrane breakdown, effect of the toxin on mushroom polyphenol oxidases and on the discolouration reaction. A possible mechanism of infection is hypothesised at the molecular level. Finally, the strategies tested until now to control the disease are discussed.

Biochemical and physiological aspects of brown blotch disease of Agaricus bisporus

Structure Determination of Tolaasin, an Extracellular Lipodepsipeptide Produced by the Mushroom Pathogen Pseudomonas tolaasii Paine.

Structure determination of tolaasin, an extracellular lipodepsipeptide produced by the mushroom pathogen, Pseudomonas tolaasii Paine

Determination of the structure of an extracellular peptide produced by the mushroom saprotroph pseudomonas reactans

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Papers

Structure Determination of Tolaasin, an Extracellular Lipodepsipeptide Produced by the Mushroom Pathogen Pseudomonas tolaasii Paine.

Structure determination of tolaasin, an extracellular lipodepsipeptide produced by the mushroom pathogen, Pseudomonas tolaasii Paine

Determination of the structure of an extracellular peptide produced by the mushroom saprotroph pseudomonas reactans