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

Abstract

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.

Surface motility in Pseudomonas sp. DSS73 is required for efficient biological containment of the root-pathogenic microfungi Rhizoctonia solani and Pythium ultimum

“…Among the great variety of antifungal metabolites produced by fluorescent Pseudomonas spp., our attention has been focused on the cyclic lipopeptides (Kochi et al, 1951;Nielsen et al, 1998Nielsen et al, , 1999Nielsen et al, , 2000Nielsen et al, , 2002. In addition, there are several examples of a close correlation between the production of cyclic lipopeptides and the ability to carry out surface motility on low-agar nutrient plates .…”

“…One group of bacteria that shows great promise with respect to protecting plant roots from fungal-induced diseases is that containing the fluorescent Pseudomonas spp. The biocontrol activity of these strains is usually caused by the synthesis of one or more antifungal factors, which include such diverse compounds as hydrogen cyanide (Voisard et al, 1989), siderophores, pterines, pyrroles (Shanahan et al, 1992), phenazines (Thomashow & Weller, 1988), phloroglucinols (Shanahan et al, 1992), peptides (Nielsen et al, 1999(Nielsen et al, , 2000Thrane et al, 2000), proteases and chitinases (Nielsen et al, 1998;Dowling & O'Gara, 1994). In fluorescent Pseudomonas strains, the biosynthesis of antifungal compounds is regulated by a cascade of endogenous signals, which is channelled through a sensor-kinase and response regulator encoded by gacAS (Corbell & Loper, 1995;Gaffney et al, 1994;Laville et al, 1992), sigma factors encoded by rpoS (Sarniguet et al, 1995) and rpoD (Schnider et al, 1995), and quorum-sensing systems (Pierson et al, 1998).…”

Effect of bacterium Pseudomonas fluorescens and low fungicide dose seed treatments on parasite fungus Aphanomyces cochlioides and sugar beet yield and quality

“…The investigation results of numerous authors prove that purified lipopeptids show antagonistic activity against fungi responsible for sugar beet root decay such as Rhizoctonia solani , Andersen et al 2003, Aphanomyces cochlioides (Nielsen et al 1999, Pythium ultimum and Pythium debarianum (Lee et al 2000, Andersen et al 2003. The above-mentioned researches indicate potential role of bacteria producing lipopeptides in fungi diseases bio-control (Thrane et al , 2001.…”

“…Due to cyclic lipopeptides production , Koch et al 2002, Andersen et al 2003 these bacteria are more and more used as biological agents (Nielsen et al 1999. The investigation results of numerous authors prove that purified lipopeptids show antagonistic activity against fungi responsible for sugar beet root decay such as Rhizoctonia solani , Andersen et al 2003, Aphanomyces cochlioides (Nielsen et al 1999, Pythium ultimum and Pythium debarianum (Lee et al 2000, Andersen et al 2003.…”

Overview: Introduction to Polysaccharides, Agroproteins, and Poly(amino acids)

“…Other areas of interest have been to use biosurfactants for the removal of hazardous chemicals, stabilization of coal slurries for pipeline transportation, cosmetics, detergent, foods, drugs and drug delivery, etc., see TableI)(i/P~/3a). (142)(143). Antifungal agent (144).…”