Vital fluorescent stains for detection of stress in Pythium ultimum and Rhizoctonia solani challenged with viscosinamide from Pseudomonas fluorescens DR54

Abstract

Viscosinamide from Pseudomonas fluorescens DR54 exerts a biocontrol effect on the plant pathogenic microfungi Pythium ultimum and Rhizoctonia solani. Evidence for physiological changes in these and four other fungi was obtained by vital fluorescent staining with Calcofluor white, Nile red, Syto 13, 3,3P-diheptyloxacarbocyanine, 5-(and-6)-carboxy FDA and 5-(and-6)-carboxy SNARF-1, acetoxymethyl, acetate. Based on studies of the fungi grown on solid agar medium and Calcofluor white staining, all isolates responded to viscosinamide treatment by an increased branching, sometimes including hyphal swelling and an increased septation. Further, the staining pattern indicated changes in the esterase activity, intracellular pH and mitochondrial organization and activity. Several of the fungi showed a reduced Nile red staining indicating a general decrease in hydrophobicity of cellular membranes or cell walls. In contrast, only Pythium spp. were stainable with the nucleic acid stain Syto 13 and showed changes in the nuclei in response to viscosinamide. Finally, it was shown that Calcofluor white, Nile red and Syto 13 could also be used to study fungal stress in situ using soil microcosms. The study demonstrated that combinations of vital fluorescent stains are suitable for detailed studies of fungal stress as induced by, e.g., bacterial antibiotics. ß 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Antifungal potential of Bacillus vallismortis R2 against different phytopathogenic fungi

“…The deformities observed were similar to those reported earlier, caused due to formation of pores by interaction of biomolecules with the fungal cell membrane resulting in shrunken and empty hyphae (Romero et al, 2007;Makovitzki et al, 2007). The formation of pores further causes an increased Ca 2+ influx which has been reported to induce excessive branching of hyphae (Thrane et al, 1999;Mortel et al, 2009). The appearance of bulbous morphology may also be attributed to the effect of APB on the cytoskeletal elements, actin and tubulin leading to collapsed cytoskeleton and un-polarized growth at the tip of hyphae (Tendulkar et al, 2007).…”

Cellular Responses of the Late Blight Pathogen Phytophthora infestans to Cyclic Lipopeptide Surfactants and Their Dependence on G Proteins

“…Microscopic analysis further revealed that the exposure of P. infestans to Mass A led to increased hyphal branching and induced the encystment of zoospores at concentrations below the CMC. Similar phenomena were described previously by Thrane et al (42,43), who exposed the oomycete Pythium ultimum and the fungus Rhizoctonia solani to viscosinamide. Those authors further hypothesized that the increased amount of branching may be the result of an increased Ca 2ϩ influx due to ion channel formation by viscosinamide (43).…”

Antibiotic and Biosurfactant Properties of Cyclic Lipopeptides Produced by Fluorescent Pseudomonas spp. from the Sugar Beet Rhizosphere

“…The hydrophobic fatty acid tail, together with the amphiphilic property of the peptide, structure may finally play an important role in penetration and binding of CLPs within biological membranes. This in turn may support their role as surfactants and as antibiotics, e.g., disrupting membrane functions leading to excess Ca 2ϩ influx into target cells (46). Functional roles of CLP surfactants in P. fluorescens.…”