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

Abstract

Pseudomonas sp. DSS73 was isolated from the rhizoplane of sugar beet seedlings. This strain exhibits antagonism towards the root-pathogenic microfungi Pythium ultimum and Rhizoctonia solani. Production of the cyclic lipopeptide amphisin in combination with expression of flagella enables the growing bacterial culture to move readily over the surface of laboratory media. Amphisin is a new member of a group of dual-functioning compounds such as tensin, viscosin and viscosinamid that display both biosurfactant and antifungal properties. The ability of DSS73 to efficiently contain root-pathogenic microfungi is shown to arise from amphisin-dependent surface translocation and growth by which the bacterium can lay siege to the fungi. The synergistic effects of surface motility and synthesis of a battery of antifungal compounds efficiently contain and terminate growth of the microfungi.

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

“…The aforesaid approves pronounced antagonistic activity of Pseudomonas fluorescens bacterium against parasitic fungus Aphanomyces cochlioides and insensibility of this benefit bacterium against fungicide low doses (Pedersen et al 2002, Andersen et al 2003. Combined seed treatment with bacterium Pseudomonas fluorescens and low doses of these chemical agents resulted in Variants see Table 3 efficient control of the pathogenic fungi growth and reproduction which in turns reflected on all sugar beet yield and quality indicators.…”

“…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.…”

“…However, fungicides largely affect human health and environment whereas pathogenic fungi became very fast resistant to them. For that reason, seed inoculation with bacteria showing antagonism against pathogenic fungi is an acceptable alternative to chemical pesticides application (Andersen et al 2003).…”

Inoculation of Sugar Beet Seed with Bacteria P. fluorescens, B. subtilis and B. megaterium – Chemical Fungicides Alternative

“…For the capacity to synthesize toxic cyclic lipopeptides (Andersen et al, 2003;Koch et al, 2002;Thrane et al, 2000) they are used as effective biological control agents (Sorensen et al, 2001). Many authors have reported that these purified lipopeptides show an antagonistic activity against certain fungi pathogenic on sugar beet roots such as Rhizoctonia solani (Andersen et al, 2003;Nielsen et al, 2000Nielsen et al, , 2002, Aphanomyces cochlioides (Raaijmakers et al, 2010;Sorensen et al, 2001), Pythium ultimum and Pythium debarianum (Andersen et al, 2003;Gorlach-Lira & Stefaniak, 2009;Lee et al, 2000;Nielsen et al, 2000;Thrane et al, 2000). This suggests that bacteria producing lipopeptides could have a potential role in the biocontrol of fungal diseases, which was approved in both laboratory and field trials (Thrane et al, , 2001.…”