Suppression of Damping-Off Disease in Host Plants by the Rhizoplane Bacterium Lysobacter sp. Strain SB-K88 Is Linked to Plant Colonization and Antibiosis against Soilborne Peronosporomycetes

Abstract

We previously demonstrated that xanthobaccin A from the rhizoplane bacterium Lysobacter sp. strain SB-K88 suppresses damping-off disease caused by Pythium sp. in sugar beet. In this study we focused on modes of Lysobacter sp. strain SB-K88 root colonization and antibiosis of the bacterium against Aphanomyces cochlioides, a pathogen of damping-off disease. Scanning electron microscopic analysis of 2-week-old sugar beet seedlings from seeds previously inoculated with SB-K88 revealed dense colonization on the root surfaces and a characteristic perpendicular pattern of Lysobacter colonization possibly generated via development of polar, brush-like fimbriae. In colonized regions a semitransparent film apparently enveloping the root and microcolonies were observed on the root surface. This Lysobacter strain also efficiently colonized the roots of several plants, including spinach, tomato, Arabidopsis thaliana, and Amaranthus gangeticus. Plants grown from both sugar beet and spinach seeds that were previously treated with Lysobacter sp. strain SB-K88 displayed significant resistance to the damping-off disease triggered by A. cochlioides. Interestingly, zoospores of A. cochlioides became immotile within 1 min after exposure to a SB-K88 cell suspension, a cell-free supernatant of SB-K88, or pure xanthobaccin A (MIC, 0.01 g/ml). In all cases, lysis followed within 30 min in the presence of the inhibiting factor(s). Our data indicate that Lysobacter sp. strain SB-K88 has a direct inhibitory effect on A. cochlioides, suppressing damping-off disease. Furthermore, this inhibitory effect of Lysobacter sp. strain SB-K88 is likely due to a combination of antibiosis and characteristic biofilm formation at the rhizoplane of the host plant.

Mining for Nonribosomal Peptide Synthetase and Polyketide Synthase Genes Revealed a High Level of Diversity in the Sphagnum Bog Metagenome

“…Most of the sequences were assigned to the phylum Proteobacteria, with the most abundant genera being Pseudomonas and especially Lysobacter. In recent years, the latter has emerged not only as a promising source of new bioactive natural products, such as antibiotics, ß-lactams, cyclic lactams, and depsipeptides, but also as a biocontrol agent for fungal plant infections (36,40,41). Furthermore, similar sequences coding for the siderophore yersiniabactin from P. syringae were detected.…”

Genetic diversity analysis of rep-PCR genomic fingerprinting of Lysobacter spp.

“…With the development of bacterial taxonomy technology and a large number of professional database updating, this bacteria was reclassified from Stenotrophomonas to Lysobacter spp. (Sullivan et al, 2003;Islam et al, 2005). Forepart, the research mainly focused on its activity of various extracellular enzymes, they act on the pathogen cell wall and other targets, causing lysis and inhibition (Reichenbach, 2006).…”

Smart biologics for crop protection in agricultural systems

“…Furthermore, the production of pathogens that express different levels of virulence, produce specific antipest molecules, or Koumoutsi et al (2004) Lysobacter sp. strain SB-K88 Aphanomyces cochlioides Islam et al (2005) B. subtilis QST713 Botrytis cinerea and R. Solani Paulitz and Belanger (2001), Kloepper et al (2004) B. subtilis BBG100 Pythium aphanidermatum Leclere et al (2005) P. fluorescens 2-79 and 30-84 Gaeumannomyces graminis var. tritici Thomashow et al (1990) Bacillus subtilis, EU07 Fusarium oxysporum f. sp.…”