Antifungal weapons of Lysobacter, a mighty biocontrol agent

Abstract

Bacteria interact with fungi in a variety of ways to inhibit fungal growth, while the underlying mechanisms remain only partially characterized. The plantbeneficial Bacillus and Pseudomonas species are well-known antifungal biocontrol agents, whereas Lysobacter are far less studied. Members of Lysobacter are easy to grow in fermenters and are safe to humans, animals and plants. These environmentally ubiquitous bacteria use a diverse arsenal of weapons to prey on other microorganisms, including fungi and oomycetes. The small molecular toxins secreted by Lysobacter represent long-range weapons effective against filamentous fungi. The secreted hydrolytic enzymes act as intermediaterange weapons against non-filamentous fungi. The contact-dependent killing devices are proposed to work as short-range weapons. We describe here the structure, biosynthetic pathway, action mode and applications of one of the best-characterized longrange weapons, the heat-stable antifungal factor (HSAF) produced by Lysobacter enzymogenes. We discuss how the flagellar type III secretion system has evolved into an enzyme secretion machine for the intermediate-range antifungal weapons. We highlight an intricate mechanism coordinating the production of the long-range weapon, HSAF and the proposed contact-dependent killing device, type VI secretion system. We also overview the regulatory mechanisms of HSAF production involving specific transcription factors and the bacterial second messenger c-di-GMP.

Biosynthesis, regulation, and engineering of natural products from Lysobacter

“…Lin et al recently reviewed the antifungal strategies of L. enzymogenes as a mighty biocontrol agent, which possesses multiple types of weapons for long-range, medium-range and short-range killing of microbial pathogens. 215 With the constant emergence of resistant pathogens and the recognized risks of toxic pesticides to human health and the environment, the search for safe and effective alternative strategies for pest control has become increasingly important. Biocontrol measures can provide green and effective management tools for crop diseases.…”

Evaluating the Mode of Antifungal Action of Heat-Stable Antifungal Factor (HSAF) in Neurospora crassa

“…The Gammaproteobacterial genus L. enzymogenes has obvious antagonistic effects on many microorganisms and has great potential application in agricultural, environmental and pharmaceutical industries [ 32 ]. HSAF, the secondary metabolite of L. enzymogenes , is known to have antifungal effects.…”

Comparative genomics provides insights into the potential biocontrol mechanism of two Lysobacter enzymogenes strains with distinct antagonistic activities

“…WspR was reported as an important diguanylate cyclase (DGC) involved in HSAF regulation in L. enzymogenes OH11. Phosphorylation activated DGC activity of WspR and weakened the WspR-CdgL interaction, thus contributing to the accumulation of the cdi-GMP-bound CdgL, which in turn decreased HSAF biosynthesis operon transcription ( Lin et al, 2021 ). In addition, Le DSF3-regulated HSAF production was dependent on the two-component regulatory system RpfC/RpfG, which has been served as the sensor/response regulator of DSF ( Slater et al, 2000 ).…”