Abstract
Lysobacter enzymogenes is an important biocontrol agent with the ability to produce a variety of lytic enzymes and novel antibiotics. Little is known about their regulatory mechanisms. Understanding these will be helpful for improving biocontrol of crop diseases and potential medical application. In the present study, we generated an hfq (encoding a putative ribonucleic acid chaperone) deletion mutant, and then utilized a new genomic marker-free method to construct an hfq-complemented strain. We showed for the first time that Hfq played a pleiotropic role in regulating the antibacterial antibiotic biosynthesis and extracellular lytic enzyme activity in L. enzymogenes. Mutation of hfq significantly increased the yield of WAP-8294A2 (an antibacterial antibiotic) as well as the transcription of its key biosynthetic gene, waps1. However, inactivation of hfq almost abolished the extracellular chitinase activity and remarkably decreased the activity of both extracellular protease and cellulase in L. enzymogenes. We further showed that the regulation of hfq in extracellular chitinase production was in part through the impairment of the secretion of chitinase A. Collectively, our results reveal the regulatory roles of hfq in antibiotic metabolite and extracellular lytic enzymes in the underexplored genus of Lysobacter.
Highlights
Lysobacter is a genus in the family of Xanthomonadaceae and is one of the most ubiquitous environmental microorganisms (Christensen and Cook, 1978)
We showed for the first time that Hfq played a pleiotropic role in regulating the antibacterial antibiotic biosynthesis and extracellular lytic enzyme activity in L. enzymogenes
The results show that this hfq plays a pleiotropic role in regulating the antibacterial antibiotic biosynthesis and extracellular lytic enzyme activity in L. enzymogenes
Summary
Lysobacter is a genus in the family of Xanthomonadaceae and is one of the most ubiquitous environmental microorganisms (Christensen and Cook, 1978). Lysobacter enzymogenes of the genus is the best characterized species. This species is known for its ability to produce a variety of extracellular lytic enzymes, including chitinase, cellulase and protease (Kobayashi et al, 2005). These enzymes are able to destroy the cell wall of pathogenic fungi and oomycetes and are highly linked to biocontrol activity of L. enzymogenes against crop pathogens (Zhang and Yuen, 2000; Palumbo et al, 2003). We have recently identified the gene cluster responsible for the biosynthesis of WAP-8294A2 in
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