Both extracellular chitinase and a new cyclic lipopeptide, chromobactomycin, contribute to the biocontrol activity of Chromobacterium sp. C61

Abstract

Chromobacterium sp. strain C61 displays antifungal activities in vitro and has been used successfully for the biocontrol of plant diseases under field conditions. In this study, the roles of extracellular chitinase and an antifungal compound produced by strain C61 were investigated to elucidate their contributions to biological control activity. The bacterium possessed a locus chi54 encoding an extracellular chitinase, and mutation of chi54 eliminated chitinase production. Production of the extracellular enzyme and expression of the chi54 transcript were increased in the wild-type strain when chitin was added to the culture medium. In vitro assays showed that purified chitinase inhibited spore germination of multiple pathogens. However, the in planta biocontrol activity of filtrates of cultures grown in the presence of chitin was lower than that of filtrates grown without chitin, indicating that correlation between chitinase and biocontrol activity was lacking. The analysis of C61 culture filtrates revealed an antifungal cyclic lipopeptide, chromobactomycin, whose structure contained a unique nonameric peptide ring. The purified chromobactomycin inhibited the growth of several phytopathogenic fungi in vitro, and plant application significantly reduced disease severity for several pathogens. Furthermore, the production of chromobactomycin was reduced in cultures amended with chitin. These data suggest that the production of both the extracellular chitinase Chi54 and the newly identified antibiotic chromobactomycin can contribute, in an interconnected way, to the suppression of plant disease by Chromobacterium sp. strain C61.

Alleviation of Abiotic and Biotic Stresses in Plants by Azospirillum

“…PGPR, especially Bacillus and Pseudomonas strains, can produce extracellular enzymes such as chitinase or glucanase, which degrade components of the membrane and cell wall of microbial pathogens (Siddiqui et al 2005 ;Maksimov et al 2011 ;Kim et al 2014 ). Moreover, certain PGPR can quench quorum-sensing (QS) signals and affect QS-dependent pathogenicity in plant pathogenic bacteria by degrading or mimicking their acyl-homoserine lactones, thereby blocking the expres sion of virulence functions (Faure and Dessaux 2007 ;Boyer and WisniewskiDyé 2009 ;Helman and Chernin 2014 ).…”

Inhibitory effect ofBacillus subtilisWL-2 and its IturinA lipopeptides againstPhytophthora infestans

“…Surprisingly, biocontrol agents (BCAs), including microorganisms and secondary metabolites, have been further researched and even considered promising and environmentally friendly alternatives to the chemicals(7). With biocontrol method development, various antibiotic peptides, including polymyxin, daptomycin, chromobactomycin, subtilin and subtilosin, which were all extracted from Bacillus spp., have been considered potential future drugs based on their broad range of antibiotic activity, reduced toxicity, and safety to our environment(3, 7, 8).…”

Chromobacterium violaceum Pathogenicity: Updates and Insights from Genome Sequencing of Novel Chromobacterium Species

“…Environmental isolates of Chromobacterium have the potential to be used in other biotechnological applications, including biocontrol of plant diseases caused by insect pests ( Chromobacterium sp. strain C-61) ( Kim et al, 2014 ), prevention of disease transmission by Anopheles gambiae and Aedes aegypti mosquitoes ( Chromobacterium sp. Csp_P) ( Ramirez et al, 2014 ), hydrogen cyanide-mediated gold recovery from electronic waste ( Tay et al, 2013 ), and production of the anti-tumoral depsipeptide FR901228 ( C. violaceum ) ( Durán and Menck, 2001 ; VanderMolen et al, 2011 ).…”