Presentation Information
[P02-245]Novel N-acylhomoserine lactone-degrading enzymes from bark compost-derived bacteria: roles in quorum-sensing inhibition and plant disease control
○Ruka Izawa1, Suzu Hiyama1, Tomohiro Morohoshi1 (1. Utsunomiya University (Japan))
Keywords:
quorum sensing,bark compost,N-acylhomoserine lactone,plant disease control
[Purpose]
Numerous plant pathogenic bacteria synthesize N-acylhomoserine lactones (AHLs), which are quorum-sensing signaling molecules that modulate the expression of virulence factors. The degradation of AHL produced by plant pathogenic bacteria reduces the expression of virulence factors. Bark compost is an organic fertilizer derived from microbial decomposition of tree bark and woody residues. AHL-degrading bacteria within bark compost are expected to enhance resistance to bacterial diseases controlled by quorum sensing. This study aimed to isolate AHL-degrading bacteria from bark composts, identify novel AHL-degrading genes, and evaluate their potential to inhibit quorum sensing in plant pathogenic bacteria.
[Method]
Bacteria were isolated from seven commercial bark composts in Japan. AHL-degrading activity was assessed using N-hexanoyl-L-homoserine lactone (C6-HSL) and N-decanoyl-L-homoserine lactone (C10-HSL). Two AHL-degrading strains, Neobacillus sp. B24 and Ochrobactrum quorumnocens B44 were selected, and their genomes were sequenced using the PacBio Revio platform. AHL-degrading gene homologs were cloned into pUC118 to evaluate AHL-degrading activity. Purified AHL-degrading enzymes were used for biochemical analysis. AHL-degrading genes were expressed in Pectobacterium carotovorum subsp. carotovorum (Pcc), and pathogenicity was assessed using potato tissue maceration assays.
[Results]
Of the 89 strains isolated from bark composts, nine strains showed the ability to degrade both C6-HSL and C10-HSL. Whole-genome sequencing of B24 and B44 revealed the presence of multiple AHL-degrading gene homologs. Among them, it was revealed that aiiN1 and aiiN2 from B24 and aiiO from B44 function as AHL-degrading genes. HPLC analysis showed that AiiN1, AiiN2, and AiiO function as AHL lactonases that hydrolyze the lactone ring. The expression of these genes in Pcc resulted in the self-degradation of AHLs and inhibited potato tissue maceration regulated by quorum sensing.
[Consideration]
Bark compost contains diverse AHL-degrading bacteria, and the discovery of three novel lactonases demonstrates its value as a source of inhibition for quorum sensing. The reduction in the pathogenicity of Pcc supports the potential of AHL-degrading bacteria as biocontrol agents. Bark compost enriched with AHL-degrading bacteria may offer an environmental strategy for controlling plant diseases.
[Conclusion]
This study identified novel AHL-degrading bacteria and AHL lactonase genes from bark composts and demonstrated their ability to inhibit quorum sensing in plant pathogenic bacteria. These findings suggest that bark compost containing AHL-degrading bacteria can enhance soil resistance to plant diseases and contribute to sustainable plant disease control.
Numerous plant pathogenic bacteria synthesize N-acylhomoserine lactones (AHLs), which are quorum-sensing signaling molecules that modulate the expression of virulence factors. The degradation of AHL produced by plant pathogenic bacteria reduces the expression of virulence factors. Bark compost is an organic fertilizer derived from microbial decomposition of tree bark and woody residues. AHL-degrading bacteria within bark compost are expected to enhance resistance to bacterial diseases controlled by quorum sensing. This study aimed to isolate AHL-degrading bacteria from bark composts, identify novel AHL-degrading genes, and evaluate their potential to inhibit quorum sensing in plant pathogenic bacteria.
[Method]
Bacteria were isolated from seven commercial bark composts in Japan. AHL-degrading activity was assessed using N-hexanoyl-L-homoserine lactone (C6-HSL) and N-decanoyl-L-homoserine lactone (C10-HSL). Two AHL-degrading strains, Neobacillus sp. B24 and Ochrobactrum quorumnocens B44 were selected, and their genomes were sequenced using the PacBio Revio platform. AHL-degrading gene homologs were cloned into pUC118 to evaluate AHL-degrading activity. Purified AHL-degrading enzymes were used for biochemical analysis. AHL-degrading genes were expressed in Pectobacterium carotovorum subsp. carotovorum (Pcc), and pathogenicity was assessed using potato tissue maceration assays.
[Results]
Of the 89 strains isolated from bark composts, nine strains showed the ability to degrade both C6-HSL and C10-HSL. Whole-genome sequencing of B24 and B44 revealed the presence of multiple AHL-degrading gene homologs. Among them, it was revealed that aiiN1 and aiiN2 from B24 and aiiO from B44 function as AHL-degrading genes. HPLC analysis showed that AiiN1, AiiN2, and AiiO function as AHL lactonases that hydrolyze the lactone ring. The expression of these genes in Pcc resulted in the self-degradation of AHLs and inhibited potato tissue maceration regulated by quorum sensing.
[Consideration]
Bark compost contains diverse AHL-degrading bacteria, and the discovery of three novel lactonases demonstrates its value as a source of inhibition for quorum sensing. The reduction in the pathogenicity of Pcc supports the potential of AHL-degrading bacteria as biocontrol agents. Bark compost enriched with AHL-degrading bacteria may offer an environmental strategy for controlling plant diseases.
[Conclusion]
This study identified novel AHL-degrading bacteria and AHL lactonase genes from bark composts and demonstrated their ability to inhibit quorum sensing in plant pathogenic bacteria. These findings suggest that bark compost containing AHL-degrading bacteria can enhance soil resistance to plant diseases and contribute to sustainable plant disease control.
Comment
To browse or post comments, you must log in.Log in