Flavobacterium columnare is the pathogenic agent of columnaris disease in aquaculture. Using a recently developed gene deletion strategy, two genes that encode the Glyco hydro_19 domain （GH19 domain） containing prot...Flavobacterium columnare is the pathogenic agent of columnaris disease in aquaculture. Using a recently developed gene deletion strategy, two genes that encode the Glyco hydro_19 domain （GH19 domain） containing proteins, ghd-1 and ghd-2, were deleted separately and together from the F. columnare G4 wild type strain. Surprisingly, the single-, Aghd-1 and Aghd-2, and double-gene mutants, Aghd-1 Aghd-2, all had rhizoid and non-rhizoid colony morphotypes, which we named Aghd-1, Aghd-2, Aghd-1 Aghd-2, and NAghd-1, NAghd-2, and NAghd-1 Aghd-2. However, chitin utilization was not detected in either these mutants or in the wild type. Instead, skimmed milk degradation was observed for the mutants and the wild type; the non-rhizoid strain NAghd-2 exhibited higher degradation activity as revealed by the larger transparent circle on the skimmed milk plate. Using zebrafish as the model organism, we found that non-rhizoid mutants had higher LDs0 values and were less virulent because zebrafish infected with these survived longer. Transcriptome analysis between the non-rhizoid and rhizoid colony morphotypes of each mutant, i.e., NAghd-1 versus （vs） Aghd-1, NAghd-2 vs Aghd-2, and NAghd-1 Aghd-2 vs Aghd-1 Aghd-2, revealed a large number of differentially expressed genes, among which 39 genes were common in three of the pairs compared. Although most of these genes encode hypothetical proteins, a few molecules such as phage tail protein, rhs element Vgr protein, thiol-activated cytolysin, and TonB-dependent outer membrane receptor precursor, expression of which was down-regulated in non-rhizoid mutants but up-regulated in rhizoid mutants, may play a role F. columnare virulence.展开更多
基金Supported by the Chinese Academy of Sciences(No.XDA08010207)the National Key Technology R&D Program of China(No.2012BAD25B02)the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2016FBZ04)
文摘Flavobacterium columnare is the pathogenic agent of columnaris disease in aquaculture. Using a recently developed gene deletion strategy, two genes that encode the Glyco hydro_19 domain （GH19 domain） containing proteins, ghd-1 and ghd-2, were deleted separately and together from the F. columnare G4 wild type strain. Surprisingly, the single-, Aghd-1 and Aghd-2, and double-gene mutants, Aghd-1 Aghd-2, all had rhizoid and non-rhizoid colony morphotypes, which we named Aghd-1, Aghd-2, Aghd-1 Aghd-2, and NAghd-1, NAghd-2, and NAghd-1 Aghd-2. However, chitin utilization was not detected in either these mutants or in the wild type. Instead, skimmed milk degradation was observed for the mutants and the wild type; the non-rhizoid strain NAghd-2 exhibited higher degradation activity as revealed by the larger transparent circle on the skimmed milk plate. Using zebrafish as the model organism, we found that non-rhizoid mutants had higher LDs0 values and were less virulent because zebrafish infected with these survived longer. Transcriptome analysis between the non-rhizoid and rhizoid colony morphotypes of each mutant, i.e., NAghd-1 versus （vs） Aghd-1, NAghd-2 vs Aghd-2, and NAghd-1 Aghd-2 vs Aghd-1 Aghd-2, revealed a large number of differentially expressed genes, among which 39 genes were common in three of the pairs compared. Although most of these genes encode hypothetical proteins, a few molecules such as phage tail protein, rhs element Vgr protein, thiol-activated cytolysin, and TonB-dependent outer membrane receptor precursor, expression of which was down-regulated in non-rhizoid mutants but up-regulated in rhizoid mutants, may play a role F. columnare virulence.
