Siderophores Produced by the Fish Pathogen Flavobacterium columnare Strain MS-FC-4 Are Not Essential for Its Virulence
Siderophores Produced by the Fish Pathogen Flavobacterium columnare Strain MS-FC-4 Are Not Essential for Its Virulence
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DOI：
10.1128/aem.00948-22
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发表时间：
2022-08-15
影响因子：
4.4
通讯作者：
McBride, Mark J.
中科院分区：
文献类型：
--
作者：
Conrad, Rachel A.;Evenhuis, Jason P.;McBride, Mark J.
柱状杆菌病是淡水养殖面临的一大难题，由柱状黄杆菌引起。柱状黄杆菌可引起野生和水产养殖淡水鱼柱状杆菌病，但对其致病因素知之甚少，控制措施也十分有限。柱状芽孢杆菌的致病机理还不清楚，目前控制柱状杆菌病的方法也不够充分。从宿主获取铁对许多细菌病原体的致病性和毒力是重要的。F.Columnare铁的获取尚未得到详细研究。我们发现了一些基因，这些基因被预测在铁摄取的铁载体生产中起作用。预测编码铁载体合成、输出、摄取和调节所需蛋白质的基因从柱孢杆菌菌株MS-FC-4中被删除。对突变体进行了铁载体生产缺陷、铁限制条件下的生长缺陷以及对斑马鱼和虹鲑鱼的毒力检测。获得了缺乏全部铁载体活性的突变体。这些突变体在铁限制条件下培养时表现出生长缺陷，但它们对斑马鱼和虹鳟鱼的毒力与野生型相似，表明在所测试的条件下，MS-FC-4铁载体不是毒力所必需的。由柱状黄杆菌引起的柱状杆菌病是淡水养殖面临的一大难题。对赤霉菌的毒力因子知之甚少，控制措施也是有限的。铁的获取机制，如铁载体，对其他病原体的毒力很重要。我们鉴定了F.Columnare铁载体生物合成、输出和摄取基因。这些基因的缺失消除了铁载体的产生，并导致了铁限制条件下的生长缺陷，但不会改变虹鱼或斑马鱼的毒力。结果表明，在所测试的条件下，柱孢杆菌菌株MS-FC-4铁载体不是关键的毒力因子，但对于在自然水生环境或水产养殖系统中铁限制条件下的生存可能是重要的。
Columnaris disease, which is caused by Flavobacterium columnare, is a major problem for freshwater aquaculture. Little is known regarding F. columnare virulence factors, and control measures are limited.Flavobacterium columnare causes columnaris disease in wild and aquaculture-reared freshwater fish. F. columnare virulence mechanisms are not well understood, and current methods to control columnaris disease are inadequate. Iron acquisition from the host is important for the pathogenicity and virulence of many bacterial pathogens. F. columnare iron acquisition has not been studied in detail. We identified genes predicted to function in siderophore production for ferric iron uptake. Genes predicted to encode the proteins needed for siderophore synthesis, export, uptake, and regulation were deleted from F. columnare strain MS-FC-4. The mutants were examined for defects in siderophore production, for growth defects in iron-limited conditions, and for virulence against zebrafish and rainbow trout. Mutants lacking all siderophore activity were obtained. These mutants displayed growth defects when cultured under iron-limited conditions, but they retained virulence against zebrafish and rainbow trout similar to that exhibited by the wild type, indicating that the F. columnare MS-FC-4 siderophores are not required for virulence under the conditions tested. IMPORTANCE Columnaris disease, which is caused by Flavobacterium columnare, is a major problem for freshwater aquaculture. Little is known regarding F. columnare virulence factors, and control measures are limited. Iron acquisition mechanisms such as siderophores are important for virulence of other pathogens. We identified F. columnare siderophore biosynthesis, export, and uptake genes. Deletion of these genes eliminated siderophore production and resulted in growth defects under iron-limited conditions but did not alter virulence in rainbow trout or zebrafish. The results indicate that the F. columnare strain MS-FC-4 siderophores are not critical virulence factors under the conditions tested but may be important for survival under iron-limited conditions in natural aquatic environments or aquaculture systems.