Arnadottir Helga, Hvanndal Iris, Andresdottir Valgerdur, Burr Sarah E, Frey Joachim, Gudmundsdottir Bjarnheidur K
Institute for Experimental Pathology, University of Iceland, Keldur v/Vesturlandsveg, IS-112 Reykjavík, Iceland.
J Bacteriol. 2009 Jan;191(1):403-10. doi: 10.1128/JB.00847-08. Epub 2008 Oct 24.
Infections by the bacterium Aeromonas salmonicida subsp. achromogenes cause significant disease in a number of fish species. In this study, we showed that AsaP1, a toxic 19-kDa metallopeptidase produced by A. salmonicida subsp. achromogenes, belongs to the group of extracellular peptidases (Aeromonas type) (MEROPS ID M35.003) of the deuterolysin family of zinc-dependent aspzincin endopeptidases. The structural gene of AsaP1 was sequenced and found to be highly conserved among gram-negative bacteria. An isogenic Delta asaP1 A. salmonicida subsp. achromogenes strain was constructed, and its ability to infect fish was compared with that of the wild-type (wt) strain. The Delta asaP1 strain was found to infect Arctic charr, Atlantic salmon, and Atlantic cod, but its virulence was decreased relative to that of the wt strain. The 50% lethal dose of the AsaP1 mutant was 10-fold higher in charr and 5-fold higher in salmon than that of the wt strain. The pathology induced by the AsaP1-deficient strain was also different from that of the wt strain. Furthermore, the mutant established significant bacterial colonization in all observed organs without any signs of a host response in the infected tissue. AsaP1 is therefore the first member of the M35 family that has been shown to be a bacterial virulence factor.
嗜水气单胞菌无色亚种感染会在多种鱼类中引发严重疾病。在本研究中，我们发现嗜水气单胞菌无色亚种产生的一种有毒的19 kDa金属肽酶AsaP1，属于锌依赖性天冬氨酸锌内肽酶氘解素家族的细胞外肽酶组（气单胞菌型）（酶学委员会编号M35.003）。对AsaP1的结构基因进行了测序，发现其在革兰氏阴性菌中高度保守。构建了一个同基因的缺失asaP1的嗜水气单胞菌无色亚种菌株，并将其感染鱼类的能力与野生型菌株进行了比较。发现缺失asaP1的菌株能够感染北极红点鲑、大西洋鲑和大西洋鳕，但其毒力相对于野生型菌株有所降低。AsaP1突变体在红点鲑中的50%致死剂量比野生型菌株高10倍，在鲑鱼中高5倍。缺失AsaP1的菌株诱导的病理学也与野生型菌株不同。此外，该突变体在所有观察到的器官中都建立了显著的细菌定植，而在感染组织中没有任何宿主反应的迹象。因此，AsaP1是M35家族中第一个被证明是细菌毒力因子的成员。
