Schurtz T A, Hornick D B, Korhonen T K, Clegg S
Department of Microbiology, University of Iowa, Iowa City 52242.
Infect Immun. 1994 Oct;62(10):4186-91. doi: 10.1128/iai.62.10.4186-4191.1994.
The type 3 fimbriae of enteric bacteria mediate agglutination, in vitro, of erythrocytes treated with tannic acid. The gene encoding the polypeptide, MrkD, that mediates this agglutination reaction was placed downstream of an inducible promoter, and the ability of MrkD alone to facilitate hemagglutination was determined. Although Escherichia coli transformants could be shown to produce the MrkD protein, hemagglutination did not occur in the absence of other mrk gene products. In addition, the MrkD polypeptide did not cross the bacterial outer membrane unless a fimbrial chaperone protein was also present. Analysis of the frequency of the mrkD gene within the genus Klebsiella indicated that this gene is conserved in strains of Klebsiella oxytoca but not in other fimbriate Klebsiella species. In the small number of strains of Klebsiella pneumoniae that do possess a related mrkD gene, this determinant could be found on a plasmid in one strain. The ability of type 3 fimbriate bacteria to adhere to type V collagen was found to be a function of a specific MrkD polypeptide. This adhesin is frequently found in strains of K. oxytoca but is rarely associated with the type 3 fimbriae of K. pneumoniae.
肠道细菌的3型菌毛在体外介导经单宁酸处理的红细胞发生凝集。编码介导这种凝集反应的多肽MrkD的基因被置于一个可诱导启动子的下游，并测定了单独的MrkD促进血凝的能力。尽管可以证明大肠杆菌转化体能产生MrkD蛋白，但在没有其他mrk基因产物的情况下不会发生血凝。此外，除非还存在菌毛伴侣蛋白，MrkD多肽不会穿过细菌外膜。对克雷伯菌属内mrkD基因频率的分析表明，该基因在产酸克雷伯菌菌株中保守，但在其他有菌毛的克雷伯菌物种中不保守。在少数确实拥有相关mrkD基因的肺炎克雷伯菌菌株中，这一决定因素在一个菌株中可位于质粒上。发现3型菌毛细菌黏附于V型胶原的能力是一种特定MrkD多肽的功能。这种黏附素常见于产酸克雷伯菌菌株中，但很少与肺炎克雷伯菌的3型菌毛相关。
