Phetcharaburanin Jutarop, Hong Huynh A, Colenutt Claire, Bianconi Irene, Sempere Lluis, Permpoonpattana Patima, Smith Karen, Dembek Marcin, Tan Sisareuth, Brisson Marie-Clémence, Brisson Alain R, Fairweather Neil F, Cutting Simon M
School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK.
Mol Microbiol. 2014 Jun;92(5):1025-38. doi: 10.1111/mmi.12611. Epub 2014 Apr 24.
The BclA protein is a major component of the outermost layer of spores of a number of bacterial species and Clostridium difficile carries three bclA genes. Using insertional mutagenesis each gene was characterized and spores devoid of these proteins had surface aberrations, reduced hydrophobicity and germinated faster than wild-type spores. Therefore the BclA proteins were likely major components of the spore surface and when absent impaired the protective shield effect of this outermost layer. Analysis of infection and colonization in mice and hamsters revealed that the 50% infectious dose (ID50 ) of spores was significantly higher (2-logs) in the bclA1(-) mutant compared to the isogenic wild-type control, but that levels of toxins (A and B) were indistinguishable from animals dosed with wild-type spores. bclA1(-) spores germinated faster than wild-type spores yet mice were less susceptible to infection suggesting that BclA1 must play a key role in the initial (i.e. pre-spore germination) stages of infection. We also show that the ID50 was higher in mice infected with R20291, a 'hypervirulent' 027 strain, that carries a truncated BclA1 protein.
BclA蛋白是多种细菌孢子最外层的主要成分，艰难梭菌携带三个bclA基因。利用插入诱变对每个基因进行了表征，缺乏这些蛋白质的孢子具有表面畸变、疏水性降低且比野生型孢子萌发更快的特点。因此，BclA蛋白可能是孢子表面的主要成分，缺失时会损害最外层的保护屏障作用。对小鼠和仓鼠的感染与定殖分析表明，与同基因野生型对照相比，bclA1(-)突变体中孢子的50%感染剂量（ID50）显著更高（高2个对数级），但毒素（A和B）水平与用野生型孢子给药的动物无差异。bclA1(-)孢子比野生型孢子萌发更快，但小鼠对感染的易感性较低，这表明BclA1在感染的初始（即孢子萌发前）阶段必定起关键作用。我们还表明，感染携带截短BclA1蛋白的“超毒力”027菌株R20291的小鼠中ID50更高。
