Wirth R
Institut für Genetik und Mikrobiologie der LMU, Lehrstuhl für Mikrobiologie, München, Germany.
Eur J Biochem. 1994 Jun 1;222(2):235-46. doi: 10.1111/j.1432-1033.1994.tb18862.x.
The sex pheromone system of Enterococcus faecalis was discovered by observing a clumping reaction of E. faecalis strains during conjugative transfer of plasmids. It was found that only a special type of E. faecalis plasmids, the so-called sex pheromone plasmids, are transferred via this mechanism. Various experiments, especially by the group of D. B. Clewell, led to the formulation of a model describing how the sex pheromone system works. Small linear peptides, the so-called sex pheromones, are excreted by strains not possessing the corresponding sex pheromone plasmid. Donor strains harboring the plasmid do not produce the corresponding sex pheromone; they react to the presence of the peptide by production of a plasmid-encoded adhesin, the so-called aggregation substance. This adhesin allows contact between the non-motile mating partners; after conjugative transfer of the plasmid, the former recipient possesses and replicates the new plasmid. Thereby the population of E. faecalis strains is shifted to a high percentage of donor strains. This is especially true because a donor strain will still excrete sex pheromones corresponding to plasmids it does not harbor; therefore, such a strain can also function as recipient for other sex pheromone plasmids it does not possess. Various aspects of this unique plasmid collection mechanism have been studied during the last few years. The data indicate that, with the exception of pAM373, all sex pheromone plasmids possess one DNA region which is highly similar to and codes for the adhesin. It is also becoming more and more clear that regulatory functions/proteins are not conserved between different sex pheromone plasmids. Induction of adhesin synthesis needs the action of a regulatory cascade composed of unique features; at the moment we are just beginning to understand this cascade. By sequencing the first structural gene for one of those adhesins, we realized that the aggregation substance might act also as an adhesin for eucaryotic cells, probably by interaction with integrins. At least in the case of the in vitro cultured pig kidney tubulus cell line LLC-PK1 this idea could be verified. An interesting aspect of the sex pheromone system of E. faecalis is its evolution. I will discuss the idea that two different components, both of which well might contribute to virulence of the opportunistic pathogenic bacterium, were combined in the species E. faecalis to result in this unique plasmid collection system.
粪肠球菌的性信息素系统是通过观察质粒接合转移过程中粪肠球菌菌株的聚集反应而发现的。研究发现，只有一种特殊类型的粪肠球菌质粒，即所谓的性信息素质粒，是通过这种机制进行转移的。各种实验，特别是由D. B. 克莱韦尔团队进行的实验，促成了一个描述性信息素系统工作原理的模型的形成。小线性肽，即所谓的性信息素，由不携带相应性信息素质粒的菌株分泌。携带该质粒的供体菌株不产生相应的性信息素；它们通过产生一种质粒编码的黏附素，即所谓的聚集物质，来对该肽的存在做出反应。这种黏附素使不能运动的交配伙伴之间得以接触；质粒进行接合转移后，原来的受体就拥有并复制新的质粒。由此，粪肠球菌菌株群体中供体菌株的比例会大幅增加。尤其如此是因为一个供体菌株仍会分泌与其未携带的质粒相对应的性信息素；因此，这样的菌株也可以作为它不拥有的其他性信息素质粒的受体。在过去几年里，人们对这种独特的质粒收集机制的各个方面进行了研究。数据表明，除了pAM373之外，所有性信息素质粒都有一个与黏附素高度相似并编码黏附素的DNA区域。越来越明显的是，不同性信息素质粒之间的调控功能/蛋白质并不保守。黏附素合成的诱导需要由独特特征组成的调控级联反应的作用；目前我们才刚刚开始了解这个级联反应。通过对其中一种黏附素的第一个结构基因进行测序，我们意识到聚集物质可能也作为真核细胞的黏附素起作用，可能是通过与整合素相互作用。至少在体外培养的猪肾小管细胞系LLC - PK1的情况下，这个想法得到了验证。粪肠球菌性信息素系统的一个有趣方面是它的进化。我将讨论这样一种观点，即两种不同的成分，很可能都对这种机会致病菌的毒力有贡献，在粪肠球菌物种中结合在一起，从而产生了这种独特的质粒收集系统。
