Laboratory for Molecular Genetics of Industrial Microorganisms, Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444/a, P,O, Box 23, Belgrade 11010, Serbia.
BMC Microbiol. 2011 Dec 19;11:265. doi: 10.1186/1471-2180-11-265.
Aggregation may play a main role in the adhesion of bacteria to the gastrointestinal epithelium and their colonization ability, as well as in probiotic effects through co-aggregation with intestinal pathogens and their subsequent removal. The aggregation phenomenon in lactococci is directly associated with the sex factor and lactose plasmid co-integration event or duplication of the cell wall spanning (CWS) domain of PrtP proteinase.
Lactococcus lactis subsp. lactis BGKP1 was isolated from artisanal semi-hard homemade cheese and selected due to its strong auto-aggregation phenotype. Subsequently, non-aggregating derivative (Agg-) of BGKP1, designated as BGKP1-20, was isolated, too. Comparative analysis of cell surface proteins of BGKP1 and derivative BGKP1-20 revealed a protein of approximately 200 kDa only in the parental strain BGKP1. The gene involved in aggregation (aggL) was mapped on plasmid pKP1 (16.2 kb), cloned and expressed in homologous and heterologous lactococci and enterococci. This novel lactococcal aggregation protein was shown to be sufficient for cell aggregation in all tested hosts. In addition to the aggL gene, six more ORFs involved in replication (repB and repX), restriction and modification (hsdS), transposition (tnp) and possible interaction with mucin (mbpL) were also located on plasmid pKP1.
AggL is a new protein belonging to the collagen-binding superfamily of proteins and is sufficient for cell aggregation in lactococci.
聚集作用可能在细菌黏附于胃肠道上皮细胞及其定殖能力中起主要作用，也可能通过与肠道病原体的共同聚集及其随后的清除而发挥益生菌作用。乳球菌中的聚集现象与性因子和乳糖质粒的共整合事件或 PrtP 蛋白酶的细胞壁跨越（CWS）结构域的重复直接相关。
从传统半硬自制奶酪中分离出乳球菌亚种乳球菌 BGKP1，因其具有较强的自聚集表型而被选中。随后，分离出非聚集衍生菌（Agg-）BGKP1-20。对 BGKP1 和衍生菌 BGKP1-20 的细胞表面蛋白进行比较分析，仅在亲本菌株 BGKP1 中发现了约 200 kDa 的蛋白质。参与聚集的基因（aggL）位于质粒 pKP1（16.2 kb）上，在同源和异源乳球菌和肠球菌中进行克隆和表达。这种新型乳球菌聚集蛋白足以在所有测试的宿主中引起细胞聚集。除了 aggL 基因外，质粒 pKP1 上还定位了另外六个与复制（repB 和 repX）、限制和修饰（hsdS）、转位（tnp）和可能与粘蛋白相互作用（mbpL）有关的 ORF。
AggL 是一种属于胶原蛋白结合蛋白超家族的新蛋白，足以引起乳球菌的细胞聚集。
