%0 Journal Article
%T Cloning and expression of a novel lactococcal aggregation factor from Lactococcus lactis subsp. lactis BGKP1
%A Milan Kojic
%A Branko Jovcic
%A Ivana Strahinic
%A Jelena Begovic
%A Jelena Lozo
%A Katarina Veljovic
%A Ljubisa Topisirovic
%J BMC Microbiology
%D 2011
%I BioMed Central
%R 10.1186/1471-2180-11-265
%X 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.The aggregation phenomenon in lactococci has been studied for more than thirty years. It was found to be directly associated with a sex factor and lactose plasmid co-integration event [1] or duplication of the cell wall spanning (CWS) domain of PrtP proteinase [2]. Lactose plasmid conjugation in Lactococcus lactis 712 and in the related strains C2 and ML3, frequently involves plasmid co-integration with a sex factor. Moreover, this phenomenon is often associated with a cell aggregation phenotype and high frequency transfer ability [3-5]. The lactococcal sex factor exists integrated in the chromosome [6], although it can be excised as a closed circular form and lost from the cell [1]. Deletion and over-expression experiments confirmed that CluA is the only sex factor component responsible for aggregation in L. lactis. This 136 kDa surface-bound protein, encoded by the chromosomally located sex factor of Lactococcus lactis subsp. cremoris MG1363, is assoc
%U http://www.biomedcentral.com/1471-2180/11/265