The aim of this study was to identify heavy metal detoxification system in Rhizobium leguminosarum bv. trifolii isolated from Trifolium repens inhabiting old (70-100 years) Zn-Pb waste heaps in Poland by PCR reaction with czcD1 and czcD2 primers. By sequence analysis, four different genotypes of obtained amplicons were identified among eight examined isolates. Their sequence similarity ranged 91-99 %. They indicated the highest sequence identity to the hypothetical lysine exporter gene of R. leguminosarum bv. trifolii WSM1325 (91-97 %) and 76-81 % sequence similarity to hypothetical lysine exporter genes of R. leguminosarum bv. trifolii WSM2304 and R. etli CFN42 and CIAT652. On phylogenetic tree of obtained amplicons, all four studied R. leguminosarum bv. trifolii genotypes formed common monophyletic cluster with R. leguminosarum bv. trifolii WSM1325 at 100 % bootstrap support showing that all four amplicons obtained in PCR with czcD1 and czcD2 primers are fragments of hypothetical lysine exporter gene (lysE). We also suggest that Lys efflux exporter may participate in heavy metal transport out of R. leguminosarum bv. trifolii cells.