Characterization of the replication and stabilization systems present in the plasmid pSmeLPU88b of Ensifer meliloti

PISTORIO, M.; TORRES TEJERIZO, G. A.; CASTELLANI, L; NILSSON, J; LAGARES, A.

Seattle

Congreso; Plasmid Biology 2018; 2018

International Society for Plasmid Biology

Rhizobia are Gram-negative bacteria with ability to fix atmospheric N2 insymbiotic association with the root of legumes. Current evidence shows that rhizobiacarry in most cases variable number of plasmids related to their symbiosis and freeliving,being a common feature the presence of several plasmid replicons within asame strain. We has been studying the cryptic plasmids in Ensifer meliloti, and themobilization properties of two cryptic plasmids (pSmeLPU88b and pSmeLPU88a)from the strain E. meliloti LPU88 were reported (1, 2).To further characterize pSmeLPU88b plasmid the full sequence was achieved.pSmeLPU88b was 35.9 kb in size, had an average GC % of 58.56 and 40 CDS. Thereplication modules were identified in silico: one belonging to the repABC type, andthe other related to the repC family of plasmid replication regions. Both regionsresulted nearly identical to the homologous elements from plasmid pMBA9a presentin an isolate from Canada (3). In addition, we identify downstream of the repABCsystem three CDS that present homologies with recombinases and with toxinantitoxinsystems. The antitoxin is related to the Phd_YefM, type II toxin-antitoxinsystemand the toxin belongs to PemK-like, MazF-like toxin family. It is noteworthythat the three CDS observed present the same genetic structure in pSmeLPU88band in other rhizobial plasmid (pRmeGR4a, pSMED03 pSINME01) and in all casesthey are found downstream of the repABC operon.By cloning each replication system in suicide plasmids we demonstrated that anyof them can support plasmid replication in the E. meliloti genetic background.Incompatibility analysis of the cloned rep systems results in the curations of theparental plasmid. Interestingly, both obtained plasmids can coexist together withoutselection.1. M. Pistorio, M. F. Del Papa, L. J. Balagué, A. Lagares, FEMS Microbiol Lett 225, 15 (Aug 8, 2003).2. M. Pistorio et al., FEMS Microbiol Lett 345, 22 (Aug, 2013).3. R. J. Watson, R. Heys, Plasmid 55, 87 (2006).