melitensis. In this work, we use as a clumping strain a B. melitensis 16M strain overexpressing aiiD (an AHL-acylase that destroys the QS signal molecules) called MG210. The characterization of the clumps produced by this strain allowed us to demonstrate the presence of exopolysaccharide(s), DNA and OMVs, three classical components of extracellular matrices. Copanlisib Moreover, here, we provide the first structural information on the complex exopolysaccharide produced by B. melitensis 16M since we found that its molecular weight is about 16 kDa and that it is composed of glucosamine, glucose and mostly mannose. In addition, we found the presence of 2- and/or 6- substituted

mannosyl residues, which provides the first insights into the linkages involved in this polymer. We demonstrate that the MG210 strain displays increased adherence properties both on polystyrene and on HeLa cell surfaces. Taken together, our data reinforce the evidences that B. melitensis could form biofilms in its lifecycle. All the strains

and plasmids used in this study are listed in Table 1. Brucella strains were grown with shaking at 37 °C in 2YT medium (10% yeast extract, 10 g L−1 tryptone, 5 g L−1 NaCl) containing appropriate antibiotics from an initial OD600 nm of 0.05. The Escherichia coli DH10B (Gibco BRL) and S17-1 strains were grown in Luria–Bertani medium with appropriate Lumacaftor datasheet antibiotics. Chloramphanicol and nalidixic acid were used at 20 and 25 μg mL−1, respectively. For exopolysaccharide purifications, Brucella were grown in RPMI 1640 medium supplemented with 10 g L−1 of d-xylose and appropriate antibiotics. DNA manipulations were performed according to standard techniques (Ausubel et al., 1991). Restriction enzymes were purchased from Roche, and primers were purchased from Invitrogen. Derivatives of the replicative plasmids pRH001 and pRH002 17-DMAG (Alvespimycin) HCl (Hallez et al., 2007) harboring aiiDsuis or aiiDmelitensis were constructed using the Gateway technique (Invitrogen). The destination

vectors pRH001 and pRH002 harbor a chloramphenicol resistance (cat) marker and the toxic cassette ccdB. This group of genes is flanked by attR1 and attR2 recombination sites. The wild-type allele corresponding to the total AiiD protein of Brucella suis (amino acids 1–761) was amplified with primers AiiD-B1 (5′-ATGAACGTCGCGAGTGCC-3′) and AiiD-B2 (5′-AAGATGGCTGCATAATC-3′). The wild-type allele corresponding to the total AiiD protein of B. melitensis (amino acids 1–782) was amplified with primers AiiD-B3 (5′-ATGAACGTCGCGAGTGCC-3′) and AiiD-B4 (5′-AAGATGCCTGCATAATCAGG-3′). Brucella melitensis 16M genomic DNA was used as the template for all amplifications. The resulting PCR products (aiiDsuis and aiiDmelitensis, respectively) were cloned into pDONR201 (Invitrogen Life Technologies) by the BP reaction as described previously (Dricot et al., 2004).