The plates were allowed to solidify and then 10-μl portions of the test CFTRinh-172 strain suspension were spotted on the surface of the agar. These plates were then incubated at 37°C overnight. Production of bacteriocin by the test strain and/or the susceptibility of the indicator strain were indicated by the presence of a small clear zone of growth inhibition around the test strain.

PCR-based detection of the mcb locus Chromosomal DNA was prepared from eight M. catarrhalis strains and used in PCR with the oligonucleotide primers AA247 (5′-TGCCATTGCCAAAGAGAC-3′) and pLQ510-rp1 (5′-CACCATATGACAATCTATTAG-3′). AA247 was located in the mcbA ORF and pLQ510-rp1 was located check details in the mcbC ORF. Nucleotide sequences of the mcbABCI genes from M. catarrhalis strain O12E were deposited at GenBank and assigned the following accession numbers:

mcbA, EU780917; mcbB, EU780918; mcbC, EU780919; mcbI, EU780920. The mcbABCI genes from M. catarrhalis strain V1120 were deposited at GenBank and assigned the following accession numbers: mcbA, EU755328; mcbB, EU755329; mcbC, EU755330; mcbI, EU755331. Inactivation of selected genes in pLQ510 The mcbB ORF was inactivated by ligating a kanamycin resistance cassette [49] into the BsiWI site within this ORF in pLQ510; the new plasmid was designated pLQ510.mcbB::kan. The mcbC ORF was inactivated by inserting a kanamycin resistance cassette into the HpaI site in this ORF; the new plasmid was designated pLQ510.mcbC::kan. Construction of deletion mutations BIBW2992 in the chromosome of M. catarrhalis strain O12E To construct an in-frame deletion in the mcbA gene, primers AA262 (5′- GAAGT AAATCGTCAGATGG-3′) and AA349 (5′-AGGGCGGAATAGACTAGACAT-3′) were used to amplify a DNA fragment containing the 345 nucleotides (nt) upstream of the mcbA ORF together with the first 21 nt of this ORF, using chromosomal DNA from strain O12E as a template. Primers AA350 (5′-AGTCTATTCCGCCCTCCGCT ATATAGT CTCACAGGTAAAATTTAA-3′) and AA250 (5′-AAAACTGGCTGG GCAGATG-3′) were used

to amplify the last 30 nt of the mcbA ORF together with 855 nt of the downstream DNA. The resultant two PCR products were used as templates in overlapping extension PCR [50] using primers AA262 and AA250. The new PCR product was used in a plate transformation system Anacetrapib [51] to transform M. catarrhalis strain O12E. Transformants were screened by colony-PCR using primers AA262 and AA251 (5′-AGATTGCTCACTCGTCCAC-3′); this latter primer binds downstream of AA250. One transformant shown to contain the desired deletion in the mcbA gene was designated O12EΔmcbA. For the construction of an in-frame deletion in the mcbB ORF, primers AA247 (5′-TGCCATTGCCAAAGAGAC-3′) and AA346 (5′-AATATTCTTTAAAAAATC CAT-3′) were used to amplify 830 nt upstream of the mcbB ORF together with the first 21 nt of the mcbB ORF using chromosomal DNA from strain O12E as the template.