Characterization of maltocin P 28 , a novel phage tail - like bacteriocin from 1 Stenotrophomonas maltophilia

24 Stenotrophomonas maltophilia is an important global opportunistic pathogen for which 25 limited therapeutics are available because of the emergence of multidrug-resistant strains. 26 A novel bacteriocin, maltocin P28, which is produced by S. maltophilia strain P28, is the 27 first-identified phage tail-like bacteriocin from S. maltophilia. Maltocin P28 resembles a 28 contractile but non-flexible phage tail structure based on electron microscopy, and is 29 sensitive to trypsin, proteinase K, and heat. SDS-PAGE analysis of maltocin P28 revealed 30 two major protein bands of approximately 43 and 20 kDa. The N-terminal amino acid 31 residues of these two major subunits were sequenced, and the maltocin P28 gene cluster 32 was located on the S. maltophilia P28 chromosome. Our sequence analysis results 33 indicate that this maltocin gene cluster consists of 23 ORFs, and that its gene organization 34 is similar to the P2 phage genome and R2 pyocin gene cluster. ORF17 and ORF18 35 encode the two major structural proteins, which correspond to gpFI (tail sheath) and 36 gpFII (tail tube) of P2 phage, respectively. We found that maltocin P28 had bactericidal 37 activity against 38 of 81 tested S. maltophilia strains. Therefore, maltocin P28 may be a 38 promising therapeutic substitute to antibiotics for S. maltophilia infections. 39