Detection of phages infecting Bacteroides fragilis HSP40 using a specific DNA probe

Nine bacteriophage isolates of Bacteroides fragilis, obtained from urban se wage and pig faeces samples using four different host strains HSP40, RYC402 3, RYC2056 and RYC3318), were compared on the basis of morphology, host ran ge, DNA restriction patterns, DNA hybridisation and protein composition. Al l the phages are siphovirus and. as judged from cleavage by restriction end onucleases, their genome is composed of double-stranded DNA of similar size (approximate to 51-kb). Host range analysis differentiated two types of ph ages: (1) phages that clearly infect B, fragilis strains HSP 40 (B40-2, B23 -1, B23-2, B23-3 and B23-4, of which B40-8 is the phage type). and (2) the group of bacteriophages that were not infectious for HSP30 (B56-1, B56-2 an d B18-1). Similarity in DNA restriction patterns and protein characteristic s was found in the HSP30 infectious phages. Anti-B40-8 serum recognised onl y the proteins of the phages of this type. Although all phages showed simil ar major protein sizes, minor specific bands were detected. Bacteriophages B56-1, B56-2 and B18-1 showed heterogeneity in their DNA restriction profil es although some degree of DNA-DNA homology between all genomes was observe d. Southern blot analysis with phage B40-8 DNA based probes idenified a 1.5 -kb DNA region homologous for all HSP40 phage isolates, but absent in the g enome of the other phage isolates that did not infect this bacterial strain . The homologous region was used as a specific probe to specifically detect B. fragilis HSP40 phages. (C) 2000 Elsevier Science B.V. All rights reserv ed.