Occurrence of Bacteriophages Infecting Bacteroides fragilis and Other Viruses in Polluted Marine Sediments

Abstract

Numbers of B.fragilis bacteriophages in comparison to coliphages, enteroviruses and rotaviruses were evaluated by different methods in sediments of a coastal area near Barcelona which receives substantial amounts of pollution of domestic origin. Phages infecting B.fragilis should be eluted from sediments prior to their enumeration, in the same way as solid-associated animal viruses have to.Phages infecting B.fragilis were better eluted by glycine buffer at alkaline pH than by a caotropic agent (beef extract-sodium nitrate). Such differences between glycine buffer and sodium nitrate were not evident when enteroviruses and rotaviruses were eluted from sediments. This suggests that elution with glycine buffer is preferable for bacteriophages, while the use of caotropic agents is advisable for animal viruses, because of the simplicity of the methodology. In the studied area, coliphages were the more abundant viruses. Also, B.fragilis phages outnumbered rotaviruses and enteroviruses by a factor of more than ten. The ratios between phages active against B.fragilis and either enteroviruses or rotaviruses in marine sediments were similar to the ratios found in sewage, thus indicating that they have a similar fate.