Prevalence ofBacillus anthracis-Like Organisms and Bacteriophages in the Intestinal Tract of the EarthwormEisenia fetida

Stable infection ofBacillus anthracis laboratory strains with environmental bacteriophages confers survival phenotypes in soil and earthworm intestinal niches (R. Schuch and V. A. Fischetti, PLoS One 4:e6532, 2009). Here, the natural occurrence of two suchB. anthracis -infective bacteriophages, Wip1 and Wip4, was examined in the intestines ofEisenia fetida earthworms as part of a 6-year longitudinal study at a Pennsylvania forest site. The Wip1 tectivirus was initially dominant before being supplanted by the Wip4 siphovirus, which was then dominant for the next 3 years. In a host range analysis of a wide-ranging group ofBacillus species and related organisms, Wip1 and Wip4 were both infective only towardB. anthracis and certainB. cereus strains. The natural host of Wip4 remained constant for 3 years and was aB. cereus strain that expressed aB. anthracis -like surface polysaccharide at septal positions on the cell surface. Next, a novel metagenomic approach was used to determine the extent to which suchB. cereus - andB. anthracis -like strains are found in worms from two geographical locations. Three different enrichment strategies were used for metagenomic DNA isolation, based either on the ability ofB. cereus sensu lato to form heat-resistant spores, the sensitivity ofB. anthracis to the PlyG lysin, or the selective amplification of environmental phages cocultured withB. anthracis . Findings from this work indicate thatB. cereus sensu lato and its phages are common inhabitants of earthworm intestines.