Many bacteria produce secreted virulence factors called exotoxins. Exotoxins are often encoded by mobile genetic elements, including bacteriophage (phage). Phage can transfer genetic information to the bacteria they infect. When a phage transfers virulence genes to an avirulent bacterium, the bacterium can acquire the ability to cause disease. It is important to understand the role played by the phage that carry these genes in the evolution of pathogens. This is the first report of an environmental reservoir of a bacterial exotoxin gene in an atypical host. Screening bacterial isolates from the environment via PCR identified an isolate with a DNA sequence >95% identical to the Staphylococcus aureus enterotoxin A gene (sea). 16S DNA sequence comparisons and growth studies identified the environmental isolate as a psychrophilic Pseudomonas spp. The results indicate that the sea gene is present in an alternative bacterial host, providing the first evidence for an environmental pool of exotoxin genes in bacteria.

This is the first report of an environmental reservoir of a bacterial exotoxin gene harbored in an atypical host in the environment. Screening bacterial isolates from the environment via seaspecific PCR identified an isolate with a DNA sequence >95% identical to the Staphylococcus aureus enterotoxin A gene (sea). 16S DNA sequence comparisons identified the environmental isolate as a Pseusodomonad. Laboratory studies confirmed that this Pseudomonad is psychrophilic. The results indicate that the sea gene is present in an alternative bacterial host, providing the first evidence for an environmental reservoir of exotoxin genes in bacteria. Transfer of these genes between phage and alternative bacterial hosts may promote the evolution of novel human diseases.