Conclusion: The order of the genes on the chromosome is the same, but the position and orientation of the F factor differs among the strains.

I 8.19 The order of gene transfer in a series of different Hfr strains indicates that the E. coli chromosome is circular.

(pig) to human E. coli. The transfer of R plasmids also occurs in sewage, soil, lake water, and marine sediments.

Perhaps most significantly, the transfer of R plasmids is not restricted to bacteria of the same or even related species. R plasmids with multiple antibiotic resistances have been transferred in marine waters from E. coli and other human-inhabiting bacteria (in sewage) to the fish bacterium Aeromona salmonicida and then back to E. coli through raw salmon chopped on a cutting board. These results indicate that R plasmids can spread easily through the environment, passing among related and unrelated bacteria in a variety of common situations. That they can do so underscores both the importance of limiting antibiotic use to treating medically important infections and the importance of hygiene in everyday life.

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