A genomically modified marker strain of Escherichia coli

Contamination of the environment with human sewage represents a serious public health concern in which Escherichia coli plays a central role, either directly as a human pathogen or indirectly through its use as an indicator organism. There is thus an ongoing effort to better understand the behavior of E. coli within such environments. Useful to such studies is the ability to readily detect a specific E. coli population and distinguish it from similar indigenous bacteria. Herein, we report the construction of an E. coli strain (PCPHR) that expresses a Stable Artificial RNA (SAR) from the chromosomal rrnH operon. The SAR product is present in large numbers of copies/cell and thus provides an enhanced detection signal without significant effect on the wild-type growth rate. Detection can be accomplished by any of several routine molecular methods. Preliminary studies suggest SAR expression levels correlate positively with growth. PCPHR is immediately available for use as a marker strain for E. coli in application in the arena of public health or environmental studies.