This gene was also employed for the development of an electrochemical sensor by . The lacZ gene, coding for lactose permease, was employed to develop a sensor for the detection of E. coli in the work of . This gene was previously shown to be specific for E. coli by . Another gene of interest which emerged in the recent years for E. coli detection in water samples is ybbW, encoding a putative Allantoin transporter . Based on extensive research on STEC pathogenicity in the last few years, it was concluded that all E. coli strains containing at least one stx gene coding for toxin production may potentially cause human infection and the nucleic acidbased detection should focus on targeting these genes . Several subtypes of each stx gene exist that were categorised into two groups of genes -stx1 and stx2 and having any subtype of stx in a genome or a combination may be pathogenic. Therefore, the sensors developed by based on one of the stx genes are considered to be the most specific for STEC.