Abstract

Drinking water can be exposed to different biological contaminants from the source, through the pipelines, until reaching the final consumer or industry. Some of these are pathogenic bacteria and viruses which may cause important gastrointestinal or systemic diseases. The microbiological quality of drinking water relies mainly in monitoring three indicator bacteria of faecal origin, Escherichia coli, Enterococcus faecalis and Clostridium perfringens, which serve as early sentinels of potential health hazards for the population. Here we describe the analysis of three chimeric fluorescent protein bullets as biosensor candidates for fast detection of E. coli in drinking water. Two of the chimeric proteins (based on GFP-hadrurin and GFP-pb5 chimera proteins) failed with respect to specificity and/or sensitivity, but the GFP-colS4 chimera protein was able to carry out specific detection of E. coli in drinking water samples in a procedure encompassing about 8 min for final result and this biosensor protein was able to detect in a linear way between 20 and 103 CFU of this bacterium. Below 20 CFU, the system cannot differentiate presence or absence of the target bacterium. The fluorescence in this biosensor system is provided by the GFP subunit of the chimeric protein, which, in the case of the better performing sensor bullet, GFP-colS4 chimera, is covalently bound to a flexible peptide bridge and to a bacteriocin binding specifically to E. coli cells. Once bound to the target bacteria, the excitation step with 395 nm LED light causes emission of fluorescence from the GFP domain, which is amplified in a photomultiplier tube, and finally this signal is converted into an output voltage which can be associated with a CFU value and these data distributed along mobile phone networks, for example. This method, and the portable fluorimeter which has been developed for it, may contribute to reduce the analysis time for detecting E. coli presence in drinking water.

Highlights

  • Water is an essential resource for all life forms and its quality is under constant challenge at water treatment plants and along transportation pipes towards consumers tap

  • We describe the development of a portable biosensor system (578 g) for fast (8 min) and sensitive (10 CFU/L) detection of E. coli in drinking water samples, with a linear range for over 20 to 103 CFU

  • Three different biosensor chimera proteins have been designed and tested for specific binding to E. coli cells in drinking water samples, in order to achieve an easy and fast detection method based on fluorescence

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Summary

Introduction

Water is an essential resource for all life forms and its quality is under constant challenge at water treatment plants and along transportation pipes towards consumers tap Throughout this journey, and especially in its source, water is exposed to an increasing number of infectious, chemical and radioactive pollutants that can be ingested by humans, causing serious health problems [1]. Drinking water can be the gateway to our organism for different pathogens, such as parasites, fungi, bacteria, or viruses; by means of faecal contamination or improper water treatment [2] Countries such as Norway or the USA have described massive outbreaks of intestinal parasites such as Giardia, Cryptosporidium and Entamoeba, due to problems along the networks of water supply [3], [4]. Access to clean drinking water is essential, leading to significant health benefits [10]

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