**1. Introduction**

The risks due to bacterial contamination and infection to healthcare system and socio-economic stability as well as to environment and food contamination have become global issues [1]. The current approaches are usually not performing well in complex mixtures of opposing microorganisms and environmental conditions devoid of enrichment step. These approaches comprise old-fashioned plating and antibodies-based assays. Therefore, in the skipping of enrichment step, almost all present experiments are not satisfactorily sensitive to sense a distinct or a very small quantity of target bacteria [2]. In contrast, the approaches like hybridization-based assays (ELISA) and polymerase chain reaction (PCR) are sensitive; however, these cannot differentiate the live cells from the dead ones, thus require an augmentation

step for specificity and are laborious and expensive. These restrictions can be potentially overwhelmed by developing a biosensor. Biosensor development needs a specific and sensitive bio-probe that can withstand elevated temperature, extreme pH and remain active in diverse and complicated environment. Bacteriophages being sensitive and specific to host bacterium, and showing activity in diverse ionic concentrations are potent agents in biosensor development for detection of bacteria. Phages naturally deliver specificity in recognition of particular bacterial strain to attach, and specifically sense preferred bacterial spectra. Swift recognition offered by phage-based detection can improve the tracing and remediation of bacterial contamination [3]. The main issue that comes with development of phage based biosensor is active and oriented phages immobilization on substrate surface. The benefit of phage immobilization during biosensor development is that phages remain active for long time period, retain physiological activities with high densities, and having high bacterial cells capture efficiencies. Thus, showing improved detection limits that leads to possible development of phage-based biosensor for rapid and accurate bacterial detection [4]. Bacteriophage based biosensor development involve the following phage related approaches: (i) Observing the released phage particles during lytic cycle in the presence of host bacterium, (ii) monitoring released intracellular lysed cell component in the course of phage-mediated bacterial lysis, (iii) detection of inhibited bacterial growth in the presence of specific phages, (iv) use of stained phages for bacterial capture, and (v) observing the expression of cloned reporter gene in genetically modified phages that is expressed after bacterial infection [5].
