Food and waterborne pathogens are the leading causes of illnesses worldwide. However, the current protocols for pathogen detection are expensive and time consuming. Bacteriophages (phages) are viruses that selectively infect bacterial species, resulting in lysis and self-propagation in a targeted and efficient manner. Therefore, using phages as a new bacterial detection platform reduces cost and time and improves detection specificity. The T4 phage has a broad host range for detecting E. coli, making it an ideal candidate to engineer for use as a biorecognition element. However, the T4 phage genome is complex and has compounded modifications such as cytosine hydroxylmethylation and glucosylation; thus, classical phage engineering approaches are ineffective or inefficient in permitting insertions of reporter probes or modifications of host range. Here, the CRISPR-Cas9 system is adapted to mediate genome engineering of the T4 phage, resulting in >99% editing efficiency. Furthermore, reporter T4 phage were transcriptionally optimized, resulting in a 6-fold increase in the output signal, a marked improvement of phage-based bio-detection platform.