Accurate and swift detection of bacteria is essential in various fields, including medical diagnostics, food safety, and environmental monitoring. Conventional methods such as culture-based assays and polymerase chain reaction (PCR) often face limitations, including lengthy processing times and the need for specialized lab equipment. Synthetic biology, however, provides a groundbreaking alternative by designing synthetic genetic circuits that are capable of sensing and responding to specific bacterial biomarkers. These circuits incorporate genetic elements such as biosensors, logic gates, and reporter systems, enabling highly specific and sensitive detection of pathogenic bacteria. Recent innovations in synthetic biology have introduced advanced tools such as CRISPR-based bacterial biosensors, microfluidic-integrated detection systems, and cell-free biosensors. These advancements not only improve detection speed and accuracy but also address biosafety concerns. Despite these promising developments, challenges such as genetic circuit stability, environmental variability, and regulatory hurdles still hinder widespread adoption. Overcoming these obstacles will require integrating artificial intelligence (AI) for circuit optimization, enhancing biocontainment strategies, and fostering interdisciplinary collaboration. Such efforts will drive the development of next-generation bacterial detection systems. This chapter delves into the principles of synthetic circuit design for bacterial detection, highlights key applications, discusses existing challenges, and explores emerging trends that are shaping the future of this dynamic field. By addressing these aspects, this chapter aims to provide a comprehensive understanding of how synthetic biology is revolutionizing bacterial detection.