Sentinel Microbes: Target-Specific Intestinal Biosensors for Real-Time Gut Environment Monitoring Section 1: Abstract The human intestinal tract is a highly dynamic and complex ecosystem where imbalances in metabolite levels, inflammation markers, and pathogen signals heavily dictate systemic health. Traditional diagnostic modalities often rely on invasive procedures or episodic stool samples, which lack the temporal resolution required to capture transient physiological shifts. Furthermore, classical diagnostic assays are frequently prone to sample degradation during processing and cannot provide real-time, in situ analytical feedback.