Liquid-liquid phase separation (LLPS) serves as a key mechanism driving numerous essential biological processes. In eukaryotic cells, LLPS facilitates the formation of membraneless organelles (MLOs) by promoting the local enrichment of biomacromolecules such as proteins and nucleic acids, thereby establishing compartmentalization to enhance biochemical reaction efficiency. Under stress conditions, it also helps protect critical cellular components, including mRNA and proteins. Growing evidence in recent years indicates that LLPS-driven biomolecular condensation similarly occurs in prokaryotes. For instance, under environmental stresses (such as oxidative stress, nutrient deprivation, or antibiotic exposure), bacteria can form biomolecular condensates via LLPS that perform MLOs-like functions, improving the stress adaptability of bacteria. Proposed protective mechanisms include shielding proteins from irreversible inactivation or degradation, activating protein quality control systems, and inducing a dormant state to promote survival. Moreover, under physiological conditions, LLPS is involved in core cellular processes in bacteria, such as plasmid partitioning, chromosome segregation, transcriptional regulation, cell division, DNA replication, and repair. This review systematically summarizes the mechanisms by which biomolecular aggregates form in bacteria under both physiological and stress conditions, with a focus on how LLPS-mediated phase transitions enhance bacterial fitness and environmental adaptability. We also aim to provide insights into novel antibacterial strategies targeting LLPS.