Intratumoral microbiota, as an important component of the tumor microenvironment, have attracted increasing attention in recent years for their roles in tumor initiation, progression, and therapeutic regulation. Accumulating evidence indicates that low-abundance yet relatively stable microbial communities are present in a variety of solid tumors, exhibiting marked tumor-type specificity and spatial heterogeneity. Current studies suggest that intratumoral microorganisms contribute to tumor progression through multiple mechanisms, including activation of oncogenic signaling pathways, modulation of chronic inflammatory responses, remodeling of the immunosuppressive microenvironment, and regulation of metabolic reprogramming and drug responsiveness. Meanwhile, their bidirectional effects on chemotherapy, radiotherapy, targeted therapy, and immunotherapy highlight their potential roles in determining therapeutic sensitivity and the development of resistance. Despite existing challenges such as low microbial biomass, contamination control, and difficulties in functional validation, advances in spatial multi-omics and single-cell technologies are continuously enhancing the potential clinical value of intratumoral microbiota in tumor diagnosis, prognostic assessment, and precision therapy. This review summarizes the sources, colonization mechanisms, biological functions, roles in therapeutic modulation, and clinical applications of intratumoral microbiota, aiming to provide a theoretical basis for future research and clinical translation.

Osteomyelitis is an inflammatory bone disorder that includes both infectious and noninfectious forms and remains a major cause of bone destruction, impaired skeletal repair, and long-term disability. Although bacterial infection is the predominant cause, disease progression is influenced by interactions among microorganisms, host immunity, inflammation, and bone remodeling. This review critically evaluates current evidence from genome-wide association and Mendelian randomization studies, clinical investigations, and experimental animal models. Clinical studies demonstrate that osteomyelitic bone contains polymicrobial communities enriched with anaerobic and biofilm-forming bacteria, whereas oral microbial dysbiosis differs between chronic bacterial and chronic nonbacterial osteomyelitis. Experimental studies indicate that gut microbial dysbiosis is associated with impaired intestinal barrier function, altered microbial metabolites, systemic inflammation, and delayed bone repair. Current evidence therefore suggests that microbial communities detected at local sites are associated with infection, biofilm formation, and local inflammatory responses, whereas the gut microbiome may influence systemic immunity, inflammatory tone, and bone remodeling. Although microbiome-targeted interventions have shown beneficial effects in experimental models, current evidence remains largely associative, and mechanistic and longitudinal studies are limited. A better understanding of microbiome-host interactions may facilitate the development of microbiome-based strategies for the prevention and treatment of osteomyelitis.