The microbiome of the head and neck region.

The head and neck region is a host to a diverse and complex microbiome, comprising of very specific microbial communities across different anatomical niches such as the oral cavity, nasal sinuses, pharynx, larynx, salivary glands, and middle ear. The existence of these communities is determined by various factors such as physicochemical conditions, local environment and host genetics playing a critical role in maintaining mucosal integrity, immune modulation, colonization resistance, and thereby achieving metabolic homeostasis. As the human ages, the microbiome constantly evolves, influenced by diet, hormonal changes, and lifestyle even causing disruptions such as dysbiosis linked to diseases like head and neck squamous cell carcinoma (HNSCC). This chapter attempts to explore the anatomical and ecological diversity, site-specific microbial compositions, functional roles, developmental trajectories, and the challenges in understanding these microbial communities. Even though there were significant advances in sequencing technologies helping in identifying the microbial protective and pathogenic potential, hurdles like sampling difficulties and low biomass contamination tend to complicate the research process. Therefore it is of utmost importance to understand the baseline microbiome thereby helping in laying a foundation for studying its role in HNSCC, creating a pathway for microbial diagnostics and curative therapies.