Final answer:
To study host-microbiota relationships in the laboratory, gnotobiotic animals, metagenomics, and quorum sensing are commonly used. Metagenomics involves studying collective genomes of microbes in an environment, while quorum sensing relates to bacterial communication and behaviors influenced by population density.
Step-by-step explanation:
To study host-microbiota relationships in the laboratory, researchers can employ several methods. Gnotobiotic animals are those that are either germ-free or have a known microbiota, making them ideal for studying host-microbe interactions without outside influence. Metagenomics is the analysis of genetic material recovered directly from environmental samples, which allows for the study of communities of organisms, rather than isolating and culturing a single type of microbe. This method is particularly useful for understanding the collective genomes and interactions within a microbial community. Quorum sensing is a mechanism by which bacteria communicate and coordinate behavior based on their population density. While not a direct method for studying host-microbe interactions, insights into quorum sensing can influence how we understand and potentially control microbial behaviors relevant to their relationships with hosts. The term microbiota refers to all microorganisms in a certain region of the human body (Option C) or in a certain geographic region (Option D), and it includes not just symbiotic relationships but all microorganisms within that environment, whether they are interacting or existing independently.