Seminar

The Human Microbiome in Health and Disease

Alejandro Mira, PhD

Bacteria inhabiting the human body play important roles for health that are still not fully understood. Those bacteria inhabit our gut, respiratory tract, skin, oral cavity, urinary tract, etc, and can be considered as an organ whose function needs to be elucidated. An important fraction of the human-associated microbiota has not been cultured and therefore the use of DNA techniques has revolutionized the research in the field. Metagenomics is the study of all genes present in the bacterial community obviating the need for culture and the recent development of second and third-generation sequencing techniques has allowed researchers to describe the composition and genetic repertoire of the human microbiome to an unprecedented level of detail. We have applied these techniques to describe the microbiota associated to the respiratory tract, the human breast milk, the stomach, the gut and specially the oral cavity, where we have identified a new bacterial species, named Streptococcus dentisani, that appears to protect the teeth against dental caries. Other microbiome research has allowed us to study susceptibility to stomach ulcer and to identify bacteria that can serve as biomarkers of colorectal cancer. Finally, the combination of flow-citometry and cell sorting with massive sequencing has served us to identify the bacteria recognized by different antibodies in the oral cavity, the gut and the breast milk. Thus, the combination of these techniques will serve to unravel the function of our microbial partners in health and disease.