Xuesong He, PhD, DDS
Trained as a dentist and microbiologist, Xuesong He started his academic career by studying regulation of virulence gene expression in some of the main oral pathogens, including the cariogenic bacterium Streptococcus mutans, and periodontal pathogen, Fusobacterium nucleatum.
In the past few years, with the explosion of the knowledge in the diversity and complexity of host-associated microbiome, as well as the increased appreciation of their crucial role in human health, Dr. He has expanded his research interests to tackle the new challenges in oral microbiome research. The following are his main areas of research interest:
1) “Domestication” of yet-to-be cultured microbes
One of the biggest challenges in oral microbial research is to culture those yet-to-be cultured species for detailed physiological/pathogenic analysis. By using a novel culturing method, He’s team successfully isolated and cultivated from oral cavity the first TM7 strain (named TM7x), which belongs to TM7, a bacterial phylum that is omnipresent, particularly in the human oral cavity, and associated with periodontal disease. They also revealed its unique epibiotic/parasitic lifestyle with its bacterial hosts. Furthermore, TM7 belongs to Candidate Phyla Radiation (CPR), a unique class of bacteria revealed by the most recent metagemonics-based approach. Thus far, TM7 remains the only phylum with cultivated representatives in the CPR group. Currently, He’s group is using TM7x and its bacterial host as a model system to better understand CPR bacteria, which take up >15% of the bacterial domain.
2) Understanding the social structure and community functionality of host-associated microbiome
It is well established that host-associated microbiome interferes with the colonization of microbes of foreign origins, a phenomenon referred to as colonization resistance. Using an in vitro multispecies model system, He’s group revealed for the first time the sophisticated structure and functional organization of a colonization resistance pathway within a microbial community, providing evidence of the social functionality within microbial community. They are currently using a comprehensive genetic and multi-omics approach to reveal the detailed mechanisms governing this intriguing and ecologically relevant phenomenon.
3) Studying the ecological importance of individual bacterial species within host-associated microbiome
Another major challenge to studying human microbiome and its associated diseases is the lack of effective tools to achieve targeted modulation of individual species and to study its ecological function within multispecies communities. He’s team was the first to develop a proof of concept that makes it possible to examine the ecological importance of individual species within a complex microbial community by knocking out or knocking down one particular species with a targeted antimicrobial and then tracking the impact on the rest of the species within the same community. Currently, using this approach, He’s team is in the process of identifying and studying “keystone” species whose removal could result in the collapse of the normal community structure and have significant impact on community functionality.
The ultimate research goal of He’s lab is to combine the culture-dependent physiological/pathogenic study and culture-independent multispecies multi-omics analysis to achieve comprehensive and systemic understanding of oral microbiome and its impact on human health.
Beijing University, School of Dental Medicine, Beijing, China, DDS, 1997, Dental Science
Indiana University, Bloomington, IN, PhD. 2006, Microbiology
UCLA School of Dentistry, Los Angeles, CA, Postdoc, 2006-2010, Oral Microbiology