Bacterial Interspecies Interactions and Microbial Community Assembly

Microbial communities play central roles in the development and maintenance of human health and in the functioning of the Earth’s ecosystems. The microbial biodiversity of many environments has been thoroughly studied in recent years, yet the dominant processes shaping microbiota assembly remain unresolved. In this thesis, I leverage a bottom-up approach to experimentally build synthetic microbial communities and to test the prevalence of different ecological and evolutionary forces. High-throughput experiments in nanoliter droplets show a wide occurrence of bacterial interactions in the form of one species or consortium affecting the abundance and yield of another species. Positive and negative interactions appear unavoidable in bacterial co-cultures when growth is permitted, with growing bacteria typically facilitating non-growing bacteria. In this thesis, I also show that bacterial interspecies interactions in the C. elegans intestine are mostly competitive and hierarchical. Interestingly, simple two-species microbiotas can predict the composition of three-species and eight-species microbiotas in this nematode. Finally, we found that the importance of interspecies interactions is robust to bacterial strains with and without previous exposure to the C. elegans gut, and to worm mutants with different immune activities. These results show that constructing and characterizing synthetic microbial communities can elucidate fundamental principles for the control of microbial communities.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Microbiology Graduate Program

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2021

Author dc:creator

• Ortiz Lopez, Anthony F.

Advisor dc:contributor.advisor

• Gore, Jeff

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright MIT

Licence dc:rights.uri

• http://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/140145

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/140145