Summary: The overall objective of this proposal is to expand from co-culture to tri-culture of the
pathogenic yeast, Candida albicans, and bacteria, Pseudomonas aeruginosa and Staphylococcus
aureus, with unprecedented spatiotemporal resolution and the ability to meet different culture
requirements in an effort to model the complexity observed in microbiome. In nature, microbial life occurs
in a concourse where interactions such as cell-cell signaling or metabolite trading between the same
species and often across kingdoms are key to their survival. In human respiratory and gastrointestinal
tracts, the balance between competition and cooperation between fungi and bacteria is of particular
importance as these interactions can determine the outcome of highly invasive infections. Microbial
communities often grow in matrices called biofilms with intricate spatial structure, and many coexist as
micro-colonies separated by a few hundred micrometers. This spatial structure has been hypothesized to
be important in microbial ecology. Modeling the microbial interactions in a well-controlled and spatially
analogous manner is of great interest in microbiome engineering and developing new biological
technologies. The vast majority of microbial models or the microbe-host systems, however, are limited to
mixed or binary cultures that either are challenging to track changes occurring in individual populations,
or lack the compatibility to support different nutrient and environmental requirements for different species.
In particular, co-culturing anaerobic and aerobic bacteria is impossible with current technologies. Here,
the PI proposes a unique “fluitrode” platform that circumvents the aforementioned bottlenecks. The
research will test four hypotheses: (1) Different microbe species cultured in a spatially controlled manner
have significant advantages over standard mixed cultures; (2) Effect of spatial resolution on the
communication between C. albicans and P. aeruginosa can be revealed using the fluitrode platform; (3)
Differences in microbial communication between aerobic and anaerobic states can be revealed with the
heterogeneous culturing platform; and (4) The expansion to tri-culture C. albicans, P. aeruginosa and S.
aureus can lead to the construction of a synthetic microbiome of many more species with individual
culturing media, optimal spatial resolution, and heterogeneous oxygen requirements. Successful
culturing of the three species will lead to establishing synthetic microbiome with more complexity as well
as more controllability that is impossible with other approaches. In the short term, the synthetic
microbiome will expedite scientific communities to understand the intricate cell-cell interactions in native
microbiome. In the long term, better models of polymicrobial interactions will pave the way to developing
better treatments for microbial-based diseases, which is a major public health concern.