Sam Augustine and Dr. Alan Harker, Microbiology

Ecology is the study of the interactions of living organisms with each other and their environment. In microbiology there has been relatively little done in this field compared to the macro-biological world. In traditional macro-scale ecology an environment is clearly delineated by physical boundaries, access to resources and competition.

Ecological boundaries in the microbial world are not so easily determined. A grain of sand can easily house thousands of microbes, all or some of these microbes could e interacting at various levels. In the next moment a raindrop washes off half of the community, how does this affect competition? What is a stable microbial community? How do the traditional factors of ecology directly control microbial communities?

My project was to construct a stable artificial microbial consortium. This community would consist of ten to twelve different microbes growing together in a single medium (resource base) of known composition. Individual members of the community would need to be identifiable phenotypically (expressed physical characteristics). The relative populations of the various constituents would also need to be repeatable.

Individual microbes were isolated from various sources and grown up on a nutrient agar petri dish. After finding and separating approximately 22 different microbes, each of them were introduced into a separate nutrient broth and incubated for 24 hours. Following growth in nutrient broth of individual strains of microbes, a single tube of nutrient broth was inoculated with broth from all 22 tubes.

This new tube was then incubated over a period of a week changing the broth each day to provide new nutrients for the microbes. I created a control by inoculating a petri dish (plating) with the same broth on the first day. Additionally each of the original tubes was plated on nutrient agar to determine their viability.

After one week of daily transfers the new tube with inoculations from the 22 tubes was plated to examine the growth of the various microbes. Almost without fail the largest number of different constituents of a consortium was five. The controls showed that previous to introduction the individual microbes were indeed viable. The control of the first day showed little more diversity than after a week.

Attempts were made to consistently reproduce consortia of the same five microbes. This effort was fruitless. After the first day the recreated consortium consisted of typically two or three distinctively identifiable microbes and after two days only one.

Upon attending the American Society for Microbiology conference and listening to lectures in the same field it was determined that the level of complexity hope for in our consortia is far advanced from any other current research. The determination was then made to simplify our model and pursue reproducible stable communities of two identifiable microbes. This is the current status of my research.

The next logical step following is to create this community. Once a community is created individual
factors affecting the viability of their interaction can be determined and further extrapolation can be
made.