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MOLECULAR PROFILING OF PLANKTONIC AND BIOFILM MICROBIAL COMMUNITIES IN HYDROPONIC GROWTH SYSTEMS.   E. Nunez, J. L. Adams and M. S. Roberts.  Dynamac Corporation, ALS Controlled Biological Systems Group, Kennedy Space Center FL 32899

Microbial biofilms have been shown to occur in association with the surfaces of many plant species. Included among these are candidate crops under evaluation by the Advanced Life Support (ALS) program for use in long-term space missions. Long-term space missions will require the capability to grow food in space and to recover nutrients, water, and air from recycled waste. A viable alternative for food production and resource recovery in space utilizes hydroponic nutrient-delivery systems. 

The high density of plants within an enclosed hydroponic system may, however, promote the development of biofilms which may compete with plants for nutrient uptake or harbor potentially pathogenic organisms. The presence of potential pathogens within a bioregenerative system could indirectly affect the efficiency of the life support system by impairing plant growth or directly impact astronaut health by allowing the growth of human pathogens. We describe here our initial efforts to quantify the population size, species richness and community composition of the biofilm component in the planktonic and biofilm communities of wheat crops in ALS hydroponic growth systems. Microbial diversity within these systems was evaluated using molecular-based techniques to profile microbial diversity in both sessile and planktonic populations. Biofilm-traps incorporating porous, scintered glass beads (Siran Carriers; Jaeger Biotech Engineering, Inc.) were used to sample nutrient solution biofilms. Planktonic and biofilm populations from each of three nutrient solution treatments (Hoaglands, filtered compost leachate, and unfiltered compost leachate) were evaluated using Terminal Restriction Fragment Length Polymorphism (T-RFLP). This DNA-based approach for community analysis allows the detection of both dominant and non-dominant ‘culturable’ populations in addition to the characterization of ‘non-culturable’ bacteria. Our results indicate that there are distinct microbial communities inhabiting the planktonic and biofilm environments within the hydroponic growth systems.