Development and Molecular Characterization of Microbial Inocula for Initiation of Graywater Waste Processing Systems on Long-Term Space Flights

Microorganisms will be an integral part of biologically based waste processing systems used for water purification or nutrient recycling on space flights. Establishment of these systems with a defined group of microorganisms will provide a standardized means for conferring specific properties to the system. The purpose of this study was to develop microbial inocula (a defined, constructed community and an undefined community) for initiation of plant-based graywater waste processing systems. To this end, small-subunit 16S rDNA sequence analysis was used to describe the population composition of microbial communities from a plant-based graywater waste treatment system and from an industrial wastewater treatment plant (WWTP). The clonal library of organisms from the graywater-degrading rhizosphere community suggested that members of the Cytophagales and Proteobacteria phylogenetic groups dominated. The clonal library of organisms from industrial WWTP was taxonomically more diverse. The phylogenetic analysis provided the basis for the selection of organisms for use in the constructed community and for the selection of a source of an undefined, complex microbial inoculum. The constructed and the industrial WWTP sludge communities were inoculated into a model plant-based waste processing system to evaluate their survival. Based on plant, microbiological and molecular biological measures, it appeared that both inoculated communities were able to become established and persist in the system.