Microbial genetic diversity in advanced life support systems.

摘要

To sustain manned, long-duration space travel and planetary exploration, NASA has established an Advanced Life Support (ALS) Program to develop a closed-loop system for oxygen, water, and food supplies. Although the importance of microorganisms in the functioning of the biological systems used in space has been recognized, little research has been conducted on the species diversity of the microorganisms responsible for resource recycling. Therefore, the microbial diversity in three ALS systems was analyzed with molecular biological techniques.; Since interactions between microorganisms and plant roots have a significant impact on plant growth and crop yields, microbial diversity on the rhizoplanes of five candidate crops grown in hydroponic or a solid matrix was characterized using 16S rRNA genes, and species diversity and community compositions varied among the different crops and growth matrices.; Biofilters have been widely used for removal of odors and volatile compounds from contaminated off-gas streams; however, the microbial ecology of the reactors is not well understood. Therefore, shifts of species richness and composition of both ammonia oxidizing bacteria (AOB) and total microorganisms were examined by using ammonia monooxygenase (amoA) and 16S rRNA genes, respectively, during the operation of a laboratory scale ammonia biofilter. Decreases were observed in the number of total microbial species during the 102 day trial, and community composition changed. Although the number of species of AOB did not change significantly with time, changes in population structure were observed.; To examine the possibility of producing potable water from wastewater, two fixed-film biological wastewater treatment reactors were tested for organic carbon and ammonia removal. Spatial distributions of the total, ammonia oxidizing, and denitrifying bacteria in biofilms at the end of the test were investigated by using 16S rRNA, amoA, and nitrous oxide reductase genes, respectively. In both reactors, the same spatial distribution patterns were observed between the total and AOB on the one hand, and denitrifying bacteria on the other. Decreases in the total microbial species richness were observed in both reactors, and increases in the AOB and decreases denitrifying bacteria in the ammonia removal reactor by comparing the inoculum and after 91 day test samples.