Characterization of cellulolytic and fermentative processes, with emphasis on Clostridium species in wetland soils

In anaerobic environments such as wetlands soils, microbial processes and microbial community structure are a function of chemical parameters. Two of the major microbial groups present in wetlands are cellulolytic and fermentation species that provide carbon to other groups. It is likely that any biogeochemical changes in these environments may affect these groups, hence affecting the entire microbial food web. This study was conducted with soil and detrital material collected from three different sites in the Everglades Water Conservation Area 2A, characterized by different levels of eutrophication.; Microcosm experiments indicated that carbon cycling mechanisms are more active in eutrophic soils than in oligotrophic soils. Eutrophic and transition soils possess microbial communities or well-established microbial associations that can eliminate excess fatty acids or other by-products. Most probable number (MPN) enumeration of fermentative organisms, and total consumption of glucose and acetate production in the first 7 days in eutrophic and oligotrophic soils indicated similar activities of fermentative bacteria in the two soils, emphasizing the importance of syntrophic activity (syntrophs and hydrogenotrophic methanogenesis) in fermentation patterns. Plant type as carbon and nutrient source appeared to be significant only in eutrophic soils, based on methanogenesis; and it seemed that sawgrass stimulated carbon cycling. However, MPN fermentative bacteria indicated that cattail has greater impact, possibly because of its higher soluble fraction. Results from microcosms containing different levels of phosphorus and microcosms with plant material suggested that phosphorus might not be limiting for microorganisms in oligotrophic soils.; Culture-independent techniques targeting the 16S rRNA genes of Clostridium species revealed significant differences in Clostridium assemblage structure based on origin of soil samples. Especially, Clostridium Clusters I, IV, and XIV communities appeared to be affected by eutrophication. Possibility of application of T-RFLP method was explored on these soils. Only Cluster XIV was found to be suitable for T-RFLP application to monitor microbial changes in Everglades soils.; Eutrophication clearly affected carbon cycling mechanisms in Everglades soils. Results showed that fatty-acid-consuming bacteria associated with hydrogen-scavenging methanogens play an important role in carbon cycling. This association affects fermentative and cellulolytic organisms. The present study contributed to a greater understanding of carbon cycling mechanism in wetland environments and provided a molecular database that will contribute to monitoring of ecosystem restoration technologies.