Distribution And Abundance Detection Of Electrochemical Activity Bacteria In The Lake Sediments And The Wastewater Treatment Plant

Electrochemically active bacteria (EAB), which are able to transfer electrons to extracellular electron acceptors, play important roles in biogeochemical cycling of many elements, environmental remediation and bioenergy recovery. Pervious ecological researches of EAB have been mainly focused on marine environmental, few works were focused on freshwater wetlands and artificial environments. Due to the complexity in metabolic pathways and the diversity of genes and enzymes which are related to extracellular electron transfer, there are no common molecular methods for the identification and quantification of EAB. This thesis was mainly focused on the distribution and abundance of two typical EAB (Shewanella spp. and Geobacter spp.) in the sediments of Chao Lake. And a simple WO3-MPN approach was developed through coupling WO3 nanoclusters and most proable number (MPN) for the detection and enumeration of EAB in environments.1. The distribution and abundance of Shewanella spp. and Geobacter spp. in the sediments of Chao Lake were investigated. The NFH and AB samples from Chao Lake sediments showed the highest abundance of Shewanella spp. and Geobacter spp., about 103-108 copies per gram dry sediment. Pearson correlation analysis showed that the contents of ammonium, phosphate and organic matters were the major environmental factors which affected the population sizes Shewanella spp. and Geobacter spp. The abundant nitrogen and phosphorus were the main causes of eutrophication in Chao Lake, we speculate that the abundance of Shewanella spp. and Geobacter spp. may be affected by the eutrophication of Chao Lake.2. EAB play important roles in biogeochemical cycling of many elements, environmental remediation, wastewater treatment and bioenergy recovery. Methods to effectively and rapidly probe the abundance of EAB in environments are highly desirable. In this work, a novel approach was developed through coupling WO3 nanoclusters and most probable number (MPN) for rapid and sensitive detection and enumeration of EAB. In this approach, a WO3 probe was applied to rapidly identify EAB and the MPN method was used to count EAB. Such an integrated approach was successfully applied to detect and estimate the population size of two main model EAB, Shewanella oneidensis MR-1 and Geobacter sulfurreducens DL-1. The results were comparable with those obtained by the direct 4’,6-diamidino-2-phenylindole (DAPI) counting and colony-forming unit (CFU) counting methods. The WO3-MPN approach was also used to detect and count EAB in environmental samples from the sediments of a freshwater lake (9.9×104 to 4.1×106 cells per gram dry sediment), and wastewater and mixed liquor samples in a municipal wastewater treatment plant (1.0×103 to 7.5×105 cells per milliliter). This work provides a simple, effective, and reliable method to evaluate the population sizes of EAB with high selectivity, which has a great potential for facilitating practical applications of EAB in natural and engineered environments.