Browsing by Author "Paulse, Arnelia N. (Arnelia Natalie)"
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- ItemSoil stabilization by microbial activity(Stellenbosch : Stellenbosch University, 2003-03) Paulse, Arnelia N. (Arnelia Natalie); Wolfaardt, Gideon M.; Van Huyssteen, L.; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.ENGLISH ABSTRACT: Microorganisms play an important role in the stability and maintenance of the ecosystem and in the condition of the soil. However, in their natural environment, microorganisms often experience changing and hostile conditions. They therefore need to be able to adapt physiologically and modify their micro-environment. Biofilm formation is one mechanism to establish favorable micro-environments. The extracellular polymeric substances (EPS) that are typically associated with biofilm formation may also have an impact on soil structure. The aim of this project was to evaluate the potential of microbial manipulation on EPS production and the possible impact thereof on soil structure in order to improve water retention. Specific objectives of this study included the screening of natural environments for EPS-producers, developing techniques to observe EPS production and accumulation in the pores between soil particles, measuring the effect of EPS production on soil water hydraulic gradient, as well as determining the fate and impact of EPS-producers when introduced to naturally-occurring soil microbial communities. Several environmental samples have been screened for EPS-producing microorganisms. Soil columns were then inoculated with these EPS-producers and the passage of 20 mlaliquots water through the columns measured at 3 or 4-day intervals. Microbes isolated from soil, through their EPS production capability proved to retain water more effectively than was the case for water-borne EPS-forming microbes. This phenomenon was further studied using flow cells, filled with soil and inoculated with the EPS-producers isolated from either soil or water. Fluorescence microscopy showed that the soil microbes produced EPS that clogged pores between sand particles more effectively. This clogging resulted in lowering the soil water hydraulic gradient. To evaluate the effect of EPS-producers on existing soil microbial communities, cell counts, Biolog™whole-community carbon utilization studies and T-RFLP (terminal-restriction fragment length polymorphism) analyses were performed. Shifts in the soil microbial community could not be readily seen by observing microbial numbers and T-RFLP-analysis, but was noticeable in carbon utilization patterns.