This report presents data from a series of experiments that were conducted to determine the properties of autoaggregation and the triggers that cause it to occur in two predominant bacterial strains.  These strains were isolated from the activated sludge component of wastewater treatment.  The growth and aggregation curves of both bacterial strains were plotted.  Possible mechanisms of autoaggregation (e.g. gene expression or quorum sensing) and the effects of varying factors like nutrient and pH levels on autoaggregation were examined.  A method for disaggregating samples was also developed.  The results show that autoaggregation is non-growth phase-dependent, and is not induced by quorum sensing.  However, it is affected by gene expression and has been shown to be dependent on high cell densities.  It can also be triggered by hostile growth environments such as low nutrient levels or high pH levels.  These results contribute towards suggesting methods of modifying the activated sludge process to increase its efficiency.

Student Name:  Ian Chan Zhi Wen (Diploma in Biotechnology)

Supervisor:  Dr F.B. Pichler, School of Biological Sciences, University of Auckland