Microbial molecular ecology and genetics

We investigate the population dynamics/genomics of bacteria and bacteriophages in wastewater. We are also interested in the evolution of mobile genetic elements in bacteria and the molecular mechanisms involved in their successful dissemination.

Microbiology of Wastewater Foaming and Bulking

Activated sludge systems are used to treat wastewater globally. Most suffer from sludge bulking where the biomass fails to separate effectively from the liquid phase, and the generation of highly stable microbiological foams on the surface of aerated reactors. These events cause major operational, environmental, cosmetic and health related problems. It is now clear that a diverse range of unusual filamentous bacteria are responsible for bulking and foaming. Yet many of these bacteria have never been cultured or characterized.  There are now an array of molecular techniques to help us identify these filamentous bacteria in situ, andnew techniques for rapidly and cheaply sequencing DNA. It is now possible to sequence their entire genomes and find out what the metabolic potential of each filamentous bacterium is.

Having such information will provide us with vital clues as to how we might control bacterial growth in activated sludge systems, and hence reduce bulking problems. This work involves collaboration with Bugworks, an Australian company specialising in the management of bulking episodes in full scale treatment processes.

We know that most of the bacteria involved in the stabilization of foams belong to the Actinobacteria, and include the genera Gordonia, Skermania, Dietzia, Nocardia, Rhodococcus and Tsukamurella.  One environmentally friendly approach to prevent foaming is to apply lytic phages to reduce the bacterial cell numbers below the threshold required for foam stabilization. This research is conducted in collaboration with Prof Robert Seviour. It includes phage isolation and characterization and examines the potential of phage therapy for developing a universal permanent resolution for foaming.