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Faculty of Science & Engineering
Flinders University
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Professor Amanda GoodmanContact Details
Key Responsibilities
Teaching
ResearchMicrobiology is of fundamental importance in environmental science. Of the organisms inhabiting planet Earth, microorganisms are the most ancient, are the most ubiquitous, have the most diverse biochemistry, and are responsible for biogeochemical cycling. Every environmental niche, even those too harsh for the existence of higher organisms, is occupied by microorganisms which are well-adapted to exist in each particular environment. Because of their small size and potential for rapid generation times, microbial populations can change, often within hours, to adapt to changing physicochemical conditions. A major problem facing Australia today is the same throughout the world - an increasing population with its demand for more and better food, clean air and water, and adequate health care. If we were to understand fully how microorganisms exploit their environments and how their responses to changing conditions are regulated, we would be in a position to make use of microbial reactions more effectively in all biological areas.We are investigating several areas of the regulation of bacterial gene expression in marine environments, including expression of genes in cells in biofilms, regulation of gene transfer in biofilms, and regulation of enzyme secretion. Bacteria appear to have different physiological characteristics as sessile organisms in a biofilm compared to when they are suspended in their planktonic form in the aqueous phase. There is little information on the mechanisms as to how such specific physiological changes occur. It is not known how physicochemical conditions within the biofilm influence bacterial metabolic changes. Virtually all studies on the physiology of marine bacteria have been carried out on cells grown in liquid or agar media, yet the majority of the biosphere's microbial populations live in biofilms. A major goal of our study is to understand how the physiology of immobilized bacteria, as found in biofilms, is substantially different to that of the same organism in the aqueous phase. To do this, we are isolating identifying, cloning and sequencing genes that are switched on by biofilm physicochemical conditions. We wish to investigate the expression of these genes in single cells in situ within the biofilm. Our studies involve using techniques such as fluorescent in situ hybridisation, in situ PCR and scanning confocal laser microscopy (SCLM). Among bacteria in biofilms there are increased opportunities for transfer of mobile genetic elements. Many important traits, such as antibiotic and heavy metal resistance, the capacity to degrade organic pollutants, nitrogen fixation etc., are carried by conjugative plasmids in bacteria. An understanding of horizontal gene transfer in bacteria in natural environments will enable us to make use of, or manipulate, the genetic capabilities of natural microbial communities more effectively. To achieve this, we must first understand bacterial behaviour in well-designed model ecosystems. We have developed a continuous once-through flow system for investigating plasmid transfer among marine bacteria in mixed species biofilms. We have found that plasmid transfer frequencies are affected significantly by the order and length of time of surface colonisation by each particular strain. A major goal is to identify individual pasmid-bearing cells in situ, whilst maintaining the 3-dimensional hydrated structure of the biofilm, using molecular genetics techniques and SCLM. We are investigating the mechanism of secretion of extracellular enzymes in non pathogenic marine bacteria. We are cloning and sequencing extracellular proteases and chitinases from marine strains and determining whether these proteins are "self-secreting" or whether they require other secretion factors. As there is little known about secretory mechanisms of marine bacteria generally, we believe that by sequencing such genes from different strains, and investigating the ability of the secretory sequences to effect translocation of heterologous proteins to the culture medium, we will achieve a better understanding of such phenomena. PhD students
Honours students
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