The well-attended May meeting held at the Surrey Hotel in Grey Lynn, Auckland, was addressed by Ms Adrienne Burnie, Proprietor and Principal Microbiologist at Biodet Services Ltd, Consulting Microbiologists. The title of the presentation was “Biodeterioration of materials – the role of a Consulting Microbiologist”. The talk commenced with some background on Biodet since it was founded many years ago by Dr Elizabeth Ebbett, who chose Biodet as the company name being a shortening of the term biodeterioration.

Biodeterioration is the interaction of materials with micro-organisms in the presence of moisture which can result in Microbiologically Influenced Corrosion (MIC) of metals.  Adrienne described the initiation of biofilms on metals and the propagation of MIC, which is an electrochemical process that is assisted by the presence of certain strains of bacteria.  She then outlined the various types of micro-organisms that can support MIC, on metals including (a) slime formers (e.g. pseudomonas), iron-oxidising bacteria (e.g. gallionella), anaerobic bacteria (e.g. sulphate reducing bacteria) and sulphur-oxidising bacteria. The laboratory techniques, such as culturing, by which microbiologists test and microscopically examine and identify various micro-organisms in the laboratory was then described, with some great coloured slides.

Adrienne then outlined a number of case studies, starting with the background to the well-known MIC biocorrosion failure of sheet wall steel piling at the Ohau Channel in Rotorua. Non-metallic materials, such as fabrics are also vulnerable to biodeterioration. She then described the impact of microbes on building materials such as untreated wood and fibre-cement sheet cladding. The fuel delivery industry, particularly diesel fuel storage, has also suffered from various microbial deterioration problems, as has valuable marine cargo stored in damp conditions during transit in ships.

Adrienne concluded by noting that consulting microbiologists deal with many types of biodeterioration problems, including insurance claims, legal cases and disputes. She hoped that her talk had made the role of a consulting microbiologist better understood. After an extensive Q&A session, the ACA Auckland Committee Chair Matt Vercoe thanked Adrienne for her enlightening and thought-provoking presentation.


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