The role of extracellular products in copper colonisation

Three strains of Pseudomonas bacteria were isolated from copper water pipes showing pitting corrosion. The effects of temperature and copper concentration on growth and exopolymer production were investigated. Various differences were noted between the organisms when grown as pure cultures and as a mixed culture; from the pure culture work some of the contributions made by each organism to the mixed culture can be deduced. It would appear that the production of extracellular products varies with temperature and that polymer production and growth are enhanced in a mixed culture. All three strains grown as pure cultures showed a decrease in growth at lower temperatures as the copper concentration was increased. This effect was altered when the organisms were grown as a mixed culture. It was noted that copper tolerance was conferred on one of the organisms (a yellow strain of Ps. paucimobilis) by the presence of the other two. These results can be used to explain some of the observations made on the colonisation of copper by bacteria associated with pipe corrosion.