The interaction of a manganese-oxidising bacterium as part of a biofilm growing on distribution pipe materials

The deposition of manganese wit hin a biofilm growing on the surface of hig h-density polyethlene (HDPE) and polyvinychloride (PVC) was studied over a period of four mont hs. The manganese rich water used in the study was inoc ulated with a manganese oxidising Pseudomonas spp. The level of Mn2+ in the water was monitored and was found to decrease as the biofilm formation inc reased. This was confirmed by energy dispersive X-ray spectroscopy (EDS) an alysis which showed the detection of manganese was dependent on the presenc e of a biofilm. After two months a 100% removal of Mn2+ was observed in all the flasks inoculated by the Pseudomonas spp. and manganese micro-nodules, the formation of which were reported in Murdoch and Smith (1999), were bei ng formed in large clusters across the surfaces of both the HDPE and PVC. T he manganese peak area from the EDS spectrum analysis of the micro-nodules was significantly larger than was measured in the biofilm when these micro- nodules were absent. The scanning confocal laser microscope (SCLM) images o f three-week samples showed high bacterial activity around areas where mang anese micro-nodules were starting to form on the pipe surface.