Pedomicrobium

The association of Mn oxides with the surfaces of microbial cells is well known (Larsen et al., 1999). Oxidation of Mn by Pedomicrobium has been shown to occur enzymatically, and the deposition of the manganous oxide occurs on extracellular acidic polysaccharides (Sly et al., 1990a; Larsen et al., 1999). The mechanism of Mn II oxidation by Pedomicrobium is a two-step process involving adsorption of Mn through surface charges and ionic attraction, and subsequent oxidation to Mn oxide (Larsen et al., 1999). Larsen et al. (1999) showed that the Mn oxidising enzyme was located in the outer cell membranes and that enzyme activity was copper-dependent. Recent research in the laboratory has shown that the gene encoding the Mn oxidising enzyme is a putative multicopper oxidase with four copper binding sites.

Mn is considered a secondary contaminant, which includes substances in water that cause offensive taste, odour, colour, corrosion, foaming, or staining but have no direct effect on health (Herman, 1996). In fact, small concentrations of Mn in our diet are essential to human health (Keen et al., 1999).

Therefore, Mn is regarded as a nuisance metal in water distribution systems as in the insoluble oxide form it reduces the aesthetic quality of the water. The presence of Mn results in the accumulation of metal oxides in biofilm on the surfaces of water mains, which may slough off resulting in brown-black colour and turbidity that are characteristics of Mn related dirty water (Sly et al., 1990b). The sediments produced are responsible for the taste and staining properties of water, which commonly affects laundry, porcelain, dishes, utensils and swimming pools (Vaner et al., 1996).

Cox T. L, and Sly L. I; (1997); ‘Phylogenetic relationships and uncertain taxonomy of Pedomicrobium species’; International Journal of Systematic Bacteriology 47(2):377–380.
Garrity G. M., Winters M. and Searles D. B.; (2001); ‘Taxonomic outline of the procaryotic genera Bergey’s manual of systematic bacteriology, Second Edition Release 1.0.
Keen C. L., Ensunsa J. L. and Watson M. H.; (1999); ‘Nutritional aspects of manganese from experimental studies’; Neurotoxicology 20:213-23.
Larsen E. I., Sly L. I. and McEwan A. G.; (1999); ‘Manganese(II) adsorption and oxidation by whole cells and a membrane fraction of Pedomicrobium sp. ACM 3067’; Archives of Microbiology 171:257–264.
Sly L. I.; Arunpairojana V. and Hodgkinson M. C.; (1988a); ‘Pedomicrobium manganicum from drinking-water distribution systems with manganese-related “dirty water” problems’; Systematic and Applied Microbiology 11:75–84.
Sly L. I., Hodgkinson M. C. and Arunpairojana, V; (1988b); ‘Effect of water velocity ion the early development of manganese depositing biofilm in a drinking water system’; FEMS Microbiology ecology 53:175–186.
Sly L. I., Hodgkinson M. C. and Arunpairojana, V; (1988c); ‘The importance of high aesthetic potable water in tourist and recreational areas’; Water Science Technology 21:183–187.
Stahl D. A., Key R., Flesher B., and Smit J.; (1992); ‘The phylogeny of marine and freshwater Caulobacter reflects their habitat’; Journal of Bacteriology 174:2193–2198.
Vaner D., Skipton S., Hay, D. and Jasa P.; (1996); ‘Drinking water: recommended practices to manage iron and manganese in a domestic water supply’; Water Resource Management 96(12):80–86.