Faecal coliforms and faecal streptococci community in the underground water in an equatorial area in Cameroon (Central Africa): the importance of some environmental chemical factors.

A bacteriological and chemical study was carried out within 1 year on spring and well water of Yaounde. It assessed the importance of some chemical factors on some faecal bacterial communities. The monthly average densities of faecal coliforms and faecal streptococci varied, respectively, from 1 to 72 x 10(2) CFU 100 ml(-1), and from 1 to 31 x 10(2) CFU 100 ml(-1) of water. These bacterial abundances undergo spatio-temporal fluctuations. These spring and well waters which are slightly bicarbonate, are acidic, soft, with low to average mineralisation. Most of the chemical characteristics of these waters are relatively stable with time, with respect to apparent spatial fluctuations. The degree of correlation between chemical parameters and the abundance dynamics of isolated bacteria is heterogeneous. In an artificially constituted spring biotope, the increase in pH, electrical conductivity, concentration of dissolved oxygen, chloride, sodium, potassium, calcium and magnesium favoured (P<0.01) the abundance of faecal coliforms and faecal streptococci. The high concentration of dissolved CO2 reduces (P<0.001) the abundances of these bacteria. They would nevertheless have developed such a mechanism allowing to minimise inhibitory effects of some environmental factors. In the well water, the ecology of faecal streptococci and faecal coliforms undergoes a relative instability, probably due to the variability of the resultant interaction network.