Sulphide ion-selective electrode studies concerning Desulfovibrio species of sulphate-reducing bacteria

Abstract

The sulphide ion-selective electrode has been used for further studies on the Desulfovibrio species of sulphate-reducing bacteria. Emphasis has been placed on D. vulgaris, which thrives in sodium dithionite metabolic medium, which provides an alternative sulphur source to sulphate. The bacterium also grows well in media containing certain organic materials, namely, cysteine, cystine and glutathione as alternative sulphur sources to sulphate. The bacterium does not grow with methionine as the sulphur source and this is attributed to the relative stability of the C–S–C bonds, which are not adjacent to the amino group.

The growth of D. vulgaris is retarded with barium sulphate or elemental sulphur as sulphur sources. However, under certain circumstances there is less retardation with flowers of sulphur.

More general parameters have also been studied including age of starter culture, inoculum size, poising agents, pH and yeast stimulator. The active life of D. gigas was significantly less than for D. desulfuricans and D. vulgaris. Growth was more vigorous as the inoculum size was increased, while the optimum pH was between 7 and 8. Poising agents are less essential for sub-culturing from fresh starter cultures than for older ones, while yeast extract accelerates the growth of D. vulgaris.

Acetate is confirmed to be inappropriate as an organic carbon nutrient. D. vulgaris is considerably less sensitive to the salinity of the culture media (up to 3%m/V sodium chloride) than D. desulfuricans and D. gigas which were generally inactive, even with 1%m/V sodium chloride.

Finally, sodium tetraborate(III)(2%m/V) and 2,4-dinitrophenol (2%m/V) are confirmed as effective bactericides for D. vulgaris, which is the most robust of the three species (D. desulfuricans, D. gigas and D. vulgaris) studies in this work.