No abstract

The origin of hydrogen sulfide in southeastern Montana groundwaters was investigated. Sulfate-reducing bacteria were detected in 25 of 26 groundwater samples in numbers ranging from 2.0 × 10 1 to greater than 2.4 × 10 4 bacteria per 100 ml. Stable sulfur isotope fractionation studies indicated a biological role in sulfate reduction. However, sulfate-reducing activity as determined by use of a radioactive sulfur isotope was observed in only 1 of 16 samples. It is postulated that bacterial dissimilatory sulfate reduction is responsible for a major portion of the sulfide produced in these groundwaters and that these bacteria are most likely active in the adsorbed state, possibly in subsurface microzones where environmental conditions are conducive to sulfate reduction.

Two methods are described for measurement of bacterial injury in water. Laboratory time preceding cell division measured with slide cultures and spheroplast formation after lysozyme treatment were accurate and rapid measurements of bacterial damage.

Physiological and morphological changes in Escherichia coli exposed to oligotrophic natural waters and reagent grade water were studied. Several lines of evidence indicated that short-term exposure in water causes cellular envelope damage. Increasing susceptibility to lysozyme, lag time before cell division, and injury as defined by differential counts on selective and nonselective media occurred with exposure time. Electron micrographs of injured cells showed morphological changes in the cell envelope.

The physiological basis of the Eijkman elevated-temperature test for differentiating fecal from nonfecal coliforms was investigated. Manometric studies indicated that the inhibitory effect upon growth and metabolism in a nonfecal coliform at 44.50C involved cellular components common to both aerobic and fermentative metabolism of lactose. Radioactive substrate incorporation experiments implicated cell membrane function as a principal focus for temperature sensitivity at 44.5°C. A temperature increase from 35 to 44.50C drastically reduced the rates of [14C]glucose uptake in nonfecal coliforms, whereas those of fecal coliforms were essentially unchanged. In addition, relatively low levels of nonfecal coliform ,B-galactosidase activity coupled with thermal inactivation ofthis enzyme at a comparatively low temperature may also inhibit growth and metabolism of nonfecal coliforms at the elevated temperature.