Characterization of microbial populations of the borden aquifer

The indigenous microbial population of the Borden aquifer (Canada Forces Base Borden, Ontario, Canada) is largely aerobic and heterotrophic in nature, although a potential capacity for anaerobic nitrate reduction is present. The population possesses oligotrophic and psychrotrophic components. Chemolithotrophic and sulfate‐reducing organisms are rare. The latter, at least, are present although not detected with the MPN procedure used in this study. The recoverable, viable population is normally rather sparse (<10 to 104 CFU/g dry weight), and microbial communities are localized. Distinct populations were observed, even from samples taken within a small area (<5.5 m2) at one depth. These displayed varying metabolic capabilities when provided with 0.1% yeast extract, dissolved creosote components, and/or inorganic nutrients. On the basis of biochemical tests, most aquifer isolates seemed to possess either very broad or very restricted metabolic capabilities. The diameter of populations from pristine and recently contaminated zones within the aquifer was: distinctly different, and microbial numbers in the latter area were much greater.