Abstract
Based upon the observation that an oilfield appeared to possess an endospore-forming microbial population that was selected for by its microbiocide program, a hypothesis was formed that exposing endospore-capable bacteria to low dosing of microbiocides, particularly to those chemistries that are not identified as fast-acting, will facilitate endospore formation.
Clostridium sporogenes was chosen as the test organism, as this genus is commonly found in oilfields, its members possess metabolisms that are known to cause corrosion, and they have previously been described in literature as directly causing MIC. Clostridium cultures, after exposure to microbiocides, were stained according to the Schaeffer-Fulton method and scored for the presence of endospores.
Of the ten microbiocides and combinations thereof that were tested, only diamine acetate, both alone and in a combination product, conclusively stimulated sporulation. Doses greater than 50 ppm allowed the endospore-capable Clostridium to sporulate rather than perish. In field scenarios where endospore-producing bacteria are present, these spores will rapidly return to vegetative cells once the chemical has either passed or becomes diluted to more tolerable concentrations. This scenario, over time, would select for this population of bacteria to become the majority and render the microbiocide program ineffective.
