Practice question

Biostimulation enhances pollutant degradation capacity of indigenous microbial communities already adapted to site conditions without introducing foreign organisms, focusing instead on relieving nutritional, redox or environmental constraints limiting rate. Petroleum hydrocarbons, chlorinated solvents and pesticides often persist not due to absence of degraders carrying alkB alkane hydroxylase, xylE catechol dioxygenase or dehH haloacid dehalogenase genes, but because electron acceptor oxygen, nitrogen as ammonium, phosphorus as phosphate, or carbon as electron donor scarce, causing C:N:P imbalance away from optimal 100:10:1 for microbial growth. Addition of slow-release oleophilic fertilizers such as Customblen, Inipol EAP22 containing oleic acid, urea and lauryl phosphate, oxygen releasing compounds magnesium peroxide OrCal, or molasses as carbon source stimulates bloom, increasing viable counts from 10^4 to 10^7 colony forming units per gram within weeks and accelerating mineralization kinetics described by Monod equation. Marine oil spills Exxon Valdez demonstrated success of nutrient augmentation. Unlike bioaugmentation seeding lab-grown strains facing intense competition and predation, biostimulation leverages already competitive autochthonous microbiota reducing ecological risk and cost, with monitoring via quantitative PCR of catabolic genes confirming stimulation effect rather than mere microbial presence.