Practice question

Bioaugmentation deliberately introduces selected allochthonous or enriched autochthonous microorganisms with laboratory-verified superior degradative capabilities to contaminated sites where native community density or catabolic potential insufficient to achieve remediation goals within regulatory timeframe. Pure cultures or consortia such as Alcanivorax borkumensis specialized for branched alkanes, Dehalococcoides mccartyi containing tceA, bvcA and vcrA reductive dehalogenase genes for complete detoxification of tetrachloroethene to ethene, and genetically engineered strains expressing broad-substrate biphenyl dioxygenase bphA for polychlorinated biphenyls are cultivated in fermenters to high density 10^10 cells per mL, sometimes encapsulated in protective carriers like alginate, biochar or agar to improve survival against desiccation, predation and pH stress upon inoculation. Success hinges on compatibility with abiotic matrix, ability to compete with indigenous flora for nutrients, retention of catabolic plasmids without horizontal transfer of antibiotic resistance markers, and avoiding biofouling. Contrasted with biostimulation which merely amends nutrients, bioaugmentation provides specific biocatalyst itself especially useful for recalcitrant xenobiotics requiring pathways absent naturally. Field implementation demands risk assessment under TSCA, monitoring via 16S rRNA amplicon sequencing and functional gene arrays to track persistence.