env-microbiology Environment

Bacteria such as Shewanella and Geobacter oxidize organic substrates under anaerobic conditions and transfer electrons to the anode surface directly through outer-membrane cytochromes and conductive pili, without soluble mediators. This extracellular respiration pathway is mediated by protein systems such as Mtr and PilA, and because current output is coupled to substrate oxidation rates, these cells are used both for energy recovery from wastewater and as living biosensors.

Anammox bacteria use nitrite as the electron acceptor to oxidize ammonium straight to nitrogen gas, with no external organic carbon needed. Compared with conventional nitrification–denitrification, this shortcut saves roughly 60% of the aeration and yields far less excess sludge. Full-scale plants in Rotterdam and elsewhere already treat digester sidestreams this way, confirming the process works at engineering scale.

Bioaugmentation introduces exogenous microorganisms or consortia with specific degradative capabilities into a contaminated environment to accelerate breakdown of target pollutants — for example, adding Dehalococcoides strains to drive reductive dechlorination of chlorinated solvents. Natural attenuation instead relies on indigenous microbial communities plus physical and chemical processes at the site, lowering contaminant concentrations without intervention. The former acts faster but requires sustaining survival and competitiveness of the inoculated strains; the latter costs less yet is constrained by the metabolic potential of native flora and site hydrogeology.