Microbiological mechanisms and effects of dissimilatory iron reduction on combined contaminants bio-transformation: A review

Although dissimilatory iron-reducing bacteria (DIRB) has been executed to degrade organic matters and reduce heavy metals simultaneously due to its unique extracellular electron transfer (EET) mechanism, there is still a challenge to define a synergistic way for combined pollution control. Organic matters and heavy metals can serve as electron donators and acceptors respectively, and electrons will be indirectly transferred interactively via bio-transmembrane. Many literatures indicated that dissimilatory iron reduction (DIR) can induce the ferric redox formation, and consequently promote the bio-metabolic activity, which could stimulate a series of beneficial reactions, such as bio-Fenton. Unfortunately, up to now, little was known about how and why DIRB can execute the above bio-transformation. A deep insight into EET and a systematic illustration of the DIRB-driving reactions will be helpful for understanding how DIRB works. The objective of this review is to focus on clarifying the EET of typical DIRB and revealing how DIR strengthen the combined pollution treatment. Most importantly, several gaps in the application of DIRB have been identified, along with proposed solutions, offering an innovative approach to addressing these challenges.