Role of multiheme cytochromes involved in extracellular anaerobic respiration in bacteria

Abstract

Heme containing proteins are involved in a broad range of cellular functions, from oxygen sensing and transport to catalyzing oxidoreductive reactions. The two major types of cytochrome (b‐type and c‐type) only differ in their mechanism of heme attachment, but this has major implications for their cellular roles in both localization and mechanism. The b‐type cytochromes are commonly cytoplasmic, or are within the cytoplasmic membrane, while c‐type cytochromes are always found outside of the cytoplasm. The mechanism of heme attachment allows for complex c‐type multiheme complexes, having the capacity to hold multiple electrons, to be assembled. These are increasingly being identified as secreted into the extracellular environment. For organisms that respire using extracellular substrates, these large multiheme cytochromes allow for electron transfer networks from the cytoplasmic membrane to the cell exterior for the reduction of extracellular electron acceptors. In this review the structures and functions of these networks and the mechanisms by which electrons are transferred to extracellular substrates is described.

Electroactivity across the cell wall of Gram-positive bacteria

“…2 B). This arrangement is different from what is typical observed in electroactive Gram-negative bacteria, where porin-cytochrome complexes composed by a β-barrel porin and one or two MHC are responsible for electron transfer across the outer membrane [82] .…”

Challenges in engineering conductive protein fibres: Disentangling the knowledge

“…Despite this effort, uncertainty over the conduction mechanism remains. One particularly controversial point is whether extracellular cytochromes are necessary to enable longrange extracellular electron transfer, [32][33][34][35] or whether, as evidence suggests, aromatic residue rich pili alone can facilitate electronic conduction. [18,[36][37][38][39][40] Dissimilar experimental conditions such as the state of the material and surrounding environment have been highlighted as possible culprits.…”

Syntrophic Hydrocarbon Degradation in a Decommissioned Off-Shore Subsea Oil Storage Structure

“…In addition, genes for multiheme c-type cytochromes, potentially involved in direct interspecies electron transfer as well as in metal oxides reductions [ 55 ], were identified in MAGs related to Pelobacter, Anaerolineae and Actinobacteria . Genes for hydrocarbon degradation were also identified in Pelobacter and Anaerolineae MAGs, suggesting that syntrophic hydrocarbon degradation processes might also involve direct interspecies electron transfer between members of the microbial community.…”