Interspecific electron transport (IET) can promote the
cometabolism
of microorganisms, so it is of great significance in environmental
remediation. Herein, a coculture of autotrophic sulfur-oxidizing bacteria
(SOB) and heterotrophic sulfate-reducing bacteria (SRB) was constructed
to biodegrade oxytetracycline (OTC) (upgraded to 120.9 ± 3.9
μg mg–1 protein d–1) under
inorganic conditions, and the biodegradation was markedly improved
(1.5 times) after loading biosynthetic FeS (bio-FeS). The increase
of the NAD+/NADH ratio and ATPase activity indicated that
more electrons generated by intracellular metabolism inside the SOB
(lacking the OTC enzyme) outflowed extracellularly to the SRB via
the IET chain in the coculture system. Linear sweep voltammetry (LSV)
and I–t analysis indicated that bio-FeS on
the SRB could enhance direct interspecific electron transport (DIET)
mainly via c-Cyts, together with the mediated interspecific
electron transport (MIET) via flavins, thus accelerating the OTC efflux.
Community analysis demonstrated that the SRB introduction increased
the abundance of genes related to environmental information, cell
motility, membrane transport, and signal transduction in the coculture
system. This discovery revealed the feasibility of antibiotic degradation
using heterotrophic bacteria (such as SRB) under inorganic conditions
and deepened the understanding of the antibiotic degradation in biogeochemical
cycles involving carbon, nitrogen, and sulfur in natural ecosystems.