Biodegradation of the xenobiotic organic disulphide 4,4′-dithiodibutyric acid by Rhodococcus erythropolis strain MI2 and comparison with the microbial utilization of 3,3′-dithiodipropionic acid and 3,3′-thiodipropionic acid

Abstract

Application of the non-toxic 3,3′-thiodipropionic acid (TDP) and 3,3′-dithiodipropionic acid (DTDP) as precursors for the microbial production of polythioesters (PTEs), a class of biologically persistent biopolymers containing sulphur in the backbone, was successfully established previously. However, synthesis of PTEs containing 4-mercaptobutyrate (4MB) as building blocks could not be achieved. The very harmful 4MB is not used as a PTE precursor or as the carbon source for growth by any known strain. As a promising alternative, the harmless oxidized disulfide of two molecules of 4MB, 4,4′-dithiodibutyric acid (DTDB), was employed for enrichments of bacterial strains capable of biodegradation. Investigation of novel precursor substrates for PTEs and comparison of respective strains growing on TDP, DTDP and DTDB as sole carbon source was accomplished. A broad variety of bacteria capable of using one of these organic sulphur compounds were isolated and compared. TDP and DTDP were degraded by several strains belonging to different genera, whereas all DTDB-utilizing strains were affiliated to the species Rhodococcus erythropolis. Transposon mutagenesis of R. erythropolis strain MI2 and screening of 7500 resulting mutants yielded three mutants exhibiting impaired growth on DTDB. Physiological studies revealed production of volatile hydrogen sulphide and accumulation of significant amounts of 4MB, 4-oxo-4-sulphanylbutanoic acid and succinic acid in the culture supernatants. Based on this knowledge, a putative pathway for degradation of DTDB was proposed: DTDB could be cleaved into two molecules of 4MB, followed by an oxidation yielding 4-oxo-4-sulphanylbutanoic acid. A putative desulphydrase probably catalyses the abstraction of sulphur, thereby generating succinic acid and hydrogen sulphide.

Biodegradation of the Organic Disulfide 4,4′-Dithiodibutyric Acid by Rhodococcus spp

“…3A). As also described by Wüb-beler et al (17), a considerable amount of 4-oxo-4-sulfanylbutyric acid was detected in the culture supernatants of the wild type and the transposon-induced mutants (Fig. 3B).…”

“…According to the DTDB degradation pathway proposed previously (17) (Fig. 1), the initial step is the reduction of the disulfide bond, resulting in the formation of two 4MB molecules.…”

“…Finally, 4-oxo-4-sulfanylbutyric acid is presumably desulfurized into succinic acid by a putative desulfhydrase, thus releasing the sulfur moiety as volatile hydrogen sulfide (17).…”

The Cysteine Dioxygenase Homologue from Pseudomonas aeruginosa Is a 3-Mercaptopropionate Dioxygenase

“…Similarly, little is known about bacterial enzymes involved in 3-MPA metabolism. Strains from the Pseudomonas family are capable of 3-MPA utilization (28). Conversion of 3-SPA to 3-sulfinopropionyl-CoA in Proteobacteria has been attributed to succinylCoA synthetase, (44,45); however, enzymatic oxidation of 3-MPA to 3-SPA remains to be identified.…”

Novel Characteristics of Succinate Coenzyme A (Succinate-CoA) Ligases: Conversion of Malate to Malyl-CoA and CoA-Thioester Formation of Succinate Analogues In Vitro

“…Later, other investigators showed the participation of the SucCD of Advenella mimigardefordensis DPN7 T in the degradation pathway of 3,3=-dithiodipropionic acid (DTDP), a precursor for the production of polythioesters in bacteria (25)(26)(27)(28). In this strain, DTDP is metabolized via the intermediate product 3-sulfinopropionate (3SP) (29)(30)(31).…”