Aerobic Degradation of Mercaptosuccinate by the Gram-Negative BacteriumVariovorax paradoxusStrain B4

Abstract

The Gram-negative bacterium Variovorax paradoxus strain B4 was isolated from soil under mesophilic and aerobic conditions to elucidate the so far unknown catabolism of mercaptosuccinate (MS). During growth with MS this strain released significant amounts of sulfate into the medium. Tn5::mob-induced mutagenesis was successfully employed and yielded nine independent mutants incapable of using MS as a carbon source. In six of these mutants, Tn5::mob insertions were mapped in a putative gene encoding a molybdenum (Mo) cofactor biosynthesis protein (moeA). In two further mutants the Tn5::mob insertion was mapped in the gene coding for a putative molybdopterin (MPT) oxidoreductase. In contrast to the wild type, these eight mutants also showed no growth on taurine. In another mutant a gene putatively encoding a 3-hydroxyacyl-coenzyme A dehydrogenase (paaH2) was disrupted by transposon insertion. Upon subcellular fractionation of wild-type cells cultivated with MS as sole carbon and sulfur source, MPT oxidoreductase activity was detected in only the cytoplasmic fraction. Cells grown with succinate, taurine, or gluconate as a sole carbon source exhibited no activity or much lower activity. MPT oxidoreductase activity in the cytoplasmic fraction of the Tn5::mob-induced mutant Icr6 was 3-fold lower in comparison to the wild type. Therefore, a new pathway for MS catabolism in V. paradoxus strain B4 is proposed: (i) MPT oxidoreductase catalyzes the conversion of MS first into sulfinosuccinate (a putative organo-sulfur compound composed of succinate and a sulfino group) and then into sulfosuccinate by successive transfer of oxygen atoms, (ii) sulfosuccinate is cleaved into oxaloacetate and sulfite, and (iii) sulfite is oxidized to sulfate.Mercaptosuccinate (MS) is a chiral multifunctional intermediate in organic synthesis, and it has been widely employed in the synthesis of various biologically active sulfur-containing compounds such as antileukemic (64), antimicrobial (43, 59), and antitubercular (17) pharmaceuticals. More recently, MS has also been used as a building block for the synthesis of novel polyanionic inhibitors of human immunodeficiency virus and other viruses (47). In addition, the sodium salt of the anionic Au(I) complex of MS is an effective antiarthritis drug (59).The metabolism of MS in bacteria was initially investigated in Alcaligenes sp., a strain isolated from soil, which was able to use MS as a sole carbon, sulfur, and energy source for growth, with concomitant production of sulfate as an end product (31). Subsequent experiments could not establish a direct relation between thiosulfate oxidase activity and utilization of MS by this bacterium (32). The phototrophic bacterium Rhodopseudomonas sp. used MS as substrate for so-called organolithotrophy and transformed it to fumarate with concomitant sulfide release (79). This indicates that MS is catabolized by different pathways depending on the microorganism. However, these were the only studies on the catabolism of MS, and no enzymes involved in catabolism...

Iron-Dependent Enzyme Catalyzes the Initial Step in Biodegradation of N -Nitroglycine by Variovorax sp. Strain JS1663

“…Selective enrichment with NNG as the sole carbon source yielded an isolate that grew on NNG as the sole source of carbon and nitrogen The 16S rRNA gene sequence of strain JS1663 is most similar to that of Variovorax sp. strain RA8 (99% identity over 1,526 nucleotides [nt]) (34), Variovorax defluvii strain 2C1-b (99% identity over 1,498 nt) (35), and Variovorax paradoxus strain B4 (98% identity over 1,543 nt) (36). However, the JS1663 and V. paradoxus genome sequences share only 83% average nucleotide identity, which suggests that the strains belong to different species within the Variovorax genus (37).…”

Genome‐guided insights into the versatile metabolic capabilities of the mercaptosuccinate‐utilizing β‐proteobacterium Variovorax paradoxus strain B4

“…(ii) Cleavage of sulfosuccinate yields oxaloacetate and sulfite. (iii) Sulfate is then obtained by the oxidation of sulfite (Carbajal‐Rodríguez et al ., ) (Fig. ).…”

“…paradoxus strain B 4. During MS degradation, previously postulated by Carbajal‐Rodríguez et al ., , MS is first converted to sulfinosuccinate and then to sulfosuccinate probably by the putative molybdopterin oxidoreductase. The enzyme catalysing the desulfonation reaction from sulfosuccinate to oxaloacetate and sulfite could not be identified, yet.…”

Microbial utilization of the industrial wastewater pollutants 2-ethylhexylthioglycolic acid and iso-octylthioglycolic acid by aerobic Gram-negative bacteria

“…In past, our laboratory has isolated and characterized many different bacterial strains with the capability of utilizing various OSCs (Bruland et al 2009a, b;Carbajal-Rodríguez et al 2009;Wübbeler et al 2006Wübbeler et al , 2008Wübbeler et al , 2009). Due to the similarities of the respective substrates regarding the chemical structures, growth experiments were conducted with these bacterial strains using solid MSM containing 0.1% (v/v) EHTG or IOTG as sole carbon and energy source.…”