Mechanisms of H ₂ S Production from Cysteine and Cystine by Microorganisms Isolated from Soil by Selective Enrichment

Abstract

Hydrogen sulfide (H2S) is a major component of biogenic gaseous sulfur emissions from terrestrial environments. However, little is known concerning the pathways for H2S production from the likely substrates, cysteine and cystine. A mixed microbial culture obtained from cystine-enriched soils was used in assays (50 min, 37°C) with 0.05 M Tris-HCl (pH 8.5), 25 i,mol of L-cysteine, 25 ,imol of L-cystine, and 0.04 ,mol of pyridoxal 5'-phosphate. Sulfide was trapped in a center well containing zinc acetate, while pyruvate was measured by derivatization with 2,4-dinitrophenylhydrazine. Sulfide and total pyruvate production were 17.6 and 17.2 nmol mg of proteinmmi', respectively. Dithiothreitol did not alter reaction stoichiometry or the amount of H2S and total pyruvate, whereas N-ethylmaleimide reduced both H2S and total pyruvate production equally. The amount of H2S produced was reduced by 96% when only L-cystine was included as the substrate in the assay and by 15% with the addition of propargylglycine, a specific suicide inhibitor of cystathionine

Rapid detection of hydrogen sulfide produced by pathogenic bacteria in focused growth media using SHS-MCC-GC-IMS

“…The pathway for cysteine utilisation for H2S production has been somewhat explored, with cysteine desulfhydrase identified as the enzyme responsible [14], resulting in the formation of pyruvic acid, ammonia, and H2S, which is then liberated as a gas [16]. However, there is also evidence that H2S may be induced in response to excess cysteine as a protective mechanism against toxicity [17][18][19].…”

Microbial dark matter driven degradation of carbon fiber polymer composites

“…Amongst the four most abundant lineages in the composite microbiome, we detected this capacity in MAGs from CPR/Patescibacteria, Deltaproteobacteria and Chloroflexi . Two distinct microbial pathways can produce hydrogen sulfide by the anaerobic respiration of sulfate/sulfite 39 , or by degradation of the amino acid cysteine 40 . While both of these metabolic capacities were detected in the composite microbiome, degradation of cysteine was observed to be more abundant.…”

“…Prior research has demonstrated gradients of oxygen in biofilms including the presence of anoxic regions that could support highly active sulfate reducing microbes 43 . Third, H 2 S may also be produced by degradation of cysteine which is likely an abundant component of organic-rich biofilms 40 . We propose that the interplay between the degradation of the binding matrix (acrylate, bisphenol A, esters) through chain scission of chemical bonds and the production of gases (H 2 S, H 2 ) that can cause physical damage and potential bloating of the polymer structure contributes towards accelerated degradation of polymer composites.…”

Complete assimilation of cysteine by a newly isolated non-sulfur purple bacterium resembling Rhodovulum sulfidophilum (Rhodobacter sulfidophilus)

“…Sulfide was not detected in stoichiometric amounts compared to cysteine consumption, perhaps because of background activities of transaminases, which might lead to an increased cysteine consumption without concomitant sulfide production. While Collins and Monty (1973) found a 1:1 stoichiometry with a fivefold-enriched cysteine desulfhydrase fraction of Salmonella typhimurium, other authors did not observe equimolar formation of pyruvate and sulfide by enriched enzyme fractions or crude extracts (Guarneros and Ortega 1970;Kredich et al 1973;Morra and Dick 1991).…”