Recent Advances in Metabolic Pathways of Sulfate Reduction in Intestinal Bacteria

Abstract

Sulfate is present in foods, beverages, and drinking water. Its reduction and concentration in the gut depend on the intestinal microbiome activity, especially sulfate-reducing bacteria (SRB), which can be involved in inflammatory bowel disease (IBD). Assimilatory sulfate reduction (ASR) is present in all living organisms. In this process, sulfate is reduced to hydrogen sulfide and then included in cysteine and methionine biosynthesis. In contrast to assimilatory sulfate reduction, the dissimilatory process is typical for SRB. A terminal product of this metabolism pathway is hydrogen sulfide, which can be involved in gut inflammation and also causes problems in industries (due to corrosion effects). The aim of the review was to compare assimilatory and dissimilatory sulfate reduction (DSR). These processes occur in some species of intestinal bacteria (e.g., Escherichia and Desulfovibrio genera). The main attention was focused on the description of genes and their location in selected strains. Their coding expression of the enzymes is associated with anabolic processes in various intestinal bacteria. These analyzed recent advances can be important factors for proposing possibilities of metabolic pathway extension from hydrogen sulfide to cysteine in intestinal SRB. The switch from the DSR metabolic pathway to the ASR metabolic pathway is important since toxic sulfide is not produced as a final product.

Evaluation of Physiological Parameters of Intestinal Sulfate-Reducing Bacteria Isolated from Patients Suffering from IBD and Healthy People

“…Sulfate consumption, H 2 S production, lactate consumption and acetate accumulation play an important role in the environment, concerning the development of the intestinal bowel diseases [17,35,50,51]. Desulfovibrio spp.…”

“…are related to the occurrence and development of the IBD since it can be very often found in the intestines and feces of people and animals with this ailment. SRB use sulfate as a terminal electron acceptor [21,50,51]. These facts can lead us to the conclusion that sulfate present in different food commodities (some bread, soy flour, dried fruits, brassicas and sausages, as well as some beers, ciders and wines) [49] could be an important factor in the development of bowel disease.…”

Adenosine-5′-Phosphosulfate- and Sulfite Reductases Activities of Sulfate-Reducing Bacteria from Various Environments

“…Generally, a reduction of sulfate became a dominant biological process in the water environment (oceans and deposits), resulting in sulfidic anoxic conditions from 2.5 to 0.6 billion years ago [54,55]. Currently, it is well known that SRB are able to colonize habitats that are different from the aquatic anaerobic environment where microorganisms have existed for a long time; in particular, the intestinal tract of animals (sea urchins, rodents, cows) and humans [56,57], where microorganisms need to adapt to new living conditions. The confirmation of this is that affinity data for substrates indicate that high affinity was shown for sulfite by SRB strains isolated from natural ecotopes, mainly in the soil environment.…”

“…This enzyme is also found in some phototrophic and chemotrophic sulfur oxidizers, where it is proposed to operate in the reverse direction (reverse sulfite reductase, rDSR) [54,70]. To confirm this, a recombinant Vib-7M strain was constructed that contained gene CysK coded O-acetyl-serine(thiol)lyase, which is an enzyme catalyzing the reaction of inorganic sulfide with O-acetyl-serine to form the S-containing amino acid l-cysteine [56]. Mutant strains are capable of higher speeds (1.5 times) using sulfate compared with the strains that are in the intestines of animals with colitis.…”

Sulfate-Reducing Bacteria of the Oral Cavity and Their Relation with Periodontitis—Recent Advances

“…In connection to the observed increase of incidence of SRB in the oral cavity in patients with periodontitis, the possibility of toxic effects of H 2 S on oral epithelial cells is being considered, which could lead to the onset and further development of the disease [5][6][7]17]. H 2 S acts as an inhibitor of cellular cytochrome oxidase, and may also have a secondary effect, by breaking down disulfide bonds in proteins, which affects granulocytes and their function within the immune system [18,19].…”