Production of Hydrogen Sulfide by Streptomyces odorifer

By use of various trapping systems, as well as lead acetate papers, Streptomyces odorifer was shown to produce hydrogen sulfide. Other sulfur-containing compounds may be produced by S. odorifer, but the amounts obtained were too small for detailed analysis. It was suggested that hydrogen sulfide might be a part of the earthy-odor complex produced by S. odorifer.     

Selective Medium for Hydrogen Sulfide Production by Salmonellae

Triple Sugar Iron Agar does not reveal hydrogen sulfide production by all Salmonella organisms nor does it permit clear-cut separation of those nonsalmonellae which produce H(2)S. Numerous media with varied combinations of nutrients, inhibitors, selective agents, pH levels, and metal salts were tested for H(2)S production of cultures of Salmonella, Citrobacter, Edwardsiella, Arizona, Proteus, Providencia, Klebsiella, and Enterobacter. An agar medium has been devised which promotes growth and H(2)S production (generally within 6 hr) by Salmonella, Arizona, and Edwardsiella but which inhibits hydrogen sulfide production or growth of all other gram-negative organisms tested (including Citrobacter) or inhibits both. The use of this medium should facilitate the selection and identification of Salmonella.     

Production of Hydrogen Cyanide by Pseudomonas flurescens

Two Pseudomonas fluorescens isolates were found to produce hydrogen cyanide when cultured on either Trypticase soy agar supplemented with 0.5% yeast extract or on irradiation-sterilized chicken.     

Hydrogen Sulfide Production by Bacteria and Sulfmyoglobin Formation in Prepacked Chilled Beef

Meat stored at 1 to 2 C under low oxygen tensions, either in gas-impermeable packs or in controlled atmospheres, occasionally exhibited an undesirable green exudate. The green pigment was identified spectrophotometrically as sulfmyoglobin. The conversion of myoglobin to sulfmyoglobin resulted from the production of H(2)S by bacteria tentatively identified as Pseudomonas mephitica. This organism produced H(2)S only when the oxygen tension was about 1% and the pH of the meat was 6.0 and above.     

Production of Hydrogen Sulfide by Streptomycetes and Methods for its Detection

The ability of streptomycetes to produce hydrogen sulfide is generally used for taxonomic purposes. It was found that the previously used method, the blackening of Peptone Iron Agar, does not clearly indicate formation of hydrogen sulfide. It was shown that the blackening of a lead acetate strip is the most accurate indicator for H₂S-producing streptomycetes. A great variety of organic and inorganic sulfur compounds were examined and compared, and the choice of the most suitable sulfur source and method for the detection of hydrogen sulfide is discussed.     

Extrachromosomal Nature of Hydrogen Sulfide Production in Escherichia coli

Two strains of Escherichia coli which produce hydrogen sulfide appear to have acquired this ability via transfer of genetic material from another genus.     

Relative Incidence of Alteromonas putrefaciens and Pseudomonas putrefaciens in Ground Beef

Of 65 H₂S-producing isolates from seven samples of ground beef, 64 were found to be Alteromonas putrefaciens. Isolates of Pseudomonas putrefaciens were not encountered. The mean guanine-plus-cytosine content of DNAs from 10 of the representative isolates, obtained from thermal denaturation determinations, was 46.5 ± 1.0 mol%, which is consistent with the designation A. putrefaciens.     

Effects of pH and Lactate on Hydrogen Sulfide Production by Oral Veillonella spp.

Indigenous oral bacteria in the tongue coating such as Veillonella have been identified as the main producers of hydrogen sulfide (H₂S), one of the major components of oral malodor. However, there is little information on the physiological properties of H₂S production by oral Veillonella such as metabolic activity and oral environmental factors which may affect H₂S production. Thus, in the present study, the H₂S-producing activity of growing cells, resting cells, and cell extracts of oral Veillonella species and the effects of oral environmental factors, including pH and lactate, were investigated. Type strains of Veillonella atypica, Veillonella dispar, and Veillonella parvula were used. These Veillonella species produced H₂S during growth in the presence of l-cysteine. Resting cells of these bacteria produced H₂S from l-cysteine, and the cell extracts showed enzymatic activity to convert l-cysteine to H₂S. H₂S production by resting cells was higher at pH 6 to 7 and lower at pH 5. The presence of lactate markedly increased H₂S production by resting cells (4.5- to 23.7-fold), while lactate had no effect on enzymatic activity in cell extracts. In addition to H₂S, ammonia was produced in cell extracts of all the strains, indicating that H₂S was produced by the catalysis of cystathionine γ-lyase (EC 4.4.1.1). Serine was also produced in cell extracts of V. atypica and V. parvula, suggesting the involvement of cystathionine β-synthase lyase (EC 4.2.1.22) in these strains. This study indicates that Veillonella produce H₂S from l-cysteine and that their H₂S production can be regulated by oral environmental factors, namely, pH and lactate.     

Heat Production by the Denitrifying Bacterium Pseudomonas fluorescens and the Dissimilatory Ammonium-Producing Bacterium Pseudomonas putrefaciens during Anaerobic Growth with Nitrate as the Electron Acceptor

The heat production rate and the simultaneous nitrate consumption and production and consumption of nitrite and nitrous oxide were monitored during the anaerobic growth of two types of dissimilatory nitrate reducers. Pseudomonas fluorescens, a denitrifier, consumed nitrate and accumulated small amounts of nitrite or nitrous oxide. The heat production rate increased steadily during the course of nitrate consumption and decreased rapidly concomitant with the depletion of the electron acceptors. A mean experimental enthalpy change value of −800 kJ/mol of nitrate and a mean growth yield value of 33 g (dry weight)/mol of nitrate consumed were obtained for different concentrations of nitrate. For Pseudomonas putrefaciens, a dissimilatory ammonium producer, the nitrate consumption resulted in an accumulation of nitrite and nitrous oxide. Nitrite consumption commenced after depletion of the nitrate; consequently, two phases were noted in the heat production rate curve during growth. A mean experimental enthalpy change value of −810 kJ/mol of nitrate was obtained for different concentrations of nitrate.     

Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase

The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H₂S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be −123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation.     

The Microbial Community of Poultry Farm Waste and Its Role in Hydrogen Sulfide Production

Microbiology - The microbiota of chicken litter remains largely unexplored, despite its leading role in the formation of volatile odorants and unpleasant odors. One of the main components of the...     

Enhancement of the Bactericidal Effect of Antibiotics by Inhibition of Enzymes Involved in Production of Hydrogen Sulfide in Bacteria

Molecular Biology - Counteraction of the origin and distribution of multidrug-resistant pathogens responsible for intra-hospital infections is a worldwide issue in medicine. In this brief review,...     

Effects of Light Intensity and Oxidized Nitrogen Sources on Hydrogen Production by Chlamydomonas reinhardii

Chlamydomonas reinhardii cells, after a period of dark anaerobic adaptation, evolve H₂ not only in the dark but also in the light. Our results show that high irradiances impair prolonged H₂ evolution, while under low irradiances or darkness H₂ evolution proceeds for more than 50 hours. NO₃⁻ and NO₂⁻ suppress H₂ evolution both in the dark or under low irradiance. Apparently the cells prefer these oxidized nitrogen sources to protons as electron acceptors, since both NO₃⁻ and NO₂⁻ become reduced to NH₄⁺, which is excreted to the culture medium in high amounts. H₂ evolution started once these oxidized anions were largely depleted from the medium. Moreover, H₂ evolution was consistently associated with NH₄⁺ excretion even if NH₄⁺ was already present in high amounts in the medium. This observation indicates that the cells utilize not only their carbohydrate but also their protein reserves as sources of reducing power for H₂ evolution. This conclusion was supported by the observation that when nitrogen-starved cells were made anaerobic in a nitrogen-free medium, they not only evolved H₂ at very high rates but excreted concomitantly NH₄⁺ up to concentrations in the millimolar range.     

Enhanced Biological Hydrogen Production from Escherichia coli with Surface Precipitated Cadmium Sulfide Nanoparticles

The precipitation of cadmium sulfide nanoparticles is induced on the surface of Escherichia coli , and the biological hydrogen production efficiency under visible light (VL) irradiation is investigated. When endogenous [Ni–Fe]‐hydrogenase is anaerobically induced, an additional 400 µmol of hydrogen gas is generated within 3 h from the hybrid system suspension (50 mL) under VL irradiation (2000 W m^?2), corresponding to an increase in hydrogen production of ≈30%. The apparent quantum efficiencies of the hybrid system under 470 and 620 nm VL irradiation are 7.93% and 9.59%, respectively, which are higher than those of many photoheterotrophic bacteria. Furthermore, the mechanism of the enhanced hydrogen evolution is investigated. The interaction between photogenerated electrons and cells of E. coli is confirmed by heat‐treatment, electron‐scavenger, and separation studies. The acceleration of pyruvate generation, inhibition of lactate fermentation, increase of formate concentration, stimulation of hydrogenase activity, and elevation of nicotinamide adenine dinucleotide (NAD)H/NAD ratio in the hybrid system are responsible for the enhanced hydrogen production. A feasibility study is also conducted using wastewater and natural sunlight for the hydrogen production by the hybrid system. An additional 120 µmol of hydrogen is generated from the hybrid system within 3 h under these conditions using natural resources.