The phs gene and hydrogen sulfide production by Salmonella typhimurium.

Salmonella typhimurium produces H2S from thiosulfate or sulfite. The respective pathways for the two reductions must be distinct as mutants carrying motations in phs, chlA, and menB reduced sulfite, but not thiosulfate, to H2S, and glucose repressed the production of H2S from thiosulfate while it stimulated its production from sulfite. The phs and chlA mutants also lacked a methyl viologen-linked thiosulfate reductase activity present in anaerobically grown wild-type cultures. A number of hydroxylamine, transposon Tn10 insertion, and Mu d1(Apr lac) operon fusion mutants defective in phs were characterized. One of the hydroxylamine mutants was an amber mutant, as indicated by suppression of its mutation in a supD background. The temperature-sensitive phs mutants produced H2S and methyl viologen-linked thiosulfate reductase at 30 degrees C but not at 42 degrees C. The reductases in all such mutants grown at 30 degrees C were as thermostable as the wild-type enzyme and did not differ in electrophoretic relative mobility, suggesting that phs is not the structural gene for thiosulfate reductase. Expression of beta-galactosidase in phs::Mu d1(Apr lac) mutants was dependent on anaerobiosis and the presence of reduced sulfur. It was also strongly influenced by carbon source and growth stage. The results are consistent with a model in which the phs gene encodes a regulatory protein essential for the reduction of thiosulfate to hydrogen sulfide.

Use of conductance methods to predict bacterial counts in fish.

Conductance methods to measure bacterial growth are more rapid than conventional methods for assessing the load of spoilage bacteria in fish. With the correct choice of medium, an estimate of the count can be obtained within 24 h which shows a very good correlation with the conventional methods. Moreover, the conductance changes correlate better with counts of those organisms thought to be responsible for spoilage. The Malthus conductance instrument provides an automated system capable of the simultaneous monitoring of 128 different samples, resulting in considerable savings of time and effort over traditional plate counting techniques.

Desulfuration of cysteine and methionine by Fusobacterium nucleatum.

Fusobacterium nucleatum is a Gram-negative anaerobic rod-shaped bacterium frequently isolated from human dental plaque. It is capable of the desulfuration of cysteine and methionine, resulting in the formation of sulfide and thiol volatiles, respectively. Intact cells, as well as cell-free extracts produced by French pressure cell lysis of F. nucleatum, hydrolyzed radiolabeled cysteine to produce sulfide, pyruvic acid, and ammonia. The hydrolysis products of radiolabeled methionine were a volatile thiol, ketobutyrate, and ammonia. Both activities were associated with the cytoplasmic component, not the membrane. The desulfuration mechanisms are heat-labile, inhibited by the presence of excess substrate, and rates are dependent upon substrate concentration. These dissimilar pathways by F. nucleatum can account in part for the presence of sulfur-containing volatile products that occur in the mouth.

[S. typhimurium strains which are H2S negative in TSI medium]. / Tsi besiyerinde h2s teskil etmeyen s. typhimurium susslari.

During an epidemic in the premature ward of Ankara Pediatric Hospital which lasted for almost 25 days, 15 cases were diagnosed and H2S (TSI medium) negative S. typhimurium strains were isolated 23 times on the specimens obtained from these patients. Specimens consisted of mainly stools but two were blood samples, one was a lung aspirate and two were pathologic materials obtained from the elbow and hip joints of the same patient. When these strains were transferred to Braun-Ozek B Medium, they were able to produce H2S which was detected because of the strong blackening on the lead acetate paper. Component replacement studies were performed to show which were necessary for the production of H2S in this second media. According to the results of this studies Pepton witte + meat extract broth + Na2S2O3 . 5H2O were found essential for the production of H2S in Braun-Ozek B. Medium. When this medium was prepared with the incorporation of ferrous ammonium sulfate instead of Na2S2O3, 5H2O, the production of H2S decreased and delayed.

Spurious hydrogen sulfide production by Providencia and Escherichia coli species.

Hydrogen sulfide production was noted in two Escherichia coli strands and one Provaidenica alcalifaciens (Proteus inconstans A) strain isolated from clinical stool specimens durin the summer of 1979. An investigation into this phenomenon revealed the predence of Eubacterium lentum, an anaerobe, growing in synergism with the Enterobacteriaceae and producing H2s. The implications of this association are discssed with reference to clinical microbiology laboratory practice.

Identification of Proteus morganii and distinction from other Proteus species.

The identification of Proteus morganii in the clinical laboratory is complicated by the differences in incidence of hydrogen sulfide (H2S) production recorded by different sources. Since this quality appeared to be a frequent feature of strains of P. morganii at the author's center, all isolates of this species were studied over a six-month period. During this time, 12 of 21 were found to produce scant H2S in Kligler's iron agar (KIA) and triple-sugar iron (TSI) agar butts. The strains were, in every respect, biotypical, and were easily distinguished from other species of Enterobacteriaceae by biochemical study. They also possessed the features of high resistance to cephalothin and ampicillin and relative sensitivity to tetracycline, unlike strains of Proteus mirabilis. It is concluded that weak H2S production in TSI or KIA medium is a frequent normal characteristic of P. morganii, and its presence should not deter microbiologists from correctly identifying isolates manifesting this quality.

[Sequence of formation of gaseous products during anaerobic decomposition of cellulose in the presence of several electron acceptors]. / Posledovatel'nost' obrazovaniia gazoobraznykh produktov pri anaérobnom razlozhenii tselliulozy v prisutstvii neskol'kikh aktseptoro élektrona.

The course of anaerobic cellulose decomposition by a mixed microbial association was studied in the presence of nitrate and sulfate ions in the medium. The succession of reductive processes was evaluated by the formation of gaseous products, i. e. nitrogen, hydrogen sulfide, and methane. The sequence of processes in the course of cellulose degradation was determined by the energy yield of oxidative-reductive reactions. Sulfate reduction predominated if lactate was assimilated by the same microbial association, while denitrification prevailed when the association used acetate.

Genetic and molecular characterization of an Escherichia coli plasmid coding for hydrogen sulfide production and drug resistance.

An H(2)S-producing variant of Escherichia coli (strain 142) isolated from a urinary tract infection was found to be resistant to high levels of tetracycline, ampicillin, streptomycin, and sulfonamide. The H(2)S trait segregated spontaneously at a frequency of 2.5 x 10(-3). No segregation was observed for the drug resistance determinants. Neither ethidium bromide nor acridine orange affected the rate of segregation of the drug resistance determinants or the trait for H(2)S production. Antibiotic resistance and hydrogen sulfide production were conjugally transferred to E. coli K-12 recipients at a frequency of approximately 10(-5) per donor cell. Antibiotic resistance and hydrogen sulfide production were also transduced as a single unit with phage P1L4. Genetic data, based on the segregation of resistance determinants and the H(2)S trait among transconjugant and transductant classes, suggested the presence of two R plasmids. Plasmid DNA was isolated by cesium chloride-ethidium bromide centrifugation. Two plasmid species were detected by agarose gel electrophoresis of purified plasmid DNA, a large molecule of about 80 x 10(6) daltons (designated pSR12) and a small molecular species of approximately 5.5 x 10(6) daltons (designated pSR13). Transformation studies using purified plasmid DNA showed that the large pSR12 plasmid confers resistance to ampicillin, tetracycline, and streptomycin and also carries the gene(s) for H(2)S production. The small pSR13 plasmid confers resistance to streptomycin and sulfonamide.

[Participation of sulfate reducing bacteria in copper precipitation]. / Uchastie sul'fatredutsiruiushchikh bakterii v osazhdenii medi

Chemical precipitation of copper by hydrogen sulphide at three values of pH (3.0; 5.0; 7.0) did not result in complete elimination of the metal from a solution. If sulphate reducing bacteria and a source of organic substance, for instance, disintegrated reed, are introduced into the medium, the microorganisms begin to grow, the redox potential decreases, hydrogen sulphide is formed, and copper is completely eliminated from a solution within 10--15 days in model experiments.

Hydrogen sulphide production as an aid to the identification of Vibrio parahaemolyticus.

In this study 18 strains of Vibrio parahaemolyticus from food and 8 from humans were tested for hydrogen sulphide production on various modifications of Russel's Triple Sugar slopes and on TSI. All strains showed a characteristic surface browning on RTS with Andrade's indicator. This was not seen when RTS with phenol red as indicator or TSI were used. Appearance of this phenomenon allows unknown strains to be suspected as being Vibrio parahaemolyticus.

[Salmonella typhimurium masked as an Enterobacter species (author's transl)]. / Salmonella typhi-murium in der Maske einer Enterobacter-Species

A bacterial strain at first sight appearing to be an Enterobacter species causing enteritis could be identified as Salmonella typhimurium showing only a low formation of H2S. This small degree of H2S formation could not be demonstrated on commercial media ready for use. The high antibiotics resistance of the strain in question points to the possibility of its having undergone several antibiotics passages without recognition. Thus, serological verification is recommended in the case of so-called Enterobacter species appearing as agents of enteritis.

Stable isotope fractionation by Clostridium pasteurianum. 1. 34S/32S: inverse isotope effects during SO4-2- and SO3-2- reduction.

During growth on minimal salts--sucrose media supplemented with various concentrations (10-4-10-2 M) of sodium sulfate, Clostridium pasteurianum grew at a normal rate and only evolved sulfide in late stages of growth on 10-2 M SO4-2-. The evolved sulfide was slightly enriched in 34S as compared to the medium sulfur. On the other hand, sulfide was evolved during growth on all concentrations of sulfite tested. Large normal and inverse isotopic effects were observed in the evolved sulfide during SO3-2- reductions. In contrast, the intracellular sulfur showed much smaller fractionations. The complexity of the isotopic patterns suggests that a dissimilatory sulfite reductase system may be induced by high concentrations of sulfite.

The characterisation of Campylobacter sputorum subspecies mucosalis isolated from pigs.

A comparison is made between the recognised subspecies of Campylobacter sputorum isolated from humans and cattle and the previously unrecognised catalase negative vibrios isolated from porcine intestinal adenomatosis. The characters of the porcine strains warrant their inclusion within the species Campylobacter sputorum. Differentiation between all three is possible in the laboratory and we propose that, in addition to the recognised subspecies, sputorum and bubulus, the pig strains be accorded subspecies rank and called mucosalis. Other porcine strains characterised as C coli formed a heterogeneous group but could be differentiated from porcine C sputorum strains by their pigment and catalase production, sodium chloride tolerance, antigenic and a number of other characters.

Polarographic assay of hydrogen peroxide accumulation in microbial cultures.

A method is described for determining low concentrations of hydrogen peroxide by using a polarographic oxygen electrode to measure the oxygen released into solution on addition of catalase. A sample can be assayed directly without prior manipulation in 3 min. The method is capable of assaying hydrogen peroxide concentrations as low as 7 muM. The method has proved extremely useful for the assay of hydrogen peroxide secreted into milk by lactic acid bacteria.