Dissimilatory Sulfate- and Sulfur-Reducing Prokaryotes

The microbial reduction of elemental sulfur to hydrogen sulfide under anaerobic conditions has been observed and described repeatedly during the past 100 years (Beijerinck, 1895; Omelianski, 1904; Pelsh, 1936; Roy and Trudinger, 1970; Starkey, 1937; Woolfolk, 1962). Many different prokaryotic and eukaryotic microorganisms were shown to be able to reduce elemental sulfur in nonspecific, incidental side reactions in the course of their regular fermentative metabolism. Thiosulfate, methylene blue, aldehydes, or other compounds were also reduced. Under these circumstances, it is questionable whether the reduction of elemental sulfur plays any significant role in the normal metabolism of such cells (Roy and Trudinger, 1970).

The Dissimilatory Sulfate-Reducing Bacteria

Publisher Summary This chapter discusses the microbial formation and degradation of minerals in detail. It has been characteristic of microbiology and other disciplines that the tempo of man's research activities has been in direct proportion to his needs and his welfare. Thus, the diseases of man received early are stressed by microbiologists. Man's dependence upon agriculture for his food supply gave impetus to soil microbiology with special emphasis on plant diseases and soil fertility, and resulted in establishing the importance of microorganisms in the cycles of carbon, nitrogen, phosphorus, and sulfur in nature. Much less attention was paid to other natural activities of microorganisms, except where such obvious occurrences as the evolution of H2S, H2, and CH4, from stagnant bodies of water or the deposition of iron oxides in swamps and bogs demanded attention. By and large, microbiologists concerned themselves with the metabolism of organic matter and virtually ignored the inorganic environment.

Microbial Formation and Degradation of Minerals

Background: The ideal identification of Staphylococcus aureus clinical isolates requires a battery of tests and this is costly in resource limited settings. In many developing countries, the tube coagulase test is usually confirmatory for S. aureus and is routinely done using either human or sheep plasma. This study evaluated Mannitol salt agar and the deoxyribonuclease (DNase) test for improving the efficiency of the tube coagulase test in resource limited settings. The efficiency of human and sheep plasma with tube coagulase tests was also evaluated. Methods: One hundred and eighty Gram positive, Catalase positive cocci occurring in pairs, short chains or clusters were subjected to growth on Mannitol salt agar, deoxyribonuclease and tube coagulase tests. Of these, isolates that were positive for at least two of the three tests (n = 60) were used to evaluate the performance of the tube coagulase test for identification of S. aureus, using PCR-amplification of the nuc gene as a gold standard. Results: Human plasma was more sensitive than sheep plasma for the tube coagulase test (sensitivity of 91% vs. 81% respectively), but both plasmas had very low specificity (11% and 7% respectively). The sensitivity and specificity of the tube coagulase test (human plasma) was markedly improved when Mannitol salt agar and DNase were introduced as a tri-combination test for routine identification of Staphylococcus aureus (100% specificity and 75% sensitivity). The specificity and sensitivity of Mannitol salt agar/DNase/tube coagulase (sheep plasma) combination was 100% and 67%, respectively. Conclusion: The efficiency of the tube coagulase test can be markedly improved by sequel testing of the isolates with Mannitol salt agar, DNase and Tube coagulase. There is no single phenotypic test (including tube coagulase) that can guarantee reliable results in the identification of Staphylococcus aureus.

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Identification of Staphylococcus aureus : DNase and Mannitol salt agar improve the efficiency of the tube coagulase test

All plants, animals and bacteria require sulphur for the synthesis of proteins. The biological transformation of sulphur in natural environments is a nutrient cycling process comprising both aerobic and anaerobic components (Postgate 1984). In its highest oxidation state, sulphur exists as the sulphate ion (SO:-) which is reduced to sulphide (Sz-) by most bacteria, fungi and plants before incorporation into amino acids. This process is termed assimilatory sulphate reduction and is purely a biosynthetic process. However, any sulphur compound with an oxidation state above that of sulphide ( 2) can potentially function as an electron acceptor for the oxidation of carbon substrates by biological processes (Goldhaber & Kaplan 1974). For example, during dissimilatory sulphate reduction, the sulphate ion is utilized as an oxidant for the degradation of organic material. An equivalent amount of sulphide is formed per mole of sulphate reduced (Berner 1974): 2CH,O + SO:-+ H,S + 2HCO;

Physiology and ecology of the sulphate-reducing bacteria.

Studies on thermophilic sulfate reducing bacteria. I. Identification of Sporovibrio desulfuricans as Clostridium nigrificans.

L forms were induced from 15 of 16 strains of Listeria monocytogenes on penicillin gradient plates incubated under aerobic conditions. The culture medium for maintenance of these L forms must contain an electrolyte in a concentration of 1% or sucrose in a concentration of 10%. The electrolytes NaCl, KCl, or MgSO(4) were used in both induction and maintenance media. Induction of L forms occurred more rapidly on media containing KCl. Listeria L forms had the same fermentation reactions as the parent bacterium. The L-form growth in liquid medium was slow, not extensive, and appeared as clumps on the bottom of culture tubes. The morphology of Listeria L forms was similar to that reported for other bacterial L forms. The L forms derived from strain 10403, serotype 1, were stable after two or more passages on penicillin media. They did not revert to the bacterial form after 40 subcultures on penicillin-free media. Some L-form colonies derived from strain 10403 did revert to the bacterial form when transferred directly from induction plates to penicillin-free media. Studies of the growth characteristics for L forms derived from strain 10403 gave the following results: an optimal temperature of 30 C, high electrolyte or sucrose concentration necessary for induction and maintenance, and no requirement for serum.

Listeria monocytogenes L Forms I. Induction, Maintenance, and Biological Characteristics

Bayliss, Berenice G. (Washington State University, Pullman), and Elizabeth R. Hall. Plasma coagulation by organisms other than Staphylococcus aureus. J. Bacteriol. 89:101-105. 1965.-Approximately 200 organisms were investigated for their ability to clot human and rabbit plasma. Various anticoagulants were used in preparing the plasma: acid-citrate-dextrose, ethylenediaminetetraacetate, balanced oxalate, potassium and sodium oxalates, and heparin. Twelve organisms were found which coagulated citrated plasma in less than 8 hr: four strains of Streptococcus faecalis; two strains of S. faecalis var. zymogenes; three strains of S. faecalis var. liquefaciens; and one strain each of S. pyogenes, Escherichia coli, and Serratia marcescens. Six strains of coagulase-positive Staphylococcus were selected for use as controls. Experiments were performed to determine the mechanism by which these microorganisms coagulated citrated plasma. As this was the only plasma clotted, it was presumed that the citrate was utilized by the microorganisms, thereby releasing the calcium which was then made available so that normal physiological clotting could occur. To test this hypothesis, a chromatographic method was employed to determine the presence or absence of citrate. Coagulation tests, by use of increasing amounts of citrate, showed a linear relationship between the amount of citrate in the plasma and the coagulation time. It was demonstrated that the organisms must be actively metabolizing to clot citrated plasma. Proof for this was obtained by using a cell-free filtrate, to which thimerosal had been added to inhibit growth, instead of whole cultures for the coagulation test. Only the coagulase-positive staphylococci coagulated the citrated plasma under these conditions. From the results obtained, it was concluded that plasma coagulation by these organisms was by citrate utilization.

Plasma coagulation by organisms other than staphylococcus aureus.

Physiological saline was found to be very detrimental to the viability of Listeria monocytogenes. The LD50 value was substantially reduced when peptone was used as the suspending fluid rather than saline. Normal splenic tissue was not inhibitory to the survival of Listeria. In experimentally infected mice, L. monocytogenes survived for 8 days in the peritoneal cavity and for at least 11 days in the spleen.

Survival of Listeria monocytogenes in experimentally infected mice.

Listeria monocytogenes was successfully isolated from experimentally infected mice by placing homogenized tissues in phosphate-buffered saline (PBS), trypsin, peptone, or pepsin followed by incubation at 37 C for 24 hr. A larger number of Listeria isolates were recovered from the trypsin or PBS splenic homogenate suspensions incubated at 37 C for 2 hr than from the other diluent suspensions. Holding infected tissues at 4 C for at least 3 months did not increase the efficiency of Listeria isolation. Listeria L-forms were not isolated from mice injected with the bacterial form. The in vitro viability of Listeria L-forms suspended in PBS or PBS splenic homogenate was greatly reduced when held at 4 C.

Elizabeth R. Hall

Papers

Studies on thermophilic sulfate reducing bacteria. I. Identification of Sporovibrio desulfuricans as Clostridium nigrificans.

Listeria monocytogenes L Forms I. Induction, Maintenance, and Biological Characteristics

Plasma coagulation by organisms other than staphylococcus aureus.

Survival of Listeria monocytogenes in experimentally infected mice.

Rapid Method for the Isolation of Listeria monocytogenes from Experimentally Infected Mice