摘要:

During growth on minimal salts – sucrose media supplemented with various concentrations (10−4–10−2 M) of sodium sulfate,Clostridium pasteurianumgrew at a normal rate and only evolved sulfide in late stages of growth on 10−2 M SO42−. The evolved sulfide was slightly enriched in34S 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 SO32−reductions. In contrast, the intracellular sulphur 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.

ISSN:0008-4166    

DOI:10.1139/m75-034

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Batch and chemostat cultures ofStreptococcus cremorisHP andStreptococcus lactis829 were examined for lactose-negative (lac−) mutants on indicator agar. In batch cultures,S.cremorisHP gave less than 1% of the total count aslac−colonies whileS.lactis829 consistently contained about 15% of the total aslac−colonies. In chemostat cultures ofS.cremorisHP in 2% skim milk containing casamino acids and yeast extract (0.1% each), the percentage oflac−colonies increased markedly when the temperature of growth was 18 °C but not when the temperature of growth was 25 °C. The percentage oflac−colonies in chemostat cultures in the skim milk medium at 25 °C was about the same as that in batch cultures. On the other hand, when chemostat cultures ofS.lactis829 in the skim milk medium were grown at several temperatures between 18 and 33 °C, the percentage oflac−colonies was markedly lower than that found in batch cultures of this organism. Cultivation ofS.cremorisHP in chemostats with yeast extract – lactose broth at low temperatures (14–18 °C resulted in cultures that gave plate counts on lactose agar, which were as much as 50% lower than counts on glucose agar but did not result in the selection oflac−mutants. Cultivation ofS.lactis829 in chemostats with yeast extract – glucose broth at low temperature (18 °C resulted in a selection of cells givinglac−colonies and atypical (small)lac+colonies. The results show that cultivation ofS.cremorisHP andS.lactis829 in chemostats sometimes gave rise to altered populations. Conditions causing a change in one organism did not necessarily cause a similar change in the other. The results indicate that the successful propagation of lactic streptococci in chemostats for use as starter cultures in the dairy industry will require the careful establishment of optimum conditions for every strain so as to minimize the possible selection of undesirable populations.

ISSN:0008-4166    

DOI:10.1139/m75-035

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A simplified procedure is presented for releasing and concentrating indigenous microbial cells from soil for viewing by transmission electron microscopy as thin sections or replicas of frozen-etched preparations. This procedure is compared with two others reported earlier, and their relative merits are discussed as concerns the choice of procedure for the cellular information desired from the soil. Freeze-etching showed that the cell types and size distributions for cells which have been released and concentrated from soil are in general agreement with those for cells in a crude soil slurry in which no attempt to release and concentrate cells was made. Microcolonies were present both in the crude slurry and in the discard soil debris centrifugation pellets from the cell release and concentration procedures. In contrast to the historic assumptions, these microcolonies, as well as some individual cells embedded in soil debris could not be broken up and (or) dislodged so that they would be washed from the soil. The relative numbers of these cells remaining with the soil debris, however, could not be quantitated in the present study.

ISSN:0008-4166    

DOI:10.1139/m75-036

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Soil was sterilized by various procedures, and then the resident microorganisms were physically separated and concentrated from the soil for viewing by transmission electron microscopy as thin sections and frozen-etched preparations. Remaining cell viability in the soil was tested by conventional plating before and after enrichment culture. The soil proved to be sterile after treatment with60Co radiation, prolonged autoclaving, prolonged dry heat application at 200C, or glutaraldehyde (if followed by subsequent mild heating), and could be considered sterile after OsO4treatment. Treatment with glutaraldehyde alone, or 160C dry heat for 3 h, did not sterilize the soil. Cellular fine structure was altered or destroyed by the heat treatments, but was not affected to any extent by any of the other treatments including glutaraldehyde followed by mild heating. These findings are considered in relation to the residual biological information observable by electron microscopy in soil samples which have been sterilized to eliminate possible pathogens before handling of the soil. These findings are also considered with the objective of obliterating the fine structure of the indigenous microorganisms during soil sterilization so that electron microscopy studies can be made of microorganisms inoculated into and grown in the presterilized soil.

ISSN:0008-4166    

DOI:10.1139/m75-037

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Morphological and density measurements were made on planktonic bacteria from a subalpine lake. The observations were then used to predictin situsinking rates from certain theoretical considerations. The predicted rates agreed well with observed sinking rates (on the order of 1 mm day−1). A simple analysis showed that sinking terms can be neglected in explaining distributions of unattached bacteria, except perhaps in relation to the presence of "bacterial plates."

ISSN:0008-4166    

DOI:10.1139/m75-038

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Staphylococcus aureusstrain S-6, which produces enterotoxin type B (SEB), and strain 10-275, a high toxin-producing mutant derived from S-6, display pronounced differences in dye sensitivity, osmotic stability, and bacitracin sensitivity. Such characteristics are consistent with the concept that strain 10-275 is a membrane mutant of strain S-6. Some membrane mutants ofS.aureusstrain 14458 exhibit about two- to three-fold increases in SEB production whereas other membrane mutants show about twofold increases in α-hemolysin production. It is suggested that specific and independent membrane mutations control the secretory processes resulting in the extracellular elaboration of these exoproteins.

ISSN:0008-4166    

DOI:10.1139/m75-039

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

After a brief exposition to glucose,Thiobacillus acidophiluswas isolated from a culture of iron-grownT.ferrooxidans. Physicochemical analysis of its DNA showed a G + C content of 62.9–63.2%. The new isolate grows best at 25–30 °C and at pH 3.0. Growth is possible between pH 1.5 and 6.0.Thiobacillus acidophilusis apparently strictly aerobic. Ammonium salts are the only suitable source of nitrogen. The bacterium is a facultative autotroph. In addition to elemental sulfur, it obtains energy from organic compounds such asD-glucose,D-galactose,D-fructose,D-mannitol,D-xylose,D-ribose,D-arabinose,L-arabinose, sucrose, sodium citrate, malic acid,dl-aspartic acid, anddl-glutamic acid.Thiobacillus acidophiluspossesses the key enzymes of the tricarboxylic acid (TCA) cycle including NAD- and NADP-linked isocitric dehydrogenase and α-ketoglutarate dehydrogenase, and the key enzymes of the hexose monophosphate pathway (glucose-6-phosphate and 6-phosphogluconate dehydrogenase, and fructose 1,6-diphosphate aldolase). NADH oxidase has been found in particulate fraction of extracts. Rhodanese and thiosulfate oxidase have also been detected.

ISSN:0008-4166    

DOI:10.1139/m75-040

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Vero cells were more suitable then BHK-21 cells for the detection of rubella-specific 1gG antibodies because the nonspecific fluorescence was minimal. However, BHK-21 cells were found more sensitive than Vero cells for the detection of rubella-specific IgM antibodies.

ISSN:0008-4166    

DOI:10.1139/m75-041

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Filtered water extract of Gabalong soil with a recent history of take-all in wheat caused lytic plaques to form in agar cultures of a virulent strain ofGaeumannomyces graminisvar.tritici. The plaques resembled those produced byBdellovibrioon plates seeded with bacteria. However, there was no evidence of the presence of bacteria, viruses, or mycoplasmas.The lytic factor was transmissible in culture filtrates to fresh subcultures of the fungus. Exposure of young healthy colonies to sublethal doses of ultraviolet light also induced transmissible lysis. The lytic factor was heat-stable, passed through a 25-nm filter, and was not affected by nuclease (enzymes) or severe irradiation with UV light. It also induced lysis in several other strains ofG.graminis. Lysis was always preceded by a growth-stimulatory effect on the fungus.The lytic factor was active as a volatile chemical which induced transmissible lysis and continued to be formed, apparently as a self-perpetuating agent, in lysing cultures of the fungus.

ISSN:0008-4166    

DOI:10.1139/m75-042

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Specific activities of 14 enzymes of the Embden–Meyerhof–Parnas and pentose phosphate pathways were determined in extracts of resting spores and vegetative mycelia ofEntomophthora pyriformis. All these enzymes were detected in mycelial extracts, whereas only nine were detectable in resting spore extracts. Activities of detectable spore enzymes were much lower than those of the corresponding mycelial enzymes with the exception of triosephosphate dehydrogenase, which had higher activity in spore extracts. The enzyme deficiencies noted point to the inability of either pathway to function in dormant spores.

ISSN:0008-4166    

DOI:10.1139/m75-043

出版商:NRC Research Press    

年代:1975

数据来源: NRC