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Biomedical subjects

T D Brock

Publications and source records attributed to T D Brock.

At least 73 records · Page 4Linked to original sources
PubMed1971

Microbial life at 90 C: the sulfur bacteria of Boulder Spring.

The physiology of the bacteria living in Boulder Spring (Yellowstone National Park) at 90 to 93 C was studied with radioactive isotope techniques under conditions approximating natural ones. Cover slips were immersed in the spring; after a fairly even, dense coating of bacteria had developed, these cover slips were incubated with radioactive isotopes under various conditions and then counted in a gas flow or liquid scintillation counter. Uptake of labeled compounds was virtually completely inhibited by formaldehyde, hydrochloric acid, and mercuric bichloride, and inhibition was also found with streptomycin and sodium azide. The water of Boulder Spring contains about 3 mug of sulfide per ml. Uptake of labeled compounds occurs only if sulfide or another reduced sulfur compound is present during incubation. The pH optimum for uptake of radioactive compounds by Boulder Spring bacteria is 9.2, a value near that of the natural spring water (8.9). Many experiments with a variety of compounds were performed to determine the temperature optimum for uptake of labeled compounds. The results with all the compounds were generally similar, with broad temperature optima between 80 and 90 C, and with significant uptake in boiling (93 C) but not in superheated water (97 C). The results show that the bacteria of Boulder Spring are able to function at the temperature of their environment, although they function better at temperatures somewhat lower. The fine structure of these bacteria has been studied by allowing bacteria in the spring to colonize glass slides or Mylar strips which were immediately fixed, and the bacteria were then embedded and sectioned. The cell envelope structure of these bacteria is quite different from that of other mesophilic or thermophilic bacteria. There is a very distinct plasma membrane, but no morphologically distinct peptidoglycan layer was seen outside of the plasma membrane. Instead, a rather thick diffuse layer was seen, within which a subunit structure was often distinctly visible, and connections frequently occurred between this outer layer and the plasma membrane. The thick outer layer usually consisted of two parts, the outer part of which was sometimes missing. Within the cells, structures resembling ribosomes were seen, and regions lacking electron density which probably contained deoxyribonucleic acid were also visible.

Acetates↗
PubMed1971

Effect of growth temperature on the lipid composition of Thermus aquaticus.

The complex lipids of Thermus aquaticus include phospholipids, glucolipids, carotenoids, and vitamin K(2) isoprenologues. The phospholipids account for 30% of the total lipids and have been identified as phosphatidylethanolamine (4%), phosphatidylglycerol (3%), phosphatidylinositol (10%), cardiolipin (3%), and phosphatidic acid (1%). The major phospholipid contained three fatty acids, a long-chain unsaturated amine, and one glycerol per phosphate and accounted for 80% of the lipid phosphate. The carotenoids accounted for 60% of the membrane lipid. The majority of the carotenoids were very polar. Mono- and diglucosyldiglyceride and the 35-, 40-, and 45-carbon vitamin K(2) isoprenologues were also identified. All these lipids were localized in the membrane of T. aquaticus. When the growth temperature was increased from 50 to 75 C and measured at 5 C intervals, there was a progressive increase in the total lipid content. The phospholipids increased 2-fold, the carotenoids increased 1.8-fold, and the glucolipids increased 4-fold between cells grown at 50 C and 75 C. The vitamin K(2) level did not change. The proportions of the individual lipids within each lipid class remained constant as the temperature of growth was raised. Metabolic studies indicated turnover of the diacyl phospholipids during pulse-chase experiments at rates comparable with mesophilic bacteria. The major phospholipid and the carotenoids did not turn over.

Acetone↗
PubMed1970

A thermophilic, acidophilic mycoplasma isolated from a coal refuse pile.

A thermophilic, acidophilic procaryote lacking a cell wall has been isolated from a coal refuse pile which had undergone self-heating. Electron micrographs, chemical assays for hexosamine, and the inability of vancomycin to inhibit growth confirm the lack of a cell wall. The apparent ability of the organism to reproduce by budding and the low guanine plus cytosine content of its DNA indicate a relation to the mycoplasmas. The temperature optimum of the organism is 59 degrees C, and growth occurs over a range of 45 degrees to 62 degrees C. No growth occurs at 37 degrees C or at 65 degrees C. The optimum pH for growth is between 1 and 2, and growth occurs between pH 0.96 and 3.5 but does not occur at pH 0.35 and only poorly at pH 4.0. We propose to call this organism Thermoplasma acidophila. The existence of this organism extends considerably the range of habitats in which mycoplasma may occur.

Cell Wall↗
PubMed1970

Limits of microbial existence: temperature and pH.

A microscopic survey made to detect the presence of bacteria in hot springs of varying temperature and pH characteristics revealed that in neutral and alkaline hot springs bacteria are found at temperatures up to the boiling point of water (92 degrees to 100 degrees C, depending on the altitude). In hot springs of increasing acidity the upper temperature limit at which bacteria are found decreases; at pH 2 to 3 the upper temperature limit is 75 degrees to 80 degrees C. Bacteria have thus been able to evolve with the ability to grow at either high temperature or high acidity, but not at both high temperature and high acidity. These results suggest that there are physicochemical limitations of the environment beyond which life is impossible.

Bacteria↗
PubMed1970

Growth rate of Sphaerotilus in a thermally polluted environment.

In situ growth of Sphaerotilus on microscope slides immersed in a thermally polluted stream was studied. Ultraviolet radiation was used to differentiate between passive attachment of organisms from the water and growth of the organisms on the slides. Colonization of the slides in this environment took place solely by means of swarmer cells. A generation time of 2.3 hr was obtained at a water temperature of 18-22 C.

Bacteriological Techniques↗
PubMed1970

Thermostable aldolase from Thermus aquaticus.

Data are presented on the purification and properties of the thermostable fructose-1,6-diphosphate aldolase of Thermus aquaticus, a nonsporulating, extreme thermophile. The enzyme shows little activity at temperatures below 60 C and optimal activity at about 95 C. The enzyme was purified 43-fold by diethylaminoethyl cellulose column chromatography and Sephadex G-200 gel filtration. The enzyme is activated by high concentrations of NH(4) (+) and low concentrations of Fe(2+) and Co(2+) and is strongly inhibited by ethylenediaminetetraacetic acid (EDTA). The activation by Fe(2+) and Co(2+) and the inhibition by EDTA are both reversed by dialysis. The enzyme is greatly activated by cysteine and less so by other sulfhydryl compounds. Activation by cysteine is reversible by dialysis. The purified enzyme had a molecular weight as determined by Sephadex G-200 gel filtration of 140,000; after incubation of enzyme with cysteine, another molecular species was also found with a molecular weight of 70,000. The purified enzyme is stable at low protein concentrations to 97 C but is rapidly inactivated at 105 C. In cysteine the enzyme is more heat labile; heat inactivation in the presence of cysteine is prevented by substrate, although, in the absence of cysteine, substrate partially labilizes the enzyme to heat. The temperature optimum for enzyme activity is several degrees lower in the presence of cysteine than in its absence, and the K(m) is threefold lower. It is concluded that the T. aquaticus enzyme resembles some other aldolases of Rutter's class II, except for its extreme heat stability. The T. aquaticus enzyme is compared with that of Bacillus stearothermophilus, a moderate thermophile. Although the T. aquaticus enzyme is considerably more heat stable, the enzymes from the two thermophiles have many similarities. New data are presented which show that the B. stearothermophilus aldolase is metal ion-dependent, in disagreement with earlier reports.

Bacillus↗
PubMed1970

Fine structure of Thermus aquaticus, an extreme thermophile.

Electron microscopic studies using thin sections revealed that Thermus aquaticus has a structure similar to that of most other gram-negative bacteria. The cell envelope is tripartite: plasma membrane, thin middle layer, and a thicker and irregular outer layer. The outer layer appears to be joined to the plasma membrane by a series of connections and, when seen in tangential section, the outer layer appears as a series of parallel bands. The cell division mechanism resembles that of typical gram-negative bacteria. Large spherical bodies designated "rotund bodies" are formed as a result of the association of a number of separate cells. In this association the outer envelope layers of the cells fuse and pull away from the middle layer. The rotund body thus appears as a series of rods, usually lying in parallel around the periphery of the sphere, completely connected by means of the fused outer layer.

Bacteria↗
PubMed1969

Bacterial growth rates above 90 degrees C in Yellowstone hot springs.

Growth rates of bacteria living in boiling springs have been measured by determining rate of increase in cell numbers on microscope slides immersed in the springs. Distinction between growth and passive attachment was made with ultraviolet radiation. In all cases, slides irradiated at intervals had significantly fewer bacteria than controls. Estimated generation times ranged from 2 to 7 hours, values which are comparable to those of aquatic bacteria living in less extreme environments.

Bacteria↗
PubMed1969

Molecular heterogeneity of isolates of the marine bacterium Leucothrix mucor.

Two collections of strains of Leucothrix mucor were isolated, one of world-wide origin and the other originating from a restricted area around San Juan Island, Friday Harbor, Washington. These two collections were compared on the basis of morphological, nutritional, and physiological properties, deoxyribonucleic acid base composition, and mobility by starch-gel electrophoresis of isocitric dehydrogenase and malic dehydrogenase. Despite the fact that all the strains were similar in most characteristics, significant molecular heterogeneity was found in the enzyme electrophoresis studies. This heterogeneity was just as great in the local collection as it was in the world collection. Even strains originating from the same microenvironment exhibited molecular heterogeneity.

Bacteria↗
PubMed1969

Thermus aquaticus gen. n. and sp. n., a nonsporulating extreme thermophile.

The isolation of a new thermophilic bacterium, Thermus aquaticus gen. n. and sp. n., is described. Successful enrichment requires incubation at 70 to 75 C, and the use of nutrient media relatively dilute with respect to the organic components. Strains of T. aquaticus have been isolated from a variety of thermal springs in Yellowstone National Park and from a thermal spring in California. The organism has also been isolated from man-made thermal habitats, such as hot tap water, in geographical locations quite distant from thermal springs. Isolates of T. aquaticus are gram-negative nonsporulating nonmotile rods which frequently form long filaments at supraoptimal temperatures or in the stationary phase. All isolates form a yellow cellular pigment, probably a carotenoid. A characteristic structure formed by all isolates is a large sphere, considerably larger than a spheroplast. These large spheres, as well as lysozyme-induced spheroplasts, are resistant to osmotic lysis. Deoxyribonucleic acid base compositions of four strains were determined by CsCl density gradient ultracentrifugation and found to be between 65.4 and 67.4 moles per cent guanine plus cytosine. The growth of all isolates tested is inhibited by fairly low concentrations of cycloserine, streptomycin, penicillin, novobiocin, tetracycline, and chloramphenicol. Nutritional studies on one strain showed that it did not require vitamins or amino acids, although growth was considerably faster in enriched than in synthetic medium. Several sugars and organic acids served as carbon sources, and either NH(4) (+) or glutamate could serve as nitrogen source. The organism is an obligate aerobe and has a pH optimum of 7.5 to 7.8. The optimum temperature for growth is 70 C, the maximum 79 C, and the minimum about 40 C. The generation time at the optimum is about 50 min. The possible relationships of this new genus to the myxobacteria, flexibacteria, and flavobacteria are discussed.

Anti-Bacterial Agents↗
PubMed1969

Warm-water strain of Leucothrix mucor.

The physiological properties and temperature responses of the first strain of Leucothrix mucor ever to be isolated from a warm, tropical seacoast area are described.

Bacteria↗
PubMed1968

Molecular aspects of specific cell contact.

Complementary macromolecules were isolated from yeasts of opposite mating type. These cell-surface molecules neutralize each other as do antibodies and antigens. Both yeast factors are glycoproteins of low molecular weight. Other specific cell associations may be due to the interaction of such complementary macromolecules.

Agglutination↗