Showing papers by "Thomas D. Brock published in 1968"

Distinction between Bacterial and Algal Utilization of Soluble Substances in the Sea

Abstract: SUMMARY: The presence of numerous bacteria and diatoms attached to the sand grains of a littoral beach have been shown by fluorescence microscopy. Bacteria and diatoms were found in a viable condition to depths exceeding 10 cm. The rate of uptake of [14C]-acetate was measured over the range 10–5000 μg./l. and the results analysed by Michaelis-Menten kinetics. By the use of autoradiography it was shown that the bacteria alone were responsible for the uptake of [3H]-acetate. It is concluded that algal heterotrophy is negligible in sea waters.

Molecular aspects of specific cell contact.

Abstract: 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.

Measurement of Steady-State Growth Rates of a Thermophilic Alga Directly in Nature

Abstract: Steady-state growth rates of thermophilic algae can be determined directly in nature in the flowing waters of a hot spring channel by measuring the rate of loss of algal cells when the channel is darkened. The half time of the loss rate in the steady state is identical to the generation time. We studied the unicellular blue-green alga Synechococcus in Yellowstone National Park. Temperature and flow rate remained relatively constant throughout the experiment. Quantitative cores were taken and homogenized; the algal cells were then counted by use of a Petroff-Hausser counting chamber. After ascertaining that the algal population was in a steady state, the channel was darkened in such a way that neither flow rate nor temperature was altered. The population began to decrease within 1 day; the loss rate was exponential with time for 2 to 3 decades. Half times were then calculated from these loss rates. The growth rates found were considerably lower than those for the same organism in laboratory culture. The results suggest that in nature the organism may be an obligate phototroph. In two cases, after the algal populations decreased to an undetectable level, the dark covers were removed and the rate of recolonization was measured. The kinetics of recolonization were different from the kinetics of washout.

Relationship between Environmental Temperature and Optimum Temperature of Bacteria along a Hot Spring Thermal Gradient

Abstract: SUMMARY The temperature optima of bacteria occurring at various temperatures along the thermal gradient of a hot spring in Yellowstone Park was studied directly in nature by measuring the rate of incorporation in the dark of [14C]glucose or 14CO2. Bacteria found at environmental temperatures over the range 35-70° were studied. For each temperature, the optimum for glucose and CO2 incorporation was similar to the environmental temperature.

The Adaptation of Heterotrophic Microcosms to Different Temperatures

Abstract: Heterotrophic microcosms were developed at a variety of temperatures from 2°C to 75°C, using as inocula a mixed microbial flora from a wide variety of sources. Even after extensive cross—seeding, each microcosm developed a characteristic flora and fauna, showing that temperature alone is able to control species conposition. Experiments using C14— clucose showed that the microcosms through the range 25°—75°C were optimally adapted to the temperature at which they were developed. Those developed at temperatures below 25°C were not optimally adapted. See full-text article at JSTOR

Taxonomic confusion concerning certain filamentous blue-green algae(1).

Abstract: Throughout a long history many filamentous bacteria may have been identified in natural collections as blue-green algae. This problem has been especially acute regarding the thermophilic species of hot springs, especially at the higher temperatures. It is suggested that in the absence of pure cultures, the minimal criteria for distinguishing filamentous bacteria from blue-green algae microscopically should be: (1) observation of the chlorophyll fluorescence with a fluorescent microscope and (2) demonstration of light-dependent (14) CO2 fixation autoradiographically. Pure cultures of a number of filamentous thermophiles have been obtained from habitats at temperatures above 60 C. These cultures resemble microscopically the natural material, grow only heterot rophically, and do not contain chlorophyll.

Mutual repression of haploid genes in diploid yeast.

Abstract: THE expression of the same genes can be studied in both haploid and diploid cells of certain yeasts. If the genes control primarily haploid mating type traits, then it is interesting to know whether these genes are expressed in the diploid which does not mate. In the agglutinative yeast, Hansenula wingei, the two haploid mating types (strains 5 and 21) produce cell surface glycoproteins which are complementary and which are responsible for the strong adhesion between cells during sexual agglutination1–3. The diploid hybrid, however, is completely non-agglutinative. This lack of agglutination in the diploid could be the result of a mutual repression of the synthesis of both complementary agglutination factors, or synthesis followed by mutual neutralization or inactivation of these glycoproteins. We have evidence that the genes controlling the haploid agglutination types are mutually repressed in the diploid.

The temperature optimum of the intestinal flora of the rat.

Abstract: Two types of experiments were performed to determine if the microbial flora of the intestinal tract of the rat was optimally adapted to body temperature. The first involved the preparation of agar-...