Chemoautotrophism, as exemplified by Nitrosomonas, Thiobacillus, and other bacteria, represents a unique mode of existence. Eowever, as more intimate knowledge of both autotrophic and heterotrophic metabolism is attained, the problem of defining what is unique about a chemoautotroph appears to become more difficult. Koffier and Wilson (1951) suggested that the uniqueness may lie not in the ability to oxidize inorganic molecules, but rather in the ability to couple the energy obtained from these oxidations to the energy requiring reactions of the cell. It was perhaps with some similar thought in mind that Woods and Lascelles (1954) pointed-out, in their introduction to a symposium on autotrophic microorganisms, that "There ap
An investigation has been carried out with the objective of relating losses in semipermeability of cellulose acetate (DS 2.5) reverse‐osmosis membranes to microbiological degradation (enzymic hydrolysis). Three sources of potentially destructive organisms were selected for study. One source was a set of degraded cellulose acetate reverse‐osmosis membranes; the other two sources were a surface soil sample and a lake bottom mud. From these, a total of 23 microbial isolates were obtained by culturing and enrichment. The isolates were characterized by staining and microscopic examination. Sterilized membranes were shaken continuously with sterile broths containing each isolate. In addition, membranes were placed on sterile agar and streaked with each isolate. Reverse‐osmosis testing of the membranes shaken in broth revealed losses in salt rejection of certain samples after 2 months. Visual observation of agar‐plated membranes showed complete degradation of several samples from each of the three sources of microorganisms. Infrared examination of degraded membranes showed up to 50% loss of acetyl content from the desalinating surface. No salt‐rejecting capability remained in these membranes. Cellulose triacetate membranes were resistant to degradation under conditions identical to those causing degradation of membranes having acetate DS of 2.3–2.5.
The ability of some microorganisms to survive a stress treatment such as freeze drying has been shown to improve when aging the cells is done before drying. Hutton and Shirey (1951) described the beneficial effects of adding filtrates from aged cultures to cell paste of Brucella abortus before freeze drying. Record and Taylor (1953) showed that an exudate of Escherichia coli offered protection to Escherichia coli and to other organisms as well. These investigators have suggested that this biological activity is due to a substance from bacteria and that it is effective in relatively small concentrations. We have studied the action of this viability protective factor (VPF) and have separated it from other constituents of the bacterial exudate. Also it has been partially characterized. The work reported here concerns the extraction of VPF from Brucella abortus and the measurement of its activity upon the survival of this organism during freeze drying. MATERIALS AND METHODS The culture employed was Brucella abortus BAI strain A-19 grown in a tryptose-cerelose broth at 32 C. This medium had the following composition in g/L: tryptose (Difco), 20.0; cerelose, 10.0; NaCl, 5.0; and 10 ml of a Seitz filtered solution containing 25 mg of thiamin hydrochloride (per L) which was added aseptically after the other ingredients had been autoclaved. Two per cent agar was added when a solid medium was desired. In order to obtain cell paste for the production 1 The major portion of this investigation was conducted as part of the work performed under Research and Development contract no. DA-18-064-CML-2410 for Camp Detrick,
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