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Biomedical subjects

W D Murray

Publications and source records attributed to W D Murray.

11 recordsLinked to original sources
PubMed1986

Symbiotic Relationship of Bacteroides cellulosolvens and Clostridium saccharolyticum in Cellulose Fermentation.

In coculture, Bacteroides cellulosolvens and Clostridium saccharolyticum fermented 33% more cellulose than did B. cellulosolvens alone. Also, cellulose digestion continued at a maximum rate 48 h longer in coculture. B. cellulosolvens hydrolyzes cellulose and supplies C. saccharolyticum with sugars and a growth factor replaceable by yeast extract. Alone, B. cellulosolvens exhibited an early cessation of growth which was not due to nutrient depletion, low pH, or toxic accumulation of acetic acid, ethanol, lactic acid, H(2), CO(2), cellobiose, glucose, or xylose. However, a 1-h incubation of B. cellulosolvens spent-culture medium with C. saacharolyticum cells starved for growth factor allowed a resumption of B. cellulosolvens growth. The symbiotic relationship of this naturally occurring coculture is one of mutualism, in which the cellulolytic microbe supplies the saccharolytic microbe with nutrients, and in turn the saccharolytic microbe removes a secondary metabolite toxic to the primary microbe.

Journal Article↗
PubMed1981

Effects of nickel, cobalt, and molybdenum on performance of methanogenic fixed-film reactors.

The conversion of acetic acid to methane and carbon dioxide by a mixed methanogenic population from an anaerobic fixed-film digestor was stimulated by the addition of nickel (100 nM) and cobalt (50 nM) and especially by the addition of these elements in combination. Molybdenum addition (50 nM) was only slightly stimulatory when added in combination with both nickel and cobalt. The addition of these trace metals to anaerobic fixed-film digestors, which treat food processing waste, greatly enhanced reactor performance. Total gas and methane productions were increased 42%, greater volumes of waste could be effectively treated, and reactor residence time was shortened. However, the lag period for reactor start-up was not reduced. Tests showed that reactor performance was increased because trace nutrient addition allowed accumulation of a thicker methanogenic fixed film.

Journal Article↗
PubMed1980

Cold-sensitive mutant with defective growth at 5 degrees C from a psychrotrophic bacterium.

A cold-sensitive (CS) mutant of the psychrotroph, Bacillus psychrophilus, was obtained by N-methyl-N'-nitro-N-nitrosoguanidine mutagenization and penicillin counterselection. In the presence of citrate, the wild-type grew well at both 5 and 20 degrees C whereas the CS mutant grew well at 20 degrees C (the permissive temperature) but, at 5 degrees C (the restrictive temperature), grew at a reduced rate for two to three generations followed by a complete plateau in growth. Upon return of the CS mutant to 20 degrees C, after a delay of about 40 h, growth resumed at the appropriate rate. The CS mutant exhibited growth rates similar to parental rates on a wide variety of carbon sources at 5 degrees C, but when Krebs cycle intermediates were used as substrates and in the presence of an equimolar amount of citrate, the typical cold-sensitive growth pattern occurred. Comparison of oxidative phosphorylation in the parent and CS mutant indicated that no phosphorylation occurred at 5 degrees C in the CS mutant during the plateau in growth. Examination of the effect of temperature on ATPase activity showed that at 5 degrees C the specific activity of ATPase isolated from the CS mutant grows at 5 degrees C was 15-fold less than the ATPases isolated from wild-type cells grown at either 5 or 20 degrees C and 10.5-fold lower than ATPase from CS mutant cells grown at 20 degrees C. The large reduction in CS mutant ATPase activity at 5 degrees C appears to be at least partly due to an effect on synthesis since citrate did not inhibit preformed ATPase.

Adenosine Triphosphatases↗
PubMed1968

Primary "acquired" hypogammaglobulinaemia and amyloidosis.

The clinical details and post-mortem findings are given of a patient who had primary ;acquired' hypogammaglobulinaemia and was found at necropsy to have amyloidosis. The relationship of gamma globulin deficiency to amyloidosis is discussed, and the possible relevance of the hypogammaglobulinaemia to the formation and nature of amyloid is noted. It is suggested that a disordered immune response may be an essential prerequisite for the development of amyloidosis.

Agammaglobulinemia↗