Influence of growth temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus

Abstract

The influence of temperature on glucose metabolism of a psychrotrophic strain of Bacillus cereus was investigated. The pH of the growth medium and sporeforming frequencies of B. cereus varied when grown at 32, 20, or 7 C. Radiorespirometric analyses revealed that vegetative cells of B. cereus metabolized glucose by simultaneous operation of the Embden-Meyerhof-Parnas pathway and the pentose phosphate pathway. As the growth temperature decreased, glucose was metabolized with increased participation of the pentose phosphate pathway. The shift of cells grown at a higher temperature to a lower temperature increased the relative participation of the pentose phosphate pathway, whereas the shift of cells grown at low temperatures to a higher temperature had the opposite effect. Cells of late logarithmic phase grown at 20 and 7 C oxidized acetate by the tricarboxylic acid cycle reaction. However, cells grown at 32 C failed to oxidize acetate to CO2 to any appreciable extent. The extracellular products resulting from the metabolism of glucose decreased as the growth temperature was lowered. Organic acids were the major extracellular products of cultures grown at 32 and 20 C. Acetic acid, lactic acid, and pyruvic acid together accounted for 86.1 and 78.9%o of extracellular radioactivity, respectively, at the two temperatures. The relative ratio of these three acids varied between the temperatures. Little or no acid accumulated at 7 C.

Temperature-mediated changes in microbial carbon use efficiency and <sup>13</sup>C discrimination

“…tributed to the observed δ 13 C of respired CO 2 (Dijkstra et al, 2011;Tcherkez et al, 2012). It could simply result from a proportionally increasing flux through respiratory pathways, with associated stronger expression of 13 C discrimination by the enzymes involved (Tcherkez et al, 2012), or could result from increasing temperatures altering the relative fluxes through respiratory pathways (Chung et al, 1976;Wittmann et al, 2007;Dijkstra et al, 2011) such that the overall observed respiratory 13 C discrimination increased with temperature. This may be possible given that respiratory pathways can exhibit distinct fractionation factors (Bathellier et al, 2009 and references therein) and prompt different, specific C atoms to undergo decarboxylation from the two glucose units of the substrate cellobiose, which contain non-randomly distributed 13 C atoms (Rossmann et al, 1991;Gleixner and Schmidt, 1997).…”

Temperature-mediated changes in microbial carbon use efficiency and <sup>13</sup>C discrimination

“…tributed to the observed δ 13 C of respired CO 2 (Dijkstra et al, 2011;Tcherkez et al, 2012). It could simply result from a proportionally increasing flux through respiratory pathways, with associated stronger expression of 13 C discrimination by the enzymes involved (Tcherkez et al, 2012), or could result from increasing temperatures altering the relative fluxes through respiratory pathways (Chung et al, 1976;Wittmann et al, 2007;Dijkstra et al, 2011) such that the overall observed respiratory 13 C discrimination increased with temperature. This may be possible given that respiratory pathways can exhibit distinct fractionation factors (Bathellier et al, 2009 and references therein) and prompt different, specific C atoms to undergo decarboxylation from the two glucose units of the substrate cellobiose, which contain non-randomly distributed 13 C atoms (Rossmann et al, 1991;Gleixner and Schmidt, 1997).…”

Effect of Sugars on d -Arabitol Production and Glucose Metabolism in Saccharomyces rouxii

“…in this study were similar in design to those described by Wang (40). The methods used were modified from those of several authors (3,11,30). Cells for the radiorespirometric experiments were grown and harvested as described above.…”

“…At the termination of the experiment, the flasks were chilled and the cells were separated from the buffer medium by centrifugation. The radioactivity in the cells and medium was determined as described by Chung et al (11). The counting efficiency of 14C was approximately 90%, and quenching was corrected for by the internal standard method.…”