RADIOCHEMICAL INVESTIGATION OF RESPIRATION OF SPORES OF BACILLUS CEREUS

The endogenous respiration of 14C-labelled spores of B. cereus was measured through the 14CO2 produced, and the rate expressed as Q (μl CO2/hxmg). New upper limits for respiration in various conditions have been set. Dry spores had no measurable activity; Q<10-4 at room temperature and <10-3 at 35° C. For wet spores of different harvests, at 30°C, Q lay between 0.0013 to 0.067. Near 40° C, respiration showed a maximum. Thermal history has a great influence on Q. CO2 production by heat-killed spores is attributed largely to infection. Water or 10-3m sodium phosphate buffer (pH=6.5) gave equal spore respiration, in strong NaCl it was less. Azide enhanced respiration dramatically. A temporary increase was also found with non-radioactive glucose. Exogenous respiration of spores in glucose exceeded endogenous respiration. Endogenous and exogenous respiration of vegetative forms were much larger than those of spores and were time-dependent. The ratio of minimum (endogenous, dry spores) and maximum (exogenous, wet vegetative cells) respiration was at least 3x105. © 1969 Springer-Verlag.