ENHANCEMENT OF ATP LEVELS AND GLUCOSE-METABOLISM DURING AN INFECTION BY CHLAMYDIA - NMR-STUDIES OF LIVING CELLS

The Chlamydia species are obligate intracellular bacteria that prolife rate only within the infected cell. Since the extracellular bacteria a re metabolically inert and there are no cell free systems for characte rizing Chlamydia metabolism, we studied metabolic changes related to A TP synthesis and glycolysis in HeLa cells infected with Chlamydia psit taci during the course of the a-day infection cycle using noninvasive P-31 and C-13 NMR methods. We find that the infection stimulates ATP s ynthesis in the infected cell, with a peak of ATP levels occurring mid way through the infection cycle, when most of the metabolically active bacteria are proliferating. The infection also stimulates synthesis o f glutamate with a similar time course as for ATP. The stimulation is apparently due to an enhancement in glucose consumption by the infecte d cell, which also results in an increased rate of lactate production and glutamate synthesis as well as higher glycogen accumulation during the infection. Concurrently, infection leads to an increase in the ex pression of the glucose transporter, GLUT-1, on HeLa cells, which may account for the enhanced glucose consumption. The chlamydiae are thus able to stimulate glucose transport in the host cell sufficiently to c ompensate for the extra energy load on the cell represented by the inf ection.