Flow-microcalorimetric investigations on the relationship between heat production and light emission of photobacterium phosphoreum

Abstract

A flow microcalorimeter and two different photo detectors are used to monitor the heat production and the light emission of growing cultures of Photobacterium phosphoreum, respectively. Heat production of bacteria is considered as a general indicator of the function and intensity of the bacterial metabolism. Light production is a special property of luminous bacteria. In the Microtox(R)-test the light emission of P. phosphoreum is used to evaluate the toxicity of water polluting compounds. This study shows that the light emission of a growing culture of P. phosphoreum does not run parallel with the heat production. The light emission starts when the logarithmic growth phase of the bacteria is already far advanced. During the microcalorimetric lag-phase even a decrease of the light emission of the inoculated bacteria can be observed. Referred to the Microtox(R)-test it has to be noted that the test is run while the enzymatic system of the bacteria which is responsible for their luminescence is not active. The term “toxic” should be used with restriction in connection with this test.