OBLIGATE PHOTOAUTOTROPHY OF GREEN BACTERIA 155 



TABLE 3 



The effect of C. thiosulfatophilum extract on aconitate hydratase activity 



Except where noted, the enzyme was assayed by following TPN reduction 

 coupled to isocitrate dehydrogenase 



Source of 

 enzyme 



Protein in 

 assay (//g) 



Chlorobium Absorbancy 

 Substrate extract change in 



(//g protein) 10 min 



Per cent 

 inhibition 



* Extract was dialyzed 



* Assayed by absorbancy increase at 240 m// 



activities of extracts of other organisms was examined. Variable 

 results were obtained. Some extracts of C. thiosulfatophilum had no 

 effect; with other preparations some inhibition resulted. Table 3 shows 

 part of an experiment in which inhibition was obtained. In the same 

 experiment, the aconitate hydratase activities of Chloropseudomonas 

 ethylicum, R. rubrum, and Rhodomicrobium vannielii were decreased 

 from 10 to 30 per cent by the addition of C. thiosulfatophilum extract. 

 The inhibition was not removed by dialyzing the extract. Since inhibi- 

 tion was never severe, it appears unlikely that the inability to demon- 



TABLE 4 



Enzymes involved in succinate oxidation in the green 

 photo synthetic bacteria 



Bacterium 



Succinic 

 dehydrogenase 



Fumarate 

 hydratase 



DPN-malate 

 dehydrogenase 



fxmoles/min/g 

 chlorophyll 

 Chlorobium 28 



thiosulfatophilum 



Chloropseudomonas not assayed 

 ethylicum 



Hmoles/min/g protein 

 285 22 



233 



2170 



