14 METABOLIC PATHWAYS IN MICROORGANISMS 



TABLE 1.5 



Non-oxidative Breakdown of Ribose-5-Phosphate 

 by A. suhoxydans Extract 



* Values for total sugars are given as pentose equivalents (jumoles 

 carbon/5). 



The tubes were incubated in vacuo with 10 ^tmoles ribose-5-phos- 

 phate, 100 /xmoles tris buffer at pH 8.0, 20 jumoles sodium fluoride, 

 0.15 ml. cell-free extract, and water to 2 ml. The reaction was 

 stopped by adding 1.6 ml. of 10% trichloroacetic acid. Pentose was 

 assayed in the reaction mixtures according to Mejbaum (20), hexose 

 and sedoheptulose with the sulfuric acid-cysteine reaction (21), and 

 triose-phosphate as alkali-hydrolyzable phosphate. Magnesium was 

 omitted. [After Hauge et al. (22).] 



of the CO2 produced from glucose arises via the pentose 

 cycle; in fact, A. suhoxydans is unique in this respect among 

 organisms studied to date. The active existence of the 

 pentose cycle in this organism makes more reasonable the 

 finding that the Krebs cycle appears absent. This latter 

 difference is the first clear one between A. suhoxydans and 

 related Pseudomonas species, several of which rely heavily 

 on the Entner-Doudoroff pathway for glucose breakdown 

 (24). 



Other results, summarized in Fig. 1.4, which deserve spe- 

 cial mention are the following. 



