Chapter 54 



Notes on the Natural History of 

 Rhodopseudomonas palustris 



Stanley Scher, Barbara Scher and S. H. Hutner 



F 



rom van Niel's (11) classical studies it is known that no speci- 

 fic substrate selects witli certainty any of the five facultative 

 aerobic species of Athiorhodaceae ( purple nonsulf ur photosynthe- 

 tic bacteria ) . Each species had a different set of vitamin require- 

 ments (2); R. palustris was set off from the others by requiring 

 p-aminobenzoic acid (PABA). The findings that many, perhaps 

 most, fresh water and marine phytoplankton organisms require 

 vitamin B12, thiamine and biotin (in decreasing order of frequen- 

 cy) (6) emphasized the seemingly unique PABA auxotrophy of 

 R. palustris among photosynthetic organisms. 



The present paper describes details of the enrichment and 

 isolation procedure for obtaining benzoic acid-utilizing strains, 

 and growth and manometric studies with such strains. We also 

 outline some observations on the appearance of a vitamin B12 

 requirement for growth at supra-optimal temperature. 



MATERIALS AND METHODS 



Enrichment and Isolation 



Purple bacteria utilizing aromatic substrates for anaerobic 

 growth were isolated from soil or mud collected from fresh-water 

 streams or marine intertidal flats along the northern California 

 coast. Table 1 gives the medium used. Purple bacteria developed 

 in anaerobic bottle cultures in light at room temperature. At pH 

 7.2-7.4 growth was proportional to benzoate concentration with 

 the range 1-100 mg per 100 ml culture medium. Pure cultures 



* Aided by grants from the American Cancer Society and the National Aeronautics 

 and Space Administration. 



580 



