Chapter 6 



Cultivation and Properties of 

 Thiovulum majus Hinze* 



J. W. M. La Riviere 



Xhe study of the physiology of the colorless sulfur bacteria has 

 been seriously hampered by the technical difficulties involved 

 in their isolation and cultivation, Thiobacillus (19) being the one 

 outstanding exception. Consequently their role as chemo-auto- 

 trophs and as participants in the sulfur cycle is far from satis- 

 factorily defined and needs further investigation; this should be 

 rewarding also from a comparative point of view because of the 

 close morphological relationships between this group and some 

 organisms known to be heterotrophic or photosyntlietic ( 15, 18 ) . 



Chemo-autotrophy has been fimily established for Thiobacil- 

 lus species, and claimed for Beggiatoa and Thiothrix (2, 9), 

 though this has never been confirmed. The isolation of hetero- 

 trophic Beggiatoa strains by various workers {cf. 6) has cast 

 doubt on the validity of the earlier claims. 



From ecological observations and culture experiments it 

 seems probable, however, that many of the larger colorless sulfur 

 bacteria require both H^S and O2 in low concentrations. As a 

 result conventionally prepared media, initially satisfactory for 

 growth, rapidly become inadequate through auto-oxidation and 

 microbial oxidation of the sulfide. Available evidence also indi- 

 cates, that in contrast to Thiobacillus, they cannot use thiosulfate 

 as oxidizable substrate. Hence their cultivation calls for special 

 techniques, aimed at maintaining the requisite H-S and Oj con- 

 centrations. This is more easily accomplished by the use of liquid 

 than of solid media, with the consequence that one must resort to 

 washing and dilution procedures for their isolation. Such methods 



* This work was carried out in part under a fellowship from the Rockefeller 

 Foundation. 



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