Chapter 51 



Studies on the Ecology of a 

 Marine Spirillum in the Chemostat 



HOLGER W. JaNNASCH 



D 



ynamic phenomena of turnover processes in the sea are 

 closely connected with the dynamic nature of growth of the 

 organisms involved. In the present paper, kinetic studies of bac- 

 terial growth under conditions approaching those of the marine 

 environment were made, and the results suggested to be quanti- 

 tatively comparable to bacterial activities in the sea. 



Because of technical difficulties, little is known about the 

 growth of bacteria in extremely dilute media like seawater. In 

 some earlier studies, glucose and peptone were found to become 

 growth limiting below concentrations ranging from 0.1 to 10 mg/ 

 L (1, 2, 15). More recently, "threshold" concentrations of differ- 

 ent nitrogen sources for growth of bacteria ranging from 0.001 to 

 0.5 mg/L were obtained by Jannasch (8). In all those studies, 

 however, the quantitative data cannot be expected to represent 

 absolute requirements, but depend on the varying growth con- 

 ditions in batch culture and on the particular criteria of growth. 

 Recently, the advantages of the continuous culture technique for 

 the study of growth relationships have been demonstrated and 

 discussed in several papers. Its application in microbial ecology 

 seems most promising. 



In the chemostat (11) or bactogen (10) one nutrient is, in 

 principle, growth limiting. A continuous flow of medium through 

 the culture vessel results in a self-adjusting steady state in which 

 the dilution rate is equal to the growth rate; conditions of growth 

 being kept constant. This principle allows separate adjustment of 

 two factors at will: the concentration of the growth-limiting sub- 

 strate in the inflowing medium (Su) which detennines the popu- 

 lation density, and the dilution rate (D) which determines the 



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