A PURE CULTURE METHOD FOR DIATOMS* 

 By Bert Cunningham 



Plate 9 



At the suggestion of Dr. G. M. Smith of the Botany Department 

 of the University of Wisconsin the writer undertook the pure culture 

 of Algae. Among others, the Diatoms proved most abundant, and 

 therefore they were selected as the subject of further work. 



Beyerinck (1890) seems to have been the first to apply the idea 

 of Koch (1882), i. e., the use of a solid media to the culture of Algae. 

 He succeeded in securing a culture of a protoccoid in a mixture of 

 gelatine and sterile pond water. Miquel (1892) was the first to 

 secure a Diatom in pure culture. He made an artificial nutrient 

 with sterile sea water and inoculated it with a couple of drops of 

 plankton material and then started cultures by fractional subdivision. 

 In 1900 Allen and Nelson used the same method but with a variation 

 of nutrient. West (1916) thought the method of Allen and Nelson 

 to be good but suggested that the materials should be poured into 

 Petrie dishes and, after a few days, the colonies should be pipetted 

 out. Richter (1903-11) secured Nitzschia palea and Navicula minus- 

 cula by the use of synthetic agar plates. His technique will be dis- 

 cussed later. Pringsheim (1912-13) used the agar method for grow- 

 ing and separating of Oscillaria and Nostoc. He mentioned the 

 occurrence of Diatoms but apparently did not follow them up. 



Returning now to the technique of Richter. This is given in his 

 Zur Physiologie der Diatomeen, published in 1909. In 1906 he started 

 a culture of Diatoms with Fucus serratus and placed them in an 

 atmosphere of hydrogen-sulfid. This reagent killed the bacteria but 

 seemed to have no serious effect upon the Diatoms. This had been 

 previously shown by Molisch. The Diatoms secured in this man- 

 ner were colorless and identified as Nitzschia putrida Benecke. Later, 

 in 1906, he secured pure cultures by dipping a tube in raw cultures, 

 holding it for a minute and then dipping it into sterile sea water. 

 The cultures secured in this way were placed on agar plates. At 

 this time he used also another method. A small piece of agar was 

 suspended in sterile sea water which had been inoculated with a few 

 drops of plankton material. In the course of a few days the diatoms 

 had reached the agar and attached themselves to it. Practically 



♦Presented at the Botany Seminar., Univ. Wis., Feb. 1920. 

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