145 



Beijerinck's sterling merit appears from a comparison of his 

 results with those of earlier investigators in the field of urea de- 

 composition, like van Tieghem, Miquel, von Jacksch, and Leube. It 

 is truethat especially Miquel had added a good deal to our knowledge 

 of the process in question, nevertheless the greater part of his obser- 

 vations bear an incidental character. On the contrary the prescriptions 

 given by Reijerinck for the accumulation of various urea bacteria 

 lead in many cases to reproducible results, thus offering a firm found- 

 ation for our knowledge of this group of bacteria. 



It is of no use to enter here into details regarding the various ac- 

 cumulation experiments described. In the hands of Beijerinck they 

 led to the isolation of the following species: Urococcus ureae Cohn 

 Urobacülus pasteurii Miquel, Urobacillus miquelii nov. spec, Uro- 

 bacillus leubei nov. spec, and Planosarcina ureae nov. spec. Careful 

 descriptions were given of all these species, aT^ly supported by beauti- 

 ful drawings. Special attention was given to the degree to which these 

 species differ in urea-decomposing activity; Urobacillus pasteurii, 

 which is able to decompose not less than 1 per cent urea present in its 

 medium, bears the palm in this respect. It should be realized that this 

 means vital activity in a medium containing finally about 13 per cent 

 of ammonium carbonate! Probably this is the upper limit for alkali 

 concentration tolerated by a living organism. 



Another culmination point in the publication is the discovery of 

 Planosarcina ureae, a gem of the microbe world. It is well known that 

 motile cocci are very rare, and the finding of a motile coccus-shaped 

 bacterium forming regular tetrads must, therefore, be deemed a first 

 rate discovery. But the further circumstance that this organism 

 presented the first indubitable case of formation of endospores in a 

 non-rod-shaped bacterium meant nothing short of a revolution in the 

 current views on bacterial morphology and life cycles. 



The exceptional character of Planosarcina ureae was apparently 

 heightened by a circumstance of a secondary nature. Several of 

 Beijerinck's pupils, in later years, found that the accumulation ex- 

 periment as prescribed by Beijerinck for Planosarcina ureae always 

 gave negative results. At one time attempts at its isolation were made 

 simultaneously in Delft, Amsterdam, Haarlem and Wageningen, but 

 in all cases the Planosarcina failed to appear. This has led to the 

 suspicion that the bacterium in question with its strongly abnormal 

 morphology might have to be considered as a disappearing species the 

 last representatives of which had incidentally been encountered by 

 Beijerinck. 



A few years ago, however, this view was shown to be untenable by 

 GiBSON who demonstrated the ubiquity of Sarcina ureae in soil. Gib- 

 SON used a procedure based on principles quite different from the 

 original method described by Beijerinck i). By applying Gibson's 



1) T. GiBSON, Archiv f. Mikrobiol. 6, 73, 1935. 



M. W. Beijerinck, His life and his work. 10 



