blocks for the erection of a theory of variability, which until now has mainly been supported
by creations of the imagination. (Beijerinck 1922 quoted in Theunissen 1996)
Beijerinck began studies on different kinds of microbes. He observed variations
occurring in Photobacterium fischeri, Lactobacillus fermentum, Chlorella, Bacillus
prodigiosus, and yeast. He thought microbes were not different from metazoans in
principle and so could provide insights into variations, and what were now called
mutations. Like Darwin’s thoughts on the influence of environments on variation, it
seemed clear to Beijerinck that the origin of the variants must in one way or another
be related to the condition of the medium in which the bacteria were grown. He
found it likely that nutritional factors or the bacteria’s own secretion products played
a role in the process (Theunissen 1996). He sought to determine the frequency of
variant formation during growth and so developed what came to be one of his major
contributions to microbiological research, selective media. He developed the technique not to isolate a single variety of a single species as we use it today. He knew
that Koch’s method of streaking plates would do that. He developed it instead to
select for all the individual variants in a species that would grow under the conditions
he created. He called this his “accumulation method.” A “perfect” accumulation
experiment, he said, would result in a culture of a single species together with all its
varieties.
Beijerinck’s view of variation was closer to that of Darwin and his gemmule
theory, though Beijerinck did not believe in gemmules, per se. The alternative
Mendelian view of his time posited that variation arose through random mutations
independent of the conditions of the organism. Beijerinck believed that the growth
conditions of microbes, as well as conditions present during the ontological development of plants and animals, somehow impacted heritable changes. He believed
that the study of microbes would reveal the laws guiding these processes. In his 1877
thesis, Beijerinck quoted Darwin: “If it were possible to expose all the individuals of
a species during many generations to absolutely uniform conditions of life, there
would be no variability” (O’Malley 2007).
Biochemical physiological traits of bacteria were examined near the turn of the
twentieth century by many investigators, but most were limited to analysis of end
products of fermentations. The chemical techniques necessary to measure cellular
reactions and intracellular contents were only then being developed and so were not
widely used. The lactic acid bacteria, because of their commercial and agricultural
importance, were among the best-studied bacteria. Sigurd Orla-Jensen was among
the leaders in these studies and proposed a “natural” classification of bacteria based
upon physiological characters in 1908 (Olsen 1950) (Fig. 2.3). He published a
proposal for a more comprehensive taxonomic scheme in 1921 in which he kept
morphological characters as a part of the system along with physiological characters (Orla-Jensen 1921). It was more “natural” in the sense that, in his opinion, it was
more logical than that proposed by the Committee of the Society of American
Bacteriologists. His background in chemical engineering is apparent in his system
as he seems to want to approach the logic of the nomenclature system adopted by
chemists for chemicals. It was not a “natural” system as usually expressed by
2 Darwin’s Science’s Impact on the Evolution of the Microbiological Sciences
31
by creations of the imagination. (Beijerinck 1922 quoted in Theunissen 1996)
Beijerinck began studies on different kinds of microbes. He observed variations
occurring in Photobacterium fischeri, Lactobacillus fermentum, Chlorella, Bacillus
prodigiosus, and yeast. He thought microbes were not different from metazoans in
principle and so could provide insights into variations, and what were now called
mutations. Like Darwin’s thoughts on the influence of environments on variation, it
seemed clear to Beijerinck that the origin of the variants must in one way or another
be related to the condition of the medium in which the bacteria were grown. He
found it likely that nutritional factors or the bacteria’s own secretion products played
a role in the process (Theunissen 1996). He sought to determine the frequency of
variant formation during growth and so developed what came to be one of his major
contributions to microbiological research, selective media. He developed the technique not to isolate a single variety of a single species as we use it today. He knew
that Koch’s method of streaking plates would do that. He developed it instead to
select for all the individual variants in a species that would grow under the conditions
he created. He called this his “accumulation method.” A “perfect” accumulation
experiment, he said, would result in a culture of a single species together with all its
varieties.
Beijerinck’s view of variation was closer to that of Darwin and his gemmule
theory, though Beijerinck did not believe in gemmules, per se. The alternative
Mendelian view of his time posited that variation arose through random mutations
independent of the conditions of the organism. Beijerinck believed that the growth
conditions of microbes, as well as conditions present during the ontological development of plants and animals, somehow impacted heritable changes. He believed
that the study of microbes would reveal the laws guiding these processes. In his 1877
thesis, Beijerinck quoted Darwin: “If it were possible to expose all the individuals of
a species during many generations to absolutely uniform conditions of life, there
would be no variability” (O’Malley 2007).
Biochemical physiological traits of bacteria were examined near the turn of the
twentieth century by many investigators, but most were limited to analysis of end
products of fermentations. The chemical techniques necessary to measure cellular
reactions and intracellular contents were only then being developed and so were not
widely used. The lactic acid bacteria, because of their commercial and agricultural
importance, were among the best-studied bacteria. Sigurd Orla-Jensen was among
the leaders in these studies and proposed a “natural” classification of bacteria based
upon physiological characters in 1908 (Olsen 1950) (Fig. 2.3). He published a
proposal for a more comprehensive taxonomic scheme in 1921 in which he kept
morphological characters as a part of the system along with physiological characters (Orla-Jensen 1921). It was more “natural” in the sense that, in his opinion, it was
more logical than that proposed by the Committee of the Society of American
Bacteriologists. His background in chemical engineering is apparent in his system
as he seems to want to approach the logic of the nomenclature system adopted by
chemists for chemicals. It was not a “natural” system as usually expressed by
2 Darwin’s Science’s Impact on the Evolution of the Microbiological Sciences
31