bacteria belonged to separate species that had heritable traits that could be passed on
stably generation after generation. To differentiate genera and species, he used their
size and shape as the primary criteria. To further distinguish them, he used their
association with, among other characters, fermentations and diseases; colony form;
pigments; and motility (Matta 2007). For the first time, physiological characters
were used in a taxonomic scheme.
Martinus Beijerinck became a student at the Landbouwschool (agricultural
school) in Wageningen, the Netherlands, and received a Ph.D. there in 1877
(Theunissen 1996) (Fig. 2.3). He studied plant galls there under the guidance of
botanist and systematist Willem F. R. Suringar. Beijerinck was attracted to the
subject by Darwin’s discussion of galls as modifications of the plant’s structure by
external agents. Darwin was interested in the possibility that the environment of an
organism could cause variations and saw galls as one possible manifestation of this
phenomenon that could be examined in detail. Beijerinck stated, “as soon as more
light is thrown on the causes of the changes which parasites bring about in the cells
that nurture them, we shall have come a step closer to the explanation of the small,
stepwise changes which, fixed by inheritance and natural selection, bring new
varieties, species etc into being.”
Beijerinck eventually became dissatisfied with the descriptive approach to botany
and took up experimental studies of plant physiology, an approach that was growing
in popularity at the time. He also took up the study of plant diseases, and this led to
his first forays into microbiology. He determined that fungal infections, like the
insect infestation with galls, activated cell growth that was normally latent in the
plant. This activation, he concluded, was the result of the action of a parasiteproduced enzyme (a newly coined term replacing “ferment”). This conclusion,
though, made him realize that this was not a process that would help answer
Darwin’s question about the cause of variability as this activation by an enzyme
would not be a heritable trait. He continued to examine variation, however, by
crossing plants. Those studies were short-lived and, in later years, he regretted
abandoning them as they might have led him to be one of the people who
rediscovered Mendel’s experiments (Theunissen 1996).
In 1885, when Beijerinck moved to Delft to work at the Nederlandsche
Gisten Spiritus Fabriek (Dutch Yeast and Spirits Factory), he embarked on serious
microbiological studies. These works, though, continued to have growth and variability themes (Theunissen 1996). The best example of this is his 1888 proof that
symbiotic microorganisms are responsible for the formation of nodules on the roots
of leguminous plants and that fixed nitrogen that was provided to the plant. Again, a
substance, likely an enzyme, was produced by the parasite that activated the growth
of plant tissue. He came to believe that microbiology could provide insights into
growth, variability, and other biological phenomena that could not be made in plants
or animals because microbes were experimentally tractable. He said in his opening
lecture at the Delft Polytechnical School in 1895:
There can be no doubt that in some bacteria changes in the external conditions of life bring
about deeper changes in the hereditary characteristics than has been observed to occur in
higher organisms, and that therefore it will be the bacteria which will provide the building
30
K. M. Noll
stably generation after generation. To differentiate genera and species, he used their
size and shape as the primary criteria. To further distinguish them, he used their
association with, among other characters, fermentations and diseases; colony form;
pigments; and motility (Matta 2007). For the first time, physiological characters
were used in a taxonomic scheme.
Martinus Beijerinck became a student at the Landbouwschool (agricultural
school) in Wageningen, the Netherlands, and received a Ph.D. there in 1877
(Theunissen 1996) (Fig. 2.3). He studied plant galls there under the guidance of
botanist and systematist Willem F. R. Suringar. Beijerinck was attracted to the
subject by Darwin’s discussion of galls as modifications of the plant’s structure by
external agents. Darwin was interested in the possibility that the environment of an
organism could cause variations and saw galls as one possible manifestation of this
phenomenon that could be examined in detail. Beijerinck stated, “as soon as more
light is thrown on the causes of the changes which parasites bring about in the cells
that nurture them, we shall have come a step closer to the explanation of the small,
stepwise changes which, fixed by inheritance and natural selection, bring new
varieties, species etc into being.”
Beijerinck eventually became dissatisfied with the descriptive approach to botany
and took up experimental studies of plant physiology, an approach that was growing
in popularity at the time. He also took up the study of plant diseases, and this led to
his first forays into microbiology. He determined that fungal infections, like the
insect infestation with galls, activated cell growth that was normally latent in the
plant. This activation, he concluded, was the result of the action of a parasiteproduced enzyme (a newly coined term replacing “ferment”). This conclusion,
though, made him realize that this was not a process that would help answer
Darwin’s question about the cause of variability as this activation by an enzyme
would not be a heritable trait. He continued to examine variation, however, by
crossing plants. Those studies were short-lived and, in later years, he regretted
abandoning them as they might have led him to be one of the people who
rediscovered Mendel’s experiments (Theunissen 1996).
In 1885, when Beijerinck moved to Delft to work at the Nederlandsche
Gisten Spiritus Fabriek (Dutch Yeast and Spirits Factory), he embarked on serious
microbiological studies. These works, though, continued to have growth and variability themes (Theunissen 1996). The best example of this is his 1888 proof that
symbiotic microorganisms are responsible for the formation of nodules on the roots
of leguminous plants and that fixed nitrogen that was provided to the plant. Again, a
substance, likely an enzyme, was produced by the parasite that activated the growth
of plant tissue. He came to believe that microbiology could provide insights into
growth, variability, and other biological phenomena that could not be made in plants
or animals because microbes were experimentally tractable. He said in his opening
lecture at the Delft Polytechnical School in 1895:
There can be no doubt that in some bacteria changes in the external conditions of life bring
about deeper changes in the hereditary characteristics than has been observed to occur in
higher organisms, and that therefore it will be the bacteria which will provide the building
30
K. M. Noll