writing articles about the appearance and evolution of photosynthesis, nitrogen
fixation, and respiration (Broda 1970, 1975a, b; Broda and Peschek 1979).
In parallel with traditional microbial physiology and biochemistry research, the
field of molecular biology was born and flourished along with the “Golden Age” of
bacterial genetics. Neither of these fields seemed to bother with examining how
evolution played any role in their respective research topics, but this is perhaps
understandable given the state of efforts to determine natural relations among
bacteria. In their training, these researchers would not have been exposed to any
bacterial evolution research since it was floundering at that time. Contrary to
Woese’s suggestion (Woese 1994), those studying microbial physiology still did take
an organismal view of their research and sought to relate the biochemical physiology
of their research subjects with their roles in nature. Relating their findings to the
evolution of their subjects had been shown to be a fruitless effort and not amenable
to experimental verification. In regard to those who attempted to study bacterial evolution, to paraphrase Ralph Wolfe who studied the physiology of methanogens, “the
heat of the [evolutionary] arguments was inversely proportional to the soundness of
the data,” and so not worth pursuing.
During these years, two apparently unrelated streams of research were appearing
that would go on to have a major impact on the resurgence of interest in microbial
evolution later. First, technological advances allowed for the sequencing of the amino
acids in proteins. These studies were done as part of efforts to examine the structure
and function of proteins. Sequences of hemoglobins, insulin, and cytochromes c
appeared in the literature.
Cytochrome c was of particular use in recognizing evolutionary relationships
since it was the most widely distributed of these proteins, found from vertebrates to
bacteria. At first, only the amino acid composition of horse heart and yeast cytochromes c was determined and comparison of those compositions was found to be
very similar, and this was thought to perhaps have evolutionary significance
(Nunnikhoven 1958). Later full amino acid sequences of cytochromes c were
determined, and the first of such publications to suggest that this information
could be of use to address evolutionary questions was published by Emanuel
Margoliash (Margoliash 1963). He used sequences of cytochromes c from horse,
man, pig, rabbit, chicken, tuna, and yeast, the most extensive collection yet assembled. He realized that the sequence similarities of these proteins must be the result of
evolution from a common primordial cytochrome c and that convergent evolution
was improbable. He stated that they were homologous in the evolutionary sense.
Sounding like Darwin, he wrote, “If, as seems likely, this conclusion can be
extended to a large variety of vertebrate and invertebrate species, as well as to the
plant kingdom, strong support would be obtained for the speculation that living
matter was effectively formed only once, within the confines of our planet, all living
forms deriving from a common precursor.” Although he did not attempt to draw any
sort of evolutionary tree, he was aware that such relationships could be derived from
these data. He said, “It should be noted that the present results are compatible only
with the commonly accepted scheme of evolution represented by series of branching
lines, and are not consistent with a simultaneous formation of all species, which then
2 Darwin’s Science’s Impact on the Evolution of the Microbiological Sciences
37
fixation, and respiration (Broda 1970, 1975a, b; Broda and Peschek 1979).
In parallel with traditional microbial physiology and biochemistry research, the
field of molecular biology was born and flourished along with the “Golden Age” of
bacterial genetics. Neither of these fields seemed to bother with examining how
evolution played any role in their respective research topics, but this is perhaps
understandable given the state of efforts to determine natural relations among
bacteria. In their training, these researchers would not have been exposed to any
bacterial evolution research since it was floundering at that time. Contrary to
Woese’s suggestion (Woese 1994), those studying microbial physiology still did take
an organismal view of their research and sought to relate the biochemical physiology
of their research subjects with their roles in nature. Relating their findings to the
evolution of their subjects had been shown to be a fruitless effort and not amenable
to experimental verification. In regard to those who attempted to study bacterial evolution, to paraphrase Ralph Wolfe who studied the physiology of methanogens, “the
heat of the [evolutionary] arguments was inversely proportional to the soundness of
the data,” and so not worth pursuing.
During these years, two apparently unrelated streams of research were appearing
that would go on to have a major impact on the resurgence of interest in microbial
evolution later. First, technological advances allowed for the sequencing of the amino
acids in proteins. These studies were done as part of efforts to examine the structure
and function of proteins. Sequences of hemoglobins, insulin, and cytochromes c
appeared in the literature.
Cytochrome c was of particular use in recognizing evolutionary relationships
since it was the most widely distributed of these proteins, found from vertebrates to
bacteria. At first, only the amino acid composition of horse heart and yeast cytochromes c was determined and comparison of those compositions was found to be
very similar, and this was thought to perhaps have evolutionary significance
(Nunnikhoven 1958). Later full amino acid sequences of cytochromes c were
determined, and the first of such publications to suggest that this information
could be of use to address evolutionary questions was published by Emanuel
Margoliash (Margoliash 1963). He used sequences of cytochromes c from horse,
man, pig, rabbit, chicken, tuna, and yeast, the most extensive collection yet assembled. He realized that the sequence similarities of these proteins must be the result of
evolution from a common primordial cytochrome c and that convergent evolution
was improbable. He stated that they were homologous in the evolutionary sense.
Sounding like Darwin, he wrote, “If, as seems likely, this conclusion can be
extended to a large variety of vertebrate and invertebrate species, as well as to the
plant kingdom, strong support would be obtained for the speculation that living
matter was effectively formed only once, within the confines of our planet, all living
forms deriving from a common precursor.” Although he did not attempt to draw any
sort of evolutionary tree, he was aware that such relationships could be derived from
these data. He said, “It should be noted that the present results are compatible only
with the commonly accepted scheme of evolution represented by series of branching
lines, and are not consistent with a simultaneous formation of all species, which then
2 Darwin’s Science’s Impact on the Evolution of the Microbiological Sciences
37