selective regimes (Rabbers et al. 2015). An example of this can be found in studies of
the influence of environments that select for growth rate vs growth yield, an old area
of study in microbiology, that use the new cultivation technique of oil emulsions
coupled with genomic analyses (Bachmann et al. 2013).
Gene and genomic sequence comparisons have demonstrated the important role
of horizontal gene transfer (HGT) in the evolution of bacteria and archaea. Despite
this, there have been relatively few examinations of the impact of HGT of chromosomal genes on population evolution during laboratory evolution experiments.
Experiments conducted with E. coli by mixing cells capable of transferring chromosomal genes by conjugation with recipient cells that were sterile showed that the
latter strains showed mixed benefits from recombination of donated genes. In some
situations recombination allowed more rapid acquisition of beneficial traits, but in
others no benefit or even deleterious effects were noted upon incorporation of
foreign DNA (Chu et al. 2018; Maddamsetti and Lenski 2018). Mixed cultures of
donors of chromosomal genes and recipients naturally competent for DNA uptake
need to be cultivated for long periods to examine the potential impact of HGT on the
evolution of strains. It is not known if this time frame is short enough to allow
laboratory examinations of this phenomenon. This area is largely unexplored at
this time.
Bacteria provide the means to examine principles of evolution, some of which
Darwin anticipated, at a level of detail that cannot be achieved with macroorganisms.
Their short generation times, the ability to control their cultivation conditions, the
availability of an extensive database of genome sequences, and the ability to
preserve in a viable state ancestral generations of cells all provide the potential to
gain undreamed of insights into the processes behind the evolution of life. A recent
review provides useful links to past studies as well as speculations about future
directions for this research (Rainey et al. 2017). In general, laboratory evolution
provides a robust means of examining many aspects of Darwin’s central theory,
Natural Selection (Cooper 2018; Lenski 2017).
2.10 Concluding Thoughts
As microbiology evolved as a discipline in the middle to late nineteenth century,
only a limited number of practitioners were trained to address evolutionary questions. Traditional evolution studies were done by those with training in zoology or
botany, largely in academic settings or by natural historians with sufficient independent means to support their studies. Microbiological studies arose along two separate
lines. Pasteur’s work gave rise to studies of the application of microbes in fermentation industries, and this later branched into agricultural applications. Those who
developed these lines of investigation usually had a background in botany and so
brought some knowledge of evolutionary theories to their work. Interest in disease
transmission at that time led to the elucidation of the “germ theory” of disease and
medical microbiology. Scientists in this line of investigation usually came without
2 Darwin’s Science’s Impact on the Evolution of the Microbiological Sciences
49
the influence of environments that select for growth rate vs growth yield, an old area
of study in microbiology, that use the new cultivation technique of oil emulsions
coupled with genomic analyses (Bachmann et al. 2013).
Gene and genomic sequence comparisons have demonstrated the important role
of horizontal gene transfer (HGT) in the evolution of bacteria and archaea. Despite
this, there have been relatively few examinations of the impact of HGT of chromosomal genes on population evolution during laboratory evolution experiments.
Experiments conducted with E. coli by mixing cells capable of transferring chromosomal genes by conjugation with recipient cells that were sterile showed that the
latter strains showed mixed benefits from recombination of donated genes. In some
situations recombination allowed more rapid acquisition of beneficial traits, but in
others no benefit or even deleterious effects were noted upon incorporation of
foreign DNA (Chu et al. 2018; Maddamsetti and Lenski 2018). Mixed cultures of
donors of chromosomal genes and recipients naturally competent for DNA uptake
need to be cultivated for long periods to examine the potential impact of HGT on the
evolution of strains. It is not known if this time frame is short enough to allow
laboratory examinations of this phenomenon. This area is largely unexplored at
this time.
Bacteria provide the means to examine principles of evolution, some of which
Darwin anticipated, at a level of detail that cannot be achieved with macroorganisms.
Their short generation times, the ability to control their cultivation conditions, the
availability of an extensive database of genome sequences, and the ability to
preserve in a viable state ancestral generations of cells all provide the potential to
gain undreamed of insights into the processes behind the evolution of life. A recent
review provides useful links to past studies as well as speculations about future
directions for this research (Rainey et al. 2017). In general, laboratory evolution
provides a robust means of examining many aspects of Darwin’s central theory,
Natural Selection (Cooper 2018; Lenski 2017).
2.10 Concluding Thoughts
As microbiology evolved as a discipline in the middle to late nineteenth century,
only a limited number of practitioners were trained to address evolutionary questions. Traditional evolution studies were done by those with training in zoology or
botany, largely in academic settings or by natural historians with sufficient independent means to support their studies. Microbiological studies arose along two separate
lines. Pasteur’s work gave rise to studies of the application of microbes in fermentation industries, and this later branched into agricultural applications. Those who
developed these lines of investigation usually had a background in botany and so
brought some knowledge of evolutionary theories to their work. Interest in disease
transmission at that time led to the elucidation of the “germ theory” of disease and
medical microbiology. Scientists in this line of investigation usually came without
2 Darwin’s Science’s Impact on the Evolution of the Microbiological Sciences
49