6.7 Connection Between Primary and Specialized
Metabolism: Their Evolution
Pathways of central metabolism comprise the primary metabolism and produce
macromolecules such as lipids, RNA, DNA, and proteins. Precursors or building
blocks for the synthesis of specialized metabolites are also produced during primary
metabolism. The importance of primary metabolism is unquestionable; however,
cells can dispense with some genes from the core pathways due to “genetic flexibility” (Noda-García and Barona-Gómez 2013). Genetic flexibility provides alternative reactions or isoenzymes to the microorganism for adapting to a new
environmental condition and giving an adaptive robustness to metabolism. Interestingly, in Amycolatopsis and Streptomyces genomes, several genes were annotated to
encode the same biochemical function in the central carbon metabolism (Bentley
et al. 2002). The evolution and genetic functionality are essential to understand the
metabolic versatility that might be useful in biotechnology. Typically, combined
functions of genes converge into a specific flux pathway; nevertheless, this is not
enough to have a precise idea of the regulation and allostery for the product of each
gene. Knowledge of regulation and allostery will help to estimate the impact of these
genetic expansions at biochemical level. Hypothetically, cells might use these
“redundant genes” in order to gain adaptation and flexibility to changing environments. Streptomyces and Amycolatopsis possess in their genomes several of these
genetic enlargements. This characteristic might justify their ability to produce such
diversity of specialized metabolites, since these biosynthetic pathways are often
linked to central metabolism and utilize common intermediates. An interesting
example of evolution and genetic expansion is the biosynthesis of polyketide in
which the multimodular polyketide synthase produces the carbon backbones for the
polyketides from carboxylic acid subunits. This carbon assembling system seems to
have evolved from fatty acid synthases. Polyketide synthetases possess acyl carrier
proteins and highly conserved domains for ketoacyl synthase. Different hypotheses
suggest that deletions, horizontal gene transfer, and duplications of these domains
gave rise to the variety of polyketides currently known (Jenke-Kodama et al. 2005;
Ridley et al. 2008).
6.8 Extreme Streptomyces and Amycolatopsis Strains
as Source of New Specialized Metabolites
Several studies in addition to the previously described above have demonstrated the
metabolic versatility of these genera. In turn, this feature made these bacteria
important biological tools today. Streptomyces and Amycolatopsis are the genera
from which most of the antibiotics currently used in clinical were obtained. Despite
the elevated number of antibiotics produced by these bacteria, it has been predicted
206
D. Costa et al.
Metabolism: Their Evolution
Pathways of central metabolism comprise the primary metabolism and produce
macromolecules such as lipids, RNA, DNA, and proteins. Precursors or building
blocks for the synthesis of specialized metabolites are also produced during primary
metabolism. The importance of primary metabolism is unquestionable; however,
cells can dispense with some genes from the core pathways due to “genetic flexibility” (Noda-García and Barona-Gómez 2013). Genetic flexibility provides alternative reactions or isoenzymes to the microorganism for adapting to a new
environmental condition and giving an adaptive robustness to metabolism. Interestingly, in Amycolatopsis and Streptomyces genomes, several genes were annotated to
encode the same biochemical function in the central carbon metabolism (Bentley
et al. 2002). The evolution and genetic functionality are essential to understand the
metabolic versatility that might be useful in biotechnology. Typically, combined
functions of genes converge into a specific flux pathway; nevertheless, this is not
enough to have a precise idea of the regulation and allostery for the product of each
gene. Knowledge of regulation and allostery will help to estimate the impact of these
genetic expansions at biochemical level. Hypothetically, cells might use these
“redundant genes” in order to gain adaptation and flexibility to changing environments. Streptomyces and Amycolatopsis possess in their genomes several of these
genetic enlargements. This characteristic might justify their ability to produce such
diversity of specialized metabolites, since these biosynthetic pathways are often
linked to central metabolism and utilize common intermediates. An interesting
example of evolution and genetic expansion is the biosynthesis of polyketide in
which the multimodular polyketide synthase produces the carbon backbones for the
polyketides from carboxylic acid subunits. This carbon assembling system seems to
have evolved from fatty acid synthases. Polyketide synthetases possess acyl carrier
proteins and highly conserved domains for ketoacyl synthase. Different hypotheses
suggest that deletions, horizontal gene transfer, and duplications of these domains
gave rise to the variety of polyketides currently known (Jenke-Kodama et al. 2005;
Ridley et al. 2008).
6.8 Extreme Streptomyces and Amycolatopsis Strains
as Source of New Specialized Metabolites
Several studies in addition to the previously described above have demonstrated the
metabolic versatility of these genera. In turn, this feature made these bacteria
important biological tools today. Streptomyces and Amycolatopsis are the genera
from which most of the antibiotics currently used in clinical were obtained. Despite
the elevated number of antibiotics produced by these bacteria, it has been predicted
206
D. Costa et al.