4 research outputs found
Global Rebalancing of Cellular Resources by Pleiotropic Point Mutations Illustrates a Multi-scale Mechanism of Adaptive Evolution
Pleiotropic regulatory mutations affect diverse cellular processes, posing a challenge to our understanding of genotype-phenotype relationships across multiple biological scales. Adaptive Laboratory Evolution (ALE) allows for such mutations to be found and characterized in the context of clear selection pressures. Here, several ALE-selected single-mutation variants in Escherichia coli's RNA polymerase (RNAP) are detailed using an integrated multi-scale experimental and computational approach. While these mutations increase cellular growth rates in steady environments, they reduce tolerance to stress and environmental fluctuations. We detail structural changes in the RNAP that rewire the transcriptional machinery to rebalance proteome and energy allocation towards growth and away from several hedging and stress functions. We find that while these mutations occur in diverse locations in the RNAP, they share a common adaptive mechanism. In turn, these findings highlight the resource allocation tradeoffs organisms face and suggest how the structure of the regulatory network enhances evolvability
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Model-driven discovery of underground metabolic functions in <i>Escherichia coli</i>
Enzyme promiscuity toward substrates has been discussed in evolutionary terms as providing the flexibility to adapt to novel environments. In the present work, we describe an approach toward exploring such enzyme promiscuity in the space of a metabolic network. This approach leverages genome-scale models, which have been widely used for predicting growth phenotypes in various environments or following a genetic perturbation; however, these predictions occasionally fail. Failed predictions of gene essentiality offer an opportunity for targeting biological discovery, suggesting the presence of unknown underground pathways stemming from enzymatic cross-reactivity. We demonstrate a workflow that couples constraint-based modeling and bioinformatic tools with KO strain analysis and adaptive laboratory evolution for the purpose of predicting promiscuity at the genome scale. Three cases of genes that are incorrectly predicted as essential in Escherichia coliāaspC, argD, and gltAāare examined, and isozyme functions are uncovered for each to a different extent. Seven isozyme functions based on genetic and transcriptional evidence are suggested between the genes aspC and tyrB, argD and astC, gabT and puuE, and gltA and prpC. This study demonstrates how a targeted model-driven approach to discovery can systematically fill knowledge gaps, characterize underground metabolism, and elucidate regulatory mechanisms of adaptation in response to gene KO perturbations
Intestinal Anti-inflammatory Effects of Oligosaccharides Derived from Lactulose in the Trinitrobenzenesulfonic Acid Model of Rat Colitis
Intestinal microbiota modulation
is becoming an interesting approach
to manage inflammatory bowel disease and can be achieved by the administration
of prebiotics. Previous studies showed the intestinal anti-inflammatory
effects of the prebiotic lactulose. The aim of the present study was
to test the preventative effects of oligosaccharides derived from
lactulose with prebiotic properties (OsLu) in the trinitrobenzenesulfonic
acid model of rat colitis and compare them with those of lactulose.
Both treatments modified bacterial profile in intestinal contents,
increasing the bifidobacteria and lactobacilli counts and up-regulating
the production of short-chain fatty acids, although OsLu generated
a larger amount. OsLu also inhibited to a greater extent different
pro-inflammatory markers such as interleukins (IL) 1, 6, 12, and 23
and chemokines (MCP-1 and CINC-1). However, both prebiotics equally
restored colonic epithelial integrity, evaluated both with a histological
score (OsLu, 9.8 Ā± 2.2; and lactulose, 12.1 Ā± 2.1, vs colitic
control, 27.3 Ā± 3.3) and by measuring several key proteins of
the mucosal barrier (MUC-2, MUC-3, and TTF-3). OsLu effect was also
associated with an inhibition of iNOS expression and a reduction of
Th17 cell activity in the inflamed tissue that facilitated the intestinal
mucosa barrier recovery. In conclusion, OsLu showed a better anti-inflammatory
profile than lactulose in this model of experimental colitis