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Martin Ackermann

Publications and source records attributed to Martin Ackermann.

6 recordsLinked to original sources
PubMed2006

DNA sequences shaped by selection for stability.

The sequence of a stretch of nucleotides affects its propensity for errors during replication and expression. Are proteins encoded by stable or unstable nucleotide sequences? If selection for variability is prevalent, one could expect an excess of unstable sequences. Alternatively, if selection against targets for errors were substantial, an excess of stable sequences would be expected. We screened the genome sequences of different organisms for an important determinant of stability, the presence of mononucleotide repeats. We find that codons are used to encode proteins in a way that avoids the emergence of mononucleotide repeats, and we can attribute this bias to selection rather than a neutral process. This indicates that selection for stability, rather than for the generation of variation, substantially influences how information is encoded in the genome.

Animals↗
PubMed2005

The effect of multifunctionality on the rate of evolution in yeast.

Multifunctional genes are expected to evolve at lower rates because mutations in such genes that improve one function might often have deleterious effects on other functions. Here we tested for an association between multifunctionality and evolutionary rates in genes of Saccharomyces cerevisiae, and we find a highly significant negative correlation between the number of biological processes in which a gene is involved in and its rate of evolution. However, the magnitude of this effect is small, and the results do not support the notion that multifunctionality limits a gene's rate of evolution.

Amino Acid Substitution↗
PubMed2004

Evolution of cooperation: two for one?

How can cooperation thrive in a selfish world? Recent evolution experiments show how bacteria themselves can generate conditions that make cooperation a winning strategy. At least in the short term.

Animals↗
PubMed2004

Evolution of niche width and adaptive diversification.

Theoretical models suggest that resource competition can lead to the adaptive splitting of consumer populations into diverging lineages, that is, to adaptive diversification. In general, diversification is likely if consumers use only a narrow range of resources and thus have a small niche width. Here we use analytical and numerical methods to study the consequences for diversification if the niche width itself evolves. We found that the evolutionary outcome depends on the inherent costs or benefits of widening the niche. If widening the niche did not have costs in terms of overall resource uptake, then the consumer evolved a niche that was wide enough for disruptive selection on the niche position to vanish; adaptive diversification was no longer observed. However, if widening the niche was costly, then the niche widths remained relatively narrow, allowing for adaptive diversification in niche position. Adaptive diversification and speciation resulting from competition for a broadly distributed resource is thus likely if the niche width is fixed and relatively narrow or free to evolve but subject to costs. These results refine the conditions for adaptive diversification due to competition and formulate them in a way that might be more amenable for experimental investigations.

Adaptation, Physiological↗
PubMed2002

Effect of low- and high-virulence Yersinia enterocolitica strains on the inflammatory response of human umbilical vein endothelial cells.

Pathogenic strains of Yersinia spp. inject a set of Yop effector proteins into eukaryotic cells by using a plasmid-encoded type III secretion system. In this study, we analyzed the inflammatory response of human umbilical vein endothelial cells (HUVECs) after infection with different Yersinia enterocolitica strains. We found that both expression of intercellular adhesion molecule 1 and release of the cytokines interleukin-6 (IL-6) and IL-8 by HUVECs are downregulated in a YopP-dependent way, demonstrating that YopP plays a major role in the inflammatory response of these cells. Infection of HUVECs with several low-virulence (biotype 2, 3, and 4) and high-virulence (biotype 1B) Y. enterocolitica strains showed that biotype 1B isolates are more efficient in inhibiting the inflammatory response than low-virulence Y. enterocolitica strains and that this effect depends on the time of contact. We extended the results of Ruckdeschel et al. and found that on the basis of the presence or absence of arginine-143 of YopP (K. Ruckdeschel, K. Richter, O. Mannel, and J. Heesemann, Infect. Immun. 69:7652-7662, 2001) all the Y. enterocolitica strains used fell into two groups, which correlate with the low- and high-virulence phenotypes. In addition, we found that high-virulence strains inject more YopP into the cytosol of eukaryotic target cells than do low-virulence strains.

Amino Acid Sequence↗