Phenotypic Plasticity and Effects of Selection on Cell Division Symmetry in Escherichia coli

Aging has been demonstrated in unicellular organisms and is presumably due to asymmetric distribution of damaged proteins and other components during cell division. Whether the asymmetry-induced aging is inevitable or an adaptive and adaptable response is debated. Although asymmetric division leads to aging and death of some cells, it increases the effective growth rate of the population as shown by theoretical and empirical studies. Mathematical models predict on the other hand, that if the cells divide symmetrically, cellular aging may be delayed or absent, growth rate will be reduced but growth yield will increase at optimum repair rates. Therefore in nutritionally dilute (oligotrophic) environments, where growth yield may be more critical for survival, symmetric division may get selected. These predictions have not been empirically tested so far. We report here that Escherichia coli grown in oligotrophic environments had greater morphological and functional symmetry in cell division. Both phenotypic plasticity and genetic selection appeared to shape cell division time asymmetry but plasticity was lost on prolonged selection. Lineages selected on high nutrient concentration showed greater frequency of presumably old or dead cells. Further, there was a negative correlation between cell division time asymmetry and growth yield but there was no significant correlation between asymmetry and growth rate. The results suggest that cellular aging driven by asymmetric division may not be hardwired but shows substantial plasticity as well as evolvability in response to the nutritional environment

Creating strategic leverage : matching company strengths with market opportunities/ Lele

xviii, 327 hal. ; 24 c

Creating strategic leverage : matching company strengths with market opportunities/ Lele

xviii, 327 hal. ; 24 c

The Marketing/Manufacturing Interface: Strategic Issues

Most firms separate the marketing and manufacturing functions into distinct organizational groups without fully considering the interactions and conflicts between the two functions. These interactions can have very significant costs for the firm, if they are not recognized. We discuss situations in which strategy and policy in the two areas are not synchronized. They include issues such as capacity decisions, shift policy, and location in manufacturing; price-promotion policy, forecasting and market intelligence in marketing. These topics are discussed in the context of case examples which illustrate problems that can arise when interactions are not recognized