Engineering complex communities by directed evolution

Directed evolution has been used for decades to engineer biological systems at or below the organismal level. Above the organismal level, a small number of studies have attempted to artificially select microbial ecosystems, with uneven and generally modest success. Our theoretical understanding of artificial ecosystem selection is limited, particularly for large assemblages of asexual organisms, and we know little about designing efficient methods to direct their evolution. Here, we have developed a flexible modelling framework that allows us to systematically probe any arbitrary selection strategy on any arbitrary set of communities and selected functions. By artificially selecting hundreds of in silico microbial metacommunities under identical conditions, we first show that the main breeding methods used to date, which do not necessarily let communities reach their ecological equilibrium, are outperformed by a simple screen of sufficiently mature communities. We then identify a range of alternative directed evolution strategies that, particularly when applied in combination, are well suited for the top-down engineering of large, diverse and stable microbial consortia. Our results emphasize that directed evolution allows an ecological structure-function landscape to be navigated in search of dynamically stable and ecologically resilient communities with desired quantitative attributes. A simulation study integrates existing artificial selection methods to develop a 'top-down' approach to engineering complex, stable microbial communities based on iterated randomization and selection of community structure and function

Pledging integrity:Oaths as forms of business management

The global financial crisis has led to a surprising interest in professional oaths in business. Examples are the MBA Oath (Harvard Business School), the Economist’s Oath (George DeMartino) and the Dutch Banker’s Oath, which senior executives in the financial services industry in the Netherlands have been obliged to swear since 2010. This paper is among the first to consider oaths from the perspective of business ethics. A framework is presented for analysing oaths in terms of their form, their content and the specific contribution they make to business ethics management: oaths may foster professionalism, facilitate moral deliberation and enhance compliance. This framework is used to analyse and evaluate the MBA Oath, the Economist’s Oath and the Banker’s Oath as well as various other similar initiatives