The influence of cultivation methods on Shewanella oneidensis physiology and proteome expression

High-throughput analyses that are central to microbial systems biology and ecophysiology research benefit from highly homogeneous and physiologically well-defined cell cultures. While attention has focused on the technical variation associated with high-throughput technologies, biological variation introduced as a function of cell cultivation methods has been largely overlooked. This study evaluated the impact of cultivation methods, controlled batch or continuous culture in bioreactors versus shake flasks, on the reproducibility of global proteome measurements in Shewanellaoneidensis MR-1. Variability in dissolved oxygen concentration and consumption rate, metabolite profiles, and proteome was greater in shake flask than controlled batch or chemostat cultures. Proteins indicative of suboxic and anaerobic growth (e.g., fumarate reductase and decaheme c-type cytochromes) were more abundant in cells from shake flasks compared to bioreactor cultures, a finding consistent with data demonstrating that “aerobic” flask cultures were O2 deficient due to poor mass transfer kinetics. The work described herein establishes the necessity of controlled cultivation for ensuring highly reproducible and homogenous microbial cultures. By decreasing cell to cell variability, higher quality samples will allow for the interpretive accuracy necessary for drawing conclusions relevant to microbial systems biology research

In search of experimental evidence for the biogeobattery

Recent work has suggested that the electrical self-potential (SP) geophysical technique may be used to non-invasively map redox conditions associated with contaminant plumes or bioremediation schemes. The proposed mechanism linking SP response and redox involves the generation of a current source and sink in the subsurface whereby electrons are transferred between anoxic and oxic environments via a conductive biofilm and/or biominerals, creating a biogeobattery. Here, we seek direct experimental evidence for the biogeobattery hypothesis, which has so far remained elusive, using a flow-through column experimental set-up specifically designed for this purpose. We successfully created contrasting redox zones, with an oxic section containing clean sand transitioning into an Fe(III)-reducing section. In experiments, Fe(III)-reduction was mediated both by a natural microbial community and by a pure culture of the model organism Shewanella oneidensis MR-1 in two separate column experiments. Visual observations and electron microscopy showed that ferrihydrite was sequentially transformed to goethite and magnetite; despite this, no SP signal was generated in either column. Electron microscopy suggested that in the pure culture column, S. oneidensis MR-1 cells did not form a continuous, interconnected biofilm but rather interacted with the iron (oxyhydr)oxide surfaces as individual cells. We thus conclude that (i) there is still no unambiguous direct proof of the biogeobattery hypothesis and (ii) development of Fe(III)-reducing conditions does not necessarily lead to SP signal generation. Overall, this study shows that key redox variations are not necessarily accompanied by a large SP response, suggesting that SP cannot be used in isolation to monitor subsurface biogeochemical conditions

A critical review of executive coaching research: a decade of progress and what's to come.

This paper aims to summarise the current state of coaching research and to provide a basis for future research which will provide a frame of reference ensuring that research builds on previous studies and adds to knowledge rather than replicating previous findings in innocence. This approach will prevent wasted effort and resources in organisations and research. The paper is divided into three sections. The first two sections review the state of research over the past hundred years, with a greater focus on the past decade when coaching research has accelerated at warp speed. The paper divides the recent research into categories; the nature of coaching, coach behaviour studies, client behaviour studies, relationship studies and executive coaching impact studies. The third section considers the future direction research may take. It identifies key questions which the authors believe should be the focus of future research and highlights the work undertaken to support coaching researchers and published by the Coaching Foundation