Achieving Robustness to Confirm Controversial Hypotheses: A Case Study in Cell Biology
Recent developments in cellular microscopy provide an interesting example of the role played by what William Wimsatt calls “robustness analysis” in the establishment of experimental results. According to a commonly accepted biochemical model, clathrin-mediated endocytosis (that is, one of the main processes by which external material is internalized by the cell via the plasma membrane) takes place only if the size of the entering object does not exceed 120–150 nm. However recent studies provide evidence that invasive bacteria whose diameter is far larger than 150 nm can enter host cells in a clathrin-dependent manner. In particular, images obtained by fluorescence microscopy indicate the presence of clathrin molecules and their active role in such processes. Yet, due to the well-known risk that artifacts introduced during the preparation of the sample may influence the results obtained with this technique, the scientific community still does not deem the currently available evidence sufficient to revise the well-established and so far unchallenged model of clathrin-mediated endocytosis. The aim of ongoing research is thus to crosscheck the results of fluorescence microscopy by means of techniques involving transmission electron microscopy. The focus of this chapter will be on the methodologies adopted in a type of “correlative microscopy” combining (cryo-) fluorescence microscopy and (cryo-) electron tomography. It will be argued that real cases of robustness analysis offer, in general, a complicated pattern in which, a multiplicity of derivations are indeed combined, but their independence comes in degree and the results they yield stand with one another in a relation of partial overlap rather than identity. It will thus appear that the situation portrayed by Wimsatt’s robustness scheme is often to be regarded as an aim to be pursued through a long and stepwise process or even as a regulative ideal directing the researchers’ efforts, rather than as a readily available option in their methodological tool-box.
KeywordsTheoretical Principle Bacterial Invasion Chemical Fixation Joint Implementation Correlative Microscopy
Writing this chapter would have been impossible without the keen help of Dr. Anna Sartori Rupp of the Institut Pasteur (Paris), who has patiently introduced me to the current state of the research on endocytosis and whose suggestions have constantly guided my work. I wish also to thank Léna Soler and Hubertus Nederbragt for helping me to improve this article.
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