Recent progress in colloid physics has led to fundamental understanding of so-called `patchy' colloids which undergo highly directional interactions with well-defined spots on their surface. These advances revealed novel phenomena and possibilities, such as designing colloidal crystal structures that are unavailable for conventional colloids with homogeneous surfaces. Interestingly, bacteria are patchy as well. Their surface heterogeneity is caused by a variety of exposed moieties expressed by the bacterium, some of which are major causes of pathogenicity. The vast majority of bacteria live in the colloidal domain, with sizes in the range of 0.2-2 micron. However, the physics of bacterial patchiness is not well understood. Building on the applicant's experience, we propose a combined experimental and simulation program to study the physics of patchy bacteria from the point of view of colloid physics. Firstly, we will attempt to characterise patchy interactions experimentally by sticking synthetic colloids to bacteria and study their role in the adhesion and collective behaviour on surfaces with confocal microscopy, particle tracking and electric fields. Secondly, we plan to simulate the self-assembly of patchy bacteria and compare with the experiments. Besides generating fundamental understanding, the outcome of our work should provide new insights for a diversity of biomedical applications, from new drugs and drug delivery protocols and combating biofilms, through new probiotic foods where beneficial bacteria are delivered to currently `hard to reach' gut targets, to lab-on-a-chip applications where bacteria are used to carry out specific tasks e.g. transporting colloidal `cargos'. The programme will allow the applicant to use all the skills he has acquired so far in a new context, and to gain hands-on experience in the fast-moving new field of `active soft matter physics' in one of the top European labs working in this area in experiments, theory and simulation.
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