ABSTRACT
This chapter discusses progress made in using atomic force microscope (AFM) to measure the adhesive and mechanical properties of microbial cell envelope proteins. Various force-measuring techniques are available to probe single molecules, including flow chamber experiments, microneedles, the biomembrane force probe, the optical and magnetic tweezers and AFM. An important prerequisite for successful molecular recognition experiments is to functionalize the AFM tip with ligands or receptors. To shed new light into the heparin-binding haemagglutinin adhesin (HBHA) binding forces, force curves were recorded between AFM tips modified with HBHA and model surfaces modified with heparin, used as a model sulphated glycoconjugate receptor. A His-tag was inserted to allow for specific detection with AFM tips terminated with nitrilotriacetic acid groups. Most commercial AFMs are user friendly, and reliable protocols are available for functionalizing tips and for immobilizing microbial cells. The nanoscale measurements were shown to correlate with microscale mycobacterial aggregation assays.
