Smell is probably the oldest sense, and it’s based on a process called chemotaxis – cells sensing and responding to chemicals in their environment. These images show single-celled organisms called Dictyostelium growing on solid gel infused with a chemical called folate, which they like to ‘eat’, after one (top), three (middle) and five (bottom) hours. Initially placed on the left hand side of the gel, the cells use up the folate there, creating a gradient of the chemical from low to high, left to right. Some adventurous cells, marked in green, begin to move towards the right hand side – the bigger the circle around them, the faster they’re moving. But others go the wrong way (red) or stay in roughly the same place (blue). Understanding what’s going on here at a molecular level helps to explain how all cells – including those in our body – sniff out the world around them.
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.
BPoD is also available in Catalan at www.bpod.cat with translations by the University of Valencia.