As long as researchers have been growing bacteria on Petri dishes using a jelly-like growth medium called agar, they have been struck by the interesting colors and growth patterns that microbes can produce from one experiment to the next. In the 1920s, Sir Alexander Fleming, the Scottish biologist who discovered penicillin, was so taken by this phenomenon that he developed his own palette of bacterial “paints” that he used in his spare time to create colorful pictures of houses, ballerinas, and other figures on the agar .
Fleming’s enthusiasm for agar art lives on among the current generation of microbiologists. In this short video, the agar (yellow) is seeded with bacterial colonies and, through the magic of time-lapse photography, you can see the growth of the colonies into what appears to be a lovely bouquet of delicate flowers. This piece of living art, developing naturally by bacterial colony expansion over the course of a week or two, features members of three bacterial genera: Serratia (red), Bacillus (white), and Nesterenkonia (light yellow).
Caption: Insulin-containing pancreatic beta cells (green) derived from human stem cells. The red cells are producing another metabolic hormone, glucagon, that regulates blood glucose levels. Blue indicates cell nuclei. Credit: The Salk Institute for Biological Studies, La Jolla, CA
In people with type 1 diabetes, the immune system kills off insulin-producing beta cells of the pancreas needed to control the amount of glucose in their bloodstream. As a result, they must monitor their blood glucose often and take replacement doses of insulin to keep it under control. Transplantation of donated pancreatic islets—tissue that contains beta cells—holds some promise as a therapy or even a cure for type 1 diabetes. However, such donor islets are in notoriously short supply . Recent advances in stem cell research have raised hopes of one day generating an essentially unlimited supply of replacement beta cells perfectly matched to the patient to avoid transplant rejection.
A couple of years ago, researchers took a major step toward this goal by coaxing induced pluripotent stem cells (iPSCs), which are made from mature human cells, to differentiate into cells that closely resembled beta cells. But a few things were troublesome. The process was long and difficult, and the iPSC-derived cells were not quite as good at sensing glucose and secreting insulin as cells in a healthy person. They also looked and, in some ways, acted like beta cells, but were unable to mature fully in the lab. Now, an NIH-funded team has succeeded in finding an additional switch that enables iPSC-derived beta cells to mature and produce insulin in a dish—a significant step toward moving this work closer to the clinical applications that many diabetics have wanted.