So this isn’t really a strictly science blog, and I’m on somewhat of a blogging hiatus. But I was completely fascinated by this recent article in Microbe magazine. (The original research article from Nature Chemical Biology is linked here.) It questions the term “quorum sensing”, which generally refers to the phenomenon of a bacterial species altering its gene expression profile when the local population reaches a critical density, or quorum. This process is mediated by small freely-diffusible signaling molecules synthesized by the individual bacteria; thus, a rise in bacterial culture density also relates to an increase in signal density. When the signaling molecules become abundant enough, the bacteria turn on a cascade of genes. In pathogenic bacteria, these genes are often associated with virulence, and quorum signaling has therefore been viewed as a possible way in which pathogenic bacteria “know” when to attack inside the human host.
Jeffrey Brinker and his collaborators at Sandia National Laboratory in Albuquerque, N.M. are now attempting to turn this idea on its head. This attack on the paradigm is based on the finding that an individual Staphylococcus aureus bacterium can sense and respond to its own signaling molecules, shifting its gene expression profile “from benign to virulent”, without the assistance of neighboring bacteria. As cool as this is, the way in which his group has gone about looking at this problem is even cooler. Brinker’s group has developed a method for isolating single bacterial cells within silica nanospheres. From the Microbe article:
An S. aureus cell “builds it own isolation chamber from lipids and soluble silicon dioxide precursors in an evaporating droplet [and then] becomes incorporated with nutrients in an endosomal-like compartment surrounded by a lipid/silica nanostructure,” Brinker says. “This construct ensures that each cell is isolated physically and chemically from other cells, while the nanostructured matrix keeps the cells from drying out. Within this confined environment, the increasing concentration of signaling molecules [induces] genetic reprogramming.”
Pretty freakin’ cool s#!t if you ask me. The best part – microbiologists can now use this novel technology to find out how bacteria carry out many of their physiological processes at the single cell level…a difficult feat indeed when you have an unruly organism that doubles 3 times an hour and can’t stop talking with its neighbors during experiments.
Don’t you just love science?!?