Occasionally, we mention a review article that we think should be called to your attention. We initiated this with a stirring piece on bacterial shape by Kevin Young; this was followed by tantalizing observations by Steven Projan on genome size and antibiotic resistance. Now we wish to highlight a review by J. A. Granick and D. K. Newman called Extracellular Respiration.
The title refers to the procurement of energy from extracellular substrates by microbes.
Energy sources used include not only nearly insoluble minerals such as iron and manganese oxides but also, surprisingly, soluble materials such as DMSO (dimethyl sulfoxide) and humic acids. This article discusses details of the microbiology and biochemistry involved in these processes and also considers the ecological implications of extracellular respiration, e.g., the spatial connection between cells and substrate, electron transfer within and between species by electrically conductive nanowires.
So, the old saying that bacteria eat rocks is literally true.