AGGREGATION IN ACTION: Dale Kaiser and Jerry Kuner’s panel of six electron micrographs shows aggregation and the formation of a fruiting body by Myxococcus xanthus strain DK 1622 cells. The researchers starved these bacteria of nutrients over the course of 72 hours by replacing a liquid growth medium with distilled water. With the addition of a calcium chloride solution, bacteria kept at a constant pH (6.8) aggregated and then formed a fruiting body—a cluster of cells that would later be filled with spores. The resulting time-lapse micrographs remain some of the clearest pictures of fruiting body formation in this gram-negative bacterium.J BACTERIOL, 151:458-61, 1982Starting in the late 1970s, Stanford University’s Dale Kaiser worked for years to visualize a certain bacterial phenomenon. Microbiologists had known that, when starved, some soil-dwelling myxobacteria aggregate, forming so-called fruiting bodies full of hardy spores. Yet capturing this behavior in action, Kaiser found, was a challenge.
Working with a strain of Myxococcus xanthus, Kaiser and his then graduate student Jerry Kuner had the idea that perhaps the medium was holding them back. They decided to abandon traditional, solid agar—which often contained impurities, compromising starvation and fouling imaging studies—and opted instead to culture the cells in a defined liquid medium.
The team at first grew M. xanthus cells in a minimally nutritive liquid medium Kaiser and another colleague described in February 1978, called CTT. Overnight, the cells formed a film at the bottom of the dish, so adherent that the researchers could replace the liquid medium with water without disturbing the bacteria, effectively starving the cells, which then aggregated and formed fruiting bodies.
Culturing a less adherent mutant strain of M. xanthus ...
