The overall bacterial population showed no evidence of limited rhamnolipid production��most of the hard agar-grown colony area is bright with PrhlA::gfp and produced rhamnolipid on methylene blue indicator plates. This suggests that the ability to form swarm tendrils depends highly upon localized rhamnolipid production close to the advancing edge of swarming cells. Localized effects were also observed when examining the cell density patterns at the advancing swarm edge. The phenotypes of cell distribution at the advancing edge on soft and hard agar were quite different after 40 hours. The phase image of the advancing swarm growing on soft agar showed a continuous swarm of bacterial cells. After 40 hours on hard agar, however, the swarm was not continuous but rather an assemblage of several distinct aggregates; there was no defined edge of the swarm zone. While the cell distribution patterns between agar types were dissimilar, cells were SCH 23390 hydrochloride motile on each of these surfaces. Many motile cells were observed on either soft or hard agar in real-time within these slowly advancing swarms. The localized PrhlA::gfp fluorescence and cell distribution corresponding with tendril formation was evident after many hours of growth. Tendril swarms on soft agar show increased and earlier expression of PrhlA::gfp fluorescence. Differentiation of swarm phenotypes between agar conditions manifested after Impentamine dihydrobromide roughly one day. Early on, when swarms were the same by eye, cells had spread #5 mm and cell density was identical by magnification for cells grown on both agar types; the PrhlA::gfp fluorescence was also indistinguishable for these 12 hour swarms. At 27 hours, the overall swarm pattern showed slight differences that were more apparent with magnification; at higher agar concentrations, some cells accumulated into dense aggregates. The differences in PrhlA::gfp fluorescence were more substantial at this time point as soft agar swarms showed greater and more confluent fluorescence than for cells growing on hard agar. Table 1 lists the relative intensity of the PrhlA::gfp fluorescence reporter at the swarm edge on these different surfaces over time. By 40 hours and 63 hours, both the PrhlA::gfp expression and cell density patterns were very different on soft versus hard agar. Tendril swarms on soft agar show edge populations with a dense continuous edge of swarming bacteria expressing much greater PrhlA::gfp fluorescence.