After point inoculation of Proteus mirabilis on the surface of 0.5% nutrient agar medium, the short rod-shaped (1 to 2 µ m long) peritrichous organism (bacteria with randomly dispersed flagella over the cell surface) differentiated into filamentous (10 to 100 µ m long) multinucleated hyperflagellated cells having 50-fold more flagella (not visible in this optical microscopic image) per unit of cell surface and exerted flagellum-dependent surface spreading growth (swarming). However, at the spreading front, there were no bacteria that were moving singly. The elongated bacteria were gathering for collaborative migration to a new surface environment. They seemed to advance as one (e.g., 10 elongated cells were moving together in the first scene of this video). Occasionally some cells were left out from the migrating group; these single cells were unable to move independently. Thus, mutual sliding of elongated cells seemed to generate unified forward migration of the bacterial cluster on surface environments. Similar collaborative swarming has been observed with other bacterial species such as Serratia marcescens . The mechanism of such dynamic collaboration remains to be determined.
Figure 1: Video: Collaborative Surface Migration of Bacteria
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