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FliL is essential for swarming: motor rotation in absence of FliL fractures the flagellar rod in swarmer cells of Salmonella enterica
Author(s) -
Attmannspacher Ursula,
Scharf Birgit E.,
Harshey Rasika M.
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06170.x
Subject(s) - salmonella enterica , swarming (honey bee) , biology , flagellum , mutant , caulobacter crescentus , microbiology and biotechnology , operon , escherichia coli , gene , genetics , bacterial protein
Summary fliL is the first gene in a flagellar operon that specifies members of the switch complex and type III export system in Salmonella enterica and Escherichia coli , but no function has been ascribed to this gene thus far. Here we report that a fliL mutant is slightly impaired for swimming but completely defective in swarming in both organisms, and have studied this phenotype further in S. enterica . We have found that on swarm agar, mutant cells release or ‘eject’ their flagellar filaments. The released filaments are attached to the hook and part of the rod structure; we have identified the distal rod protein FlgG but not the proximal rod protein FlgF in these filaments. Rod fracture was not observed if flagellar rotation was prevented by removal of proteins that supply proton flow through the motor. Based on these and other results, we propose that motors experience a higher torque on swarm agar owing to an increased proton motive force, and that FliL allows the rod to withstand the increased torsional stress. The flagella‐release phenotype of the S. enterica fliL mutant has a bearing on FliL‐dependent flagellar ejection during the swimmer‐ to stalk‐cell transition in the developmental cycle of Caulobacter crescentus .