title: Chemotaxis mediated by NarX-FrzCD chimeras and nonadapting repellent responses in Myxococcus xanthus.
abstract: Myxococcus xanthus requires gliding motility for swarming and fruiting body formation. It uses the Frz chemosensory pathway to regulate cell reversals. FrzCD is a cytoplasmic chemoreceptor required for sensing effectors for this pathway. NarX is a transmembrane sensor for nitrate from Escherichia coli. In this study, two NarX-FrzCD chimeras were constructed to investigate M. xanthus chemotaxis: NazD(F) contains the N-terminal sensory module of NarX fused to the C-terminal signalling domain of FrzCD; NazD(R) is similar except that it contains a G51R mutation in the NarX domain known to reverse the signalling output of a NarX-Tar chimera to nitrate. We report that while nitrate had no effect on the wild type, it decreased the reversal frequency of M. xanthus expressing NazD(F) and increased that of M. xanthus expressing NazD(R). These results show that directional motility in M. xanthus can be regulated independently of cellular metabolism and physiology. Surprisingly, the NazD(R) strain failed to adapt to nitrate in temporal assays as did the wild type to known repellents. The lack of temporal adaptation to negative stimuli appears to be a general feature in M. xanthus chemotaxis. Thus, the appearance of biased movements by M. xanthus in repellent gradients is likely due to the inhibition of net translocation by repellents.
authors.affiliation: Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Xu
authors.forename: Wesley P
authors.initials: WP
authors.lastname: Black
authors.forename: Emilia M F
authors.initials: EM
authors.lastname: Mauriello
authors.forename: David R
authors.initials: DR
authors.lastname: Zusman
authors.forename: Zhaomin
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016941:Myxococcus xanthus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009566:Nitrates / Q000494:pharmacology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C065626:FrzCD protein, Myxococcus xanthus; D009566:Nitrates; D011993:Recombinant Fusion Proteins; D011494:Protein Kinases; C074787:narX protein, E coli