The focus of our research is to determine how signal transduction regulates directed motility and behavior in the bacterium Myxococcus xanthus using an integrated approach that combines biochemistry, genetics, and cell biology. M. xanthus is an excellent model system to address fundamental questions concerning cell-cell signaling and directed movement as cells form multicellular biofilms and fruiting bodies as part of a complex life cycle. M. xanthus fruiting bodies are similar in many ways to biofilms formed by some pathogenic bacteria and are of public health interest since biofilms render bacteria resistant to antibiotics and are very difficult to treat in patients. Biofilm and fruiting body formation require the activity of chemosensory systems to direct cell movements. Previously, we have shown that the Frz chemosensory pathway regulates both vegetative swarming and developmental aggregation by controlling the reversal frequency of cells. Cell reversals in Myxococcus, like tumbling in flagellated bacteria, allows cells to reorient themselves and to bias directional motility based on the temporal sensing of stimuli. In the last grant period, our studie of the Frz system have allowed us to identify important proteins responsible for the functioning of the gliding motility engines. Our first specific aim is to continue our characterization of the dynamics of the motor protein AglR, a MotA homolog, at single molecule resolution. For these experiments, we are tracking the AglR motility complexes with photoactivatable localization microscopy (PALM) at millisecond intervals. These experiments should provide important information on this novel motility system. The techniques being utilized are innovative because they permit analysis of the dynamics of single molecule motors at nanometer resolution. Our second specific aim is to finalize our study of the Frz pathway by identifying the output of the pathway: the proteins that interact directly with the phosphorylated receiver domain, FrzZ. The output of the pathway is responsible for transmitting information from the Frz chemosensory pathway to the motors and the controllers of cell polarity, reversing the gliding motility and Type IV pili engines of M. xanthus. These experiments are significant because the coupling between the chemosensory system and the gliding motility engines is very different from the E. coli paradigm and likely to be utilized by other bacterial systems.

Public Health Relevance

The focus of our research is to understand how signal transduction regulates motility and multicellular interactions in the bacterium Myxococcus xanthus. Myxococcus forms fruiting bodies that are similar in many ways to biofilms formed by Pseudomonas aeruginosa and other pathogens;these are of public health interest since biofilms render bacteria resistant to antibiotics and are very difficult to treat in patients. Bioflm formation usually requires motility, chemotaxis, type IV pili and extracellular polysaccharide matrix materials;these are more easily studied in Myxococcus, a non-pathogenic bacterium, but the results are directly relevant to the understanding and control of pathogenic bacteria with similar properties.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Prokaryotic Cell and Molecular Biology Study Section (PCMB)
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Reddy, Michael K
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University of California Berkeley
Schools of Arts and Sciences
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Fu, Guo; Bandaria, Jigar N; Le Gall, Anne Valérie et al. (2018) MotAB-like machinery drives the movement of MreB filaments during bacterial gliding motility. Proc Natl Acad Sci U S A 115:2484-2489
Berleman, James E; Zemla, Marcin; Remis, Jonathan P et al. (2016) Exopolysaccharide microchannels direct bacterial motility and organize multicellular behavior. ISME J 10:2620-2632
Nan, Beiyan; Zusman, David R (2016) Novel mechanisms power bacterial gliding motility. Mol Microbiol 101:186-93
Kaimer, Christine; Zusman, David R (2016) Regulation of cell reversal frequency in Myxococcus xanthus requires the balanced activity of CheY-like domains in FrzE and FrzZ. Mol Microbiol 100:379-95
Nan, Beiyan; Bandaria, Jigar N; Guo, Kathy Y et al. (2015) The polarity of myxobacterial gliding is regulated by direct interactions between the gliding motors and the Ras homolog MglA. Proc Natl Acad Sci U S A 112:E186-93
Nan, Beiyan; McBride, Mark J; Chen, Jing et al. (2014) Bacteria that glide with helical tracks. Curr Biol 24:R169-73
Moine, Audrey; Agrebi, Rym; Espinosa, Leon et al. (2014) Functional organization of a multimodular bacterial chemosensory apparatus. PLoS Genet 10:e1004164
Kaimer, Christine; Zusman, David R (2013) Phosphorylation-dependent localization of the response regulator FrzZ signals cell reversals in Myxococcus xanthus. Mol Microbiol 88:740-53
Nan, Beiyan; Bandaria, Jigar N; Moghtaderi, Amirpasha et al. (2013) Flagella stator homologs function as motors for myxobacterial gliding motility by moving in helical trajectories. Proc Natl Acad Sci U S A 110:E1508-13
Kaimer, Christine; Berleman, James E; Zusman, David R (2012) Chemosensory signaling controls motility and subcellular polarity in Myxococcus xanthus. Curr Opin Microbiol 15:751-7

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