Predataxis behavior in Myxococcus xanthus.

Department of Microbiology, University of Iowa, 51 Newton Road, Iowa City, IA 52242, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 11/2008; 105(44):17127-32. DOI: 10.1073/pnas.0804387105
Source: PubMed

ABSTRACT Spatial organization of cells is important for both multicellular development and tactic responses to a changing environment. We find that the social bacterium, Myxococcus xanthus utilizes a chemotaxis (Che)-like pathway to regulate multicellular rippling during predation of other microbial species. Tracking of GFP-labeled cells indicates directed movement of M. xanthus cells during the formation of rippling wave structures. Quantitative analysis of rippling indicates that ripple wavelength is adaptable and dependent on prey cell availability. Methylation of the receptor, FrzCD is required for this adaptation: a frzF methyltransferase mutant is unable to construct ripples, whereas a frzG methylesterase mutant forms numerous, tightly packed ripples. Both the frzF and frzG mutant strains are defective in directing cell movement through prey colonies. These data indicate that the transition to an organized multicellular state during predation in M. xanthus relies on the tactic behavior of individual cells, mediated by a Che-like signal transduction pathway.

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    ABSTRACT: Myxococcus xanthus is a Gram-negative, soil-dwelling bacterium that glides on surfaces, reversing direction approximately once every 6 min. Motility in M. xanthus is governed by the Che-like Frz pathway and the Ras-like Mgl pathway, which together cause the cell to oscillate back and forth. Previously, Igoshin et al. (2004) suggested that the cellular oscillations are caused by cyclic changes in concentration of active Frz proteins that govern motility. In this study, we present a computational model that integrates both the Frz and Mgl pathways, and whose downstream components can be read as motor activity governing cellular reversals. This model faithfully reproduces wildtype and mutant behaviors by simulating individual protein knockouts. In addition, the model can be used to examine the impact of contact stimuli on cellular reversals. The basic model construction relies on the presence of two nested feedback circuits, which prompted us to reexamine the behavior of M. xanthus cells. We performed experiments to test the model, and this cell analysis challenges previous assumptions of 30 to 60 min reversal periods in frzCD, frzF, frzE, and frzZ mutants. We demonstrate that this average reversal period is an artifact of the method employed to record reversal data, and that in the absence of signal from the Frz pathway, Mgl components can occasionally reverse the cell near wildtype periodicity, but frz- cells are otherwise in a long nonoscillating state. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.
    Biophysical Journal 12/2014; 107(11):2700-11. DOI:10.1016/j.bpj.2014.09.046 · 3.83 Impact Factor
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    ABSTRACT: Biofilm formation is a common mechanism for surviving environmental stress and can be triggered by both intraspecies and interspecies interactions. Prolonged predator-prey interactions between the soil bacteria Myxococcus xanthus and Bacillus subtilis was found to induce the formation of a new type of B. subtilis biofilm, termed megastructures. Megastructures are tree-like brachiations, as much as 500 microns in diameter and raised above the surface between 150 to 200 microns and are filled with viable endospores embedded within a dense matrix. Megastructure formation did not depend on TasA, EspE, SinI, RemA or surfactin production and thus is genetically distinguishable from colony biofilm formation on MSgg medium. As B. subtilis endospores are not susceptible to predation by M. xanthus, megastructures appear to provide an alternative mechanism for survival. In addition, M. xanthus fruiting bodies were found in nearly all instances immediately adjacent to the megastructures, suggesting that M. xanthus is unable to acquire sufficient nutrients from cells housed within the megastructures. Lastly, a B. subtilis mutant lacking the ability to defend itself via bacillaene production, formed megastructures more rapidly than the parent. Together, the results indicate that production of the megastructure facilitates B. subtilis escape into dormancy via sporulation.
    Applied and Environmental Microbiology 10/2014; DOI:10.1128/AEM.02448-14 · 3.95 Impact Factor

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