The molecular architecture of engulfment during Bacillus subtilis sporulation
- University of California, San Diego, United States
Abstract
The study of bacterial cell biology is limited by difficulties in visualizing cellular structures at high spatial resolution within their native milieu. Here, we visualize Bacillus subtilis sporulation using cryo-electron tomography coupled with cryo-focused ion beam milling, allowing the reconstruction of native-state cellular sections at molecular resolution. During sporulation, an asymmetrically-positioned septum generates a larger mother cell and a smaller forespore. Subsequently, the mother cell engulfs the forespore. We show that the septal peptidoglycan is not completely degraded at the onset of engulfment. Instead, the septum is uniformly and only slightly thinned as it curves towards the mother cell. Then, the mother cell membrane migrates around the forespore in tiny finger-like projections, whose formation requires the mother cell SpoIIDMP protein complex. We propose that a limited number of SpoIIDMP complexes tether to and degrade the peptidoglycan ahead of the engulfing membrane, generating an irregular membrane front.
Data availability
The authors have created a library of B. subtilis tomograms accessible at: villalab.ucsd.edu/research/engulfment. We have also deposited three representative tilt-series to Electron Microscopy Data Bank (EMDB) in the form of 4x binned tomograms. The IDs are EMD-20335, EMD-20336, EMD-20337 for Figure 1D,F,H respectively.
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Representative tilt-seriesElectron Microscopy Data Bank, EMD-20335.
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Representative tilt-seriesElectron Microscopy Data Bank, EMD-20336.
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Representative tilt-seriesElectron Microscopy Data Bank, EMD-20337.
Article and author information
Author details
Funding
National Institute of Health's Director's New Innovator Award (1DP2GM123494)
- Elizabeth Villa
National Institutes of Health (RO1-GM057045)
- Kit Pogliano
- Elizabeth Villa
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Khanna et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The molecular architecture of engulfment during Bacillus subtilis sporulation
eLife 8:e45257.
https://doi.org/10.7554/eLife.45257
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