Highly Deviated Asymmetric Division in Very Low Proportion of Mycobacterial Mid-log Phase Cells - PubMed (original) (raw)
Highly Deviated Asymmetric Division in Very Low Proportion of Mycobacterial Mid-log Phase Cells
Srinivasan Vijay et al. Open Microbiol J. 2014.
Abstract
In this study, we show that about 20% of the septating Mycobacterium smegmatis and Mycobacterium xenopi cells in the exponential phase populationdivideasymmetrically, with an unusually high deviation (17 ± 4%) in the division site from the median, to generate short cells and long cells, thereby generating population heterogeneity. This mode of division is very different from the symmetric division of themajority (about 80%) of the septating cells in the Mycobacterium smegmatis, Mycobacterium marinum, and Mycobacterium bovis BCG exponential phase population, with 5-10% deviation in the division site from the mid-cell site, as reported by recent studies. The short cells and the long cells further grew and divided to generate a population. We speculate that the generation of the short cells and the long cells through the highly deviated asymmetric divisionin the low proportions of mycobacterial population may have a role in stress tolerance.
Keywords: Asymmetric cell division; hort cell.; ucleoid; ycobacterium smegmatis; ycobacterium xenopi.
Figures
Fig. (1)
TEM and SEM imaging of mid-log phase M. smegmatis and _M. xenopi_cells with highly deviated asymmetric septum/ constriction or symmetric septum.(A-D) TEM images of M. smegmatis cells with highly deviated asymmetric septum. (D) M. smegmatis cell undergoing ‘snapping post-fission’ mode of highly deviated asymmetric division. (E)M. smegmatis cell at the initiation of the septum formation. (F)M. smegmatis cell close to the completion of the asymmetric septum constriction. (G, H)M. xenopi cells with highly deviated asymmetric septum. (I-M)SEM images of M. smegmatis cells with ‘snapping post-fission’ mode of highly deviated asymmetric division. (N, O)M. smegmatis cells with symmetric septum with minor deviation. (P, Q)M. xenopi cells with symmetric septum with minor deviation. Arrow indicates the position of the highly deviated asymmetric septum or constriction, or symmetric septum with minor deviation, in the septum position from the mid-cell site (see Table 1). n indicates nucleoid.
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Fig. (2)
Position of the septum and constriction in the highly deviated asymmetrically dividing M. smegmatis and M. xenopi cells. (A, B) Placement of septum with respect to cell length from the TEM images of M. smegmatis and M. xenopi cells, respectively (n = 50 cells with septum). (C) Position of the constriction in M. smegmatis cells from live cell time-lapse images. (n = 50 cells with constriction). The average values from (A-C) have been tabulated and shown below.
Fig. (3)
Fluorescence imaging of mid-log phase live and fixed M. smegmatis and M. xenopi cells with asymmetric septum. (A). Fluorescence and the corresponding DIC image of the VBP stained live M. smegmatis cell with highly deviated asymmetric septum. (B). Fluorescence and the corresponding DIC image of the WGA-Alexa488 stained fixed M. smegmatis cell with highly deviated asymmetric septum.(C). Confocal image of fixed WGA-Alexa488 stained _M. smegmatis_cells with highly deviated asymmetric septum. (D). Highly deviated, asymmetrically dividing M. smegmatis cells stained with DAPI for nucleoid and WGA-Alexa488 for septum. The merge figure shows the WGA-Alexa488 stained septum dividing the DAPI stained nucleoids. In all the panels, the arrows indicate the position of the highly deviated asymmetric septum.
Fig. (4)
Live cell time-lapse imaging of highly deviated asymmetric division of M. smegmatis cells, with colour cartoon for the cell images.Only minimum number of panels are shown just enough to depict the phenomenon. An_M. smegmatis_ mother cell (blue) first underwent symmetric division to generate daughter cells of lengths, 3.08 µm (red) and 3.20 µm (green), with 0.12 µm difference in their lengths. One of the daughter cells (red) further underwent asymmetric division, generating a short daughter cell (2.28 µm; white) and a long daughter cell (3.66 µm; yellow), with 1.38 µm difference in their lengths. The other daughter cell (green) underwent symmetric division, generating daughter cells of lengths, 4.06 µm (pink) and 4.26 µm (cyan), with 0.2 µm difference between their lengths. One of these daughter cells (pink cell; 4.06 µm) further grew and underwent symmetric division to generate two daughter cells of lengths, 2.60 µm (blue) and 2.87 µm (green). Thus, the daughter cells of a symmetric division underwent two different modes of division. The growth rate of the short and the long cells of the asymmetric division were determined from the live cell imaging panels.
Fig. (5)
The lineage of the growth and highly deviated asymmetric division of live M. smegmatis cell and of its daughter cells, shown in Fig. (4). The growth and division lineage was traced from the images of time-lapse microscopy in Fig. (4). The zero time point does not correlate with the birth of the starting mother cell.
Fig. (6)
Live cell time-lapse imaging of highly deviated asymmetric division of mid-log phase M. smegmatis long mother cell.An M. smegmatis long mother cell (blue cell; 9.79 µm) first underwent highly deviated asymmetric division close to one pole (arrow), to generate a short daughter cell (green cell, 2.67 µm) and a longer-sized daughter cell (red cell, 7.84 µm), with the difference of 5.17 µm in their lengths. The longer-sized daughter cell (red cell, 7.84 µm) subsequently showed symmetric division with minor deviation (arrow), generating daughter cells of lengths, 4.59 µm and 4.36 µm (pink and cyan cells), with the difference of 0.23 µm in length between them. The images were observed under DIC. Arrows indicate the site of cell constriction at asymmetric or symmetric position.
## References
1. 1. Hett EC, Rubin EJ. Bacterial growth and cell division: A Mycobacterial perspective. Microbiol Mol Biol Rev. 2008;72:126–56. -PMC -PubMed 2. 1. Joyce G, Williams KJ, Robb M , et al. Cell division site placement and asymmetric growth in mycobacteria. PLoS ONE. 2012;7:e44582. -PMC -PubMed 3. 1. Singh B, Nitharwal RG, Ramesh M, Pettersson BMF, Kirsebom LA, Dasgupta S. Asymmetric growth and division in Mycobacteria spp: Compensatory mechanisms for non-medial septa. Mol Microbiol. 2013;88:64–76. -PubMed 4. 1. Santi I, Dhar N, Bousbaine D, Wakamoto Y, McKinney JD. Single-cell dynamics of the chromosome replication and cell division cycles in mycobacteria. Nature Commun. 2013;4:2470. -PubMed 5. 1. Snapper SB, Melton RE, Mustafa S, Kieser T, Jacobs WR Jr. Isolation and characterisation of efficient plasmid transformation mutants of Mycobacterium smegmatis. Mol Microbiol. 1990;4:1911–1919. -PubMed
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