Ramesh Malavika, Behra Phani Rama Krishna, Pettersson B M Fredrik, Dasgupta Santanu, Kirsebom Leif A
Department of Cell and Molecular Biology, Biomedical Centre, Box 596, SE-751 24 Uppsala, Sweden.
Microorganisms. 2025 Feb 20;13(3):475. doi: 10.3390/microorganisms13030475.
Changes in cell shape have been shown to be an integral part of the mycobacterial life cycle; however, systematic investigations into its patterns of pleomorphic behaviour in connection with stages or conditions of growth are scarce. We have studied the complete growth cycle of cultures, a Non-Tuberculous Mycobacterium (NTM), in solid as well as in liquid media. We provide data showing changes in cell shape from rod to coccoid and occurrence of refractive cells ranging from Phase Grey to phase Bright (PGB) in appearance upon ageing. Changes in cell shape could be correlated to the bi-phasic nature of the growth curves for (and the NTM ) as measured by the absorbance of liquid cultures while growth measured by colony-forming units (CFU) on solid media showed a uniform exponential growth. Based on the complete genome we identified genes involved in cell morphology, and analyses of their mRNA levels revealed changes at different stages of growth. One gene, _3 (encoding a chaperone), showed significantly increased transcript levels in stationary phase cells relative to exponentially growing cells. Based on protein domain architecture, we identified that the DnaK_3 N-terminus domain is an MreB-like homolog. Endogenous overexpression of _3 in was unsuccessful (appears to be lethal) while exogenous overexpression in resulted in morphological changes with an impact on the frequency of appearance of PGB cells. However, the introduction of an anti-sense "gene" targeting the _3 did not show significant effects. Using _3- reporter constructs we also provide data suggesting that the morphological differences could be due to differences in the regulation of _3 in the two species. Together these data suggest that, although its regulation may vary between mycobacterial species, the _3 might have a direct or indirect role in the processes influencing mycobacterial cell shape.
细胞形态的变化已被证明是分枝杆菌生命周期中不可或缺的一部分；然而，关于其与生长阶段或条件相关的多形性行为模式的系统研究却很少。我们研究了一种非结核分枝杆菌（NTM）在固体和液体培养基中的完整生长周期。我们提供的数据表明，随着老化，细胞形态从杆状变为球状，并且出现了从灰色相到明亮相（PGB）的折光细胞。细胞形态的变化与通过液体培养物的吸光度测量的[该菌]（以及NTM）生长曲线的双相性质相关，而通过固体培养基上的菌落形成单位（CFU）测量的生长显示出均匀的指数生长。基于完整的[该菌]基因组，我们鉴定了参与细胞形态的基因，对其mRNA水平的分析揭示了生长不同阶段的变化。一个基因，_3（编码一种分子伴侣），相对于指数生长的细胞，在稳定期细胞中显示出显著增加的转录水平。基于蛋白质结构域架构，我们确定DnaK_3 N端结构域是一种类似MreB的同源物。在[该菌]中内源性过表达_3未成功（似乎是致死的），而在[另一菌]中外源性过表达导致形态变化，对PGB细胞的出现频率产生影响。然而，引入靶向_3的反义“基因”并未显示出显著效果。使用_3-报告基因构建体，我们还提供数据表明形态差异可能是由于两种菌中_3调控的差异。这些数据共同表明，尽管其调控在分枝杆菌物种之间可能有所不同，但_3可能在影响分枝杆菌细胞形态的过程中具有直接或间接作用。
