Bhadani Nirbhay K, Prasad Kritika, Gupta Nisha, Sarmah Hemanta, Sengupta Tapas K
Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, Nadia, West Bengal, 741246, India.
Curr Microbiol. 2025 May 28;82(7):313. doi: 10.1007/s00284-025-04288-w.
Bacteria have been known to thrive in challenging environmental niches through diverse phenomena. Swarming is one such favourable adaptations that could help bacteria survive extreme conditions. Therefore, targeting swarming is crucial for improving our understanding of bacterial motility and preventing related infections. Bacillus cereus, which causes food poisoning, has been shown to perform swarming, and salts like NaCl can act as a food preservative to control bacterial growth. To explore the possible alterations in the swarming of Bacillus cereus in the presence of salt, the present study encompasses the effect of NaCl on the swarming characteristics of a natural bacterial isolate, Bacillus cereus MHS, with a hyperswarming phenotype. Here we report that increased NaCl in growth media could induce a reduction in swarming motility and pattern of MHS on Luria agar plates. This observed reduction in swarming was found to be associated with reduced flagellation and a reduction in the abundance of bacterial nanotubes. Gene expression studies supported the phenotypic and ultrastructure observations as the expressions of bfla and ymdB genes, involved in formations of flagella and nanotubes, respectively, were found to be reduced in the swarming MHS cells in the presence of increased NaCl. It was also observed that the salt-induced reduction in swarming of MHS is associated with the reduced expression of the quorum sensing regulator gene plcR. This study first time reports the bacterial nanotubes in a Bacillus cereus strain indicating a possible link between the bacterial nanotube formation and hyperswarming phenotype in Bacillus cereus MHS.
众所周知，细菌可通过多种现象在具有挑战性的环境生态位中茁壮成长。群体运动就是一种有利的适应性机制，可帮助细菌在极端条件下生存。因此，针对群体运动进行研究对于增进我们对细菌运动性的理解以及预防相关感染至关重要。已证实，导致食物中毒的蜡样芽孢杆菌会进行群体运动，像氯化钠这样的盐类可作为食品防腐剂来控制细菌生长。为了探究在有盐存在的情况下蜡样芽孢杆菌群体运动可能发生的变化，本研究考察了氯化钠对具有超群体运动表型的天然细菌分离株蜡样芽孢杆菌MHS群体运动特性的影响。在此我们报告，生长培养基中氯化钠含量的增加会导致MHS在Luria琼脂平板上的群体运动能力和运动模式降低。观察到的这种群体运动能力的降低与鞭毛形成减少以及细菌纳米管数量减少有关。基因表达研究支持了表型和超微结构观察结果，因为在氯化钠含量增加的情况下，参与鞭毛和纳米管形成的bfla和ymdB基因在群体运动的MHS细胞中的表达被发现有所降低。还观察到，盐诱导的MHS群体运动能力降低与群体感应调节基因plcR的表达降低有关。本研究首次报道了蜡样芽孢杆菌菌株中的细菌纳米管，表明细菌纳米管形成与蜡样芽孢杆菌MHS的超群体运动表型之间可能存在联系。
