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Quorum Sensing
Published in Vineet Kumar, Vinod Kumar Garg, Sunil Kumar, Jayanta Kumar Biswas, Omics for Environmental Engineering and Microbiology Systems, 2023
Archisman Bhunia, Kumar Narayan, Abhilasha Singh, Asmeeta Sircar, Nivedita Chatterjee
In contrast to gram-negative bacteria, gram-positive bacteria are commonly known to use segmented layers of signal transduction for cell-cell communication. This simple model of the signaling system comprises two components: histidine kinase (HK) and response regulator (RR), and is known as two-component signal transduction system (TCS) (Liu et al., 2018). Their report also highlights the types of two-/three-/multi-component signal transduction systems, such as classical, unorthodox, and hybrid (Figure 5.2). The mechanism works on the principle of phosphoryl group transfer domains. The HK receives signal molecules as a result of altered external stimuli, and autophosphorylation occurs within the conserved domains of HK along a sequence. At the same time, the cascade of signal triggers the transfer of phosphoryl group to the N-terminal of the aspartic residue in the RR (Liu et al., 2018). This further initiates the operon mechanism for gene expressions. Unlike the AHL signaling molecules in gram-negative bacteria, small sequences of post-translationally modified oligopeptides called autoinducing peptides (AIPs) act as the signal generators (Monnet and Gardan, 2015).
Bacillus altitudinis MT422188: a potential agent for zinc bioremediation
Published in Bioremediation Journal, 2022
Maryam Khan, Munazza Ijaz, Ghayoor Abbas Chotana, Ghulam Murtaza, Arif Malik, Saba Shamim
In model flagellated bacterial species such as Bacillus subtilis and Escherichia coli, the movement of bacteria toward a chemoattractant during chemotactic movement initiates a conformational change that affects the auto-phosphorylation of CheA, which is a significant histidine kinase related to the process. CheY, a regulator protein, then mediates the transfer of the phosphoryl group from CheA which enables the modulation of swimming behavior in bacteria. This phenomenon is heavily associated with the sensory adaptation by bacteria, where chemical gradients are sensed and bacteria move in response to the external stimuli (Tohidifar et al. 2020). In this study, Zn2+ was found to be a chemoattractant for B. altitudinis, triggering effective flagellar motions which resulted in positive motility behaviors (Figure 5a, b). B. subtilis is reported to have two forms of active motility, namely swimming and swarming behavior that are mediated by rotating flagella (Kearns and Losick 2003). The movement of bacterial cells is facilitated by smooth runs toward attractants, which are most commonly bacterial nutrients. These smooth runs, or swimming, can be used for their acquisition, as presumably observed in the case of Zn2+ for B. altitudinis. The results were similar to the study of Sanders, Andermann, and Ottemann (2013), where Zn2+ was reported to act as a similar chemoattractant for H. pylori.