Molecular Pathogens 2024, Vol.15, No.5, 255-262 http://microbescipublisher.com/index.php/mp 259 those that regulate spore and biofilm formation. This regulatory network allows B. subtilis to rapidly adapt to environmental and metabolic stimuli, ensuring bacterial fitness under stress conditions (Figure 2) (Ayala et al., 2020). The acetylation state of the histone-like protein HBsu has been shown to influence the resistance properties of B. subtilis spores. Specific acetylation patterns are required for proper chromosomal packaging and protection, which in turn affects the spores' resistance to heat, UV radiation, and formaldehyde exposure (Luu et al., 2022). Figure 2Bacillus subtilis responses to stress (Adopted from Ayala et al., 2020) 6.2 Sporulation efficiency and resistance in extreme environments: case of soil and marine isolates Bacillus subtilis spores are highly resistant and can survive in extreme environments, such as soil and marine habitats. The efficiency of sporulation and the resistance properties of these spores can vary significantly depending on the environmental conditions. For instance, spores produced at higher temperatures (42 °C) contain more dipicolinic acid and exhibit greater resistance to heat and lysozyme treatments compared to those produced at lower temperatures (25 °C). This variation is attributed to differences in the spore coat structure and the abundance of coat proteins like CotH, which is more heat-labile and plays a major regulatory role in coat formation at lower temperatures (Isticato et al., 2019). In high osmolarity environments, such as desiccated soil, B. subtilis faces challenges in sporulation efficiency. High salinity blocks entry into the sporulation pathway at an early stage by impairing Spo0A- and SigH-dependent transcription. This blockage prevents the bacterium from committing to a developmental program that it cannot complete under such stressful conditions. Interestingly, overproduction of the sensor kinase KinA can bypass this salt-imposed block, although it often leads to impaired morphological processes and cell lysis (Widderich et al., 2016). 7 Applied Perspectives: Importance of Bacillus subtilis in Biotechnology 7.1 New Insights into genetic regulation of stress responses Recent studies have highlighted the critical role of the alternative sigma factor SigB in the genetic regulation of stress responses in Bacillus subtilis. SigB controls a vast array of genes involved in stress adaptation and survival, including those responsible for spore and biofilm formation. The activation of SigB is finely tuned through multiple pathways that respond to various stress conditions such as energy depletion, environmental changes, and
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