Jul 2026· International Journal of Biological Macromolecules· Vol 377, pp.
153763
· 0 citations· 40 references
Medicine
TL;DR
Results showed that cdaA is critical for osmotic and ethanol tolerance but negatively modulates bile salt resistance in S. thermophilus, suggesting that absence of cdaA confers a survival advantage under bile salt stress.
Abstract
Streptococcus thermophilus is a key dairy starter culture widely used in the production of yogurt and cheese, where its robustness in stress adaptation and growth performance is critical for industrial fermentation efficiency. Cyclic di-AMP (c-di-AMP) is a key second messenger involved in regulating osmotic homeostasis and stress adaptation in bacteria. However, the role of c-di-AMP in S. thermophilus remains unexplored. Here, cdaA, encoding a diadenylate cyclase containing a conserved DisA_N domain responsible for c-di-AMP synthesis, was identified in S. thermophilus S-3 through bioinformatic analysis and validated by LC-MS/MS. The cdaA gene knockout strain, S-3ΔcdaA, was unable to synthesize c-di-AMP and exhibited a markedly shortened lag phase. Stress response assays revealed that S-3ΔcdaA was sensitive to osmotic and ethanol stress, indicating that cdaA is essential for stress tolerance. Specifically, S-3ΔcdaA showed almost no growth in chemically defined medium (CDM) supplemented with 300 mM potassium or sodium chloride, whereas the wild-type S-3 reached OD600 values of 0.72 and 0.52, respectively. Under 5% ethanol stress, the specific growth rate of S-3ΔcdaA dropped significantly to 0.35 relative to S-3 compared to 1.10 in CDM medium alone. Interestingly, S-3ΔcdaA retained the ability to grow under 0.01% oxgall stress, reaching an OD600 of 0.83, while growth of S-3 was completely abolished. It suggested that absence of cdaA confers a survival advantage under bile salt stress. Taken together, these results showed that cdaA is critical for osmotic and ethanol tolerance but negatively modulates bile salt resistance in S. thermophilus.
This study uncovers a previously unappreciated mechanism of Tps1-mediated heat adaptation in C. deneoformans, by revealing that Tps1 functions as a critical metabolic gatekeeper that safeguards glycolytic flux to sustain growth at elevated temperatures.
V. Yadav, Kahlia A. Carl, J. Heitman et al.· bioRxiv· 0 citations
This study systematically elucidates the dual inhibitory mechanisms of thermosonication against Bacillus subtilis spores through integrated transcriptomic-proteomic analysis, identifying critical genes at the regulatory level and clarifying indirect suppression through metabolic network disruption.
Lisha Song, Kairu He, Wang Han et al.· Food and Bioprocess Technolo...· 0 citations
1,6-Hexanediol (1,6-HDO) is an important chemical platform widely used in polymer and pharmaceutical industries, while its toxicity remains a major bottleneck limiting efficient microbial production. This study demonstrates that 1,6-HDO exhibited strong inhibitory effects on Escherichia coli, reducing the maximum OD600 to approximately 50% of the control level under 10 g/L stress. Transcriptomic analysis was performed under 1,6-HDO stress, identifying 779 differentially expressed genes enriched in pathways related to energy metabolism, sulfur metabolism and amino acid metabolism. To systematically identify functional targets associated with tolerance, genome-wide screening using the ASKA overexpression library identified 93 tolerance-related genes that improved E. coli growth under 1,6-HDO stress by 0.06- to 3.17-fold. Notably, multiple targets were functionally associated with energy and amino acid metabolism, consistent with the transcriptomic analysis. Furthermore, co-expression of rumA and yhbO showed the greatest improvement in growth, reaching a biomass of 9.43 under 1,6-HDO stress, which was 2.61-fold higher than that of the control strain. Collectively, this study systematically elucidates the global stress response and identifies key determinants contributing to tolerance, providing valuable targets for developing robust microbial cell factories for efficient 1,6-HDO bioproduction.
Xinyi Zhang, Lisha Qin, Hongxu Li et al.· Synthetic and Systems Biotec...· 0 citations
This study uncovers that moderate reactive oxygen species (ROS) signaling mediates aeration-dependent thermotolerance in Kluyveromyces marxianus, challenging the long-held paradigm that ROS function solely as toxic metabolic byproducts. Through integrated transcriptomic profiling and RT-qPCR validation, 19 key transcription factors regulating this adaptive response were identified, and functional assays demonstrated that targeted knockout of GSF2 and RIM101 coupled with MED15 overexpression significantly enhances hypoxic thermotolerance. The ERG6-overexpressing strain YZB559 yields 72.45 g/L xylitol at 45 °C under medium-high oxygen (MHO) condition, marking a 20% improvement over the parental strain, while the combinatorially engineered YZB639 (ΔGSF2::MED15) achieves 74.13 g/L xylitol with complete xylose consumption at 46 °C and 30.64 g/L ethanol under micro-oxygen conditions, representing a 23% increase in ethanol production. Notably, at 47 °C, the highest temperature reported for xylitol fermentation, YZB639 accumulates 51.68 g/L xylitol under constant MHO condition, and an optimized two-stage oxygen supply strategy further elevates the titer to 67.78 g/L, with robust performance also observed when using industrial xylose mother liquor as feedstock to produce 57.34 g/L xylitol. This work resolves the fundamental oxygen contradiction between thermotolerance enhancement and product biosynthesis in high-temperature fermentation, providing a transformative strategy for cost-effective and sustainable industrial biomanufacturing.
Zhongmei Hu, Yanjie Li, Na Dong et al.· Bioresource Technology· 0 citations
The data obtained allows suggesting that SsrS and CsrC small RNAs played an important role in regulation of the cell switching to formation of biofilms, and hexuronates can be used as modeling agents in clinical practice.
T. Bessonova, U. D. Kuznetsova, A. T. Magkaev et al.· Molecular Biology· 0 citations
ABSTRACT ClpX functions as a component of the ClpXP protease, a conserved intracellular protease that regulates protein turnover, stress responses, and virulence in multiple bacterial species. Our lab has established that clpX is necessary for resistance to cell envelope targeting antibiotics, such as penicillin and daptomycin in Bacillus anthracis Sterne. Previous microarray data identified the msrA/B gene encoding a bifunctional methionine sulfoxide reductase as upregulated in the ΔclpX mutant. Methionine sulfoxide reductases (Msr) repair oxidatively damaged proteins by reducing methionine sulfoxide residues back to methionine. While Msr enzymes are primarily associated with oxidative stress, cell wall antibiotics induce expression of msrA1 and msrB in S. aureus. Here, we investigated the role of MsrA/B in oxidative and cell envelope stress. Our results show that although hydrogen peroxide and paraquat induce msrA/B expression, the ΔmsrA/B strain was not susceptible to either oxidant, whereas the ΔclpX strain was sensitive to both. We also found that loss of msrA/B conferred penicillin‐specific sensitivity, but, unlike ΔclpX, increased sensitivity was not seen with other cell wall or cell membrane targeting antibiotics. Inactivation of the catalytic cysteine of either Msr domain of MsrA/B failed to complement, suggesting that the reducing activity of MsrA/B is required for penicillin resistance. These findings indicate that while MsrA/B contributes to penicillin resistance, other proteins in the ClpXP modulon must also play a role in oxidative and cell envelope stress.
Aeron B Pennington, Salina Hona, Josey I Austin et al.· MicrobiologyOpen· 0 citations