Response characteristics of the membrane integrity and physiological activities of the mutant strain Y217 under exogenous butanol stress

Strategies to improve the efficiency and quality of mutant breeding using heavy-ion beam irradiation

Heavy-ion beam irradiation (HIBI) is useful for generating new germplasm in plants and microorganisms due to its ability to induce high mutagenesis rate, broad mutagenesis spectrum, and excellent stability of mutants. However, due to the random mutagenesis and associated mutant breeding modalities, it is imperative to improve HIBI-based mutant breeding efficiency and quality. This review discusses and summarizes the findings of existing theoretical and technical studies and presents a set of tandem strategies to enable efficient and high-quality HIBI-based mutant breeding practices. These strategies: adjust the mutation-inducing techniques, regulate cellular response states, formulate high-throughput screening schemes, and apply the generated superior genetic elements to genetic engineering approaches, thereby, improving the implications and expanding the scope of HIBI-based mutant breeding. These strategies aim to improve the mutagenesis rate, screening efficiency, and utilization of positive mutations. Here, we propose a model based on the integration of these strategies that would leverage the advantages of HIBI while compensating for its present shortcomings. Owing to the unique advantages of HIBI in creating high-quality genetic resources, we believe this review will contribute toward improving HIBI-based breeding.

AlgU mediates hyperosmotic tolerance in Pseudomonas protegens SN15-2 by regulating membrane stability, ROS scavenging, and osmolyte synthesis

Pseudomonas protegens can serve as an agricultural biocontrol agent. P. protegens often encounters hyperosmotic stress during industrial production and field application. The ability of P. protegens to withstand hyperosmotic stress is important for its application as a biocontrol agent. AlgU is a global regulator responsible for stress response and biocontrol ability. However, the specific regulatory role of AlgU in the hyperosmotic adaptation of P. protegens is poorly understood. In this study, we found that the AlgU mutation disrupted the hyperosmotic tolerance of P. protegens. Many genes and metabolites related to cell envelope formation were significantly downregulated in ΔalgU compared with that in the wild-type (WT) strain under hyperosmotic conditions, and we found that the algU mutation caused membrane integrity to be compromised and increased membrane permeability. Further experiments revealed that the cell envelope integrity protein TolA, which is regulated by AlgU, contributes to cell membrane stability and osmotic tolerance in P. protegens. In addition, several genes related to oxidative stress response were significantly downregulated in ΔalgU, and higher levels of intracellular reactive oxygen species were found in ΔalgU. Furthermore, we found that the synthesis of N-acetyl glutaminyl glutamine amide is directly regulated by AlgU and contributes to the hyperosmotic adaptation of P. protegens. This study revealed the mechanisms of AlgU's participation in osmotic tolerance in P. protegens, and it provides potential molecular targets for research on the hyperosmotic adaptation of P. protegens.IMPORTANCEIn this study, we found that the extracytoplasmic function sigma factor AlgU is essential for the survival of P. protegens under hyperosmotic conditions. We provided evidence supporting the roles of AlgU in influencing cell membrane stability, intracellular reactive oxygen species (ROS) accumulation, and dipeptide N-acetylglutaminylglutamine amide (NAGGN) synthesis in P. protegens under hyperosmotic conditions. Our findings revealed the mechanisms of AlgU's participation in hyperosmotic stress tolerance in P. protegens, and they provide potential molecular targets for research on the hyperosmotic adaptation of P. protegens, which is of value in improving the biocontrol ability of P. protegens.

Integration of food raw materials, food microbiology, and food additives: systematic research and comprehensive insights into sweet sorghum juice, Clostridium tyrobutyricum TGL-A236 and bio-butyric acid

Introduction

Sweet sorghum juice is a typical production feedstock for natural, eco-friendly sweeteners and beverages. Clostridium tyrobutyricum is one of the widely used microorganisms in the food industry, and its principal product, bio-butyric acid is an important food additive. There are no published reports of Clostridium tyrobutyricum producing butyric acid using SSJ as the sole substrate without adding exogenous substances, which could reach a food-additive grade. This study focuses on tailoring a cost-effective, safe, and sustainable process and strategy for their production and application.

Methods

This study modeled the enzymolysis of non-reducing sugars via the first/second-order kinetics and added food-grade diatomite to the hydrolysate. Qualitative and quantitative analysis were performed using high-performance liquid chromatography, gas chromatography-mass spectrometer, full-scale laser diffraction method, ultra-performance liquid chromatography-tandem mass spectrometry, the cell double-staining assay, transmission electron microscopy, and Oxford nanopore technology sequencing. Quantitative real-time polymerase chain reaction, pathway and process enrichment analysis, and homology modeling were conducted for mutant genes.

Results

The treated sweet sorghum juice showed promising results, containing 70.60 g/L glucose and 63.09 g/L fructose, with a sucrose hydrolysis rate of 98.29% and a minimal sucrose loss rate of 0.87%. Furthermore, 99.62% of the colloidal particles and 82.13% of the starch particles were removed, and the concentrations of hazardous substances were effectively reduced. A food microorganism Clostridium tyrobutyricum TGL-A236 with deep utilization value was developed, which showed superior performance by converting 30.65% glucose and 37.22% fructose to 24.1364 g/L bio-butyric acid in a treated sweet sorghum juice (1:1 dilution) fermentation broth. This titer was 2.12 times higher than that of the original strain, with a butyric acid selectivity of 86.36%. Finally, the Genome atlas view, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and evolutionary genealogy of genes: Non-supervised Orthologous (eggNOG) functional annotations, three-dimensional structure and protein cavity prediction of five non-synonymous variant genes were obtained.

Conclusion

This study not only includes a systematic process flow and in-depth elucidation of relevant mechanisms but also provides a new strategy for green processing of food raw materials, improving food microbial performance, and ensuring the safe production of food additives.

Current progress on engineering microbial strains and consortia for production of cellulosic butanol through consolidated bioprocessing

In the last decades, fermentative production of n-butanol has regained substantial interest mainly owing to its use as drop-in-fuel. The use of lignocellulose as an alternative to traditional acetone-butanol-ethanol fermentation feedstocks (starchy biomass and molasses) can significantly increase the economic competitiveness of biobutanol over production from non-renewable sources (petroleum). However, the low cost of lignocellulose is offset by its high recalcitrance to biodegradation which generally requires chemical-physical pre-treatment and multiple bioreactor-based processes. The development of consolidated processing (i.e., single-pot fermentation) can dramatically reduce lignocellulose fermentation costs and promote its industrial application. Here, strategies for developing microbial strains and consortia that feature both efficient (hemi)cellulose depolymerization and butanol production will be depicted, that is, rational metabolic engineering of native (hemi)cellulolytic or native butanol-producing or other suitable microorganisms; protoplast fusion of (hemi)cellulolytic and butanol-producing strains; and co-culture of (hemi)cellulolytic and butanol-producing microbes. Irrespective of the fermentation feedstock, biobutanol production is inherently limited by the severe toxicity of this solvent that challenges process economic viability. Hence, an overview of strategies for developing butanol hypertolerant strains will be provided.

LsrB, the hub of ABC transporters involved in the membrane damage mechanisms of heavy ion irradiation in Escherichia coli

BACKGROUND

Ionizing radiation, especially heavy ion (HI) beams, has been widely used in biology and medicine. However, the mechanism of membrane damage by such radiation remains primarily uncharacterized.

PURPOSE

Transcriptomic profiles of Escherichia coli (E. coli) treated with HI illustrated the response mechanisms of the membrane, mainly ABC transporters, related genes regulated by antibiotics treatment through enrichment analyses of GO and KEGG. The networks of protein-protein interactions indicated that LsrB was the crucial one among the ABC transporters specially regulated by HI through the calculation of plugins MCODE and cytoHubba of Cytoscape. Finally, the expression pattern, GO/KEGG enrichment terms, and the interaction between nine LuxS/AI-2 quorum sensing system members were investigated.

CONCLUSIONS

Above all, results suggested that HI might perform membrane damage through regulated material transport, inhibited LuxS/AI-2 system, finally impeded biofilm formation. This work provides further evidence for the role of ABC transporters, especially LsrB, in membrane damage of E. coli to HI. It will provide new strategies for improving the precise application of HI.