Microbiological research最新文献

{"title":"Protecting plants from pathogens through arbuscular mycorrhiza: Role of fungal diversity","authors":"Hao Wang ,&nbsp;Yinglong Chen","doi":"10.1016/j.micres.2024.127919","DOIUrl":"10.1016/j.micres.2024.127919","url":null,"abstract":"<div><div>Arbuscular mycorrhizal (AM) fungi play a crucial role in protecting host plants from pathogens. AM fungal taxa show varying abilities to hinder the development of plant pathogens with various underlying mechanisms of action, and plant defense through mycorrhization should be viewed to have a continuum of several possible mechanisms. However, an additive or synergistic effect is not always achieved. This review examines the potential mechanisms by which AM fungi enhance plant tolerance and defense against pathogens, as well as the possible interactive mechanisms among AM fungal traits that may lead to facilitative and antagonistic effect on plant defense outcomes. It also provides evidence demonstrating the benefits of AM fungal consortia used so far to protect crop plants from various pathogens. It concludes by proposing some biotechnological applications aimed at unraveling the connections between AM fungal diversity and their function to enhance efficacy of plant pathogen protection.</div></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127919"},"PeriodicalIF":6.1,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142349960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of a novel antioxidant exopolysaccharide from an intestinal-originated bacteria Bifidobacterium pseudocatenulatum Bi-OTA128","authors":"Hui Wang ,&nbsp;Fangzhou Lu ,&nbsp;Xin Feng ,&nbsp;Yuchen Zhang ,&nbsp;Wenxuan Di ,&nbsp;Ming Chen ,&nbsp;Ruiyun Wu ,&nbsp;Man Rao ,&nbsp;Pengbin Yin ,&nbsp;Yanling Hao ,&nbsp;Zhengyuan Zhai","doi":"10.1016/j.micres.2024.127914","DOIUrl":"10.1016/j.micres.2024.127914","url":null,"abstract":"<div><div>Microbial exopolysaccharides (EPSs) have attracted extensive attention for their biological functions in antioxidant activities. In this study, we characterized a novel EPS produced by <em>Bifidobacterium pseudocatenulatum</em> Bi-OTA128 which exhibited the highest antioxidant capacity compared to nine other ropy bacterial strains, achieving 76.50 % and 93.84 % in DPPH· and ABTS·⁺ scavenging activity, and ferric reducing power of 134.34 μM Fe²⁺. Complete genomic analysis identified an <em>eps</em> gene cluster involved in the EPS biosynthesis of Bi-OTA128 strain, which might be responsible for its ropy phenotype. The EPS was then isolated and purified by a DEAE-Sepharose Fast Flow column. A single elution part EPS₁₂₈ was obtained with a recovery rate of 43.5 ± 1.78 % and a total carbohydrate content of 93.6 ± 0.76 %. Structural characterization showed that EPS₁₂₈ comprised glucose, galactose, and rhamnose (molar ratio 4.0:1.2:1.1), featuring a putative complex backbone structure with four branched chains and an unusual acetyl group at <em>O</em>-2 of terminal rhamnose. Antioxidant assay <em>in vitro</em> indicated that EPS₁₂₈ exhibited antioxidant potential with 50.52 % DPPH· and 65.40 % ABTS·⁺ scavenging activities, reaching 54.3 % and 70.44 % of the efficacy of standard Vitamin C at 2.0 mg/L. Furthermore, EPS₁₂₈ showed protective effects against H₂O₂-induced oxidative stress in HepG2 cells by reducing cellular reactive oxygen species (ROS) and increasing cell viability. These findings present the first comprehensive report of an antioxidant EPS from <em>B. pseudocatenulatum</em>, highlighting its potential as a natural antioxidant for applications in the food industry and clinical settings.</div></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127914"},"PeriodicalIF":6.1,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142356603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ScRNA-seq reveals trained immunity-engaged Th17 cell activation against Edwardsiella piscicida-induced intestinal inflammation in teleost","authors":"Jin Yang ,&nbsp;Shu Cui ,&nbsp;Boning Shao ,&nbsp;Yanbo Zhao ,&nbsp;Zhuang Wang ,&nbsp;Qin Liu ,&nbsp;Yuanxing Zhang ,&nbsp;Dahai Yang","doi":"10.1016/j.micres.2024.127912","DOIUrl":"10.1016/j.micres.2024.127912","url":null,"abstract":"<div><div>Mucosal immunity typically involves innate and adaptive immune cells, while the cellular mechanism of teleost's intestinal immune cells that engages gut homeostasis against bacterial infection remains largely unknown. Taking advantage of the enteric fish pathogen (<em>Edwardsiella piscicida</em>) infection-induced intestinal inflammation in turbot (<em>Scophthalmus maximus</em>), we find that β-glucan training could mitigate the bacterial infection-induced intestinal inflammation. Through single-cell transcriptome profiling and cellular function analysis, we identify that <em>E. piscicida</em> infection could tune down the activation of intestinal Th17 cells, while β-glucan-training could preserve the potential to amplify and restore the function of intestinal Th17 cells. Moreover, through pharmacological inhibitor treatment, we identify that Th17 cells are essential for ameliorating bacterial infection-induced intestinal inflammation in teleost. Taken together, these results suggest a new concept of trained immunity activation to regulate the intestinal Th17 cells’ function, which might contribute to better developing strategies for maintaining gut homeostasis against bacterial infection.</div></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127912"},"PeriodicalIF":6.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142320420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The seed endophytic microbe Microbacterium testaceum M15 enhances the cold tolerance and growth of rice (Oryza sativa L.)","authors":"Jintong Zhao ,&nbsp;Xiaoqing Liu ,&nbsp;Ligang Hou ,&nbsp;Guoshun Xu ,&nbsp;Feifei Guan ,&nbsp;Wei Zhang ,&nbsp;Huiying Luo ,&nbsp;Ningfeng Wu ,&nbsp;Bin Yao ,&nbsp;Chunyi Zhang ,&nbsp;Pierre Delaplace ,&nbsp;Jian Tian","doi":"10.1016/j.micres.2024.127908","DOIUrl":"10.1016/j.micres.2024.127908","url":null,"abstract":"<div><div>The potential of seed endophytic microbes to enhance plant growth and resilience is well recognized, yet their role in alleviating cold stress in rice remains underexplored due to the complexity of these microbial communities. In this study, we investigated the diversity of seed endophytic microbes in two rice varieties, the cold-sensitive CB9 and the cold-tolerant JG117. Our results revealed significant differences in the abundance of Microbacteriaceae, with JG117 exhibiting a higher abundance under both cold stress and room temperature conditions compared to CB9. Further analysis led to the identification of a specific cold-tolerant microbe, <em>Microbacterium testaceum</em> M15, in JG117 seeds. M15-inoculated CB9 plants showed enhanced growth and cold tolerance, with a germination rate increase from 40 % to 56.67 % at 14℃ and a survival rate under cold stress (4℃) doubling from 22.67 % to 66.67 %. Additionally, M15 significantly boosted chlorophyll content by over 30 %, increased total protein by 16.31 %, reduced malondialdehyde (MDA) levels by 37.76 %, and increased catalase activity by 26.15 %. Overall, our study highlights the potential of beneficial endophytic microbes like <em>M. testaceum</em> M15 in improving cold tolerance in rice, which could have implications for sustainable agricultural practices and increased crop productivity in cold-prone regions.</div></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127908"},"PeriodicalIF":6.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bifidobacterium breve DSM 32583 and Limosilactobacillus fermentum CECT5716 postbiotics attenuate S. aureus and IL-33-induced Th2 responses","authors":"Yacine Amar ,&nbsp;Jana Grube ,&nbsp;Martin Köberle ,&nbsp;Monika Schaubeck ,&nbsp;Tilo Biedermann ,&nbsp;Thomas Volz","doi":"10.1016/j.micres.2024.127913","DOIUrl":"10.1016/j.micres.2024.127913","url":null,"abstract":"<div><div>Over the past decades, the prevalence of allergic diseases noticeably increased in industrialized countries. The Th2 immune response plays a central role in these pathologies and its modulation using pro-/postbiotics constitutes a promising approach to prevent or alleviate disease symptoms. The aim of this <em>in vitro</em> study, was to investigate the ability of human milk-derived <em>Bifidobacterium breve</em> DSM 32583 (<em>Bb</em>) and <em>Limosilactobacillus fermentum</em> CECT5716 (<em>Lf</em>), to modulate the Th2 induced responses. To this end, Th2 cells were generated by co-culturing of human naïve Th cells with monocyte-derived dendritic cells (moDCs) either stimulated with <em>Staphylococcus aureus</em> or IL-33. The immunomodulatory effects of pro-/postbiotic preparations of <em>Bb</em> and <em>Lf</em> on moDCs and Th2 cells were evaluated in terms of maturation markers expression and cytokines production. Remarkably, the tested strains induced the anti-inflammatory cytokine IL-10 in moDCs, in a strain-, dose- and viability-dependent manner with no significant upregulation of IL-12p70 nor CD83, CD86 or HLA-DR. Interestingly, <em>Bb</em> and <em>Lf</em> postbiotics were able to dampen the Th2/Th1 response induced upon <em>S. aureus</em>- or IL-33 stimulation. They were also able to synergistically induce IL-10 in moDCs and T cells, upon co-stimulation with LPS. Finally, we observed that live probiotics triggered a mild Th1 response that was attenuated in the presence of galacto-oligosaccharides. Altogether, <em>Bb</em> and <em>Lf</em> pro-/postbiotics exhibited remarkable immune regulatory effects on both moDCs and Th2 cells. Therefore, further <em>in vivo</em> studies should be considered to validate these findings and assess their ability to prevent allergy or alleviate its symptoms in affected patients.</div></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127913"},"PeriodicalIF":6.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0944501324003148/pdfft?md5=94ac892b9643e94e3a90220961695ec3&pid=1-s2.0-S0944501324003148-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142311502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Arbuscular mycorrhizal fungi and exogenous Ca2+ application synergistically enhance salt and alkali resistance in perennial ryegrass through diverse adaptive strategies","authors":"Hongjian Wei ,&nbsp;Wenyuan He ,&nbsp;Xinjie Mao ,&nbsp;Songkai Liao ,&nbsp;Qi Wang ,&nbsp;Zhihao Wang ,&nbsp;Ming Tang ,&nbsp;Tingying Xu ,&nbsp;Hui Chen","doi":"10.1016/j.micres.2024.127906","DOIUrl":"10.1016/j.micres.2024.127906","url":null,"abstract":"<div><div>The challenge of soil salinization and alkalization, with its significant impact on crop productivity, has raised growing concerns with global population growth and enhanced environmental degradation. Although arbuscular mycorrhizal fungi (AMF) and calcium ions (Ca²⁺) are known to enhance plant resistance to stress, their combined effects on perennial ryegrass’ tolerance to salt and alkali stress and the underlying mechanisms remain poorly understood. This study aimed to elucidate the roles of Arbuscular mycorrhizal (AM) fungus <em>Rhizophagus irregularis</em> and exogenous Ca²⁺ application in molecular and physiological responses to salt-alkali stress. AM symbiosis and exogenous Ca²⁺ application enhanced antioxidant enzyme activity and non-enzymatic components, promoting reactive oxygen species (ROS) scavenging and reducing lipid peroxidation while alleviating oxidative damage induced by salt-alkali stress. Furthermore, they enhanced osmotic balance by increasing soluble sugar content (Proportion of contribution of the osmotic adjustment were 34∼38 % in shoots and 30∼37 % in roots) under salt stress and organic acid content (Proportion of contribution of the osmotic adjustment were 32∼36 % in shoots and 37∼42 % in roots) under alkali stress. Changes in organic solute and inorganic cation-anion contents contributed to ion balance, while hormonal regulation played a role in these protective mechanisms. Moreover, the protective mechanisms involved activation of Ca²⁺-mediated signaling pathways, regulation of salt-alkali stress-related genes (including <em>LpNHX1</em> and <em>LpSOS1</em>), increased ATPase activity, elevated ATP levels, enhanced Na⁺ extrusion, improved K⁺ absorption capacity, and a reduced Na⁺/K⁺ ratio, all contributing to the protection of photosynthetic pigments and the enhancement of photosynthetic efficiency. Ultimately, the combined application of exogenous Ca²⁺ and AMF synergistically alleviated the inhibitory effects of salt-alkali stress on perennial ryegrass growth. This finding suggested that exogenous Ca²⁺ may participate in the colonization of perennial ryegrass plants by <em>R. irregularis</em>, while AM symbiosis may activate Ca²⁺ pathways. Consequently, the combined treatment of AM and Ca²⁺ is beneficial for enhancing plant regulatory mechanisms and increasing crop yield under salt-alkali stress.</div></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127906"},"PeriodicalIF":6.1,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Halotolerant Enterobacter asburiae A103 isolated from the halophyte Salix linearistipularis: Genomic analysis and growth-promoting effects on Medicago sativa under alkali stress","authors":"Yulin Li ,&nbsp;Mengya Gao ,&nbsp;Weiting Zhang ,&nbsp;Yuchen Liu ,&nbsp;Shanshan Wang ,&nbsp;Huihui Zhang ,&nbsp;Xiaoyan Li ,&nbsp;Shuyu Yu ,&nbsp;Lei Lu","doi":"10.1016/j.micres.2024.127909","DOIUrl":"10.1016/j.micres.2024.127909","url":null,"abstract":"<div><p>Soil salinization negatively affects plant growth and threatens food security. Halotolerant plant growth-promoting bacteria (PGPB) can alleviate salt stress in plants via diverse mechanisms. In the present study, we isolated salt-tolerant bacteria with phosphate-solubilizing abilities from the rhizosphere of <em>Salix linearistipularis</em>, a halophyte distributed in saline-alkali soils. Strain A103 showed high phosphate solubilization activity and was identified as <em>Enterobacter asburiae</em> based on genome analysis. In addition, it can produce indole-3-acetic acid (IAA), siderophores, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Genome mining has also revealed the presence of several functional genes involved in the promotion of plant growth. Inoculation with A103 markedly improved alfalfa growth in the presence of 100 mM NaHCO₃. Under alkali stress, the shoot and root dry weights after bacterial inoculation improved by 42.9 % and 21.9 %, respectively. Meanwhile, there was a 35.9–37.1 % increase in the shoot and root lengths after treatment with A103 compared to the NaHCO₃-treated group. Soluble sugar content, peroxidase and catalase activities increased in A103-inoculated alfalfa under alkaline stress. A significant decrease in the malondialdehyde content was observed after treatment with strain A103. Metabolomic analysis indicated that strain A103 positively regulated alkali tolerance in alfalfa through the accumulation of metabolites, such as homocarnosine, panthenol, and sorbitol, which could reduce oxidative damage and act as osmolytes. These results suggest that halophytes are valuable resources for bioprospecting halotolerant beneficial bacteria and that the application of halotolerant growth-promoting bacteria is a natural and efficient strategy for developing sustainable agriculture.</p></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127909"},"PeriodicalIF":6.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142270549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plant growth-promoting microorganisms drive K strategists through deterministic processes to alleviate biological stress caused by Fusarium oxysporum","authors":"Liangyang Mao ,&nbsp;Bo Yin ,&nbsp;Zeming Ye ,&nbsp;Jie Kang ,&nbsp;Rui Sun ,&nbsp;Zhenchao Wu ,&nbsp;Jingping Ge ,&nbsp;Wenxiang Ping","doi":"10.1016/j.micres.2024.127911","DOIUrl":"10.1016/j.micres.2024.127911","url":null,"abstract":"<div><p>Soybean root rot, caused by soil-borne pathogens such as <em>Fusarium oxysporum</em>, frequently occurs in Northeast China and leads to a decline in soil health and becoming a bottleneck for soybean yield in the region. To address this issue, applying beneficial microorganisms and altering soil microbial community structure have become effective strategies. In this study, the 90-day soybean pot experiment was conducted to explore the assembly process and life strategy selection of bacterial communities in the rhizosphere of healthy (inoculated with <em>Funneliformis mosseae</em>, F group and treated with <em>Pseudomonas putida</em>, P group) and diseased (inoculated with <em>F. oxysporum</em>, O group) soybean plants, as well as the recovery effect of beneficial microorganisms on soil-borne diseases (combined treatments OP and OF). Results indicated that in healthy soils (P and F), microbial community assembly process in the soybean rhizosphere was entirely governed by heterogeneous selection (HeS, 100 %). However, inoculated with <em>P. putida</em> (OP) was primarily driven by stochastic processes (HeS 40 %, dispersal limitation (DL) 60 %), and the <em>F. mosseae</em> treatment (OF) predominantly followed a deterministic process (HeS 89 %, DL 11 %) in diseased soils. Inoculation of plant growth-promoting microorganisms (PGPMs) in diseased soil drove the life strategy of the rhizosphere bacterial community from r- to K-strategy, evident from the lower rRNA operon (rrn) copy numbers (O 3.7, OP 2.1, OF 2.3), higher G+ to G- ratios (O 0.47, OP 0.58, OF 0.57), and a higher abundance of oligotrophs (O 50 %, OP 53 %, OF 54 %). In healthy (P and F) and diseased (O, OP, OF) rhizosphere soils, OTU820, OTU6142, and OTU8841 under the K-strategy, and OTU6032 and OTU6917 under the r-strategy, which served as keystone species, had a significant promoting relationship with plant biomass and defense capabilities ( <em>p</em> ＜0.05). Additionally, inoculation of PGPMs improved autotoxin degradation and positively correlated with bacterial life strategies in both healthy and diseased soils (P, F, OP and OF) ( <em>p</em> ＜0.05). These findings enhance our understanding of soil-microbe interactions and offer new insights and precise control measures for soybean disease management and soil environment remediation.</p></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127911"},"PeriodicalIF":6.1,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142270547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PGPR inoculants journey from lab to land: Challenges and limitations","authors":"Rishu Thakur ,&nbsp;Hena Dhar ,&nbsp;Supriya Mathew ,&nbsp;Arvind Gulati","doi":"10.1016/j.micres.2024.127910","DOIUrl":"10.1016/j.micres.2024.127910","url":null,"abstract":"","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127910"},"PeriodicalIF":6.1,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0944501324003112/pdfft?md5=24c1cb53336769340fa27c7e08bab670&pid=1-s2.0-S0944501324003112-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142270548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unveiling the genetic basis and metabolic rewiring behind the galactose-positive phenotype in a Streptococcus thermophilus mutant","authors":"Haimin Hu ,&nbsp;Qingting Peng ,&nbsp;Jiahui Tai ,&nbsp;Wenhui Lu ,&nbsp;Jinhui Liu ,&nbsp;Tong Dan","doi":"10.1016/j.micres.2024.127894","DOIUrl":"10.1016/j.micres.2024.127894","url":null,"abstract":"<div><p><em>Streptococcus thermophilus</em> (<em>S. thermophilus</em>) is a widely used starter culture in dairy fermentation, but most strains are galactose-negative and only metabolize glucose from lactose hydrolysis. In this study, we aimed to uncover the mechanisms underlying the acquisition of a stable galactose-positive (Gal⁺) phenotype in a mutant strain of <em>S. thermophilus</em> IMAU10636. By treating the wild-type strain with the mutagenic agent N-methyl-N-nitro-N-nitrosoguanidine, we successfully isolated a Gal⁺ mutant, <em>S. thermophilus</em> IMAU10636Y. Comparative enzyme activity assays revealed that the mutant exhibited higher β-galactosidase and galactokinase activities, but lower glucokinase and pyruvate kinase activities compared to the wild-type. High-performance liquid chromatography analysis confirmed the mutant’s enhanced ability to utilize lactose and galactose, leading to increased glucose secretion. Integrated genome and transcriptomics analyses provided deeper insights into the underlying genetic and metabolic mechanisms. We found that the metabolism regulatory network of the glycolysis / Leloir pathway was altered in the mutant, possibly due to the upregulation of the gene expression in the <em>gal</em>R-<em>gal</em>K intergenic region. This likely led to increased RNA polymerase binding and transcription of the <em>gal</em> operon, ultimately promoting the Gal⁺ phenotype. Additionally, we identified a mutation in the <em>scr</em>R gene, encoding a LacI family transcriptional repressor, which also contributed to the Gal⁺ phenotype. These findings offer new perspectives on the metabolic rewiring and regulatory mechanisms that enable <em>S. thermophilus</em> to acquire the ability to metabolize galactose. This knowledge can inform strategies for engineering and selecting Gal⁺ strains with desirable fermentation characteristics for dairy applications.</p></div>","PeriodicalId":18564,"journal":{"name":"Microbiological research","volume":"289 ","pages":"Article 127894"},"PeriodicalIF":6.1,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142270638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}