The uvrA gene is involved in oxidative and acid stress responses in Lactobacillus helveticus CNBL1156

Comparison of Lactiplantibacillus plantarum isolates from the gut of mice supplemented with different types of nutrients: a genomic and metabolomic study

Many studies have focused on the influence of dietary supplements on gut microbiota composition, but limited research have reported their effects on specific bacterial species in the gut. Lactiplantibacillus plantarum is one of the most widely studied probiotics, with a wide range of sources and good environmental adaptability. In this study, in order to elucidate the adaptation strategies of L. plantarum to the gut of mice supplemented with carbohydrates, peptides and minerals, whole genome resequencing and intracellular metabolites detection were performed, and high-frequency mutant genes and differential metabolites were screened. The results suggested different types of dietary supplements do have different effects on L. plantarum from the gut of mice. Additionally, KEGG annotation unveiled that the effects of these dietary supplements on the gene level of L. plantarum primarily pertained to environmental information processing, while the differential metabolites were predominantly associated with metabolism. This study provided new perspectives on the adaptive mechanism of L. plantarum in response to the host's gut environment, suggesting that the diversity of the genome and metabolome of L. plantarum was correlated with dietary supplements. Furthermore, this study offered useful guidance in the effective utilization of dietary supplements.

Effect of salinity on genes involved in the stress response in mangrove soils

Mangroves are a challenging ecosystem for the microorganisms that inhabit them, considering they are subjected to stressful conditions such as high and fluctuating salinity. Metagenomic analysis of mangrove soils under contrasting salinity conditions was performed at the mouth of the Ranchera River to the Caribbean Sea in La Guajira, Colombia, using shotgun sequencing and the Illumina Hiseq 2500 platform. Functional gene analysis demonstrated that salinity could influence the abundance of microbial genes involved in osmoprotectant transport, DNA repair, heat shock proteins (HSP), and Quorum Sensing, among others. In total, 135 genes were discovered to be linked to 12 pathways. Thirty-four genes out of 10 pathways had statistical differences for a p-value and FDR < 0.05. UvrA and uvrB (nucleotide excision repair), groEL (HSP), and secA (bacterial secretion system) genes were the most abundant and were enriched by high salinity. The results of this study showed the prevalence of diverse genetic mechanisms that bacteria use as a response to survive in the challenging mangrove, as well as the presence of various genes that are recruited in order to maintain bacterial homeostasis under conditions of high salinity.

Insight into the acid tolerance mechanism of Acetilactobacillus jinshanensis subsp. aerogenes Z-1

Several lactic acid bacteria (LAB) are double-edged swords in the production of Sichuan bran vinegar; on the one hand, they are important for the flavour of the vinegar, but on the other hand, they result in vinegar deterioration because of their gas-producing features and their acid resistance. These characteristics intensify the difficulty in managing the safe production of vinegar using strains such as Acetilactobacillus jinshanensis subsp. aerogenes Z-1. Therefore, it is necessary to characterize the mechanisms underlying their acid tolerance. The results of this study showed a survival rate of 77.2% for Z-1 when exposed to pH 3.0 stress for 1 h. This strain could survive for approximately 15 days in a vinegar solution with 4% or 6% total acid content, and its growth was effectively enhanced by the addition of 10 mM of arginine (Arg). Under acidic stress, the relative content of the unsaturated fatty acid C18:1 (n-11) increased, and eight amino acids accumulated in the cells. Meanwhile, based on a transcriptome analysis, the genes glnA, carA/B, arcA, murE/F/G, fabD/H/G, DnaK, uvrA, opuA/C, fliy, ecfA2, dnaA and LuxS, mainly enriched in amino acid transport and metabolism, protein folding, DNA repair, and cell wall/membrane metabolism processes, were hypothesized to be acid resistance-related genes in Z-1. This work paves the way for further clarifying the acid tolerance mechanism of Z-1 and shares applicable perspectives for vinegar brewing.

Bicyclol Alleviates Atherosclerosis by Manipulating Gut Microbiota

Atherosclerosis (AS) is associated with high morbidity and mortality, thus imposing a growing burden on modern society. Herb-derived bicyclol (BIC) is a versatile bioactive compound that can be used to treat AS. However, its efficacy in AS is not yet described. Here, it is shown that BIC normalizes gut microflora dysbiosis induced by a high fat diet in Apoe^(-/-) mice. Metagenome-wide association study analysis verifies that the modulation on carbohydrate-active enzymes and short-chain fatty acid generating genes in gut flora is among the mechanisms. The gut healthiness, especially the gut immunity and integrity, is restored by BIC intervention, leading to improved systemic immune cell dynamic and liver functions. Accordingly, the endothelial activation, macrophage infiltration, and cholesterol ester accumulation in the aortic arch are alleviated by BIC to lessen the plaque onset. Moreover, it is proved that the therapeutic effect of BIC on AS is transmissible by fecal microbiota transplantation. The current study, for the first time, demonstrates the antiatherosclerotic effects of BIC and shows that its therapeutic value can at least partially be attributed to its manipulation of gut microbiota.

iTRAQ-based quantitative proteomic reveals proteomic changes in Serratia sp. CM01 and mechanism of Cr(Ⅵ) resistance

OBJECTIVE

Serratia sp. CM01 is a wild strain with the resistance and reduction ability of chromium(Ⅵ). The aim of this study it to investigate the underlying mechanisms of the Cr(Ⅵ) tolerance and reduction of strain CM01, and to explore its response to environmental pollution pressure at the molecular level.

METHODS

The iTRAQ technique was utilized to investigate the differentially expressed protein patterns related to the Cr(Ⅵ)-resistance in wild-type strain CM01 and domesticated CM01. RT-qPCR was used to verify the expression levels of several functional genes. The cell surface hydrophobicity and autoaggregation, the intracellular glucose content, and the total superoxide dismutase (SOD) activity were determined.

RESULTS

In total, 2750 proteins were detected and identified in WT CM01 and domesticated CM01. Compared with WT CM01, the iTRAQ results of 646 proteins were found to be significantly differentially expressed in domesticated CM01. There were 343 up-regulated and 303 down-regulated proteins, which mainly related to carbohydrate metabolism, stress responses, amino acid metabolism and some other systems. RT-qPCR results showed that the expression level of seven genes in domesticated CM01 were consistent with the iTRAQ proteomic profiles. The cell surface hydrophobicity, self-aggregation, intracellular glucose content and total SOD activity of domesticated CM01 with Cr(Ⅵ) treatment were significantly higher than without Cr(Ⅵ) treatment.

CONCLUSION

Domesticated CM01 displayed a complex biological network to exhibit the tolerance of Cr(Ⅵ), which may be attributed to the following aspects: (a) CM01 reduced the consumption of glucose by inhibiting the metabolism of carbohydrates, which was an energy-saving survival mode. (b) The inositol phosphate metabolism pathway played an important role. (c) Oxidative stress proteins enhanced the adaptability. (d) CM01 enhanced biosynthesis of hydrophobic amino acids to resistance to Cr(Ⅵ). (e) Several key systems and proteins, such as UvrABC system, Lon protease, porin OmpC, also may play an important role.

Altered Metabolic Strategies: Elaborate Mechanisms Adopted by Oenococcus oeni in Response to Acid Stress

Oenococcus oeni plays a key role in inducing malolactic fermentation in wine. Acid stress is often encountered under wine conditions. However, the lack of systematic studies of acid resistance mechanisms limits the downstream fermentation applications. In this study, the acid responses of O. oeni were investigated by combining transcriptome, metabolome, and genome-scale metabolic modeling approaches. Metabolite profiling highlighted the decreased abundance of nucleotides under acid stress. The gene-metabolite bipartite network showed negative correlations between nucleotides and genes involved in ribosome assembly, translation, and post-translational processes, suggesting that stringent response could be activated under acid stress. Genome-scale metabolic modeling revealed marked flux rerouting, including reallocation of pyruvate, attenuation of glycolysis, utilization of carbon sources other than glucose, and enhancement of nucleotide salvage and the arginine deiminase pathway. This study provided novel insights into the acid responses of O. oeni, which will be useful for designing strategies to address acid stress in wine malolactic fermentation.

Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic review

Lactic acid bacteria (LAB) are the most frequently used probiotics in fermented foods and beverages and as food supplements for humans or animals, owing to their multiple beneficial features, which appear to be partially associated with their antioxidant properties. LAB can help improve food quality and flavor and prevent numerous disorders caused by oxidation in the host. In this review, we discuss the oxidative stress tolerance, the antioxidant capacity related herewith, and the underlying mechanisms and signaling pathways in probiotic LAB. In addition, we discuss appropriate methods used to evaluate the antioxidant capacity of probiotic LAB. The aim of the present review is to provide an overview of the current state of the research associated with the oxidative stress tolerance and antioxidant capacity of LAB.

Global transcriptomic and proteomics analysis of Lactobacillus plantarum Y44 response to 2,2-azobis(2-methylpropionamidine) dihydrochloride (AAPH) stress

Our previous study demonstrated that Lactobacillus plantarum Y44 exhibited antioxidant activity. However, the physiological characteristics of L. plantarum Y44 exposure to oxidative stress was not clear. In this research, the differentially expressed proteins and genes in L. plantarum Y44 under 2,2-azobis(2-methylpropionamidine) dihydrochloride (AAPH) stress at different concentrations were studied by using integrated transcriptomic and proteomic methods. Under 100 mM AAPH stress condition, 1139 differentially expressed genes (DEGs, 546 up-regulated and 593 down-regulated) and 329 differentially expressed proteins (DEPs, 127 up-regulated and 202 down-regulated) were observed. Under 200 mM AAPH stress condition, 1526 DEGs (751 up-regulated and 775 down-regulated) and 382 DEPs (139 up-regulated and 243 down-regulated) were observed. Overall, we found that L. plantarum Y44 fought against AAPH induced oxidative stress by up-regulating antioxidant enzymes and DNA repair proteins, such as ATP-dependent DNA helicase RuvA, adenine DNA glycosylase, single-strand DNA-binding protein SSB, DNA-binding ferritin-like protein DPS, thioredoxin reductase, protein-methionine-S-oxide reductase and glutathione peroxidase. Additionally, cell envelope composition of L. plantarum Y44 was highly remodeled by accelerating peptidoglycan and teichoic-acid (LTA) biosynthesis and modulating the fatty acids (FA) composition to achieve a higher ratio of unsaturated/saturated fatty acids (UFAs/SFAs) against AAPH stress. Moreover, metabolism processes including carbohydrate metabolism, amino acid biosynthesis, and nucleotide metabolism altered to respond to AAPH-induced damage. Altogether, our findings allow us to facilitate a better understanding of L. plantarum Y44 against oxidative stress. SIGNIFICANCE: This study represents an integrated proteomic and transcriptomic analysis of Lactobacillus plantarum Y44 response to 2,2-azobis(2-methylpropionamidine) dihydrochloride (AAPH) stress. Differentially expressed proteins and genes were identified between the proteome and transcriptome of L. plantarum Y44 under different AAPH stress. AAPH-induced response of L. plantarum Y44 appears to be primarily based on ROS scavenging, DNA repair, highly remodeled cell surface and specific metabolic processes. The knowledge about these proteomes and transcriptomes provides significant insights into the oxidative stress response of Lactobacillus plantarum.

The Potential of Lactobacillus spp. for Modulating Oxidative Stress in the Gastrointestinal Tract

The gastrointestinal (GI) tract is crucial for food digestion and nutrient absorption in humans. However, the GI tract is usually challenged with oxidative stress that can be induced by various factors, such as exogenous pathogenic microorganisms and dietary alterations. As a part of gut microbiota, Lactobacillus spp. play an important role in modulating oxidative stress in cells and tissues, especially in the GI tract. Oxidative stress is linked with excessive reactive oxygen species (ROS) that can be formed by a few enzymes, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs). The redox mechanisms of Lactobacillus spp. may contribute to the downregulation of these ROS-forming enzymes. In addition, nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf-2) and nuclear factor kappa B (NF-κB) are two common transcription factors, through which Lactobacillus spp. modulate oxidative stress as well. As oxidative stress is closely associated with inflammation and certain diseases, Lactobacillus spp. could potentially be applied for early treatment and amelioration of these diseases, either individually or together with prebiotics. However, further research is required for revealing their mechanisms of action as well as their extensive application in the future.

Improving the acetic acid tolerance and fermentation of Acetobacter pasteurianus by nucleotide excision repair protein UvrA

Acetic acid bacteria (AAB) are widely used in acetic acid fermentation due to their remarkable ability to oxidize ethanol and high tolerance against acetic acid. In Acetobacter pasteurianus, nucleotide excision repair protein UvrA was up-regulated 2.1 times by acetic acid when compared with that without acetic acid. To study the effects of UvrA on A. pasteurianus acetic acid tolerance, uvrA knockout strain AC2005-ΔuvrA, uvrA overexpression strain AC2005 (pMV24-uvrA), and the control strain AC2005 (pMV24), were constructed. One percent initial acetic acid was almost lethal to AC2005-ΔuvrA. However, the biomass of the UvrA overexpression strain was higher than that of the control under acetic acid concentrations. After 6% acetic acid shock for 20 and 40 min, the survival ratios of AC2005 (pMV24-uvrA) were 2 and 0.12%, respectively; however, they were 1.5 and 0.06% for the control strain AC2005 (pMV24). UvrA overexpression enhanced the acetification rate by 21.7% when compared with the control. The enzymes involved in ethanol oxidation and acetic acid tolerance were up-regulated during acetic acid fermentation due to the overexpression of UvrA. Therefore, in A. pasteurianus, UvrA could be induced by acetic acid and is related with the acetic acid tolerance by protecting the genome against acetic acid to ensure the protein expression and metabolism.

Whole-transcriptome analysis of oxidative stress response genes in carotenoid-producing Enterococcus gilvus

Whole-transcriptome analysis of aerobic stress response gene in Enterococcus gilvus was performed using RNA-sequencing to identify carotenoid-based stress response genes in lactic acid bacteria. The expression of gene responsible for pyruvate dehydrogenase complex synthesis was highly upregulated after aerobic treatment. In addition, the expression of transcriptional regulator spx and genes encoding UvrABC system protein was also upregulated.

UvrA expression of Lactococcus lactis NZ9000 improve multiple stresses tolerance and fermentation of lactic acid against salt stress

Lactococcus lactis is subjected to several stressful conditions during industrial fermentation including oxidation, heating and cooling, acid, high osmolarity/dehydration and starvation. DNA lesion is a major cause of genetic instability in L. lactis that usually occurs at a low frequency, but it is greatly enhanced by environmental stresses. DNA damages produced by these environmental stresses are thought to induce DNA double-strand breaks, leading to illegitimate recombination. Nucleotide excision repair (NER) protein UvrA suppresses multiple stresses-induced illegitimate recombination. UvrA protein can survive a coincident condition of environmental harsh conditions, multiple stress factors supposedly encountered in the host and inducing UvrA in L. lactis. In this study the expression of UvrA and growth performance and viability of control strain L. lactisVector and recombinant strain L. lactisUvrA under multiple stress conditions were determined. The recombinants strain had 30.70 and 52.67% higher growth performances when subjected to acidic and osmotic stresses conditions. In addition, the L. lactisUvrA strain showed 1.85-, 1.65-, and 2.40-fold higher biomass, lactate production, and lactate productivity, compared with the corresponding values for L. lactisVector strain during the osmotic stress. Results demonstrated NER system is involved in adaptation to various stress conditions and suggested that cells with a compromised UvrA as DNA repair system have an enhanced protection behavior in L. lactis NZ9000 against DNA damage.

Stress Physiology of Lactic Acid Bacteria

Lactic acid bacteria (LAB) are important starter, commensal, or pathogenic microorganisms. The stress physiology of LAB has been studied in depth for over 2 decades, fueled mostly by the technological implications of LAB robustness in the food industry. Survival of probiotic LAB in the host and the potential relatedness of LAB virulence to their stress resilience have intensified interest in the field. Thus, a wealth of information concerning stress responses exists today for strains as diverse as starter (e.g., Lactococcus lactis), probiotic (e.g., several Lactobacillus spp.), and pathogenic (e.g., Enterococcus and Streptococcus spp.) LAB. Here we present the state of the art for LAB stress behavior. We describe the multitude of stresses that LAB are confronted with, and we present the experimental context used to study the stress responses of LAB, focusing on adaptation, habituation, and cross-protection as well as on self-induced multistress resistance in stationary phase, biofilms, and dormancy. We also consider stress responses at the population and single-cell levels. Subsequently, we concentrate on the stress defense mechanisms that have been reported to date, grouping them according to their direct participation in preserving cell energy, defending macromolecules, and protecting the cell envelope. Stress-induced responses of probiotic LAB and commensal/pathogenic LAB are highlighted separately due to the complexity of the peculiar multistress conditions to which these bacteria are subjected in their hosts. Induction of prophages under environmental stresses is then discussed. Finally, we present systems-based strategies to characterize the "stressome" of LAB and to engineer new food-related and probiotic LAB with improved stress tolerance.

Stress tolerance and virulence of insect-pathogenic fungi are determined by environmental conditions during conidial formation

The virulence to insects and tolerance to heat and UV-B radiation of conidia of entomopathogenic fungi are greatly influenced by physical, chemical, and nutritional conditions during mycelial growth. This is evidenced, for example, by the stress phenotypes of Metarhizium robertsii produced on various substrates. Conidia from minimal medium (Czapek's medium without sucrose), complex medium, and insect (Lepidoptera and Coleoptera) cadavers had high, moderate, and poor tolerance to UV-B radiation, respectively. Furthermore, conidia from minimal medium germinated faster and had increased heat tolerance and were more virulent to insects than those from complex medium. Low water-activity or alkaline culture conditions also resulted in production of conidia with high tolerance to heat or UV-B radiation. Conidia produced on complex media exhibited lower stress tolerance, whereas those from complex media supplemented with NaCl or KCl (to reduce water activity) were more tolerant to heat and UV-B than those from the unmodified complex medium. Osmotic and nutritive stresses resulted in production of conidia with a robust stress phenotype, but also were associated with low conidial yield. Physical conditions such as growth under illumination, hypoxic conditions, and heat shock before conidial production also induced both higher UV-B and heat tolerance; but conidial production was not decreased. In conclusion, physical and chemical parameters, as well as nutrition source, can induce great variability in conidial tolerance to stress for entomopathogenic fungi. Implications are discussed in relation to the ecology of entomopathogenic fungi in the field, and to their use for biological control. This review will cover recent technologies on improving stress tolerance of entomopathogenic fungi for biological control of insects.

Mechanism analysis of acid tolerance response of bifidobacterium longum subsp. longum BBMN 68 by gene expression profile using RNA-sequencing

To analyze the mechanism of the acid tolerance response (ATR) in Bifidobacterium longum subsp. longum BBMN68, we optimized the acid-adaptation condition to stimulate ATR effectively and analyzed the change of gene expression profile after acid-adaptation using high-throughput RNA-Seq. After acid-adaptation at pH 4.5 for 2 hours, the survival rate of BBMN68 at lethal pH 3.5 for 120 min was increased by 70 fold and the expression of 293 genes were upregulated by more than 2 fold, and 245 genes were downregulated by more than 2 fold. Gene expression profiling of ATR in BBMN68 suggested that, when the bacteria faced acid stress, the cells strengthened the integrity of cell wall and changed the permeability of membrane to keep the H⁺ from entering. Once the H⁺ entered the cytoplasm, the cells showed four main responses: First, the F₀F₁-ATPase system was initiated to discharge H⁺. Second, the ability to produce NH₃ by cysteine-cystathionine-cycle was strengthened to neutralize excess H⁺. Third, the cells started NER-UVR and NER-VSR systems to minimize the damage to DNA and upregulated HtpX, IbpA, and γ-glutamylcysteine production to protect proteins against damage. Fourth, the cells initiated global response signals ((p)ppGpp, polyP, and Sec-SRP) to bring the whole cell into a state of response to the stress. The cells also secreted the quorum sensing signal (AI-2) to communicate between intraspecies cells by the cellular signal system, such as two-component systems, to improve the overall survival rate. Besides, the cells varied the pathways of producing energy by shifting to BCAA metabolism and enhanced the ability to utilize sugar to supply sufficient energy for the operation of the mechanism mentioned above. Based on these reults, it was inferred that, during industrial applications, the acid resistance of bifidobacteria could be improved by adding BCAA, γ-glutamylcysteine, cysteine, and cystathionine into the acid-stress environment.

Compromised DNA damage repair promotes genetic instability of the genomic magnetosome island in Magnetospirillum magneticum AMB-1

Magnetotactic bacteria (MTB) are capable of synthesizing nano-sized, intracellular membrane-bound magnetosomes. To learn more about the genetic factors involved in magnetosome formation, transposon mutagenesis was carried out by conjugation using a hyperactive mariner transposon to obtain nonmagnetic mutants of Magnetospirillum magneticum AMB-1. A mutant with defect in uvrA gene encoding the DNA binding subunit of the UvrABC complex responsible for the process of nucleotide excision repair, was obtained. Growth, magnetosome formation and maintenance of magnetosome island (MAI) were further analyzed in the absence of UvrA. Interruption of uvrA led to decreased capacity to form magnetosome when cultured in the presence of oxygen. The deficiency in UvrA also resulted in an accelerated loss of the MAI under aerobic conditions indicating that the nucleotide excision repair system guards against the instability of the MAI. The incapacity of MTB to efficiently initiate recombination mediated by RecA rescued the instability of MAI observed in uvrA mutant. Elevated recombination activity resulting from the accumulation of unrepaired mutations may thus account for the instability of MAI in the absence of UvrA.

Transcriptome analysis of probiotic Lactobacillus casei Zhang during fermentation in soymilk

Lactobacillus casei Zhang is a widely recognized probiotic bacterium, which is being commercially used in China. To study the gene expression dynamics of L. casei Zhang during fermentation in soymilk, a whole genome microarray was used to screen for differentially expressed genes when grown to the lag phase, the late logarithmic phase, and the stationary phase. Comparisons of different transcripts next to each other revealed 162 and 63 significantly induced genes in the late logarithmic phase and stationary phase, of which the expression was at least threefold up-regulated and down-regulated, respectively. Approximately 38.4% of the up-regulated genes were associated with amino acid transport and metabolism notably for histidine and lysine biosynthesis, followed by genes/gene clusters involved in carbohydrate transport and metabolism, lipid transport and metabolism, and inorganic ion transport and metabolism. The analysis results suggest a complex stimulatory effect of soymilk-based ecosystem on the L. casei Zhang growth. On the other hand, it provides the very first insight into the molecular mechanism of L. casei strain for how it will adapt to the protein-rich environment.

Genes and molecules of lactobacilli supporting probiotic action

Lactobacilli have been crucial for the production of fermented products for centuries. They are also members of the mutualistic microbiota present in the human gastrointestinal and urogenital tract. Recently, increasing attention has been given to their probiotic, health-promoting capacities. Many human intervention studies demonstrating health effects have been published. However, as not all studies resulted in positive outcomes, scientific interest arose regarding the precise mechanisms of action of probiotics. Many reported mechanistic studies have addressed mainly the host responses, with less attention being focused on the specificities of the bacterial partners, notwithstanding the completion of Lactobacillus genome sequencing projects, and increasing possibilities of genomics-based and dedicated mutant analyses. In this emerging and highly interdisciplinary field, microbiologists are facing the challenge of molecular characterization of probiotic traits. This review addresses the advances in the understanding of the probiotic-host interaction with a focus on the molecular microbiology of lactobacilli. Insight into the molecules and genes involved should contribute to a more judicious application of probiotic lactobacilli and to improved screening of novel potential probiotics.