The impact of heterologous catalase expression and superoxide dismutase overexpression on enhancing the oxidative resistance in Lactobacillus casei

Chloroxylenol at environmental concentrations can promote conjugative transfer of antibiotic resistance genes by multiple mechanisms

The intergeneric conjugative transfer of antibiotic resistance genes (ARGs) is recognized as an important way to the dissemination of antibiotic resistance. However, it is unknown whether the extensive use of chloroxylenol (para-chloro-meta-xylenol, PCMX) in many pharmaceutical personal care products will lead to the spread of ARGs. In this study, the abilities and mechanisms of PCMX to accelerate the intergeneric conjugative transfer were investigated. Results showed that exposure of bacteria to environmental concentrations of PCMX (0.20-1.00 mg/L) can significantly stimulate the increase of conjugative transfer by 8.45-9.51 fold. The phenotypic experiments and genome-wide RNA sequencing revealed that 0.02-5.00 mg/L PCMX exposure could increase the content of alkaline phosphatase and malondialdehyde, which are characteristic products of cell wall and membrane damage. In addition, PCMX could lead to excessive production of reactive oxygen species (ROS) by 1.26-2.00 times, the superoxide dismutase and catalase produced by bacteria in response to oxidative stress were not enough to neutralize the damage of ROS, thus promoting the conjugative transfer. Gene Ontology enrichment analysis indicated that cell membrane permeability, pili, some chemical compounds transport and energy metabolism affected conjugative transfer. This study deepened the understanding of PCMX in promoting propagation of ARGs, and provided new perspectives for use and treatment of personal care products.

Common Inflammatory Mechanisms in COVID-19 and Parkinson's Diseases: The Role of Microbiome, Pharmabiotics and Postbiotics in Their Prevention

In the last decade, metagenomic studies have shown the key role of the gut microbiome in maintaining immune and neuroendocrine systems. Malfunction of the gut microbiome can induce inflammatory processes, oxidative stress, and cytokine storm. Dysfunction of the gut microbiome can be caused by short-term (virus infection and other infectious diseases) or long-term (environment, nutrition, and stress) factors. Here, we reviewed the inflammation and oxidative stress in neurodegenerative diseases and coronavirus infection (COVID-19). Here, we reviewed the renin-angiotensin-aldosterone system (RAAS) involved in the processes of formation of oxidative stress and inflammation in viral and neurodegenerative diseases. Moreover, the coronavirus uses ACE2 receptors of the RAAS to penetrate human cells. The coronavirus infection can be the trigger for neurodegenerative diseases by dysfunction of the RAAS. Pharmabiotics, postbiotics, and next-generation probiotics, are considered as a means to prevent oxidative stress, inflammatory processes, neurodegenerative and viral diseases through gut microbiome regulation.

Biomarkers and Utility of the Antioxidant Potential of Probiotic Lactobacilli and Bifidobacteria as Representatives of the Human Gut Microbiota

Lactobacilli and bifidobacteria are an important part of human gut microbiota. Among numerous benefits, their antioxidant properties are attracting more and more attention. Multiple in vivo and in vitro studies have demonstrated that lactobacilli and bifidobacteria, along with their cellular components, possess excellent antioxidant capacity, which provides a certain degree of protection to the human body against diseases associated with oxidative stress. Recently, lactobacilli and bifidobacteria have begun to be considered as a new source of natural antioxidants. This review summarizes the current state of research on various antioxidant properties of lactobacilli and bifidobacteria. Special emphasis is given to the mechanisms of antioxidant activity of these bacteria in the human gut microbiota, which involve bacterial cell components and metabolites. This review is also dedicated to the genes involved in the antioxidant properties of lactobacilli and bifidobacteria strains as indicators of their antioxidant potential in human gut microbiota. Identification of the antioxidant biomarkers of the gut microbiota is of great importance both for creating diagnostic systems for assessing oxidative stress and for choosing strategies aimed at restoring the normal functioning of the microbiota and, through it, restoring human health. In this review, the practical application of probiotic strains with proven antioxidant properties to prevent oxidative stress is also considered.

Enhanced Antioxidant Activity in Streptococcus thermophilus by High-Level Expression of Superoxide Dismutase

Superoxide dismutase (SOD) plays an essential role in eliminating oxidative damage of lactic acid bacteria. Streptococcus thermophilus, an important probiotic lactic acid bacterium, often inevitably suffers from various oxidative stress during dairy fermentation. In this study, to confer high-level oxidative resistance, the sod gene from Lactobacillus casei was heterologous expressed in S. thermophilus S-3 using our previous constructed native constitutive promoter library. The enzyme activity of SOD was significantly enhanced in engineered S. thermophilus by promoter #14 (2070 U/mg). Furthermore, the strategy of multi-copy sod-expressing cassettes was employed to improve SOD activity. The maximum activity (2750 U/mg) was obtained by the two-copy sod recombinant, which was 1.5-fold higher than that of one-copy recombinant. In addition, the survival rate of multi-copy sod recombinants was increased about 97-fold with 3.5 mmol/L H₂O₂ treatment. To our knowledge, this is the first report of multi-copy sod gene expression in S. thermophilus, which exerts a positive effect on coping with oxidative stress to enhance the potential of industrial application.

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.

Biochemical responses of rice roots to cold stress

BACKGROUND

Cold stress is the main factor that reduces rice yield in subtropical areas, especially at the seedling stage. Most of the current studies on cold stress focus the responses of rice shoots to cold stress. Limited studies are available on that of rice roots to cold stress. This study aimed to illustrate the biochemical responses of rice root under cold treatment, and subject to the establishment of cold stress-related biochemical traits for rice breeding or cropping-adjustment.

RESULTS

Our results showed that the growth of rice seedling diminished under cold stress with difference extents among eight rice cultivars of most productive in Taiwan. Under cold treatments, the tested cultivars with higher growth rate had a higher level of hydrogen peroxide (H₂O₂) in the shoots but had a lower level in the roots. In contrast, the tested cultivates with low growth rate had higher levels of H₂O₂ in the roots but a lower level in the shoots. Meanwhile, higher MDA contents and higher cell-damage related electrolyte leakage were also found in the roots not in the shoots, suggesting that cold stress might induce oxidative stress in the roots, not in the shoots. Furthermore, the activity analysis of four antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT), ascorbic peroxidase (APX), and glutathione reductase (GR), revealed that cold stress could increase SOD and CAT activities in the roots.

CONCLUSIONS

In summary, low H₂O₂ and low MDA contents along with lower SOD and CAT activities in rice root could be the biochemical traits of cold responses in rice seedlings. The results are hoping to have a contribution to the rice breeding or cropping-adjustment on cold tolerance.

Production of optically pure L(+)-lactic acid from waste plywood chips using an isolated thermotolerant Enterococcus faecalis SI at a pilot scale

Utilization of renewable and low-cost lignocellulosic wastes has received major focus in industrial lactic acid production. The use of high solid loadings in biomass pretreatment potentially offers advantages over low solid loadings including higher lactic acid concentration with decreased production and capital costs. In this study, an isolated Enterococcus faecalis SI with optimal temperature 42 °C was used to produce optically pure L-lactic acid (> 99%) from enzyme-saccharified hydrolysates of acid-impregnated steam explosion (AISE)-treated plywood chips. The L-lactic acid production increased by 10% at 5 L scale compared to the similar fermentation scheme reported by Wee et al. The fermentation with a high solid loading of 20% and 35% (w/v) AISE-pretreated plywood chips had been successfully scaled up to process development unit scale (100 L) and pilot scale (9 m³), respectively. This is the first report of pilot-scale lignocellulosic lactic acid fermentation by E. faecalis with high lactic acid titer (nearly 92 g L^-1) and yield (0.97 kg kg^-1). Therefore, large-scale L-lactic acid production by E. faecalis SI shows the potential application for industries.

Use of recombinant Lactobacillus sakei for the prevention and treatment of radiation-induced enteritis

Radiation-induced enteritis is one of the most common complications in patients under radiotherapy at abdominal or pelvic cavity. Up to 50% of patients treated with pelvic radiotherapy has been reported radiation-induced acute enteritis, and half of them developed chronic enteritis. Overproduction of free radicals, activation of inflammatory pathways and vascular endothelial dysfunction were considered as the primary mechanisms of radiation-induced enteritis. Because probiotics have been demonstrated as a promising potential candidate for treating intestinal diseases, it may be a safer and more effective radioprotector for the enteritis compared to conventional chemical agents with inherent toxicities. Here, we propose that a recombinant Lactobacillus sakei would decrease the complications or symptoms significantly through against different pathogenic mechanisms simultaneously. Therefore, application of higher radiation dose for tumor control would be feasible when co-treating with recombinant Lactobacillus sakei.

Effect of superoxide dismutase and manganese on superoxide tolerance in Lactobacillus casei strain Shirota and analysis of multiple manganese transporters

The Lactobacillus casei/paracasei group accumulates a high level of manganese, which works to scavenge superoxide anions produced during aerobic growth. The genome of L. casei strain Shirota, however, also codes the gene for superoxide dismutase (SOD), sodA, which catalyzes the dismutation of superoxide anion into hydrogen peroxide and oxygen. We anticipated that the SOD and/or manganese may contribute to the aerobic growth of L. casei Shirota and tried to clarify how L. casei Shirota can eliminate the toxicity of superoxide anion. When the sodA of L. casei Shirota was cloned and expressed in Escherichia coli as well as in L. casei Shirota, there was no increase in SOD activity detected, meaning that the protein is in an inactive form, even if it is produced in L. casei Shirota. We next focused on the role of the manganese transport system of L. casei Shirota. One ABC-type manganese transporter (mtsCBA cluster) and three NRAMP-type manganese transporters (mntH1, mntH2, and mntH3) are coded in the genome. To clarify the role of these genes, we disrupted one or more of these manganese transporter genes in different combinations and analyzed the intracellular manganese levels. As a result, we found that NRAMP-type manganese transporters coded by mntH1 and mntH2 and ABC-type manganese transporter coded by mtsCBA cluster are complementarily involved in the accumulation of intracellular manganese and are necessary for aerobic growth of L. casei Shirota. These results indicate that intracellular manganese accumulated by multiple complementary manganese transporters, but not SOD, plays a pivotal role in tolerance to superoxide in L. casei Shirota.

A bioluminescent test system reveals valuable antioxidant properties of lactobacillus strains from human microbiota

Oxidative stress cause serious damages in human organism resulting in multiple diseases. Antioxidant therapy includes diet, the use of chemical agents or commensal bacteria such as lactobacilli. This study aims to evaluate the antioxidant (AO) activity of cell-free culture supernatants of lactobacilli, isolated from different parts of the human body. A test system based on Escherichia coli MG1655 strains carrying plasmids encoding luminescent biosensors pSoxS-lux and pKatG-lux inducible by superoxide anion and hydrogen peroxide, respectively, was used to analyze cell-free culture supernatants of lactobacilli. Bioluminescent detection systems are suitable for quick screening of AO activity of lactobacilli. The majority of strains (51 out of 81) belonging to six different species demonstrated various levels of antioxidant activity. This activity was confirmed using the trolox equivalent method. The genome of one of the strains showing high AO activity was sequenced, and the genes putatively involved in AO capacity were determined. Potencies of standard AO and CFS from the most active Lactobacillus strains. Percentages of decrease in the detected luminescence (IAO%) in the presence of AO or CFS are presented. L. br.-L. brevis, L. pl. -L. plantarum, L. rh.-L. rhamnosus.

circRNA_0046367 Prevents Hepatoxicity of Lipid Peroxidation: An Inhibitory Role against Hepatic Steatosis

Hepatic steatosis reflects the miRNA-related pathological disorder with triglyceride accumulation and lipid peroxidation, which leads to nonalcoholic steatohepatitis, liver fibrosis/cirrhosis, and even hepatocellular carcinoma. Circular RNA (circRNA)/miRNA interaction reveals a novel layer of epigenetic regulation, yet the miRNA-targeting circRNA remains uncertain in hepatic steatosis. Here, we uncover circRNA_0046367 to be endogenous modulator of miR-34a that underlies hepatic steatosis. In contrast to its expression loss during the hepatocellular steatosis in vivo and in vitro, circRNA_0046367 normalization abolished miR-34a's inhibitory effect on peroxisome proliferator-activated receptor α (PPARα) via blocking the miRNA/mRNA interaction with miRNA response elements (MREs). PPARα restoration led to the transcriptional activation of genes associated with lipid metabolism, including carnitine palmitoyltransferase 2 (CPT2) and acyl-CoA binding domain containing 3 (ACBD3), and then resulted in the steatosis resolution. Hepatotoxicity of steatosis-related lipid peroxidation, being characterized by mitochondrial dysfunction, growth arrest, and apoptosis, is resultantly prevented after the circRNA_0046367 administration. These findings indicate a circRNA_0046367/miR-34a/PPARα regulatory system underlying hepatic steatosis. Normalized expression of circRNA_0046367 may ameliorate the lipoxidative stress on the basis of steatosis attenuation. circRNA_0046367, therefore, is suggested to be potential approach to the therapy of lipid peroxidative damage.

Large-Scale Phylogenomics of the Lactobacillus casei Group Highlights Taxonomic Inconsistencies and Reveals Novel Clade-Associated Features

Although the genotypic and phenotypic properties of the Lactobacillus casei group have been studied extensively, the taxonomic structure has been the subject of debate for a long time. Here, we performed a large-scale comparative analysis by using 183 publicly available genomes supplemented with a Lactobacillus strain isolated from the human upper respiratory tract. On the basis of this analysis, we identified inconsistencies in the taxonomy and reclassified all of the genomes according to their most closely related type strains. This led to the identification of a catalase-encoding gene in all 10 L. casei sensu stricto strains, making it the first described catalase-positive species in the Lactobacillus genus. Moreover, we found that 6 of 10 L. casei genomes contained a SecA2/SecY2 gene cluster with two putative glycosylated surface adhesin proteins. Altogether, our results highlight current inconsistencies in the taxonomy of the L. casei group and reveal new clade-associated functional features. IMPORTANCE The closely related species of the Lactobacillus casei group are extensively studied because of their applications in food fermentations and as probiotics. Our results show that many strains in this group are incorrectly classified and that reclassifying them to their most closely related species type strain improves the functional predictive power of their taxonomy. In addition, our findings may spark increased interest in the L. casei species. We find that after reclassification, only 10 genomes remain classified as L. casei. These strains show some interesting properties. First, they all appear to be catalase positive. This suggests that they have increased oxidative stress resistance. Second, we isolated an L. casei strain from the human upper respiratory tract and discovered that it and multiple other L. casei strains harbor one or even two large, glycosylated putative surface adhesins. This might inspire further exploration of this species as a potential probiotic organism.