Lactiplantibacillusplantarum JS19-adjunctly fermented goat milk alleviates D-galactose-induced aging by modulating oxidative stress and intestinal microbiota in mice.

Oxidative stress is a crucial factor in the age-related decline in physiological, genomic, metabolic, and immunological functions. We screened Lactiplantibacillus plantarum JS19 (L. plantarum JS19), which has been shown to possess therapeutic properties in mice with ulcerative colitis. In this study, L. plantarum JS19-adjunctly fermented goat milk (LAF) was employed to alleviate D-galactose-induced aging and regulate intestinal flora in an aging mouse model. The oral administration of LAF effectively improved the health of spleen and kidney in mice, while mitigating the hepatocyte and oxidative damage induced by D-galactose. Additionally, LAF alleviated D-galactose-induced dysbiosis of the intestinal flora by reducing the abundance of harmful bacteria Desulfovibrio and Helicobacter, while greatly promoting the growth of beneficial Rikenellaceae_RC9_gut_group and Eubacterium. Biomarker 5-hydroxyindole-3-acetic acid was found to be positively linked with those harmful bacteria, while bio-active metabolites were strongly correlated with the beneficial genus. These observations suggest that LAF possesses the capability to mitigate the effects of D-galactose-induced aging in a mouse model through the regulation of oxidative stress, the gut microbiota composition, and levels of fecal metabolites. Consequently, these findings shed light on the potential of LAF as a functional food with anti-aging properties.

Milk-derived antimicrobial peptides incorporated whey protein film as active coating to improve microbial stability of refrigerated soft cheese.

Nisin is the first FDA-approved antimicrobial peptide and shows significant antimicrobial activity against Gram-positive bacteria, but only a weakly inhibitory effect on Gram-negative bacteria. The aim of this study was to prepare whey protein-based edible films with the incorporation of milk-derived antimicrobial peptides (αs2-casein151-181 and αs2-casein182-207) and compare their mechanical properties and potential application in cheese packaging with films containing nisin. These two antimicrobial peptides showed similar activity against B. subtilis and much higher activity against E. coli than bacteriocin nisin, representing that these milk-derived peptides had great potential to be applied as food preservatives. Antimicrobial peptides in whey protein films caused an increase in film opaqueness and water vapor barrier properties but decreased the tensile strength and elongation at break. Compared to other films, the whey protein film containing αs2-casein151-181 had good stability in salt or acidic solution, as evidenced by the results from scanning electron microscope and Fourier transform infrared spectroscopy. Whey protein film incorporated with αs2-casein151-181 could inhibit the growth of yeasts and molds, and control the growth of psychrotrophic bacteria present originally in the soft cheese at refrigerated temperature. It also exhibited significant inhibitory activity against the development of mixed culture (E. coli and B. subtilis) in the cheese due to superficial contamination during storage. Antimicrobial peptides immobilized in whey protein films showed a higher effectiveness than their direct application in solution. In addition, films containing αs2-casein151-181 could act as a hurdle inhibiting the development of postprocessing contamination on the cheese surface during the 28 days of storage. The films in this study exhibited the characteristics desired for active packaging materials.

Untargeted metabolomics analysis of probiotic jujube juice and its anti-obesity effects on high-fat-diet-induced obese mice.

BACKGROUND: Dietary intervention, including polyphenol consumption, is recognized as an effective strategy to prevent obesity. Although fermented jujube juice (FJJ) with lactic acid bacteria has been shown to be rich in polyphenols and have strong antioxidant properties, little is known about its anti-obesity properties. RESULTS: Untargeted metabolomics was employed to identify and analyze the differential metabolites between FJJ and raw jujube juice. A total of 431 metabolites belonging to diverse classes and with various functional active ingredients were quantitatively identified. The animal experiments results showed that FJJ administration for 13 weeks significantly inhibited high-fat-diet-induced body and epididymal adipose weight gain, and improved the serum lipid parameters in obese mice. Additionally, DNA-sequencing results revealed that FJJ treatment increased Akkermansia abundance in the gut and changed the composition of fecal microbiota by decreasing the Firmicutes/Bacteroidota ratio and Helicobacter pylori abundance. CONCLUSION: These findings suggest that FJJ contributes to regulating lipid accumulation and gut microbiota composition in high-fat-diet-induced obese mice, which helps to prevent obesity. Hence, FJJ has the potential to be a beneficial beverage for controlling obesity. © 2024 Society of Chemical Industry.

Utilization of two plant polysaccharides to improve fresh goat milk cheese: Texture, rheological properties, and microstructure characterization.

This study aimed to evaluate the effects of added jujube polysaccharide (JP) and Lycium barbarum polysaccharide (LBP) on the texture, rheological properties, and microstructure of goat milk cheese. Seven groups of fresh goat milk cheese were produced with 4 levels (0, 0.2, 0.6, and 1%, wt/wt) of JP and LBP. The goat milk cheese containing 1% JP showed the highest water-holding capacity, hardness, and the strongest rheological properties by creating a denser and more stable casein network structure. In addition, the yield of goat milk cheese was substantially improved as a result of JP incorporation. Cheeses containing LBP expressed lower fat content, higher moisture, and softer texture compared with the control cheese. Fourier-transform infrared spectroscopy and low-field nuclear magnetic resonance analysis demonstrated that the addition of JP improved the stability of the secondary protein structure in cheese and significantly enhanced the binding capacity of the casein matrix to water molecules due to strengthened intermolecular interactions. The current research demonstrated the potential feasibility of modifying the texture of goat milk cheese by JP or LBP, available for developing tunable goat milk cheese to satisfy consumer preferences and production needs.

Therapeutic effect of Lactobacillus plantarum JS19 on mice with dextran sulfate sodium induced acute and chronic ulcerative colitis.

BACKGROUND: Ulcerative colitis is associated with intestinal inflammation and dysbiosis. Previous studies have shown that probiotics are potential agents for treatment of inflammatory bowel disease (IBD). Jiang-shui is a traditional fermented vegetable that is rich in lactic acid bacteria (LABs), but the preventive effect of LABs in jiang-shui on IBD is not yet fully understood. RESULTS: We isolated 38 LAB strains from jiang-shui, and Lactobacillus plantarum JS19 exhibited the strongest antioxidant activity among them. Our data indicate that oral administration of L. plantarum JS19 significantly inhibited body weight loss, colon shortening and damage, and reduced the disease activity index score in the mice with dextran sulfate sodium (DSS)-induced colitis. In addition, L. plantarum JS19 also alleviated inflammatory responses and oxidative stress through reducing lipid peroxidation, tumor necrosis factor-α expression, and myeloperoxidase activity and enhancing the antioxidant enzyme activity. Importantly, L. plantarum JS19 significantly rebalanced DSS-induced dysbiosis of gut microbiota. CONCLUSION: L. plantarum JS19 may be used as a potential probiotic to prevent IBD, particularly ulcerative colitis. © 2022 Society of Chemical Industry.

A label-free electrochemical aptasensor based on a gold nanoparticle/carbon nanotube/metal-organic framework nanohybrid for ultrasensitive detection of streptomycin in milk samples.

In this work, a novel electrochemical aptasensor was designed for the sensitive and specific detection of STR in milk samples. First, a gold nanoparticle@poly(diallyldimethylammonium chloride) nitrogen-doped carbon nanotube/polyethyleneimine-functionalized metal-organic framework (MOF) (Au@P-N-CNT/PEI-MIL-101(Cr)) composite was synthesized and characterized by various technique. The Au@P-N-CNT/PEI-MIL-101(Cr) composite was then modified on a bare glassy carbon electrode (GCE) surface, providing a favorable platform (Au@P-N-CNT/PEI-MIL-101(Cr)/GCE) for aptamer immobilization and current signal amplification. The STR aptamer was grafted to the Au@P-N-CNT/PEI-MIL-101(Cr)/GCE through the formation of Au-S bonds and π-π stacking interactions. The immobilized STR aptamer binds specifically STR, resulting in an obvious decrease in the current signal. Under the optimal experimental conditions, the linear range of the electrochemical aptasensor for STR detection was 0.01-250 nM which the detection limit (LOD) was calculate as 2.31 nM. This strategy is expected to be a novel platform for the rapid and sensitive detection of STR.

An ultrasensitive sandwich-type electrochemical aptasensor using silver nanoparticle/titanium carbide nanocomposites for the determination of Staphylococcus aureus in milk.

A novel sandwich-type electrochemical aptasensor for the detection of Staphylococcus aureus (S. aureus) was developed. S. aureus aptamers were self-assembled onto the surface of a glassy carbon electrode (GCE) modified with nanocomposites comprising titanium carbide embedded with silver nanoparticles (AgNPs@Ti3C2) through hydrogen bonds and the chelation interaction between phosphate groups and Ti ions. In addition, the self-assembled aptamers were immobilized on CuO/graphene (GR) nanocomposites via π-π stacking interactions to serve as a signal probe. In the presence of the target S. aureus, the sandwich-type recognition system reacted on the surface of GCE, and the CuO/GR nanocomposites catalyzed the hydrogen peroxide + hydroquinone reaction producing a strong current response. Under the optimal experimental conditions, the current response of the aptasensor was linearly correlated with the concentration of S. aureus (52-5.2 × 107 CFU mL-1) with a low detection limit of 1 CFU mL-1. The aptasensor displayed good repeatability and excellent selectivity for S. aureus detection. Moreover, this aptasensor was applied to the detection of S. aureus in cow, sheep, and goat milk samples, affording recoveries ranging from 92.64 to 109.58%. This research provides a new platform for the detection of pathogenic bacteria and other toxic and harmful substances in food.

Zinc in cereal grains: Concentration, distribution, speciation, bioavailability, and barriers to transport from roots to grains in wheat.

Zinc (Zn) is an essential micro-nutrient for humans, and Zn deficiency is of global concern. In addition to inherited and pathological Zn deficiencies, insufficient dietary intake is leading cause, especially in those consuming cereal grains as a stable food, in which Zn concentration and bioavailability are relatively low. To improve Zn levels in the human body, it is important to understand the accumulation and bioavailability of Zn in cereal grains. In recent years, knowledge on the molecular mechanisms underlying Zn uptake, transport, homeostasis, and deposition within cereal crops has been accumulating, paving the way for a more targeted approach to improving the nutrient status of crop plants. In this paper, we briefly review existing studies on the distribution and transport pathways of Zn in major small-grained cereals, using wheat as a case study. The findings confirm that Zn transport in plants is a complex physiological process mainly governed by Zn transporters and metal chelators. This work reviews studies on Zn uptake, transport, and deposition in wheat plants, summarizes the possible barriers impairing Zn deposition in wheat grains, and describes strategies for increasing Zn concentration in wheat grains.

A novel electrochemical aptasensor based on layer-by-layer assembly of DNA-Au@Ag conjugates for rapid detection of aflatoxin M1 in milk samples.

Aflatoxin M1 (AFM1) is a common toxin in dairy products that causes acute and chronic human health disorders. Thus, the development of a rapid and accurate AFM1 detection method is of vital importance for food safety monitoring. This work was to develop a novel electrochemical aptasensor for sensitive and specific determination of AFM1. The dendritic-like nanostructure was formed on the gold electrode surface by layer-by-layer assembly of gold-silver core-shell nanoparticles modified with DNA conjugates. In the presence of AFM1, the specific recognition between AFM1 and Apt caused the disassociation of the DNA controlled dual Au@Ag conjugates from the surface of the electrode, causing less methylene blue to bind to the surface and weakening the electrochemical signal. The more AFM1 there is, the weaker the electrochemical signal. Transmission electron microscope results showed that the successfully synthesized Au@Ag nanoparticles exhibited a core-shell structure with Au as core and Ag as shell, and their average diameter was about 30 nm. Under optimal conditions, the electrochemical aptasensor showed a wide detection ranging from 0.05 ng mL-1 to 200 ng mL-1, and a low detection limit of 0.02 ng mL-1. Moreover, the proposed strategy has been successfully applied to the detection of AFM1 in cow, goat, and sheep milk samples with satisfactory recoveries ranging from 91.10% to 104.05%. This work can provide a novel rapid detection method for AFM1, and also provide a new sensing platform for the detection of other toxins.

Storage stability of texture, organoleptic, and biological properties of goat milk yogurt fermented with probiotic bacteria.

Introduction: Goat milk is an attractive food due to its high nutritional values, easy digestibility and hypoallergenicity, but has an undesirable "goaty" flavor. Methods: In this study, goat yogurt was fermented with four probiotics, respectively, including Lactobacillus acidophilus (GYA), Bifidobacterium animalis (GYB), Lactobacillus casei (GYC) and Lactobacillus plantarum (GYP), and tested for texture, organoleptic, and biological properties during a 4-week storage period at the refrigerated temperature. Results: All goat yogurt with probiotics showed an increase on titratable acidity and a corresponding downward trend on pH value. Viable counts of L. acidophilus and L. casei were above 6 log cfu/mL at the end of the storage, which met the minimum standards for viable probiotic bacteria in yogurt specified by the Food and Agriculture Organization of United Nation (FAO). The texture and organoleptic characteristics of fermented goat milk depended on the strain and the storage period. DPPH free radical scavenging rate and ferric reducing antioxidant power activity gradually increased in all goat yogurts during the storage and yogurt with probiotic bacteria showed higher values than those of GY0. Discussion: Among all probiotic containing goat yogurts, GYC exhibited the desirable characteristics of hardness, adhesiveness, water holding capacity, antioxidant activity during the whole storage. Furthermore, the addition of L. casei effectively weakened the goaty flavor and enhanced the overall acceptability. Thus, fermented goat milk with L. casei is optional for the development of goat milk product with satisfactory texture properties, pleasant sensory quality and high bioactivity.

Physicochemical and textural characteristics and volatile compounds of semihard goat cheese as affected by starter cultures.

Today, cheese is valued because of its high nutritional value and unique characteristics. Improving the texture and flavor of cheese by selecting suitable starter cultures is an important way to promote the development of cheese industry. The effect of starter cultures on the physicochemical and textural properties and volatile compounds during the ripening of semihard goat cheese were investigated in this work. Different starter cultures-mesophilic (M) and thermophilic starters (T), Lactobacillus plantarum ssp. plantarum ATCC 14917 (Lp), a mix of the M and T starters (M1), and mix of the M, T, and Lp starters (M2)-were used in the production of the goat cheeses. Volatile compounds were determined by a solid-phase microextraction/gas chromatography-mass spectrometric (SPME/GC-MS) method. The results showed that the moisture content of cheeses produced with the 5 kinds of starter cultures decreased after maturation, whereas ash content increased. The pH values of goat cheeses decreased first and then increased during maturity, and the pH value of M2 cheese was the lowest among the cheeses. The hardness and chewiness of the cheeses increased with increasing maturity, whereas cohesiveness, springiness, and resilience showed the opposite tendency. The 60-d-old cheese made with Lp had the highest chewiness, cohesiveness, springiness, and resilience, whereas the 60-d-old cheese made with M2 had the highest hardness. A total of 53 volatile components were identified by SPME/GC-MS, and carboxylic acids, alcohols, ketones, and esters were the 4 major contributors to the characteristic flavors of the cheeses. Volatile components and their contents differed greatly among the produced cheeses. The M2 cheese contained the highest relative content of the main volatile compounds (90.10%), especially butanoic acid and acetoin. Through a comprehensive comparison of the results, we concluded that M2 cheese had a dense texture and milky flavor, and M2 is a potential starter culture candidate for the production of goat cheese.

Quantitative Assessment of Phenolic Acids, Flavonoids and Antioxidant Activities of Sixteen Jujube Cultivars from China.

Increasing attention has been paid to the nutritional values and pharmacological effects of Ziziphus jujuba. Therefore, in this study, four phenolic and flavonoid fractions of 16 jujube cultivars from different geographic regions of China were separated and quantified. In addition, the antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) scavenging method and the ferric reducing antioxidant power (FRAP) assay. The total phenols and flavonoids contents ranged from 253.4 to 494.9 mg GAE/100 g and 125.3 to 425.4 mg rutin/100 g, respectively. Subsquently, a total of 10 phenolic acids and two flavonoids were identified, and most quantified phenolic acids with antioxidant activity were mainly present in the glycosided and insoluble-bound phenolic fractions. The results of this study indicate that some jujube cultivars, especially Zanghuang Z. jujuba, Leling Z. jujuba, and Jiaxian Z. jujuba could be selected to promote a healthy diet due to their more plentiful nutritional and phytochemical beneficial effects.

Genome-wide analysis of fermentation and probiotic trait stability in Lactobacillus plantarum during continuous culture.

Trait stability of Lactobacillus plantarum was studied following daily subculture over a 90-d period. Acid and bile tolerance, self-aggregation ability, cell hydrophobicity, pathogen inhibition activity, and cholesterol removal ability of cultures subcultured 30 (Lp30), 60 (Lp60), or 90 (Lp90) times were not significantly different from the original strain (Lp0). However, carbohydrate metabolism patterns did change; the Lp0 culture was unable to use d-sorbitol, α-methyl-d-mannose, and d-raffinose, whereas Lp30, Lp60, and Lp90 cultures could. Furthermore, gluconate and gentiobiose were fully used by the Lp0 culture but only poorly used by the Lp30, Lp60, and Lp90 cultures. Milk fermentation test confirmed that L. plantarum was unable to use lactose throughout laboratory evolution. Six non-synonymous mutations in genome of the Lp30, Lp60, and Lp90 cultures were identified by whole-genome sequencing, including mutant gene encoding the phosphoglycerate mutase, which is closely related to the transport and metabolism of carbohydrates. These mutations may play an important role in changes of carbohydrate metabolism patterns observed. Understanding the evolutionary characteristics of L. plantarum will help in development for food industry.

Resveratrol and Oxyresveratrol Activate Thermogenesis via Different Transcriptional Coactivators in High-Fat Diet-Induced Obese Mice.

Obesity is a global public health issue. Thermogenesis is a novel way to promote anti-obesity by consuming energy as heat rather than storing it as triacylglycerols. The browning program allows mitochondrial biosynthesis and thermogenesis-related gene expression to occur in subcutaneous white adipose tissue, which results in the formation of beige adipose tissue. Some phytochemicals have exerted the capability to activate the fat browning process. Resveratrol and oxyresveratrol are both natural stilbenoids that have been reported for their anti-obesity efficacy. However, the comparison between the two as they relate to thermogenesis as well as the differences in their underlying mechanisms are still not widely discussed. Our result reveals that both resveratrol and oxyresveratrol could elevate the expression of thermogenesis-related protein expression including UCP1 (uncoupling protein-1) and PRDM (PR domain containing 16) via Sirt1/PGC-1α (sirtuin 1/peroxisome proliferation gamma coactivator-1 α) activation. However, it is suggested that the transcriptional factor PPARα (peroxisome proliferator-activator receptor α) was activated by resveratrol (1.38 ± 0.07 fold) but not oxyresveratrol. Conversely, C/EBPß (CCAAT/enhancer-binding protein ß) was upregulated by oxyresveratrol (1.58 ± 0.05 fold) but not by resveratrol. On the other hand, CPT1 (carnitine palmitoyltransferase) was found to be significantly activated at lower concentrations of oxyresveratrol up to 1.89 ± 0.04 fold as compared to high-fat diet, and it could be a leading reason for UCP1 activation. Lastly, adiponectin expression was promoted in all experimental groups (1.53 ± 0.08 and 1.49 ± 0.11-fold in resveratrol (RES) and high oxyresveratrol (HOXY), respectively), which could be an activator for mitochondrial biosynthesis and UCP1 expression.

Laboratory Evolution Assays and Whole-Genome Sequencing for the Development and Safety Evaluation of Lactobacillus plantarum With Stable Resistance to Gentamicin.

The goal of this work was to use laboratory evolution assays and whole-genome sequencing to develop and test the safety of a probiotic, Lactobacillus plantarum, with high-level of resistance to gentamicin. The evolution of L. plantarum was evaluated under the selective pressure from gentamicin and subsequently when the selective pressure was removed. After 30 days of selective pressure from gentamicin, the minimum inhibitory concentration (MIC) of L. plantarum to gentamicin increased from 4 to 512 µg/mL and remained stable at this level. After removing the selective pressure, the resistance of L. plantarum to gentamicin decreased to 64 µg/mL after 20 days, and remained stable thereafter. Although the MIC declined it was still higher than the cut-off value recommended by EFSA, indicating that the acquisition of gentamicin-resistance was an irreversible process. Using whole-genome sequencing, gene mutations were identified in the strains that had undergone selection pressure from gentamicin as well as in the strains where the selection pressure was subsequently removed. Specifically, four non-synonymous mutations were detected including one single nucleotide polymorphism (SNP), one insertion, and two structural variants (SVs), of which the mutations in genes encoding the drug resistance MFS transporter and transcriptional regulator of AraC family were only detected in the strains under selective pressure from gentamicin. The results indicate that these mutations play an important role in increasing the resistant levels of L. plantarum to gentamicin. The mobility analysis of mutant genes confirmed that they were not located on mobile elements of the genome of highly resistant L. plantarum, indicating that horizontal gene transfer was not possible.

Optimized Extraction of Phenolics from Jujube Peel and Their Anti-inflammatory Effects in LPS-Stimulated Murine Macrophages.

The extraction of phenolics from jujube peel (PJP) was optimized using response surface methodology (RSM). A Box-Behnken design was utilized to analyze the effects of NaOH concentration, temperature, and extraction time on the total phenolic content (TPC). The results showed that RSM could be an adequate approach for modeling the extraction of PJP. The optimal extraction condition for the highest TPC was obtained with 3.4 M NaOH concentration for 67 min at 50 °C. Not only PJP but also phenolics from the jujube seed (PJS) contain considerable amounts of phenolics, particularly flavonoids. Quercetin and galangin were found to be the predominant phenolics. PJP markedly down-regulated the levels iNOS and COX-2 proteins in macrophages by inhibiting the activation of NF-κB through interfering with the MAPK signaling pathways. Compared to PJS, PJP presented higher anti-inflammatory activities, reflecting increased amounts of TPC and total flavonoid content (TFC). These findings suggest that PJP could be a potential source of anti-inflammatory agents.

Quality characteristics and antioxidant activities of goat milk yogurt with added jujube pulp.

This study aimed to evaluate the effects of the added jujube pulp on the quality characteristics and antioxidant activities of goat milk yogurt (GMY) during 28 days of refrigerated storage. Four GMY formulations were prepared, each varying in the added jujube pulp amount (Y0: not containing jujube pulp; YJ3, YJ6, YJ9: containing 3, 6, 9 g of jujube pulp per 100 g GMY, respectively). There was no significant differences in the viable counts, pH values and titratable acidities of all formulations during the storage. All formulations showed the viable counts all above 106 CFU/mL over the assessed storage period. However, YJ3 exhibited the desirable hardness, adhesiveness and water holding capacity. Moreover, the addition of jujube pulp weakened greatly the goaty flavor, improving the sensory acceptance, and increased the antioxidant activities of GMY. Therefore, GMY containing jujube pulp is optional for developing a novel goat dairy product with high added values.

Effects of ZnSO4 and Zn-EDTA broadcast or banded to soil on Zn bioavailability in wheat (Triticum aestivum L.) and Zn fractions in soil.

Human Zn deficiency is prevalent in developing countries, and staple grains are commonly bio-fortified to increase their Zn contents. We measured Zn content, distribution, and bioavailability in calcareous soil and in wheat plants (Triticum aestivum L.) in Shaanxi Province, China, when either an organic Zn-ethylenediaminetetraacetate (Zn-EDTA) or an inorganic zinc sulfate heptahydrate (ZnSO4·7H2O) Zn source was banded below the seedbed or broadcasted into soil. Compared with ZnSO4·7H2O, Zn-EDTA fertilization produced higher Zn concentration and uptake in wheat plants. However, Zn bioavailability in grain remained low, with [phytate]/[Zn] ratio >15 and the resulting estimated dietary total absorbed zinc (TAZ) < 3 mg Zn/d. ZnSO4 banded into soil had little short-term effect on grain Zn concentration but had a high residual effect and promoted the maintenance of a high concentration of the Zn fraction bound to loose organic matter (LOM-Zn) in rhizosphere soil. Both ZnSO4 and Zn-EDTA were more efficient if uniformly mixed through the soil than if banded to soil. Both ZnSO4 and Zn-EDTA had limited effects on Zn bioavailability in wheat plants due to the high rate of Zn fixation in this calcareous soil.

Influence of Bactrian camel milk on the gut microbiota.

Bactrian camel milk has become popular in the market as an important source of nutrients with diverse functional effects. In this study, the influence of Bactrian camel milk on the gut microbiota of mice was studied using metagenomic-based sequencing of the V3 and V4 hypervariable regions of the 16S rRNA gene. Bioinformatics analysis showed that Firmicutes and Bacteroidetes were the predominant phyla, accounting for more than 80% of the bacteria present. At the genus level, Allobaculum, Akkermansia, Romboutsia, Bifidobacterium, and Lactobacillus were most abundant in the gut microbiota; of these, Allobaculum and Akkermansia were the predominant genera, representing 40.42 and 7.85% of all the bacteria present, respectively. Camel milk was found to reduce relative abundance of Romboutsia, Lactobacillus, Turicibacter, and Desulfovibrio (decreased by 50.88, 34.78, 26.67, and 54.55%, respectively) in the gut microbiota compared with the control. However, some genera such as Allobaculum, Akkermansia, and Bifidobacterium in the gastrointestinal flora increased in abundance in the presence of camel milk; these genera are correlated with beneficial effects for organisms. Our research suggests that the gut microbiota should be taken into account when conducting functional studies on camel milk, and this work provides a useful foundation for further study on functions of camel milk.

Whole-genome sequencing reveals the mechanisms for evolution of streptomycin resistance in Lactobacillus plantarum.

In this research, we investigated the evolution of streptomycin resistance in Lactobacillus plantarum ATCC14917, which was passaged in medium containing a gradually increasing concentration of streptomycin. After 25 d, the minimum inhibitory concentration (MIC) of L. plantarum ATCC14917 had reached 131,072 µg/mL, which was 8,192-fold higher than the MIC of the original parent isolate. The highly resistant L. plantarum ATCC14917 isolate was then passaged in antibiotic-free medium to determine the stability of resistance. The MIC value of the L. plantarum ATCC14917 isolate decreased to 2,048 µg/mL after 35 d but remained constant thereafter, indicating that resistance was irreversible even in the absence of selection pressure. Whole-genome sequencing of parent isolates, control isolates, and isolates following passage was used to study the resistance mechanism of L. plantarum ATCC14917 to streptomycin and adaptation in the presence and absence of selection pressure. Five mutated genes (single nucleotide polymorphisms and structural variants) were verified in highly resistant L. plantarum ATCC14917 isolates, which were related to ribosomal protein S12, LPXTG-motif cell wall anchor domain protein, LrgA family protein, Ser/Thr phosphatase family protein, and a hypothetical protein that may correlate with resistance to streptomycin. After passage in streptomycin-free medium, only the mutant gene encoding ribosomal protein S12 remained; the other 4 mutant genes had reverted to the wild type as found in the parent isolate. Although the MIC value of L. plantarum ATCC14917 was reduced in the absence of selection pressure, it remained 128-fold higher than the MIC value of the parent isolate, indicating that ribosomal protein S12 may play an important role in streptomycin resistance. Using the mobile elements database, we demonstrated that streptomycin resistance-related genes in L. plantarum ATCC14917 were not located on mobile elements. This research offers a way of combining laboratory evolution techniques and whole-genome sequencing for evaluating antibiotic resistance in probiotics.