Kinetically controlled Ag+-coordinated chiral supramolecular polymerization accompanying a helical inversion

We report kinetically controlled chiral supramolecular polymerization based on ligand-metal complex with a 3 : 2 (L : Ag+) stoichiometry accompanying a helical inversion in water. A new family of bipyridine-based ligands (d-L1, l-L1, d-L2, and d-L3) possessing hydrazine and d- or l-alanine moieties at the alkyl chain groups has been designed and synthesized. Interestingly, upon addition of AgNO3 (0.5-1.3 equiv.) to the d-L1 solution, it generated the aggregate I composed of the d-L1AgNO3 complex (d-L1 : Ag+ = 1 : 1) as the kinetic product with a spherical structure. Then, aggregate I (nanoparticle) was transformed into the aggregate II (supramolecular polymer) based on the (d-L1)3Ag2(NO3)2 complex as the thermodynamic product with a fiber structure, which led to the helical inversion from the left-handed (M-type) to the right-handed (P-type) helicity accompanying CD amplification. In contrast, the spherical aggregate I (nanoparticle) composed of the d-L1AgNO3 complex with the left-handed (M-type) helicity formed in the presence of 2.0 equiv. of AgNO3 and was not additionally changed, which indicated that it was the thermodynamic product. The chiral supramolecular polymer based on (d-L1)3Ag2(NO3)2 was produced via a nucleation-elongation mechanism with a cooperative pathway. In thermodynamic study, the standard ΔG° and ΔH e values for the aggregates I and II were calculated using the van't Hoff plot. The enhanced ΔG° value of the aggregate II compared to that of the formation of aggregate I confirms that aggregate II was thermodynamically more stable. In the kinetic study, the influence of concentration of AgNO3 confirmed the initial formation of the aggregate I (nanoparticle), which then evolved to the aggregate II (supramolecular polymer). Thus, the concentration of the (d-L1)3Ag2(NO3)2 complex in the initial state plays a critical role in generating aggregate II (supramolecular polymer). In particular, NO3 - acts as a critical linker and accelerator in the transformation from the aggregate I to the aggregate II. This is the first example of a system for a kinetically controlled chiral supramolecular polymer that is formed via multiple steps with coordination structural change.

Genomic Insight into the Salt Tolerance of Enterococcus faecium, Enterococcus faecalis and Tetragenococcus halophilus

To shed light on the genetic basis of salt tolerance in Enterococcus faecium, Enterococcus faecalis, and Tetragenococcus halophilus, we performed comparative genome analysis of 10 E. faecalis, 11 E. faecium, and three T. halophilus strains. Factors involved in salt tolerance that could be used to distinguish the species were identified. Overall, T. halophilus contained a greater number of potassium transport and osmoprotectant synthesis genes compared with the other two species. In particular, our findings suggested that T. halophilus may be the only one among the three species capable of synthesizing glycine betaine from choline, cardiolipin from glycerol and proline from citrate. These molecules are well-known osmoprotectants; thus, we propose that these genes confer the salt-tolerance of T. halophilus.

Genomic insights into the non-histamine production and proteolytic and lipolytic activities of Tetragenococcus halophilus KUD23

Tetragenococcus halophilus KUD23, a non-histamine producer, was isolated from a traditional Korean high-salt fermented soybean paste, doenjang. The strain was safe in terms of antibiotic susceptibility, hemolytic activity and biofilm formation. It could grow on De Man-Rogosa-Sharpe agar containing 21% (w/v) NaCl, exhibited acid production at 15% NaCl, and had strain-specific proteolytic and lipolytic activities under salt stress. Complete genome analysis of T. halophilus KUD23 and comparative genomic analysis shed light on the genetic background behind these phenotypic characteristics, including non-production of histamine and proteolytic and lipolytic activities.

Transfer of a lincomycin-resistant plasmid between coagulase-negative staphylococci during soybean fermentation and mouse intestine passage

Staphylococcus equorum is a benign bacterium and the predominant species in high-salt fermented food. Some strains of S. equorum contain antibiotic-resistance plasmids, such as pSELNU1 that contains a lincosamide nucleotidyltransferase (lnuA) gene and confers resistance to lincomycin. Previously, we showed that pSELNU1 is transferred to other bacteria under laboratory growth conditions. However, it is not known if the plasmid can be transferred to other bacteria during food fermentation (in situ) or during passage through animal intestines (in vivo). In this study, we examined the in situ and in vivo transfer of pSELNU1 using Staphylococcus saprophyticus as a recipient. During soybean fermentation, pSELNU1 was transferred to S. saprophyticus at a rate of 1.9 × 10-5-5.6 × 10-6 per recipient in the presence of lincomycin. However, during passage through murine intestines, the plasmid was transferred at similar rates (1.3 × 10-5 per recipient) in the absence of lincomycin, indicating that the plasmid transfer is much more efficient under in vivo conditions. Based on these results, we conclude that it is prudent to examine food fermentation starter candidates for the presence of mobile genetic elements containing antibiotic resistance genes and to select candidates lacking these genes.

Colorimetric Detection of UO2+₂ Using Gold Nanoparticles Immobilized with Pillar[5]arene Complexes with Nitrophenyldiacetic Acids as a Chemoprobe

Uranium is a crucial raw material in the nuclear energy industry; however, its radioactive nature makes it a critically damaging component to both the atmosphere and human health. In this study, we report a simple and cost-effective selective colorimetric detection technique for UO²⁺₂ using nitrophenyldiacetic acids (NPD)-functionalized gold nanoparticles (Au NPs 1). The hybrid Au NPs 1 can be induced to aggregate in the presence of UO²⁺₂ ions. UO²⁺₂ can be recognized by the colorimetric response of hybrid Au NPs 1, which can be observed by a UV-Vis spectrophotometer and it is easily detectable by the naked eye. The hybrid Au NPs 1 bound by UO²⁺₂ possess a good selective response compared to other metal ions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, Mg²⁺, Ba²⁺, Ni²⁺, Zn²⁺, and Co²⁺), which can be observed by a prominent color change. The color of the hybrid Au NPs 1 changed from red to dark red upon addition of UO²⁺₂ in the presence of other metal ions. Job's plot demonstrates that one NPD moiety attached onto the surface of Au NPs 1 forms 1:1 stoichiometry with UO²⁺₂, hence providing a simple and effective colorimetric sensor for the real-time detection of UO²⁺₂.

Transfer of a mobile Staphylococcus saprophyticus plasmid isolated from fermented seafood that confers tetracycline resistance

The complete nucleotide sequence of a tetracycline-resistance gene (tetK)-carrying plasmid from a Staphylococcus saprophyticus isolate from jeotgal, a Korean high-salt-fermented seafood, was determined. The plasmid, designated pSSTET1, was 4439 bp in length and encoded typical elements found in plasmids that replicate via a rolling-circle mechanism, including the replication protein gene (rep), a double-stranded origin of replication, a single-stranded origin of replication, and a counter-transcribed RNA sequence. Additionally, the plasmid recombination enzyme gene (pre), which may be involved in inter-plasmid recombination and conjugation, was found. Each gene exhibited >94% sequence identity with those harbored in other Staphylococcus species. pSSTET1 was conditionally transferred to Staphylococcus species in a host-dependent manner and transferred to an Enterococcus faecalis strain in vitro. Antibiotic susceptibility of the transconjugants was host-dependent and transconjugants maintained a tetracycline-resistant phenotype in the absence of selective pressure over 100 generations.

Genomic insights into Staphylococcus equorum KS1039 as a potential starter culture for the fermentation of high-salt foods

BACKGROUND

Our previous comparative genomic analysis of Staphylococcus equorum KS1039 with five S. equorum strains illuminated the genomic basis of its safety and salt tolerance. However, a comprehensive picture of the cellular components and metabolic pathways involved in the degradation of macromolecules and development of sensory properties has not been obtained for S. equorum. Therefore, in this study, we examined the general metabolism of S. equorum based on information obtained from published complete genome sequences of six S. equorum strains isolated from different niches. Additionally, the utility of strain KS1039 as a starter culture for high-salt food fermentations was examined.

RESULTS

All six S. equorum strains contained genes involved in glycolysis, the tricarboxylic acid cycle, and amino acid metabolic pathways, as well as color development. Moreover, the strains had the potential to produce acetoin, butanediol, and branched chain fatty acids, all of which are important flavor compounds. None of the strains contained decarboxylase genes, which are required for histamine and tyramine production. Strain KS1039 contained bacteriocin and CRISPR/Cas gene clusters, and experimental results suggested that these genes were functional in vitro.

CONCLUSIONS

The comparative genomic analysis carried out herein provides important information on the usefulness of S. equorum KS1039 as a starter culture for the fermentation of high-salt foods in terms of safety, salt tolerance, bacteriocin production, and foreign plasmid restriction.

Effects of the predominant bacteria from meju and doenjang on the production of volatile compounds during soybean fermentation

We inoculated five starter candidates, Enterococcus faecium, Tetragenococcus halophilus, Bacillus licheniformis, Staphylococcus saprophyticus, and Staphylococcus succinus, into sterilized soybeans to predict their effectiveness for flavor production in fermented soybean foods. All of the starter candidates exhibited sufficient growth and acid production on soybean cultures. Twenty-two volatile compounds, such as acids, alcohols, carbonyls, esters, furans, and pyrazines, were detected from the control and starter candidate-inoculated soybean cultures. Principal component analysis of these volatile compounds concluded that E. faecium and T. halophilus produced a similar profile of volatile compounds to soybeans with no dramatic differences in soybean flavor. B. licheniformis and S. succinus produced the crucial volatile compounds that distinguish the flavor profiles of soybean. During soybean fermentation, phenylmethanol and 2,3,5,6-tetramethylpyrazine were determined as odor notes specific to B. licheniformis and 3-methylbutyl acetate as an odor note specific to S. succinus.

Genomic insights into the virulence and salt tolerance of Staphylococcus equorum

To shed light on the genetic background behind the virulence and salt tolerance of Staphylococcus equorum, we performed comparative genome analysis of six S. equorum strains. Data on four previously published genome sequences were obtained from the NCBI database, while those on strain KM1031 displaying resistance to multiple antibiotics and strain C2014 causing haemolysis were determined in this study. Examination of the pan-genome of five of the six S. equorum strains showed that the conserved core genome retained the genes for general physiological processes and survival of the species. In this comparative genomic analysis, the factors that distinguish the strains from each other, including acquired genomic factors in mobile elements, were identified. Additionally, the high salt tolerance of strains enabling growth at a NaCl concentration of 25% (w/v) was attributed to the genes encoding potassium voltage-gated channels. Among the six strains, KS1039 does not possess any of the functional virulence determinants expressed in the other strains.

Safety assessment of Tetragenococcus halophilus isolates from doenjang, a Korean high-salt-fermented soybean paste

We assessed the safety of 49 Tetragenococcus halophilus strains isolated from doenjang in Korea. Minimum inhibitory concentration assays showed that all strains can be considered as susceptible to ampicillin, erythromycin, penicillin G, tetracycline, and vancomycin, but resistant to ciprofloxacin based on the Enterococcus breakpoint values provided by the European Committee on Antimicrobial Susceptibility testing in 2015. Ciprofloxacin resistance was sufficiently high to consider the potential for acquisition of transmissible determinants. Two strains exhibiting potentially acquired resistance to chloramphenicol and gentamicin, and chloramphenicol alone, were identified. None of the strains exhibited α-hemolytic activity or biofilm formation; two strains exhibited weak β-hemolytic activity. Doenjang isolates produced an average of 3338.6 ppm of tyramine in the laboratory, considerably higher than the levels produced by two reference strains. All of the test strains exhibited similar cadaverine, histamine, and putrescine production patterns. Most T. halophilus strains could grow at a NaCl concentration >18%, exhibited acid production at 15% NaCl, and expressed strain-specific protease and lipase activities. The potential acquisition of transmissible determinants for antibiotic resistance and tyramine production identified in this study necessitate the need for a thorough safety assessment of T. halophilus before it can be considered for use in food fermentation processes.

Association between obesity and heart failure symptoms in male and female patients

In patients with heart failure (HF), higher body mass index (BMI) has been associated with lower rates of hospitalization and mortality (obesity paradox). Symptoms are antecedents of hospitalizations, but little is known about the relationship between BMI and symptoms and gender differences. To examine the association of BMI with symptoms in male and female patients with HF, controlling for covariates (sample characteristics, depressive symptoms and sodium intake). In this cross-sectional correlational study, patients (N = 247) provided data on BMI, symptoms and covariates. BMI was categorized into four groups: normal/underweight (<25 kg/m² ), overweight (25-29.9 kg/m² ), obese I (30-34.9 kg/m² ) and obese II/III (≥35 kg/m² ). General linear regression was used to analyse the data. The Obese II/III group had more severe HF symptoms than other groups only in male patients. In male patients, older age, Caucasian race, more comorbidities and more severe depressive symptoms were also associated with more severe symptoms. In female patients, more severe depressive symptoms, more comorbidities and higher sodium intake were associated with more severe symptoms. The obesity paradox does not fully extend to symptoms, and gender has a role in the relationship between obesity and symptoms.

Effects of dietary energy and lysine intake during late gestation and lactation on blood metabolites, hormones, milk compositions and reproductive performance in primiparous sows

The effects of energy and lysine intake during late gestation and lactation on the reproductive performance of primiparous sows were evaluated using 36 gilts. Sows were allocated to six dietary treatments according to a 3 × 2 factorial arrangement and each treatment had six replicates. Three energy levels [low (EL), medium (EM) and high (EH)] and two lysine levels [low (LL) and high (HL)] were used. Gilts with HL intake had more weight (P = 0.004) and backfat thickness (P = 0.047) gain during gestation. Similar changes in sow body conditions were observed during lactation. HL intake resulted in higher litter birth weight (P = 0.001), weaning weight (P < 0.001) and growth rate (P < 0.001) and shortened wean-to-estrus interval (P= 0.001). Energy intake influenced the fat and lactose content while lysine intake influenced the total solids and protein content in milk and colostrum. Gilts with HL had higher insulin and lower creatinine levels during post farrowing and weaning, while triglyceride concentration at weaning increased with increasing of energy intake. The basal and pulses of LH were also influenced by lysine intake. In conclusion, higher lysine intake than those recommended by National Research Council (1998) could improve performance during late gestation and lactation in primiparous sows. Key words: Energy, lysine, gestation, lactation, sows

Effects of lysine intake during late gestation and lactation on blood metabolites, hormones, milk composition and reproductive performance in primiparous and multiparous sows

Modern genotype primiparous and multiparous sows (Yorkshire x Landrace, n=48) were used to evaluate effects of dietary lysine intake during late gestation and lactation, and their interaction on reproductive performance. Sows were randomly allotted to two gestation lysine (G, 0.6% or 0.8% lysine) treatments based on parity in a 2 x 2 factorial arrangement, and each treatment had 12 replicates comprising 1 sow. Then all the sows were assigned to two lactation lysine (L, 1.0% or 1.3% lysine) treatments within parity and gestation treatments in a 2 x 2 x 2 factorial design, and each treatment comprised six replicates with 1 sow/replicate during lactation. Feeding higher lysine level during gestation increased sow body weight and backfat thickness (P=0.001) and body condition was better (P=0.001) in multiparous than that of primiparous sows. Both of the lysine levels during lactation and parity influenced sow body condition and reproductive performance (P<0.05). Higher lysine intake during lactation increased the concentrations of total solids (P=0.024), protein (P=0.001) and solids not-fat (P=0.042) in colostrum and total solids (P=0.001), protein (P=0.001), fat (P=0.001) and solids not-fat (P=0.005) in milk. Protein concentration of milk was greater (P=0.001) in multiparous sows than that of primiparous sows. Feeding of high lysine diets resulted in an increment of plasma urea N (P=0.010; P=0.047) and a decrease of creatinine (P=0.045; P=0.002) on the day of postfarrowing and weaning, respectively. Furthermore, as lysine intake increased, the secretions of insulin, FSH, and LH were increased (P<0.05) and multiparous sows showed higher (P<0.05) concentrations of FSH and LH pulses on the day of postfarrowing and weaning, respectively. These results indicated that higher lysine intake than that recommended by NRC [NRC, 1998. Nutrient Requirements of Swine, 10th ed. National Academy Press, 458 Washington, DC] could improve sow performance during late gestation and lactation. Furthermore primiparous sows need higher lysine intake than multiparous sows. Moreover, nutritional impacts on reproduction may be mediated in part through associated effects on circulating LH concentration.