Acid-base Stress Research Articles

Bacteriocin paracin wx3 biosynthesis improves antagonistic activity of Lactobacillus paracasei WX322 against soft rot of postharvest pepper

Postharvest peppers are susceptible to soft rot caused by Pectobacterium carotovorum during storage and transportation. Lactic acid bacteria (LAB) are promising antagonist to control soft rot. LAB usually exhibit strong in vitro antibacterial activity on MRS agar plates, but weak in vivo disease control activity on fruit/vegetable. This study aimed to improve the biocontrol activity of Lactobacillus paracasei WX322 in vivo. Stress conditions were firstly investigated and the results showed that starvation stress could not induce any enhancement of antibacterial activity in vitro. Acid-base stress only improved antibacterial activity in vitro, while osmotic stress under 1.5 % NaCl improved both antibacterial activity in vitro and disease control activity in vivo. To facilitate the adaptation of L. paracasei WX322 on green pepper, pepper juice was used to replace MRS medium. To facilitate the growth of L. paracasei WX322 in pepper juice, nutrient supplement was studied. The result showed that pepper juice containing 0.4 % Tween 80 and 1.5 % NaCl was the optimal induction condition which improved the antagonistic activity of L. paracasei WX322 by enhancing LAB’s metabolism. Bacteriocin production was significantly improved under the optimal induction condition. The result of RT-qPCR revealed that bacteriocin production related genes were significantly up-regulated under the optimal induction condition, including three-component system. The addition of 1 μM autoinducer peptide (AIP) in MRS significantly increased antibacterial activity of L. paracasei WX322 in vitro. Simultaneously, L. paracasei WX322 cultured in MRS containing 0.01 μM AIP had a significantly increased disease control activity. RT-qPCR further verified an increased expression of bacteriocin paracin wx3 when adding 0.01 μM AIP. These results suggest that the medium of pepper juice containing 0.4 % Tween 80 and 1.5 % NaCl can improve the in vivo disease control activity of L. paracasei WX322, which is achieved by improved bacteriocin biosynthesis regulated by three-component system.

Assessment of uric acid-lowering activity, safety and stress tolerance of Lactiplantibacillus plantarum MC14 based on whole gene sequencing and phenotyping experiments

With lifestyle changes, hyperuricemia has become a global epidemic. Recent studies have indicated that some probiotic strains may help control serum uric acid. This study aimed to screen probiotic strains with uric acid-lowering potential and subsequently analyze the safety and stress tolerance of the strain in food applications, utilizing phenotyping experiments and genome sequencing. Initially, we isolated a strain of Lactiplantibacillus plantarum MC14 with the best in vitro uric acid-lowering activity. The inosine and guanosine degradation rates of MC14 were 5.00 and 4.11 mg/L·min, respectively, and the XOD inhibition rate was 81.56% ± 3.87%. Gene analysis revealed that the MC14 strain encodes three nucleoside hydrolases and six nucleoside and nucleobase transporter proteins. Subsequently, safety assessments of the MC14 strain in food applications revealed no nitroreductase, amino decarboxylase, or tryptophanase activities, absence of hemolysis, and no antibiotic resistance gene transfer risk. Finally, stress tolerance tests on MC14 indicated robust tolerance to gastrointestinal fluids and bile salts, with survival rates exceeding 98% after 3 h in artificial gastric fluids and approximately 100.49% ± 0.15% after 8 h in artificial intestinal fluids. Additionally, MC14 demonstrated effective antibacterial properties and antioxidant capacity, and its genome was annotated with numerous stress tolerance-related genes, including 18 acid-base stress, 4 bile salt tolerance, 11 heat stress, 3 cold stress, 6 osmotic stress, and 28 oxidative stress. Our findings highlighted MC14 as a promising candidate for probiotic and food applications.

Simple Purification and Antimicrobial Properties of Bacteriocin-like Inhibitory Substance from Bacillus Species for the Biopreservation of Cheese.

Bacteriocins may be used as natural preservatives and antibiotic substitutes in various foods. However, the multistep purification process of bacteriocins results in high production costs, which is an obstacle to their commercial use and consumer accessibility. In this study, a bacteriocin-like inhibitory substance (BLIS) from Bacillus spp. isolated from Korean fermented foods was partially purified using the aqueous two-phase system (ATPS). The maximum activity of the BLIS was achieved for ATPS composed of PEG 1000 (15% [w/w])/ammonium sulfate (20% [w/w])/sodium chloride (2% [w/w]), which caused BLIS activity to increase by 3 times with a 99% recovery rate. In particular, B. amyloliquefaciens Y138-6 BLIS exhibited broad antibacterial activity, high resistance to acid-base stress, and excellent thermal stability. This antibacterial substance inhibited the growth of aerobic bacteria and fungi on the walls of cheese and ripening rooms. These antibacterial properties have been shown to increase food safety and have the potential for use as biopreservatives. Moreover, considering that the execution of the ATPS requires only salts and PEG, it is a simple, environmentally friendly, and cost-effective process and may have industrial applications in the recovery of BLIS from fermentation broth.

Characterization of structure and antioxidant activity of exopolysaccharides from endophytic Lysinibacillus sphaericus Ya6 under acid-base stress

In this study, the structure and antioxidant activity of exopolysaccharides (EPS) produced by Lysinibacillus sphaericus Ya6 under different acid-base stresses were investigated. The structure of EPS was analyzed by UV-visible and mid-IR, and the monosaccharide composition and the molecular weight were determined by High-performance liquid chromatography (HPLC) and high-performance gel permeation chromatography respectively. The findings indicated that EPS produced by Lysinibacillus sphaericus Ya6 was a homogenous polysaccharide with a molecular weight of 79.25 kDa that was composed of mannose and glucose. The molecular weight and monosaccharide composition of polysaccharides changed under acid-base stress conditions. With the addition of the acid-base stress level, the logarithmic growth period of Lysinibacillus sphaericus Ya6 was prolonged for a short while, but later growth rates and EPS production under stress conditions were all higher than under the control. In vitro determinations found that acid-base stress boosted the antioxidant activity of EPS. Particularly under conditions of alkaline stress, DPPH radical scavenging capacity and superoxide anion scavenging of EPS were higher than those of the control, and their capacities to scavenge DPPH was increased from 39.30% (the control) to 95.65% at pH 10.0, which was close to ascorbic acid's (95.77%) as a positive control.

Purification and characterization of Lactobacillus plantarum-derived bacteriocin with activity against Staphylococcus argenteus planktonic cells and biofilm.

Bacteriocins inhibit various foodborne bacteria in planktonic and biofilm forms. However, bacteriocins with antibacterial and antibiofilm activity against Staphylococcus argenteus, a pathogen that can cause food poisoning, are still poorly known. Here, the novel bacteriocin LSB1 derived from Lactobacillus plantarum CGMCC 1.12934 was purified and characterized extensively. LSB1 had a molecular weight of 1425.78Da and an amino acid sequence of YIFVTGGVVSSLGK. Moreover, LSB1 exhibited excellent stability under heat and acid-base stress and presented sensitivity to pepsin and proteinase K. LSB1 exhibited an extensive antimicrobial spectrum against both Gram-positive and Gram-negative bacteria. Minimum inhibitory concentration of LSB1 against S. argenteus_70917 was 10.36µg/ml, which was lower than that of most of the previously found bacteriocins against Staphylococcus strains. Furthermore, LSB1 significantly inhibited S. argenteus_70917 planktonic cells (p<0.01) and decreased their viability. Scanning electron microscopy analysis revealed that cell membrane permeability of S. argenteus_70917 upon exposure to LSB1 showed leakage of cytoplasmic contents and rupture, leading to cell death. In addition, biofilm formation ability of S. argenteus_70917 was significantly (p<0.01) impaired by LSB1, with the percent inhibition of 35% at 10µg/ml and 80% at 20µg/ml. Overall, this study indicates that LSB1 can be considered a potential antibacterial agent in the control of S. argenteus in both planktonic and biofilm states. PRACTICAL APPLICATION: Foodborne pathogenic bacteria, such as Staphylococcus argenteus, and their biofilms represent potential risks for food safety. In recent years, customers' demand for "natural" products has increased food control. This study describes the novel bacteriocin LSB1 produced by the lactic acid bacterium species Lactobacillus plantarum. LSB1 showed strong antibacterial and antibiofilm activity against S. argenteus as well as thermal and acid-alkaline stability. Furthermore, the mechanisms of action of LSB1 on S. argenteus were preliminarily explored. These results indicate that LSB1 might be potentially used as an effective and natural food preservative.

The breakdown of protein hydrogen bonding networks facilitates biotransformation of protein wastewaters during anaerobic digestion methanogenesis: Focus on protein structure and conformation

The low methanogenic efficiency of protein wastewater during anaerobic digestion can be attributed to the hydrolysis rate-limiting caused by the complex native structure of protein. In this study, the characterization of secondary structure alterations of protein molecules under acid-base stress was investigated and the effect of structure and conformation alterations on the methanogenic efficiency of protein wastewater biotransformation was analyzed. The optimal methane yields were obtained for protein wastewater pretreated with acid and base at pH = 3 and pH = 12, which was 29.4% and 35.7% higher than that of the control group (without pretreatment), reaching 142.6 ± 4.0 mL/g protein and 149.6 ± 16.1 mL/g protein, respectively. The time economy evaluation showed that 6 h pretreatment time was scientific and reasonable whether pH = 3 or pH = 12, since the methane gain effect reached 74.4% and 82.2% longing with the anaerobic digestion proceeded to 120 h, respectively. Endogenous fluorescence characteristics illustrated that the microenvironment of protein molecules has changed regardless of acid or alkali pretreatment. The circular dichroism (CD) analysis revealed that only the content of α-helix in the secondary structure of the protein at pH = 12 decreased by 46.3%, while the contents of β-sheet, β-turn and unordered structure were 29.5 ± 0.8%, 18.9 ± 0.6% and 32.2 ± 1.3%, respectively. The increase in the composition of the unordered structure demonstrated an irreversible damage to the hydrogen bonding network in the protein. FTIR spectroscopy further confirmed that the stretching vibrations of CO in amide I led to the destruction of the hydrogen bonding network and the unfolding of the protein structure. Thus, the above work provides new insights into the anaerobic digestion of protein wastewater for methanogenic processes from the perspective of protein structure and conformational changes.

A Novel Bacteriocin Against Shigella flexneri From Lactiplantibacillus plantarum Isolated From Tilapia Intestine: Purification, Antibacterial Properties and Antibiofilm Activity.

Few bacteriocins with antibacterial activity against Shigella flexneri have been reported. Here, a novel bacteriocin (LFX01) produced by Lactiplantibacillus plantarum strain LF-8 from the intestine of tilapia was purified and extensively characterized. LFX01 possesses a molecular weight of 1049.56 Da and an amino acid sequence of I-T-G-G-P-A-V-V-H-Q-A. LFX01 significantly inhibited S. flexneri strain 14 (S. flexneri_14) growth. Moreover, it exhibited excellent stability under heat and acid-base stress, and presented sensitivity to a variety of proteases, such as proteinase K, pepsin, and trypsin. The minimum inhibitory concentration (MIC) of LFX01 against S. flexneri_14 was 12.65 μg/mL, which was smaller than that of most of the previously found bacteriocins. Furthermore, LFX01 significantly inhibited (p < 0.05) S. flexneri_14 cells and decreased their cell viability. In addition, LFX01 could significantly (p < 0.05) inhibit biofilm formation of S. flexneri_14. Scanning electron microscopy analysis presented that the cell membrane permeability of S. flexneri_14 was demolished by LFX01, leading to cytoplasmic contents leakage and cell rupture death. In summary, a novel bacteriocin of lactic acid bacteria (LAB) was found, which could effectively control S. flexneri in both planktonic and biofilm states.

α-Ketoglutarate regulates acid-base balance through an intrarenal paracrine mechanism

Paracrine communication between different parts of the renal tubule is increasingly recognized as an important determinant of renal function. Previous studies have shown that changes in dietary acid-base load can reverse the direction of apical α-ketoglutarate (αKG) transport in the proximal tubule and Henle's loop from reabsorption (acid load) to secretion (base load). Here we show that the resulting changes in the luminal concentrations of αKG are sensed by the αKG receptor OXGR1 expressed in the type B and non-A-non-B intercalated cells of the connecting tubule (CNT) and the cortical collecting duct (CCD). The addition of 1 mM αKG to the tubular lumen strongly stimulated Cl(-)-dependent HCO(3)(-) secretion and electroneutral transepithelial NaCl reabsorption in microperfused CCDs of wild-type mice but not Oxgr1(-/-) mice. Analysis of alkali-loaded mice revealed a significantly reduced ability of Oxgr1(-/-) mice to maintain acid-base balance. Collectively, these results demonstrate that OXGR1 is involved in the adaptive regulation of HCO(3)(-) secretion and NaCl reabsorption in the CNT/CCD under acid-base stress and establish αKG as a paracrine mediator involved in the functional coordination of the proximal and the distal parts of the renal tubule.

Effects of hypothermia on rat brain pHi and phosphate metabolite regulation by 31P-NMR

The effects of arterial alphastat regulation on brain intracellular pH (pHi) and several phosphate metabolites were assessed in anesthetized rats during hypothermia (28.6 +/- 0.2 degrees C) and normothermia (36.2 +/- 0.2 degrees C) by using 31P high-field (8.5 T) nuclear magnetic resonance (NMR). There were significant differences in pHi and metabolite ratios at the two temperatures under conditions of equal minute ventilation. During hypothermia, the brain pHi was 0.09 U higher, the phosphocreatine-to-inorganic phosphate (PCR/Pi) ratio 49% larger, and Pi-to-ATP 20% lower than at normothermia. These changes were fully reversible on warming the animal. The change in brain pHi/temperature was -0.011U/degrees C (95% confidence interval -0.007 to -0.016). The brain's ability to regulate its pHi and phosphate metabolism during hypercapnic acid-base stress was studied by using 10% CO2 ventilation. Hypothermic rats showed a larger fall in brain pHi (0.145 +/- 0.01 U, 7.15-7.01) with 10% CO2 than normothermic rats (0.10 +/- 0.02 U, 7.06-6.96). Similarly ventilated rats had a larger fall in arterial pH with 10% CO2 at hypothermia (0.36 +/- 0.04 U) than normothermia (0.24 +/- 0.01 U), so the delta brain pH/delta arterial pH was the same at both temperatures. The brain PCr-to-Pi ratio decreased approximately 20% during 10% CO2 breathing in both hypothermic and normothermic animals. Brain pHi and metabolite ratios returned to base line 30-50 min after CO2 washout in both groups. In summary, lowering body temperature while maintaining constant ventilation leads to changes in brain pHi and metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain amino acid concentrations during diving and acid-base stress in turtles.

To assess the role of brain amino acid neurotransmitters in the breath hold of diving animals, concentrations of free amino acids present in the brains of turtles immediately after 2 h of apneic diving (at 20 degrees C) were measured. Additionally, the same measurements were performed on four other groups of animals subjected to 2 h of hypercapnia (8% CO2 in air), anoxia (N2 breathing), anoxia plus hypercapnia (8% CO2-92% N2), or air breathing (control). Significant changes in the concentrations of the inhibitory amino acid neurotransmitters known to affect respiration [gamma-aminobutyric acid (GABA) and taurine] were seen. GABA increased significantly in those animals subjected to anoxia, whereas taurine decreased significantly in the diving animals and increased significantly in those subjected to anoxia plus hypercapnia. These results suggest that the attenuated central ventilatory drive during diving in these animals may be related to alterations in brain concentrations of GABA and taurine.

Ventilation and CSF ions during hypocapnic HCl and HNO3 acidosis in conscious rabbits.

In conscious rabbits with preimplanted arterial, central venous, and cisterna magna catheters, we infused HNO3 or HCl to lower and maintain arterial PCO2, pH, and plasma HCO-3 at the same mean values in both groups over 9 h. The hypothesis was that greater entry into cerebrospinal fluid (CSF) of the strong anion NO-3 vs. Cl- would result in a greater decrease in CSF [HCO-3] in the HNO3 vs. the HCl experiment, even though the acid-base stress as measured by arterial PCO2 and plasma [HCO-3] was the same. The results did not support the hypothesis. With HCl acidosis, delta CSF [HCO-3] was equal to delta CSF [Cl-]. With HNO3 acidosis, delta CSF [HCO-3] was equal to delta CSF [NO-3] + delta CSF [Cl-], as both CSF Cl- and HCO-3 decreased with NO-3 entry into CSF. The change in CSF [HCO-3] appeared tightly linked to the PCO2 or the plasma [HCO-3], it did not depend on the type of acid used. The ionic mechanisms that determine the CSF [HCO-3] in metabolic acidosis appear able to utilize changes in the strong anions NO-3 and Cl- to bring about CSF acid-base regulation. The change in alveolar ventilation per unit CO2 production as reflected by the arterial PCO2 was the same in both groups, although the expired minute ventilation and respiratory frequency responses were diminished in the HNO3 vs. the HCl groups. In both groups with acidosis, tidal volume increased, whereas respiratory frequency decreased.

Acid-base stress and central chemical control of ventilation in turtles.

Central chemical control of ventilation in turtles, Chrysemys (Pseudemys) scripta, has been characterized by alterations in breathing frequency (f). To assess the effects of acid-base stress on the central ventilatory response, three groups of animals were subjected to 2 h of anoxia (98% N2-2% CO2), 2 h of hypercapnia (8% CO2 in air), or 2 h of anoxia plus hypercapnia (92% N2-8% CO2). Ventilatory responses were measured continuously, and arterial blood and cerebrospinal fluid (CSF) acid-base variables were determined after 2 h. Results show that central ventilatory responses (f) were significantly elevated in CSF acidosis caused by CO2 over those caused by the accumulation of CSF fixed acid alone (anoxia). The increases in f did not correlate with decreases in estimated CSF pH, since it was much lower in anoxia (7.19) than in hypercapnia (7.37). Our results strongly suggest that the central nervous system acidosis caused by anoxia produces centrally mediated ventilatory change in a fundamentally different way from hypercapnia.

Acute response to acid-base stress.

A method previously established in the experimental animal for predicting the acute response to either metabolic stress (bicarbonate administration) or respiratory stress(manipulation of oxygenator gas during cardiopulmonary bypass) has been extended to man. The method is based on a single nomogram. The accuracy of the nomogram is demonstrated using data from 13 patients on cardiopulmonary bypass. Similar agreement obtains between the nomogram and data reported by others. The nomogram can be used to estimate the therapeutically required dose of bicarbonate.

Acute response to acid-base stress in the dog.

ARTICLESAcute response to acid-base stress in the dogCD Russell, MM Illickal, Maloney JV Jr, HD Roeher, and EC DeLandCD Russell, MM Illickal, Maloney JV Jr, HD Roeher, and EC DeLandPublished Online:01 Sep 1972https://doi.org/10.1152/ajplegacy.1972.223.3.689MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation More from this issue > Volume 223Issue 3September 1972Pages 689-694 Copyright & PermissionsCopyright © 1972 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1972.223.3.689PubMed5055327History Published online 1 September 1972 Published in print 1 September 1972 Metrics