G-negative Bacteria Research Articles

Nitrogen-Doped Carbon Dots: A New Powerful Fluorescent Dye with Substantial Effect on Bacterial Cell Labeling.

Carbon dots (CDs)-minute carbon nanoparticles with remarkable luminescent properties, photostability, and low toxicity-show potential for various applications. CDs synthesized using citric acid and urea are the least toxic to biological environments. Here, we aimed to explore the effect of CDs synthesized using citric acid and urea at 50, 33, and 25% (CDs 1/1, 1/2, and 1/3, respectively) weight ratios in a microwave on bacterial cell fluorescence sensing and labeling. The nanoscale properties of CDs were investigated via transmission electron microscopy and dynamic light scattering particle size analysis. X-ray powder diffraction confirmed the graphitic structures of CDs. X-ray photoelectron spectroscopy revealed that the nitrogen content increased gradually with increasing urea ratios, indicating functional group changes. Transient photoluminescence decay periods demonstrated superior fluorescence intensity of CDs 1/3 under blue, green, and red lights. The use of CDs was notably more efficient than traditional methods in staining bacterial cells. Fluorescence microscopy of 10 g-positive and 10 g-negative bacteria revealed enhanced staining of Gram-positive strains, with CDs 1/3 presenting the best results. The CDs exhibited excellent photostability, maintaining poststaining fluorescence for 100 min, surpassing the performance of conventional dyes. CDs could serve as potential fluorescent dyes for the rapid discrimination of Gram-positive and Gram-negative bacteria.

In-vitro antioxidant, antimicrobial and phytochemical properties of extracts from the pulp and seeds of the African baobab fruit (Adansonia digitata L.)

Adansonia digitata, commonly known as the African Baobab plant is used widely in traditional medicine for treating of many diseases. The current study investigates the antioxidant and antimicrobial properties, and nutritional composition of the pulp and seeds from the fruit of African Baobab plant. Matured fruits were harvested and processed by separating the fruit pulp and seeds. Water, 70 % Ethanol/water mixture, and Hexane were used as solvents for extraction. Antioxidant properties of extracts in this study were investigated using the 2,2-diphenyl-1-picrylhydrazyl, hydrogen peroxidescavenging assays., Total Flavonoid Content, Total Phenolic Content, Total Tannin Content, and Total Antioxidant Capacity were also investigated. Agar Well Diffusion and Broth Dilution methods were used to estimate the antimicrobial properties of the extracts. The proximate composition of the seeds and fruit pulps was also determined. GC-MS was employed to determine the fatty acid composition. Results obtained showed the presence of Total phenolics (range 4.1–5.5 mg GAE/g), Total flavonoids (range 10.1–16.5 mg QE/g), Total Tannins (range 1.7–15.6 mg CE/g), and Antioxidants (range 2.0–14.5 mg AAE/g). The H2O2 and DPPH assays gave IC50s in the ranges of 300–1800 mg/L and 700–1600 mg/L respectively. Extract from the fruit pulp was found to inhibit the growth of a panel of 2 g-positive bacteria, 2 g-negative bacteria, and two fungi microorganisms. Fatty acids such as myristic acid, palmitic acid, and stearic acid were found to be present in oil from the seeds. Proximate components such as crude protein, crude fat, and crude fibre were found to be high. From the results, seeds and the fruit pulp of the African Baobab plant have significant antioxidant properties and can inhibit microbial growth.

Petroselinum crispum L., essential oil as promising source of bioactive compounds, antioxidant, antimicrobial activities: In vitro and in silico predictions

This exploratory study aims to identify the volatile compounds in PC-Eo (Petroselinum crispum L. essential oil) and evaluate its antioxidant and antimicrobial properties in vitro. Molecular docking, drug-likeness prediction, and pharmacokinetics (absorption, distribution, metabolism, excretion, and toxicity—ADMET) were among the in silico simulations that were used to explain the biological properties observed in vitro. For PC-Eo's chemical screening, gas chromatography-mass spectrophotometry (GC-MS) was employed. The antioxidant activity of PC-Eo was evaluated using five in vitro complementary techniques, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging activity, β-Carotene bleaching test (BCBT), reducing power (RP), and phosphomolybdenum assay (TAC). GC-MS analysis revealed that the primary components of PC-Eo are apiol (49.05 %), Myristicin (21.01 %), and 1-allyl-2,3,4,5-tetramethoxybenzene (13.14 %). The results of the in vitro antioxidant assays indicate that PC-Eo exhibits a superior antioxidant profile. The in vitro antimicrobial activity of PC-Eo was assessed against five strains, including 2 g-positive bacteria, 2 g-negative bacteria, and one fungal strain (Candida albicans). The disc-diffusion assay revealed significant antibacterial and antifungal activities against all strains, with zones of inhibition exceeding 15 mm. The microdilution test highlighted the lowest MIC and MBC values with gram-positive bacteria, ranging from 0.25 to 0.5 % v/v for MIC and 0.5–1.0 % v/v for MBC. For the fungal strain, MIC was recorded at 1.25 % and MFC at 2.5 % v/v. PC-Eo demonstrates bactericidal and fungicidal activity based on the MBC/MIC and MFC/MIC ratios. According to the ADMET study, the primary PC-Eo compounds have advantageous pharmacokinetic characteristics. These findings provide empirical support for the traditional uses of this plant and indicate its possible use as a natural remedy.

Analysis of Volatile Components and Antibacterial Activity of Silver Wormwood Essential Oils from Different Habitats by E-Nose Combined with GC-MS

Electronic nose (E-nose) combined with gas chromatography–mass spectrometry (GC-MS) was used to analyze the volatile components of silver wormwood from different habitats, and the antibacterial activity of essential oils was also studied, to provide a scientific basis for quality control of silver wormwood and rational utilization of their essential oils. In this study, the total content of essential oils in silver wormwood was determined by steam distillation; the volatile components were conducted in an overall analysis by E-nose combined with chemometrics; the volatile components were analyzed and identified by GC-MS; and two G-negative bacteria and one Gram-positive bacteria were used as test bacteria to determine the antibacterial activity of the essential oils from silver wormwood. The results showed that principal component analysis (PCA) and linear discriminant analysis (LDA) of E-nose could distinguish the essential oils of silver wormwood from different habitats, and the odor difference of essential oils was obvious. A total of 87 volatile components were identified by GC-MS, and there were significant differences in components and contents in silver wormwood from different habitats; PCA and hierarchical cluster analysis (HCA) could effectively distinguish silver wormwood from different habitats. The essential oils from silver wormwood from different habitats all had a certain inhibitory effect on Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Therefore, the combination of E-nose and GC-MS could quickly distinguish silver wormwood from different habitats and provide a reference for quality control, drug selection, and comprehensive utilization of silver wormwood.

A facile construction of NiV2O6/CeO2 nano-heterojunction for photo-operated process in water remediation reaction, antibacterial studies, and detection of D-Amino acid in peroxidase system

Global environment issues have been extended with the growth of the population and become an essential difficult. The utilization of wastewater treatment method such as photocatalytic is excellent method for this scope. The photocatalytic response can be improved by the heterojunction metal oxide catalyst due to great separation of electrons and holes. Herein, the NiV2O6/CeO2 nanocomposites as p-n heterojunction was fabricated by using the simple combustion method. The structural properties of the prepared NiV2O6/CeO2 nanocomposites were characterized via X-ray diffraction, Raman, photoluminescence, transmission/scanning electron microscopic, and FTIR/UV–vis spectroscopy analysis. The XRD depicts the cubic and triclinic crystal phase of CeO2 and NiV2O6, respectively. The measured band gap energies of CeO2, NiV2O6, and NiV2O6/CeO2 nanocomposite are 3.22 eV, 2.60 eV, and 2.01 eV, respectively. The photo-degradation ability of CeO2, NiV2O6, and NiV2O6/CeO2 nanocomposite was studied for removal of crystal violet dye under visible light irradiation. The photocatalytic response of NiV2O6/CeO2 nanocomposite was 93.3% in 120 min, and higher than the single catalysts. Antibacterial assay of NiV2O6/CeO2 was performed against two G-positive and two G-negative bacteria. The results showed that the best antibacterial activity of NiV2O6/CeO2 versus four bacterial samples. The peroxidase activity of NiV2O6/CeO2 was investigated by detection of d-aspartic acid. Based on the finding, the detection limit of 2.10 μM, which that depicts the NiV2O6/CeO2 has excellent potential in detection analysis of d-aspartic acid.

Photocatalytic and Enhanced Biological Activities of Schiff Base Capped Fluorescent CdS Nanoparticles.

In the present work, biocompatible CdS nanoparticles were synthesized using Schiff base ligand,3-((2-(-(1-(2hydroxyphenyl)ethylidene)amino)ethyl)imino)-2-pentone,by a simple ultrasonic irradiation method. The structural, morphological, and optical properties were studied using XRD, SEM, TEM, UV-visible absorption, and photoluminescence (PL) spectra. The quantum confinement effect of the Schiff base capped CdS nanoparticles was confirmed by using UV-visible and PL spectrum analysis. ThisCdS nanoparticles were an effective photocatalyst for degrading rhodamine 6G and methylene blue with a 70% and 98% degradation capacity, respectively. Furthermore, the disc-diffusion method demonstrated that CdS nanoparticles inhibit G-positive bacteria and G-negative bacteria more effectively. These Schiff base capped CdS nanoparticles were taken for anin-vitroexperiment with HeLa cells to exhibit the possibility of providing optical probes in biological applications and observed under a fluorescence microscope. In addition, MTT cell viability assays were carried out to investigate the cytotoxicity for 24h. As a result of this study, 2.5µg/ml doses of CdS nanoparticles are suitable for imaging and are effective in destroying HeLa cells. The present study suggests that the synthesized Schiff base capped CdS nanoparticles could be a potential photocatalyst, antibacterial agent, and biocompatible nanoparticle for bioimaging applications.

Application of initial anti-infectives and trends in children with septic shock

Objective: To investigate the pathogen composition, initial anti-infectives and pathogen coverage, and trends over the last 5 years in children with septic shock in pediatric intensive care unit (PICU). Methods: The single-center retrospective study included 257 children with septic shock who were admitted to PICU of Beijing Children's Hospital, Capital Medical University from 2017 to 2021. The causitive pathogen composition, initial use of anti-infective drugs, pathogen coverage, and changes in recent years were analyzed. The children were divided into sufficient and insufficient coverage groups according to whether the pathogen were sufficiently covered by initial anti-infectives; community-and hospital-acquired groups; and with and without underlying disease groups. T test, rank-sum test and Chi-square test were used for comparison between the groups to investigate the differences in pathogen, treatment and prognosis. Results: A total of 257 septic shock children were included, with 162 males and 95 females, aged 36 (12, 117) months. The pathogen positive rate was 64.6% (166/257) and the in-hospital mortality was 27.6% (71/257). In the 208 pathogen-positive samples, bacteria was the most common (57.7%, 120/208) with G-negative bacteria predominating (55.8%, 67/120), followed by viruses (26.0%, 54/208). Nearly 99.2% (255/257) of the children were treated with antibacterial at the beginning, of whom 47.1% (121/257) were treated with carbapenems combined with vancomycin or linezolid. The proportion of 3 or more antibacterial combinations was higher in children with underlying diseases and hospital-acquired septic shock than in those without underlying disease or community-acquired septic shock (27.4% (49/179) vs. 14.1% (11/78), 29.4% (52/177) vs. 10.0% (8/80), χ2=5.35,11.56,all P<0.05). The proportion of initial combination of carbapenem and vancomycin or linezolid reduced from 52.5% (21/40) to 41.3% (19/46), and of adequate pathogen coverage increased from 40.0% (16/40) to 58.7% (27/46) in the last five years. Conclusions: The initial use of antibacterial drugs is common in children with septic shock in PICU, especially in those with hospital-acquired septic shock and underlying diseases. In recent years, antimicrobial combinations have decreased, but the pathogen coverage has improved, indicating that drug selection is more reasonable and accurate.

Synthesis, Characterization and Preliminary Antimicrobial Evaluation of New Schiff bases and Aminothiadiazole Derivatives of N- Substituted Phthalimide

A new series of schiff base and aminothiadiazole derivatives of N- substituted phthalimide (I-VI) were synthesized. In this work, the intermediate 4-(1,3-dioxoisoindolin-2-yl)benzaldehyde compound (I), was formed by reaction of 4-amino benzaldehyde with phthalic anhydride in glacial acetic acid(GAA). A series of Schiff bases (IV-VI) was prepared by the reaction of benzidine with compound (I) in ethanol and presence of GAA as a catalyst to form compound (IV) which react with compound (I) and p-nitro benzyldehyde to give compound (V) and (VI) respectively. A new phthalimide thiosemi-carbazone derivative (ll) was prepared by reaction of compound (l) with thiosemi-carbazide HCl in the presence of equimolar amount of sodium acetate. Finally, a new phthalimide containing (1,3,4- thiadiazole ring) compound (III) was formed by bromine mediated “oxidative intramolecular cyclization” of compound (I) in the presence of sodium acetate. All of the final target compounds' structures were successfully synthesized and confirmed using analytical and spectroscopic data. These compounds were identified and confirmed by melting points, TLC, FT IR, and 1H NMR. While the antimicrobial effect of the new derivatives has been assessed in vitro against G-positive, G-negative bacteria and fungi activity. All screened compounds exhibited no activity against G-positive bacteria (Staph. Aureus, and Bacillus subtilis). Many of synthesized compounds displayed moderate effect against “G-negative bacteria Escherichia coli, and Klebsiella pneumonia and against Candida tropicalis”. While the best antifungal activity was obtained from compound I which has high activity against Candida tropicalis.

Citrus limon assisted green synthesis of MgO nanoparticles: Evaluation of phase, functional groups, surface morphology, thermal stability and colloidal stability

Citrus limon (the common lemon juice) assisted green combustion was used to create MgO nanostructures. The powder was heat treated for 3 h at 350 °C, and the as-synthesized and heat treated MgO nanostructures were tested by various techniques to investigate their phase composition, structure, thermal stability, colloidal stability, surface morphology, and antimicrobial activities. XRD was performed to study the single-phase cubic structure of MgO nanostructures, and the XRD results confirmed that the sizes of the MgO nanostructures are in the nanoscale range. The average crystallite sizes for as-synthesized and heat-treated samples are 7.8 nm and 19.2 nm, respectively. The functional groups in the experiment were examined using FTIR in the 400–4000 nm range. Thermal analysis of the MgO nanostructures were recorded through TG-DTA and the results confirm the MgO NPs thermally decomposed at 359.77 °C and 361.86 °C. The colloidal stability of the samples was tested using Zeta potential, it confirms that both samples are stable. The external morphology of as-synthesized and heat-treated samples were visualized through SEM. It confirms that the as-synthesized and heat treated MgO samples are nanostructures. The elemental analysis confirms the presence of Mg and O in both samples. The antimicrobial activity of MgO nanostructures tested by plate count mothed and the heat-treated sample exhibits noticeable antimicrobial performance against G-positive and G-negative bacteria.

Molecular characterization and antibacterial ability of galectin-3 and galectin-9 in Onychostoma macrolepis

Galectins belong to the β-galactoside binding protein family, which have conserved carbohydrate-recognition domains (CRDs) and participate in innate and acquired immunity in animals. In this study, two galectin genes were cloned from Onychostoma macrolepis, OmGal-3 (galectin-3) and OmGal-9 (galectin-9). The open reading frames (ORFs) of OmGal-3 and OmGal-9 contain 732 and 978 base pairs, encoding 243 and 325 amino acids, respectively. OmGal-3 contains a C-terminal CRD, but OmGal-9 contains an N-terminal CRD and a C-terminal CRD. Two galectins were expressed at varying levels in all tissues examined, with the liver showing the highest expression. The relative gene expression levels of OmGal-3 and OmGal-9 following Aeromonas hydrophila infection were significantly up-regulated in the liver and spleen, and OmGal-9 had a greater increase than OmGal-3. The recombinant OmGal-3 and OmGal-9 proteins (rOmGal-3 and rOmGal-9) were authenticated and verified by SDS-PAGE and western blotting. ROmGal-3 and rOmGal-9 agglutinated all tested bacteria, including 3 g-positive bacteria (Aeromonas hydrophila, Escherichia coli, and Vibrio parahaemolyticus) and 3 g-negative bacteria (Streptococcus agalactiae, Staphylococcus aureus, and Bacillus cereus) in vivo without Ca2+. ROmGal-3 showed strong binding both to gram-positive and gram-negative bacteria and OmGal-9 had a stronger binding activity against gram-positive bacteria. Furthermore, rOmGal-3 and rOmGal-9 exhibited dose-dependent binding capability to two classic pathogens associated molecular pattern (LPS and PGN) and two sugars (d-lactose and d-galactose), and rOmGal-3 has better binding activity at lower concentrations in LPS and PGN than rOmGal-3. The integrated analyses indicate that the two galectins probably play an important role in innate immune defense by binding to bacterial cells via the CRD domain against pathogen infection.

Heavy Metal Tolerance Trend in Extended-Spectrum β-Lactamase Encoding Strains Recovered from Food Samples.

This study evaluates bacteriological profiles in ready-to-eat (RTE) foods and assesses antibiotic resistance, extended-spectrum β-lactamase (ESBL) production by gram-negative bacteria, and heavy metal tolerance. In total, 436 retail food samples were collected and cultured. The isolates were screened for ESBL production and molecular detection of ESBL-encoding genes. Furthermore, all isolates were evaluated for heavy metal tolerance. From 352 culture-positive samples, 406 g-negative bacteria were identified. Raw food samples were more often contaminated than refined food (84.71% vs. 76.32%). The predominant isolates were Klebsiella pneumoniae (n = 76), Enterobacter cloacae (n = 58), and Escherichia coli (n = 56). Overall, the percentage of ESBL producers was higher in raw food samples, although higher occurrences of ESBL-producing E. coli (p = 0.01) and Pseudomonas aeruginosa (p = 0.02) were observed in processed food samples. However, the prevalence of ESBL-producing Citrobacter freundii in raw food samples was high (p = 0.03). Among the isolates, 55% were blaCTX-M, 26% were blaSHV, and 19% were blaTEM. Notably, heavy metal resistance was highly prevalent in ESBL producers. These findings demonstrate that retail food samples are exposed to contaminants including antibiotics and heavy metals, endangering consumers.

Kaempferia galanga Linn. Extract – A potential antibacterial agent for preservation of poultry products

Poultry is one of the most widely consumed animal-based foods in the world. Understanding the characteristics of bacterial communities present during processing and the targeted design of natural preservatives could improve the quality and safety concerns of poultry industry. In this study, pathogens and spoilage bacteria arising from the processing of poultry products were identified using high-throughput 16S rRNA sequencing and traditional culture screening. Ten dominant pathogenic and spoilage bacteria were isolated, including 8 g-positive and 2 g-negative bacteria. The mechanism and antibacterial activity of Kaempferia galanga Linn. extract (KGE), a spice added to the poultry products, against the targeted pathogenic bacteria were analyzed further. KGE exhibited significant antibacterial activity against all tested pathogenic bacteria. The antibacterial mechanism of KGE involved alteration of cell integrity and cell membrane permeability, resulting in an outflow of intracellular substances, such as nucleic acids, proteins, and alkaline phosphatase. Scanning electron microscopy further confirmed KGE-mediated cell membrane damage and cytoplasmic leakage. The chemical characterization indicated that the large amounts of acetic acid present in KGE might account for its excellent antibacterial activity. Taken together, the study confirms the excellent antibacterial activity of KGE and its potential use as a natural preservative for poultry products.

Rhodopseudomonas palustris Quorum Sensing Molecule pC-HSL Induces Systemic Resistance to TMV Infection via Upregulation of NbSIPK/NbWIPK Expressions in Nicotiana benthamiana.

G-negative bacteria produce myriad N-acyl-homoserine lactones (AHLs) that can function as quorum sensing (QS) signaling molecules. AHLs are also known to regulate various plant biological activities. p-Coumaroyl-homoserine lactone (pC-HSL) is the only QS molecule produced by a photosynthetic bacterium, Rhodopseudomonas palustris. The role of pC-HSL in the interaction between R. palustris and plant has not been investigated. In this study, we investigated the effect of pC-HSL on plant immunity and found that this QS molecule can induce a systemic resistance to Tobacco mosaic virus (TMV) infection in Nicotiana benthamiana. The results show that pC-HSL treatment can prolong the activation of two mitogen-associated protein kinase genes (i.e., NbSIPK and NbWIPK) and increase the expression of transcription factor WRKY8 as well as immune response marker genes NbPR1 and NbPR10, leading to an increased accumulation of reactive oxygen species (ROS) in the TMV-infected plants. Our results also show that pC-HSL treatment can increase activities of two ROS-scavenging enzymes, peroxidase and superoxide dismutase. Knockdown of NbSIPK or NbWIPK expression in N. benthamiana plants through virus-induced gene silencing nullified or attenuated pC-HSL-induced systemic resistance, indicating that the functioning of pC-HSL relies on the activity of those two kinases. Meanwhile, pC-HSL-pretreated plants also showed a strong induction of kinase activities of NbSIPK and NbWIPK after TMV inoculation. Taken together, our results demonstrate that pC-HSL treatment increases plant resistance to TMV infection, which is helpful to uncover the outcome of interaction between R. palustris and its host plants.

Mesoporous nanocrystalline sulfonated hydroxyapatites enhance heavy metal removal and antimicrobial activity

Heavy metal ions are major contaminants of water resources. Their high solubility in water causes serious health problems as they can be adsorbed by living species and therefore, accumulate in humans. In this study, two approaches are explored: the first is based on the manufacture of mesoporous nanocristalline sulfonated hydroxyapatite. The influence of sulfonate ligands and the structure and surface chemistry of the materials are discussed. The second approach is based on the recovery of sulfonated hydroxyapatites used as adsorbents for heavy metal removal from water, which are studied for their antibacterial properties. The single and multi-component adsorption of Pb2+, Zn2+ and Cd2+ ions is enhanced in apatite enriched with sulfonate ligands, with remarkable selectivity and efficiency. The calculated maximal single sorption capacities qe were in the order Zn2+(4.21 mmol g−1) > Cd2+(3.15 mmol g−1) > Pb2+(2.45 mmol g−1). Competition between metal ions decreases the adsorption capacity of each metal ion. Results show that Zn2+ and Cd2+ are preferentially adsorbed by sulfonated-HAp. The sulfonated hydroxyapatites are tested for their antimicrobial activity against three bacterial strains: Escherichia coli and Pseudomonas aeruginosa as Gram-negative model and Staphylococcus aureus as Gram-positive model bacteria. Results evidence the 1,3-Benzenedisulfonate-functionalized hydroxyapatite antimicrobial activity against G-positive and G-negative bacteria. The mechanisms responsible for metal-ion adsorption and antibacterial activity are discussed.

Determination of the Frequency of Microbial Agents and Drug Susceptibility Pattern of the Neonatal Sepsis in the Neonatal Intensive Care Unit at Alzahra Hospital, Tabriz, Iran

Background: Neonatal sepsis is one of the most important causes of infant mortality in developing countries. The causative organisms for sepsis are various in different regions across the world. The aim of this study was to determine the frequency of microbial agents and drug resistance pattern of the neonatal sepsis in newborns admitted to the neonatal intensive care unit (NICU) at Alzahra Hospital Tabriz, Iran.Methods: This descriptive cross-sectional study was carried out from December 2016 to January 2018 in the NICU at Alzahra Hospital Tabriz, Iran. The medical records of all neonates admitted to the NICU were investigated using the convenience sampling method. The data were collected using a two-part demographic form. Subsequently, the data were analyzed in SPSS software (version 22.0).Results: Out of 174 positive blood culture, 52.4% (n=92) and 46.6% (n=82) of Gram-negative (G) and Gram-positive (G) bacteria accounted for the cause of sepsis, respectively. The most common cause of early- and late-onset sepsis was Coagulase-Negative Staphylococci (CoNS), and the most common G-negative and G-positive bacteria were Acinetobacter and CoNS, respectively. The G-positive bacteria showed the most antibiotic susceptibility to Vancomycin (81.45%), Ampicillin (52.15%), and Imipenem (47.32%). On the other hand, the highest drug susceptibility in G-negative bacteria was related to antibiotics, such as Amikacin (73.64%), Imipenem (56.36%), and Ciprofloxacin (52.44%). Moreover, the most antibiotic resistance was associated with Oxacillin (100%), Tetracycline (100%), and Ciprofloxacin (44.4%).Conclusion: The CoNS is the main cause of early- and late-onset sepsis among the neonates admitted to the NICU at Alzahra Hospital, Tabriz, Iran. G-positive and G-negative as causative agents of sepsis showed the highest susceptibility to Vancomycin and Amikacin, respectively.

A new crustin is involved in the innate immune response of shrimp Litopenaeus vannamei

Crustin is an antimicrobial peptide (AMP) that plays a key role in the innate immunity of crustaceans. This study cloned a new crustin from Pacific white shrimp Litopenaeus vannamei, which we designated as LvCrustinB, using rapid amplification of cDNA ends (RACE). The full-length cDNA of LvCrustinB is 751 bp with an open reading frame (ORF) of 591 bp encoding a peptide of 196 amino acids that includes a putative signal sequence. LvCrustinB is a type II crustin that has a glycine-rich region and a single whey acidic protein domain (WAP) domain. The mRNA transcript of LvCrustinB was detected in all examined tissues and was found to be most abundantly expressed in the epithelium and muscle. The expression of LvCrustinB in hemocytes was significantly upregulated after L. vannamei was challenged with LPS, Vibrio parahaemolyticus, and white spot syndrome virus (WSSV). When LvCrustinB was knocked down with RNAi, the mortality rate of L. vannamei significantly increased after V. parahaemolyticus or WSSV infection. Recombinant LvCrustinB was produced using Pichia pastoris GS115 and was shown to bind to 2 g-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and 2 g-negative bacteria (Escherichia coli and V. parahaemolyticus) via polysaccharides, which included PGN, LTA, and LPS. In vivo, the recombinant LvCrustinB remarkably protected L. vannamei from V. parahaemolyticus infection. These results suggest that LvCrustinB plays an important role in innate immunity and may be potentially utilized as antibacterial agents in shrimp.

Antimicrobial activities of mesoporous nickel phosphate synthesized with low-temperature method

Mesoporous crystalline phase of nickel phosphate (m-NP) have been synthesized by a simple low-temperature hydrothermal approach. For the first time, the antimicrobial activities of m-NP are studied using different microbial media. The chemical structure and crystallinity of the m-NP are studied by XRD pattern and is confirmed by FT-IR results. The morphology is verified by scanning electron microscopy (SEM) and transmission electron micrographs (TEM). According to BET studies, the total pore volume is found to have an average value of 0.074 cc/g with surface area of 29.0 m2/g. m-NP particles are screened for antimicrobial activities against one G-positive bacteria, three G-negative bacteria and C. albicans fungal pathogen. The results show that the m-NP exhibits good antimicrobial activities against both G-positive and G-negative bacteria and against C. albicans with good selectivity against G-negative bacteria.

Targeting gut microbiota: Lactobacillus alleviated type 2 diabetes via inhibiting LPS secretion and activating GPR43 pathway

Lactobacillus G15 and Q14, two species of Lactobacillus used in the preparation of Chinese traditional fermented dairy foods, have the potential to prevent diabetes. Herein, we clarified their mechanisms by which gut microbiota relate to the control of diabetes. Results showed that G15 and Q14 improved the disorders in blood glucose and insulin. Moreover, G15 and Q14 promoted the enrichment of SCFA-producing bacteria, and upregulated the production of acetate and butyrate. Their antidiabetic effects were closely associated with SCFAs-downstream receptors and hormone secretion. Additionally, G15 and Q14 significantly shortened the number of G-negative bacteria, which subsequently decreased the levels of LPS and inflammatory factors. G15 and Q14 improved the disorganization of the intestinal mucous and the integrity of intestinal barrier. Our results indicate that Lactobacillus G15 and Q14 alleviate type 2 diabetes in a gut microbiota-dependent way via downregulating G− bacteria-related LPS secretion, as well as upregulating SCFAs-producing bacteria-related G protein-coupled receptor 43 pathway.

Essential oils and hydrophilic extracts from the leaves and flowers of Succisa pratensis Moench. and their biological activity.

This study was undertaken to evaluate the antioxidant activity of methanol and water extracts from Succisa pratensis Moench (Dipsacaceae) leaves and flowers as well as the chemical composition of the essential oils found in them and the antimicrobial activity of the oils and extracts thereof. The essential oils from S. pratensis leaves and flowers were analysed by the GC-MS. The total phenolic content was determined with Folin-Ciocalteu, that of flavonoids with aluminium chloride and that of phenolic acids with Arnov's reagent. The antioxidant activity was investigated by the DPPH radical scavenging assay. Antimicrobial activity was studied in vitro against G-positive and G-negative bacteria, and fungi using disc diffusion and broth microdilution methods. Eighty-six components of the leaf essential oil and 50 of the flower essential oil were identified. The main components of the leaf essential oil were 2-hexyl-1-octanol (5.76%) and heptacosane (5.53%), whereas hexadecanoic acid (16.10%), 8-octadecen-1-ol acetate (9.86%), methyl linolenate (8.58%), pentacosane (6.63%) and heptacosane (5.50%) were found in the flower essential oil. The essential oils exerted high antimicrobial activity (range: 0.11 to >3.44mg/ml) against the following bacteria: Pseudomonas aeruginosa, Staphylococcus aureus and fungi: Trichophyton mentagrophytes, Candida albicans, whereas the methanol and water extracts showed moderate or weak activity. The strongest antioxidant activity was shown by methanol extracts from S. pratensis leaves, IC50 = 0.09 mg/ml. There was a positive correlation between the total phenolic content and the antimicrobial activity, while for the antioxidant effect, it was not observed. The results suggest great antibacterial activity of the oils and high antioxidant activity of the methanol extract and may justify the application in treating infections.

Effects of Faidherbia albida canopy and leaf litter on soil microbial communities and nitrogen mineralization in selected Zambian soils

The nitrogen status of most Zambian soils is inherently low. Nitrogen-fixing trees such as Faidherbia albida (F. albida) could have the potential to restore soil fertility. We conducted a study to examine the role of mature F. albida trees on the soil microbial communities and overall N fertility status in Zambia. Soil samples were collected under and outside the canopies of F. albida trees in representative fields from two sites namely; Chongwe (loamy sand) and Monze (sandy loam). To assess the long term canopy effects; total N, mineral N and soil organic carbon (Corg) content were directly measured from soils collected under and outside the canopy. Short term litter effects were assessed by subtracting concentrations of biochemical properties of non-amended controls from amended soils with F. albida litter during an 8 week incubation experiment. We also determined N mineralization rates, microbial community structure—Phospholipid fatty acids, microbial biomass carbon, and labile organic carbon ( $${\text{C}}_{{{\text{org[K}}_{ 2} {\text{SO}}_{ 4} ]}}$$ ) during incubation. For the long term canopy effect, average N mineralization rate, Corg, total N and mineral N content of non-amended soils under the canopy were (all significant at p < 0.05) greater than soils outside the canopy on both sites. In the short term, amending soils with litter significantly increased N mineralization rates by an average of 0.52 mg N kg−1 soil day−1 on soil from Monze. Microbial biomass carbon measured after 4 weeks of incubation was on average significantly higher on amended soils by 193 and 334 mg C kg−1 soil compared with non-amended soils in Chongwe and Monze soils, respectively. After 6 weeks of incubation, the concentration of all selected biomarkers for major microbial groups concentrations in non-amended soils were significantly higher (all p < 0.05) under the canopy than outside in Monze soil. Using principal component analysis, we found that the segregation of the samples under and outside the canopy by the first principal component (PC1) could be attributed to a proportional increase in abundances of all microbial groups. Uniform loadings on PC1 indicated that no single microbial group dominated the microbial community. The second principal component separated samples based on incubation time and location. It was mainly loaded with G-positive bacteria, and partly with G-negative bacteria, indicating that microbial composition was dominated by these bacterial groups probably at the beginning of the incubation on Monze soils. Our results show that the improvement of soil fertility status by F. albida could be attributed to a combination of both long term modifications of the soil biological and chemical properties under the canopy as well as short term litter fall addition.