Optimization of the fermentation process and antioxidant activity of mixed lactic acid bacteria for honeysuckle beverage.

The aim of the research was to obtain a high healthcare honeysuckle beverage with strong antioxidant activity. Honeysuckle (Lonicera japonica Thunb) was used as the raw material in this experiment. The effects of fermentation temperature, fermentation time, lactic acid bacteria inoculation amount, and sugar addition amount on the sensory quality of honeysuckle beverage were investigated by single factor test and orthogonal test, and the best process was obtained. The physicochemical indexes and antioxidant activity of honeysuckle beverages fermented with lactic acid bacteria were studied. The results showed that the fermentation temperature of the beverage was 37 °C, the fermentation time was 24 h, the inoculation amount of Lactiplantibacillus plantarum and Lactobacillus acidophilus mixed starter (1:1) was 3%, and 8% white granulated sugar was added. The highest sensory score was 87.30 ± 0.17, which was the optimal process. The honeysuckle liquid mixed inoculation with Lactiplantibacillus plantarum and Lactobacillus acidophilus was fermented for 24 h. The number of viable bacteria reached 9.84 ± 0.02 lg cfu/mL, the pH value was 3.10 ± 0.01, and the total polyphenol content was 7.53 ± 0.03 mg GAE/g. The number of lactic acid bacteria, pH, total polyphenol content, and free radical scavenging rate were significantly increased (p < 0.05) compared with the non-inoculated and single-inoculated lactic acid bacteria. To sum up, it was concluded that a better quality beverage could be obtained by fermenting a solution of honeysuckle with Lactiplantibacillus plantarum and Lactobacillus acidophilus mixed fermentation agent, providing a new approach and new ideas for the development of deep processing and fermented beverages using honeysuckle.

Resistance role of Lactobacillus sp. and Lactococcus sp. to copper ions in healthy children's intestinal microorganisms.

Heavy metal exposure is closely associated with gut microbe function and tolerance. However, intestinal microbe responses in children to different copper ion (Cu2+) concentrations have not yet been clarified. Here, in vitro cultivation systems were established for fecal microbe control and Cu2+-treated groups in healthy children. 16S rDNA high-throughput sequencing, meta-transcriptomics and metabolomics were used here to identify toxicity resistance mechanisms at microbiome levels. The results showed that Lactobacillus sp. and Lactococcus sp. exerted protective effects against Cu2+ toxicity, but these effects were limited by Cu2+ concentration. When the Cu2+ concentration was ≥ 4 mg/L, the abundance of Lactobacillus sp. and Lactococcus sp. significantly decreased, and the pathways of antioxidant activity and detoxification processes were enriched at 2 mg/L Cu2+, and beneficial metabolites accumulated. However, at high concentrations of Cu2+ (≥4 mg/L), the abundance of potential pathogen increased, and was accompanied by a downregulation of genes in metabolism and detoxification pathways, which meant that the balance of gut microbiota was disrupted and toxicity resistance decreased. From these observations, we identified some probiotics that are tolerant to heavy metal Cu2+, and warn that only when the concentration limit of Cu2+ in food is 2 mg/L, then a balanced gut microbiota can be guaranteed in children, thereby providing protection for their health.

Inhibitory mechanism of quercetin on Alicyclobacillus acidoterrestris.

In this the antibacterial of quercetin against Alicyclobacillus acidoterrestris was evaluated by measuring the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Subsequently, the effect of quercetin on A. acidoterrestris cell membrane was evaluated through scanning electron microscopy (SEM), surface hydrophobicity determination, diacetate fluorescein staining and propidium iodide (PI) staining. Additionally, the effects of quercetin on intracellular macromolecules and cell metabolism were explored by measuring the culture medium protein, bacterial protein and intracellular sodium and potassium adenosine triphosphate (ATP) enzyme activity. The results revealed that quercetin exhibited the MIC and MBC values of 100 ug/mL and 400 ug/mL, respectively, against A. acidoterrestris. The SEM results revealed that quercetin could induce irreversible damage to the cell membrane effectively. Moreover, quercetin could enhance the surface hydrophobicity of A. acidoterrestris. The results of flow cytometry and fluorescence microscopy analyses revealed that quercetin could promote cell damage by altering the cell membrane permeability of A. acidoterrestris, inducing the release of nucleic acid substances from the cells. Furthermore, the determination of protein content in the culture medium, bacterial protein content, and the Na(+)/K(+)-ATPase activity demonstrated that quercetin could reduce the intracellular protein content and impedes protein expression and ATPase synthesis effectively, leading to apoptosis.

Prediction of Feed Efficiency and Performance-Based Traits in Fish via Integration of Multiple Omics and Clinical Covariates.

Fish aquaculture is a rapidly expanding global industry, set to support growing demands for sources of marine protein. Enhancing feed efficiency (FE) in farmed fish is required to reduce production costs and improve sector sustainability. Recognising that organisms are complex systems whose emerging phenotypes are the product of multiple interacting molecular processes, systems-based approaches are expected to deliver new biological insights into FE and growth performance. Here, we establish 14 diverse layers of multi-omics and clinical covariates to assess their capacities to predict FE and associated performance traits in a fish model (Oncorhynchus tshawytscha) and uncover the influential variables. Inter-omic relatedness between the different layers revealed several significant concordances, particularly between datasets originating from similar material/tissue and between blood indicators and some of the proteomic (liver), metabolomic (liver), and microbiomic layers. Single- and multi-layer random forest (RF) regression models showed that integration of all data layers provide greater FE prediction power than any single-layer model alone. Although FE was among the most challenging of the traits we attempted to predict, the mean accuracy of 40 different FE models in terms of root-mean square errors normalized to percentage was 30.4%, supporting RF as a feature selection tool and approach for complex trait prediction. Major contributions to the integrated FE models were derived from layers of proteomic and metabolomic data, with substantial influence also provided by the lipid composition layer. A correlation matrix of the top 27 variables in the models highlighted FE trait-associations with faecal bacteria (Serratia spp.), palmitic and nervonic acid moieties in whole body lipids, levels of free glycerol in muscle, and N-acetylglutamic acid content in liver. In summary, we identified subsets of molecular characteristics for the assessment of commercially relevant performance-based metrics in farmed Chinook salmon.

Apple polyphenol biotransformation using probiotics in vitro and dynamic simulated digestion by bionic rats.

BACKGROUND: The present study investigated the effects of fermentation by Lactobacillus rhamnosus zrx01 (LR-zrx01), Lactobacillus acidophilus zrx02 (LA-zrx02), and Lactobacillus plantarum zrx03 (LP-zrx03), as well as dynamic simulated digestion by bionic rats, on the biotransformation and antioxidant potential of apple polyphenols. Polyphenols were determined by ultra-high-performance liquid chromatography-mass spectrometry, the dynamic simulated digestion of fermented apple pulp was determined by bionic rats, and the antibacterial and antioxidant activities were analyzed. RESULTS: The polyphenol content of apple pulp fermented using the three strains was respectively 1.41, 1.38, and 1.36 times that of non-fermented pulp. The antibacterial activity of apple pulp improved dramatically after fermentation. Moreover, the antioxidant potential of apple pulp increased after fermentation and digestion. After dynamic simulated digestion by bionic rats, the polyphenol content in unfermented and the three fermented groups increased significantly by 1.19, 1.23, 1.20, and 1.19 times compared to that before digestion, respectively. The major polyphenols in each group with obvious changes were epicatechin, rutin, kaempferol, quercetin-3 galactoside, p-coumaric acid, and two unknown substances, 1 and 2. CONCLUSION: Fermented and digested apple polyphenols showed better biotransformation effects and mostly existed in the form of small molecules, which was conducive to the improvement of polyphenol bioavailability and beneficial to the absorption of active substances by the human body. These findings build a foundation for the development of functional food beverages. © 2023 Society of Chemical Industry.

A pilot study on lengthening potentials and biomechanical effects of double and triple hemisection on tendon with slide lengthening.

The current study explored the slide-lengthening potentials of double and triple hemisections and the biomechanical effects of different inter-hemisection distances. Forty-eight porcine flexor digitorum profundus tendons were divided into double- and triple-hemisection groups (Groups A and B) and a control group (Group C). Group A was divided into Group A1 (distance between hemisections were the same as Group B) and Group A2 (distance between hemisections corresponded to the greatest distance between hemisections in Group B). Biomechanical evaluation, motion analysis, and finite element analysis (FEA) were performed. Failure load of intact tendon was significantly highest among groups. When the distance was 4 cm, the failure load of Group A increased significantly. When the distance between the hemisections was 0.5 or 1 cm, the failure load of Group B was significantly lower than Group A. Tendon elongation and failure load of Group B were significantly lower than those in Group A when the greatest distance between hemisections was the same. Consequently, Double hemisections had a similar lengthening ability to that of triple hemisections with the same distance, but better when the distances between extreme hemisections matched. However, the driving force for the initiation of lengthening may be greater.

Study on the Interaction Mechanism of Methoxy Polyethylene Glycol Maleimide with Sweet Potato ß-Amylase.

In this study, sweet potato ß-amylase (SPA) was modified by methoxy polyethylene glycol maleimide (molecular weight 5000, Mal-mPEG5000) to obtain the Mal-mPEG5000-SPA modified ß-amylase and the interaction mechanism between SPA and Mal-mPEG5000 was investigated. the changes in the functional groups of different amide bands and modifications in the secondary structure of enzyme protein were analyzed using infrared spectroscopy and circular dichroism spectroscopy. The addition of Mal-mPEG5000 transformed the random curl in the SPA secondary structure into a helix structure, forming a folded structure. The Mal-mPEG5000 improved the thermal stability of SPA and protected the structure of the protein from breaking by the surrounding. The thermodynamic analysis further implied that the intermolecular forces between SPA and Mal-mPEG5000 were hydrophobic interactions and hydrogen bonds due to the positive values of ΔHθ and ΔSθ. Furthermore, the calorie titration data showed that the binding stoichiometry for the complexation of Mal-mPEG5000 to SPA was 1.26, and the binding constant was 1.256 × 107 mol/L. The binding reaction resulted from negative enthalpy, indicating that the interaction of SPA and Mal-mPEG5000 was induced by the van der Waals force and hydrogen bonding. The UV results showed the formation of non-luminescent material during the interaction, the Fluorescence results confirmed that the mechanism between SPA and Mal-mPEG5000 was static quenching. According to the fluorescence quenching measurement, the binding constant (KA) values were 4.65 × 104 L·mol-1 (298K), 5.56 × 104 L·mol-1 (308K), and 6.91 × 104 L·mol-1 (318K), respectively.

Relationship between gut microbiota and Chinook salmon (Oncorhynchus tshawytscha) health and growth performance in freshwater recirculating aquaculture systems.

Gut microbiota play important roles in fish health and growth performance and the microbiome in fish has been shown to be a biomarker for stress. In this study, we surveyed the change of Chinook salmon (Oncorhynchus tshawytscha) gut and water microbiota in freshwater recirculating aquaculture systems (RAS) for 7 months and evaluated how gut microbial communities were influenced by fish health and growth performance. The gut microbial diversity significantly increased in parallel with the growth of the fish. The dominant gut microbiota shifted from a predominance of Firmicutes to Proteobacteria, while Proteobacteria constantly dominated the water microbiota. Photobacterium sp. was persistently the major gut microbial community member during the whole experiment and was identified as the core gut microbiota for freshwater farmed Chinook salmon. No significant variation in gut microbial diversity and composition was observed among fish with different growth performance. At the end of the trial, 36 out of 78 fish had fluid in their swim bladders. These fish had gut microbiomes containing elevated proportions of Enterococcus, Stenotrophomonas, Aeromonas, and Raoultella. Our study supports the growing body of knowledge about the beneficial microbiota associated with modern salmon aquaculture systems and provides additional information on possible links between dysbiosis and gut microbiota for Chinook salmon.

Characterization and functional study of a chimera galectin from yellow drum Nibea albiflora.

Galectins are protein that participates in a variety of immune responses in the process of pathogenic infections. In the present study, a chimera galectin gene was screened from the transcriptome database of Nibea albiflora, which was named as YdGal-3. The results of qRT-PCR showed that the mRNA transcripts of YdGal-3 were ubiquitously distributed in all the detected tissues. After infection with Vibrio harveyi, the expression of YdGal-3 in liver, spleen, and head kidney increased significantly. Immunohistochemistry showed that YdGal-3 protein was widely expressed in the head kidney. The purified YdGal-3 protein by prokaryotic expression agglutinated red blood cells. Sugar inhibition assay showed that the agglutinating activity of YdGal-3 protein was inhibited by different sugars including lactose, D-galactose, and lipopolysaccharide. In addition, we mutated YdGal-3 His 294 into proline (P), alanine (A), glycine (G), and aspartic acid (D), it was further proved that the residue plays a key role in agglutination. YdGal-3 agglutinated some gram-negative bacteria including Pseudomonas plecoglossicida, Vibrio parahemolyticus, V. harveyi, and Aeromonas hydrophila, and exhibited antibacterial activity. These results suggested that YdGal-3 protein played an important role in the innate immunity of N. albiflora.

One-step vapor deposition of fluorinated polycationic coating to fabricate antifouling and anti-infective textile against drug-resistant bacteria and viruses.

The ongoing pandemic caused by the novel coronavirus has turned out to be one of the biggest threats to the world, and the increase of drug-resistant bacterial strains also threatens the human health. Hence, there is an urgent need to develop novel anti-infective materials with broad-spectrum anti-pathogenic activity. In the present study, a fluorinated polycationic coating was synthesized on a hydrophilic and negatively charged polyester textile via one-step initiated chemical vapor deposition of poly(dimethyl amino methyl styrene-co-1H,1H,2H,2H-perfluorodecyl acrylate) (P(DMAMS-co-PFDA), PDP). The surface characterization results of SEM, FTIR, and EDX demonstrated the successful synthesis of PDP coating. Contact angle analysis revealed that PDP coating endowed the polyester textile with the hydrophobicity against the attachment of different aqueous foulants such as blood, coffee, and milk, as well as the oleophobicity against paraffin oil. Zeta potential analysis demonstrated that the PDP coating enabled a transformation of negative charge to positive charge on the surface of polyester textile. The PDP coating exhibited excellent contact-killing activity against both gram-negative Escherichia coli and gram-positive methicillin-resistant Staphylococcus aureus, with the killing efficiency of approximate 99.9%. In addition, the antiviral capacity of PDP was determined by a green fluorescence protein (GFP) expression-based method using lentivirus-EGFP as a virus model. The PDP coating inactivated the negatively charged lentivirus-EGFP effectively. Moreover, the coating showed good biocompatibility toward mouse NIH 3T3 fibroblast cells. All the above properties demonstrated that PDP would be a promising anti-pathogenic polymeric coating with wide applications in medicine, hygiene, hospital, etc., to control the bacterial and viral transmission and infection.

Characterization of a novel antifungal protein produced by Paenibacillus polymyxa isolated from the wheat rhizosphere.

BACKGROUND: Fusarium head blight (FHB) is one of the disasters that seriously harm wheat and other small grain crops. It causes spoilage and mildew of the grain leading to a significant decline in the yield and quality of the grain. This research aimed to isolate antagonistic bacteria to purify antifungal proteins. A strain was isolated from the rhizosphere of healthy wheat in a wheat field affected by a severe FHB epidemic. This isolated strain was tentatively identified as Paenibacillus polymyxa 7F1, which displayed a strong inhibitory effect against several other pathogens. One novel antifungal protein was purified from the P. polymyxa 7F1 and successfully expressed. RESULTS: A crude culture of P. polymyxa 7F1 demonstrated antifungal activity that was stable at a temperature range of 60-90 °C and a pH range of 2.6-9.0. However, the antifungal activity of the P. polymyxa 7F1 was inhibited with proteinase K, trypsin, and neutral protease treatment. A 36 kDa protein with broad-spectrum antifungal activity was purified from the P. polymyxa 7F1. A glycosyl hydrolase domain was identified from this protein through liquid chromatography-mass spectrometry (LC-MS) analysis. A recombinant plasmid pET32a(+)/36kd for prokaryotic expression was constructed, and the renatured p36kd protein demonstrated similar antifungal activity to the 36 kDa protein purified from the P. polymyxa 7F1. CONCLUSION: A novel antifungal protein produced by P. polymyxa 7F1 was purified and expressed. The recombinant protein showed good antifungal activity as the novel purified protein. The novel antifungal protein provides an effective way to control the Fusarium head blight. © 2020 Society of Chemical Industry.

Partial purification and characterization of a broad-spectrum bacteriocin produced by a Lactobacillus plantarum zrx03 isolated from infant's feces.

Lactobacillus plantarum zrx03 was a bacteriocin-producing strain isolated from infant's feces. The fermentation supernatant produced by this strain could strongly inhibit Escherichia coli JM109 ATCC 67387, Staphylococcus aureus ATCC 25923, and Listeria monocytogenes CICC 21633, in which the diameter of inhibition zone was 12.83 ± 0.62 mm, 15.08 ± 0.31 mm, 6.75 ± 0.20 mm, respectively, compared with lactic acid bacteria N1, N2, M13, M21, M31, and M37. According to amplification of 16S rRNA gene and identification of phylogenetic tree, this strain had a 1,450 bp sequence and 100% identity to the L. plantarum strain. Based on the influence of different protease treatments, such as pepsin, trypsin, papain, and proteinase K on the antimicrobial activity, this antimicrobial substance was considered to be a natural protein. Using bacteriocin produced by this strain as study object of this experiment, it had been extracted from ammonium sulfate precipitation and different organic solvents. The results showed that ethyl acetate was selected as the optimal solution to crude extraction of bacteriocin after comparing ammonium sulfate precipitation method and organic solvent extraction method, such as n-butanol, n-hexane, dichloromethane, trichloromethane, in which the diameter of the inhibition zones was above 28 mm. Results also showed the inhibition spectrum of the obtained bacteriocin had a broad spectrum of inhibition which could inhibit Gram-positive, Gram-negative, yeast. Especially, it could effectively inhibit S. aureus ATCC 25923, Bacillus subtilis CICC 10002, Bacillus anthracis CICC 20443, E. coli JM109 ATCC 67387, and Salmonella CMCC 541, and the zone diameter of inhibition has reached more than 28 mm. Moreover, it had a good thermal stability which antibacterial activity was retained 70.58% after treatment at 121°C for 30 min, and pH-stability was between pH 2.0-9.0. These results suggested bacteriocin produced by L. plantarum zrx03 had potential application prospects in food preservation.

Tempo-spatial variations of the Ryukyu Current southeast of Miyakojima Island determined from mooring observations.

The origin, structure, and variability of the Ryukyu Current (RC) have long been debated, mostly due to limited observations. A mooring array, deployed for two years southeast of Miyakojima in the southern portion of the Ryukyu Island chain, has provided, for the first time, data confirming the existence and revealing the characteristics of the RC in that upstream region, including its velocity structure and variability. The observations show a shoreward-intensified current flowing northeastward, with a subsurface core located near the 1,000 m isobath and having a record-long mean speed of up to 19.4 cm s-1 at 500 m depth. Estimated volume transport across the observation section had mean 9.0 Sv (1 Sv = 106 m3 s-1) and standard deviation 8.7 Sv. The RC shows significant barotropic character compared with other similar mid-latitude currents.

Mapping Current Fields in a Bay Using a Coast-Fitting Tomographic Inversion.

Coast-fitting tomographic inversion that is based on function expansion using three types of normal modes (the Dirichlet, Neumann, and open boundary modes) is proposed to reconstruct current fields from the coastal acoustic tomography (CAT) data. The superiority of the method was validated while using CAT data that were obtained in 2015 in the Dalian Bay. The semidiurnal tidal and residual current fields were accurately reconstructed over the entire model domain surrounded by coasts and open boundaries. The proposed method was effective, particularly around the peripheral regions of the tomography domain and the near-coast regions outside the domain, where accurate results are not expected from the conventional inverse method based on function expansion by Fourier function series with no coast fittings. The error velocity for the semidiurnal tidal currents was 2.2 cm s-1, which was calculated from the root-mean-square-difference between the CAT-observed and inverted range-averaged currents that were obtained along the nine peripheral transmission paths. The error velocity for the residual currents estimated from the 12-h mean net residual transport at the bay mouth was 0.9 cm s-1. The errors were significantly smaller than the amplitude of the tidal and residual currents.

Analysis of differential expression proteins reveals the key pathway in response to heat stress in Alicyclobacillus acidoterrestris DSM 3922T.

For the purpose of investigating the heat resistance mechanism of Alicyclobacillus acidoterrestris, label-free quantification was used to reveal some cellular changes in A. acidoterrestris during heat stress. Totally, 545 differential expression proteins were respectively identified at heat stress of 65 °C for 5 min, of which 258 proteins were up-regulated and 287 proteins were down-regulated. These significantly changed proteins were mapped to 100 pathways and some of them were mostly related to protection or repair of macromolecules such as proteins and DNA, cell wall formation, which indicated that these proteins might play crucial roles in response to heat stress. The KEGG pathway analysis combined with protein functional analysis and further validation at mRNA level suggested that A. acidoterrestris sensed the temperature rise in environment through alterations in the secondary structure of DNA and RNA molecules. The biosynthesis of antibiotics pathway and the ribosomes might be involved in signal transduction in heat stress and further trigger a large number of proteins playing a critical role in the regulation of heat stress in A. acidoterrestris. The study firstly demonstrated the global physiological response to heat stress and the results provided a better understanding of thermal adaption mechanism of A. acidoterrestris.

Label free quantitative analysis of Alicyclobacillus acidoterrestris spore germination subjected to low ambient pH.

Inhibition of spore germination or sterilization after induction of spore germination would effectively control low pH food spoilage caused by Alicyclobacillus acidoterrestris spores. However, the characteristics and mechanisms of A. acidoterrestris spore germination in low ambient pH remains poorly understood. In this study, the germination rate of A. acidoterrestris spores at different ambient pH conditions was determined, and subsequently the proteomic profiles of A. acidoterrestris in spore germination were analysed by label-free quantification, in which the specific metabolic pathways involved were identified and key functional proteins were screened and validated using RT-qPCR (real time quantitative PCR). The suitable ambient pH value for the spore germination of A. acidoterrestris ranged from 3.0 to 5.0 with the optimum pH of 4.0. According to the LC-ESI-MS/MS (liquid chromatography electrospray ionization tandem mass spectrometry) analysis, 98 proteins of geminated spores of A. acidoterrestris incubated for 2 h at pH 3.0 were changed significantly in comparison to non-germinated spores, the expression of 20 proteins were up-regulated and that of 78 proteins down-regulated respectively. Those differential expressed proteins were mainly involved in cell wall hydrolysis, cell morphological changes, protein synthesis and folding, perception of external stimuli and signal transduction etc., and we observed that germination receptor D (GerD), cell wall hydrolase, transpeptidase, peptidase S1 and two-component regulatory system phoR were significantly up-regulated, but hydrolase NlpC/P60, peptidoglycan glycosyltransferase, spore coat proteins CotX, CotJB and the Lrp/AsnC (leucine-responsive regulatory protein/asparagine synthase C products) protein were significantly down-regulated in the experiment, which implied the important roles of identified proteins during the spore germination. Furthermore, the pathway analysis showed the possible involvement of differentially expressed proteins in the ß-lactam resistance, ribosome, biosynthesis of secondary metabolites, pyruvate metabolism, two-component system and other metabolic pathways, which indicated that synthesis and hydrolysis of cell wall, intracellular substance synthesis, energy generation and signal transduction were likely associated with the initiation of spore germination and restoration of vegetative growth. In conclusion, the quantitative proteomic landscape of A. acidoterrestris spores could provide the theoretic and experimental evidences for the hazard control of A. acidoterrestris spores in the thermal pasteurization process of acidic beverages industry.

Heterogeneous expression of DnaK gene from Alicyclobacillus acidoterrestris improves the resistance of Escherichia coli against heat and acid stress.

Alicyclobacillus acidoterrestris, an acidophilic and thermophilic bacteria, is an important microbial resource for stress resistance genes screening. In this study, DnaK gene from A. acidoterrestris was subcloned to construct the recombinant plasmid pET28a-DnaK. The successful construction of the plasmid was verified by double-enzyme digestion and sequencing analysis. The recombinant plasmid was transformed into Escherichia coli BL21 and isopropy-ß-D-thiogalactoside (IPTG) was used to induce recombinant E. coli to express DnaK gene. A 70 kD fusion protein was identified by SDS-PAGE, which suggested that DnaK gene from A. acidoterrestris was successfully expressed. The recombinant and wild BL21 were treated with high temperatures of 54, 56 and 58 °C at pH values of 5.0-7.0 to compare the effects of heterogeneous expression of the DnaK gene from A. acidoterrestris on the stress resistance. The experimental results showed that survival rate of recombinant BL21-DnaK has been improved considerably under heat and acid stresses in contrast with the wild BL21, and D-values of recombinant BL21 were 14.7-72% higher than that of wild BL21, which demonstrated that heterogeneous expression of DnaK gene from A. acidoterrestris could significantly enhance the resistance of host bacteria E. coli against heat and acid stresses.

Identification and molecular characterization of bacteriophage phiAxp-2 of Achromobacter xylosoxidans.

A novel Achromobacter xylosoxidans bacteriophage, phiAxp-2, was isolated from hospital sewage in China. The phage was morphologically and microbiologically characterized, and its one-step growth curve, host range, genomic sequence, and receptor were determined. Its morphology showed that phiAxp-2 belongs to the family Siphoviridae. Microbiological characterization demonstrated that pH 7 is most suitable for phage phiAxp-2; its titer decreased when the temperature exceeded 50 °C; phiAxp-2 is sensitive to ethanol and isopropanol; and the presence of calcium and magnesium ions is necessary to accelerate cell lysis and improve the formation of phiAxp-2 plaques. Genomic sequencing and a bioinformatic analysis showed that phage phiAxp-2 is a novel bacteriophage, consisting of a circular, double-stranded 62,220-bp DNA molecule with a GC content of 60.11% that encodes 86 putative open reading frames (ORFs). The lipopolysaccharide of A. xylosoxidans is involved in the adsorption of phiAxp-2.

Isolation and characterization of a bacteriophage phiEap-2 infecting multidrug resistant Enterobacter aerogenes.

Enterobacter aerogenes (Enterobacteriaceae) is an important opportunistic pathogen that causes hospital-acquired pneumonia, bacteremia, and urinary tract infections. Recently, multidrug-resistant E. aerogenes have been a public health problem. To develop an effective antimicrobial agent, bacteriophage phiEap-2 was isolated from sewage and its genome was sequenced because of its ability to lyse the multidrug-resistant clinical E. aerogenes strain 3-SP. Morphological observations suggested that the phage belongs to the Siphoviridae family. Comparative genome analysis revealed that phage phiEap-2 is related to the Salmonella phage FSL SP-031 (KC139518). All of the structural gene products (except capsid protein) encoded by phiEap-2 had orthologous gene products in FSL SP-031 and Serratia phage Eta (KC460990). Here, we report the complete genome sequence of phiEap-2 and major findings from the genomic analysis. Knowledge of this phage might be helpful for developing therapeutic strategies against E. aerogenes.