Cellular and proteomic responses of <Emphasis Type=Italic>Escherichia coli</Emphasis> JK-17 exposed to the <Emphasis Type=Italic>Rosa hybrida</Emphasis> flower extract

The purpose of this work was to characterize the cellular and proteomic responses of Escherichia coli JK-17 exposed to the rose flower extract (Rosa hybrida). The bacterial isolate was enriched and isolated from contaminated food. 16S rRNA sequence analyses revealed that the strain was 99% similar to the E. coli species cluster; therefore, this strain was designated E. coli JK-17. The rose flower extract showed a dose-dependent antibacterial effect on E. coli JK-17. Treatment of E. coli JK-17 with 50 and 100 mg/mL of the rose flower extract completely inhibited growth within 12 and 6 h of incubation. The stress shock proteins (SSPs) were induced with different concentrations of rose flower extract. The proteins were identified as 70-kDa DnaK and 60-kDa GroEL by SDS-PAGE and Western blot using anti-DnaK and anti-GroEL monoclonal antibodies. The levels of SSPs induced by the rose flower extract increased when the exposure time to the rose flower extract was increased. SDS-PAGE with silver staining revealed that the amount of lipopolysaccharide (LPS) in E. coli JK-17 increased or decreased with different concentrations and exposure times of the rose flower extract. To identify proteins induced by the rose flower extract, 2-dimensional electrophoresis (2-DE) was applied to soluble protein fractions of E. coli JK-17 cultures. In the pH range of 4 ∼ 7, more than 250 spots were detected on the silver stained gels. Notably, 15 protein spots were increased or decreased after treatment with the rose flower extract. Twelve up-regulated proteins were identified as chaperones (DnaK and GroEL) and porin proteins (PhoE, RfaI, RfaG, MdoH, and WzzE) by MALDITOF mass spectrometry, and three down-regulated proteins were identified, including proteins involved in energy and DNA metabolism (SdhA and GyrB), and amino acid biosynthesis (GltK). Using scanning electron microscopic analysis, some cells were shown to adopt irregular rod shapes and wrinkled surfaces after treatment with the rose flower extract. These results provide clues for better understanding the mechanism of rose flower extract-induced stress and cytotoxicity in E. coli JK-17.     

Cloning,expression, and isolation from <Emphasis Type=Italic>Escherichia coli</Emphasis> of human protein SURF-6 translationally fused to glutathione-S-transferase

cDNA of human gene Surf-6 (hSutf-6) was amplified and cloned into vector pGEX-2T for the expression in the bacterial system of protein hSURF-6 translationally fused to glutathione-S-transferase. The resulting vector is named as pGEX-2T-GST-hSurf-6. Superproducer of chimeric protein GST-hSURF-6 was obtained on the basis of Escherichia coli strain BL21-CodonPlus(DE3)-RIL. Its purification was performed by the affinity chromatography on L-glatathione-sepharose. The proportion of recombinant protein GST-hSURF-6 in the optimized conditions was not less than 15% of the total bacterial protein, and up to 7 mg of the protein was isolated from 1 liter of culture of the producer strain. The final fraction of eluate contained approximately 80% of GST-hSURF-6. The amount and the purity of the isolated protein were sufficient to immunize animals and obtain antibodies. Protein GST-hSURF-6 can also be used as an affinity ligand for revealing protein partners of hSURF-6 in human cells.     

Isolation and phenotypic characteristics of the <Emphasis Type=Italic>Escherichia coli</Emphasis> butanol-tolerant mutants

Resistance to butanol is a key factor affecting microbial ability to produce economically profitable amounts of butanol. In this study, an Escherichia coli strain capable of growth in the presence of 1.5% butanol was isolated. The mutant MG1655 ButR was characterized by increased resistance to ethanol, isopropanol, and bivalent ions but exhibited supersensitivity to osmotic shock. Compared to the wild type strain, the butanol-tolerant mutant was more sensitive to antibiotics inhibiting protein synthesis but was more resistant to membrane-penetrating antibiotics, such as surfactin. Increased content of unsaturated fatty acids was found in the membranes of butanol-tolerant mutants. It was revealed that overexpression of the genes encoding cold-shock proteins decreased butanol tolerance of both mutant and the wild-type strain. It was concluded that butanol tolerance was associated with multiple rearrangements of the cell genetic system, rather than with single mutations.     

Effect of cobalt on <Emphasis Type=Italic>Escherichia coli</Emphasis> metabolism and metalloporphyrin formation

Toxicity in Escherichia coli resulting from high concentrations of cobalt has been explained by competition of cobalt with iron in various metabolic processes including Fe–S cluster assembly, sulfur assimilation, production of free radicals and reduction of free thiol pool. Here we present another aspect of increased cobalt concentrations in the culture medium resulting in the production of cobalt protoporphyrin IX (CoPPIX), which was incorporated into heme proteins including membrane-bound cytochromes and an expressed human cystathionine beta-synthase (CBS). The presence of CoPPIX in cytochromes inhibited their electron transport capacity and resulted in a substantially decreased respiration. Bacterial cells adapted to the increased cobalt concentration by inducing a modified mixed acid fermentative pathway under aerobiosis. We capitalized on the ability of E. coli to insert cobalt into PPIX to carry out an expression of CoPPIX-substituted heme proteins. The level of CoPPIX-substitution increased with the number of passages of cells in a cobalt-containing medium. This approach is an inexpensive method to prepare cobalt-substituted heme proteins compared to in vitro enzyme reconstitution or in vivo replacement using metalloporphyrin heme analogs and seems to be especially suitable for complex heme proteins with an additional coenzyme, such as human CBS.     

Expression in <Emphasis Type=Italic>Escherichia coli</Emphasis> of the gene encoding ascorbate peroxidase from <Emphasis Type=Italic>Brassica napus</Emphasis> enhances salt tolerance of bacterial cells

Ascorbate peroxidase (APX) is an important enzyme to scavenge the reactive oxygen species (ROS), which are often caused by the salt stress. Here, APX cDNA from Brassica napus was amplified by RT-PCR and cloned into the prokaryotic expression vector pGEX-6p-1 to express BnAPX as a glutathione S-transferase (GST) fusion protein. The recombinant expression plasmid was then transformed into Escherichia coli BL21 (DE3) and induced with 0.2 mM IPTG at 28°C. The enzyme activity analysis of the induced protein showed the GST-APX protein had the similar enzyme activity with the other found APXs, which decompose H₂O₂. Moreover, the GST-APX fusion protein was purified by affinity chromatography using the glutathione-Sepharose 4B column. The purified GST-APX protein was then used to immunize rabbits to obtain the anti-BnAPX serum, which was suitable to recognize both the recombinant exogenous BnAPX and the endogenous BnAPX in vivo by western blotting and the immunohistochemical experiment. Furthermore, the immuno-fluorescent microscopy observation revealed that BnAPX was expressed in the chloroplasts. Finally, the bacteria expressing BnAPX grew much faster in the presence of 3% NaCl than the control cells, indicating that the transformant expressing BnAPX acquired resistance to salt stress.     

Overexpression of <Emphasis Type=Italic>AtLEA3-3</Emphasis> confers resistance to cold stress in <Emphasis Type=Italic>Escherichia coli</Emphasis> and provides enhanced osmotic stress tolerance and ABA sensitivity in <Emphasis Type=Italic>Arabidopsis thaliana</Emphasis>

Previous studies have shown that the late embryogenesis abundant (LEA) group 3 proteins significantly respond to changes in environmental conditions. However, reports that demonstrate their biological role, especially in Arabidopsis, are notably limited. This study examines the functional roles of the Arabidopsis LEA group 3 proteins AtLEA3-3 and AtLEA3-4 in abiotic stress and ABA treatments. Expression of AtLEA3-3 and AtLEA3-4 is upregulated by ABA, high salinity, and osmotic stress. Results on the ectopic expression of AtLEA3-3 and AtLEA3-4 in E. coli suggest that both proteins play important roles in resistance to cold stress. Overexpression of AtLEA3-3 in Arabidopsis (AtLEA3-3-OE) confers salt and osmotic stress tolerance that is characterized during germination and early seedling establishment. However, AtLEA3-3-OE lines show sensitivity to ABA treatment during early seedling development. These results suggest that accumulation of AtLEA3-3 mRNA and/or proteins may help heterologous ABA reinitiate second dormancy during seedling establishment. Analysis of yellow fluorescent fusion proteins localization shows that AtLEA3-3 and AtLEA3-4 are mainly distributed in the ER and that AtLEA3-3 also localizes in the nucleus, and in response to salt, mannitol, cold, or BFA treatments, the localization of AtLEA3-3 and AtLEA3-4 is altered and becomes more condensed. Protein translocalization may be a positive and effective strategy for responding to abiotic stresses. Taken together, these results suggest that AtLEA3-3 has an important function during seed germination and seedling development of Arabidopsis under abiotic stress conditions.     

Modulation of <Emphasis Type=Italic>Escherichia coli</Emphasis> biofilm growth by cell-free spent cultures from lactobacilli

E. coli biofilms cause serious problems in medical practice by contaminating surfaces and indwelling catheters. Due to the rapid development of antibiotic resistance, alternative approaches to biofilm suppression are needed. This study addresses whether products released by antagonistic bacteria — Lactobacillus isolates from vaginal and dairy-product samples could be useful for controlling E. coli biofilms. The effects of diluted cell-free supernatants (CFS) from late-exponential Lactobacillus cultures on the growth and biofilm production of Escherichia coli were tested. Most of the CFS applied as 10⁻² had no impact on bacterial growth, biofilm development however was influenced even by 10⁻⁴ of CFS. Initial screening by crystal violet assay showed that biofilm modulation varied between different CFS and E. coli combinations from inhibition to activation; however three of the tested CFS showed consistency in biofilm suppression. This was not due to antibacterial activity since Live/Dead fluorescence labeling showed insignificant differences in the amount of dead cells in control and treated samples. Some E. coli strain-specific mechanisms of response to the three CFS included reduction in hydrophobicity and motility. Released exoploysaccharides isolated from the three CFS stimulated sessile growth, but proteinase K reduced their inhibitory activities implying participation of protein or peptide biofilm suppression factor(s).     

RecA Proteins from <Emphasis Type=Italic>Deinococcus geothermalis</Emphasis> and <Emphasis Type=Italic>Deinococcus murrayi</Emphasis> - Cloning,Purification and Biochemical Characterisation

Background  

Escherichia coli RecA plays a crucial role in recombinational processes, the induction of SOS responses and mutagenic lesion bypasses. It has also been demonstrated that RecA protein is indispensable when it comes to the reassembly of shattered chromosomes in γ-irradiated Deinococcus radiodurans, one of the most radiation-resistant organisms known. Moreover, some functional differences between E. coli and D. radiodurans RecA proteins have also been shown.     

<Emphasis Type=Italic>Boletus kermesinus</Emphasis>, a new species of <Emphasis Type=Italic>Boletus</Emphasis> section <Emphasis Type=Italic>Luridi</Emphasis> from central Honshu,Japan

Boletus kermesinus, a new species of Boletus section Luridi, is fully described and illustrated based on the materials collected in subalpine coniferous forests of central Honshu, Japan. It has distinctive features of dark-red basidiomata having distinct viscidity in the pileus surface, usually unchanging flesh, discolorous red pores, and an entirely reticulate stipe becoming coarsely lacerate-rimose with age.     

The new pLAI (<Emphasis Type=Italic>lux</Emphasis> regulon based auto-inducible) expression system for recombinant protein production in <Emphasis Type=Italic>Escherichia coli</Emphasis>

Background  

After many years of intensive research, it is generally assumed that no universal expression system can exist for high-level production of a given recombinant protein. Among the different expression systems, the inducible systems are the most popular for their tight regulation. However, induction is in many cases less favorable due to the high cost and/or toxicity of inducers, incompatibilities with industrial scale-up or detrimental growth conditions. Expression systems using autoinduction (or self-induction) prove to be extremely versatile allowing growth and induction of recombinant proteins without the need to monitor cell density or add inducer. Unfortunately, almost all the actual auto inducible expression systems need endogenous or induced metabolic changes during the growth to trigger induction, both frequently linked to detrimental condition to cell growth. In this context, we use a simple modular approach for a cell density-based genetic regulation in order to assemble an autoinducible recombinant protein expression system in E. coli.