C55 bacteriocin produced by ETB‐plasmid positive Staphylococcus aureus strains is a key factor for competition with S. aureus strains

Exfoliative toxin (ET) produced by Staphylococcus aureus is closely associated with the onset of bullous impetigo. To date, three ETs (ETA, ETB and ETD) have been identified. The gene encoding ETB is located in a plasmid designated pETB. Bacteriocin synthesis genes are also located in this plasmid and pETB‐positive strains reportedly produce the C55 bacteriocin. In this study, the antibacterial activity against S. aureus strains of the bacteriocin produced by the pETB‐positive strain TY4 was investigated. This bacteriocin demonstrated antibacterial activity against all pETB‐negative but not pETB‐positive strains, including TY4. Additionally, a TY4? strain from which the pETB plasmid had been deleted exhibited susceptibility to the bacteriocin. Further experiments revealed that two immunity factors (orf 46‐47 and orf 48) downstream of the bacteriocin synthesis genes in the pETB plasmid are associated with immunity against the bacteriocin produced by TY4. The TY4? with orf46‐47 strain exhibited complete resistance to bacteriocin, whereas the TY4? with orf48 strain exhibited partial resistance. Whether bacteriocin affects the proportion of each strain when co‐cultured with S. aureus strains was also investigated. When TY4 or TY4? was co‐cultured with 209P strain, which is susceptible to the bacteriocin, the proportion of 209P co‐cultured with TY4 was significantly less than when 209P was co‐cultured with TY4?, whereas the proportion of TY4? with orf46‐48 co‐cultured with TY4 was greater than with TY4?. These results suggest that the C55 bacteriocin produced by pETB‐positive strains affects the proportion of each strain when pETB‐positive and ‐negative strains co‐exist.

     

Effects of disinfectants against norovirus virus‐like particles predict norovirus inactivation

Human noroviruses (NoVs) are a major cause of epidemic and sporadic acute gastroenteritis worldwide. Public and personal hygiene is one of the most important countermeasures for preventing spread of NoV infection. However, no a practicable cell culture system for NoV had been developed, initial tests of the virucidal effectiveness of anti‐NoV disinfectants and sanitizers have been performed using surrogate viruses. In this study, NoV virus‐like particles (VLPs) were used as a new surrogate for NoVs and a method for evaluating NoV inactivation using them developed. This method is based on morphological changes in VLPs after treatment with sodium hypochlorite. VLP specimens were found to become deformed and degraded in a concentration‐dependent manner. Based on these results, the effects of sodium hypochlorite on VLPs were classified into four phases according to morphological changes and number of particles. Using the criteria thus established, the efficacy of ethanol, carbonates and alkali solutions against VLPs was evaluated. Deformation and aggregation of VLPs were observed after treatment with these disinfectants under specific conditions. To determine the degradation mechanism(s), VLPs were examined by SDS‐PAGE and immunoblotting after treatment with sodium hypochlorite and ethanol. The band corresponding to the major capsid protein, VP1, was not detected after treatment with sodium hypochlorite at concentrations greater than 500 ppm, but remained after treatment with ethanol. These results suggest that VLPs have excellent potential as a surrogate marker for NoVs and can be used in initial virucidal effectiveness tests to determine the mechanism(s) of chemical agents on NoVs.     

Summer profundal hypoxia determines the coupling of methanotrophic production and the pelagic food web in a subtropical reservoir

相似文献   

The 1975 Japanese diet has a stress reduction effect in mice: search for physiological effects using metabolome analysis

Abstract

We aimed to find new physiological effects of the Japanese diet. First, to determine the key components in serum from mice fed the 1975 diet, serum from mice fed the 1960, 1975, 1990 or 2005 Japanese diet was analyzed using CE-TOFMS and LC-TOFMS. Based on these results, the key components were determined by principal component analysis. Among the identified compounds, GABA was included. Therefore, a stress reduction effect was inferred as a novel physiological effect of this diet. Next, we tested whether the 1975 diet had an actual stress reduction effect in mice. Mice were given the 1975 diet or a control diet for 4 weeks, after which they were divided into restraint stress and non-stress groups. Mice fed the 1975 diet had significantly decreased stress parameters compared with those fed the control diet. These results provide the first evidence that the 1975 Japanese diet has a stress reduction effect.     

Evaluation of the mass transfer rate using computer simulation in a three-dimensional interwoven hollow fiber-type bioartificial liver

Objectives

To determine the most efficient design of a hollow fiber-based bioreactor device for a bioartificial liver support system through comparative bioengineering evaluations.

Results

We compared two types of hollow fiber-based bioreactors, the interwoven-type bioreactor (IWBAL) and the dialyzer-type bioreactor (DBAL), by evaluating the overall mass transfer coefficient (K) and the convective coefficient (X). The creatinine and albumin mass transfer coefficients and convective coefficients were calculated using our mathematical model based on the homoporous theory and the modified Powell method. Additionally, using our model, we simulated the mass transport efficiency in clinical-scale BALs. The results of this experiment demonstrate that the mass transfer coefficients for creatinine and albumin increased proportionally with velocity with the IWBAL, and were consistently greater than that found with the DBAL. These differences were further enhanced in the simulation of the large-scale model.

Conclusions

Our findings indicate that the IWBAL with its unique 30° cross hollow fiber design can provide greater solute removal and more efficient metabolism when compared to the conventional DBAL design.

     

Changes in insulation of body tissue and wet suits during underwater exercise at various atmospheric pressures

To clarify the independent changes of insulations of body tissues (Itissue) and wet suit (Isuit) in the wet-suited subject during underwater exercise, overall heat flow from the skin (Htissue) and wet suit (Hsuit) and esophageal (Tes), skin (Tsk), and wet suit temperatures were measured at 1, 2, and 2.5 atmospheres absolute (ATA) at critical water temperature (Tcw). The average Tcw in nine wet-suited men (23-38 yr) was 22.3 +/- 0.2, 26.3 +/- 0.2, and 28.0 +/- 0.4 degrees C (SE) at 1, 2, and 2.5 ATA, respectively. At Tcw of each pressure male volunteers wearing 5-mm neoprene wet suits completed three 2-h experiments while immersed up to the neck. During one experiment the subjects remained at rest, and in the other two they exercised on an underwater ergometer at two different intensities (2 and 3 met). Tes significantly declined (P less than 0.05) over 2 h from 37.1 to 36.5 degrees C during rest in each pressure. The 2-met exercise prevented Tes from falling in all pressures, and the 3-met exercise elevated Tes by 0.2-0.3 degrees C. There was no exercise-dependent difference in Isuit, but a pressure-dependent difference was remarkable. The Itissue at rest was identical for all pressures; however, it progressively decreased as a function of exercise intensity. It is concluded that overall Itissue is entirely determined by work intensity at Tcw, but not by atmospheric pressure. On the contrary, Isuit at Tcw is solely dependent on the pressure, but not on the work intensity.     

Aromatic ring cleavage of a β-biphenyl ether dimer catalyzed by lignin peroxidase of phanerochaete chrysosporium

Under aerobic conditions homogeneous lignin peroxidase catalyzed the oxidation of 1-(4'-methoxyphenyl)-2-(2″,5′-dimethoxy-4″-phenylphenoxy)-1,3-dihydroxypropane (I) to yield four products: 1-(4'-methoxy-phenyl)-1,2,3-trihydroxypropane (X), 4-[-hydroxy--(4'-methoxyphenyl)-methyl]-1,3-dioxolane-2-one (V), 4-(4'-methoxyphenyl)-5-hydroxymethyl-1,3-dioxolane-2-one (VI) and 5-hydroxy-5-carbomethoxy-4-phenyl-oxol-3-en-2-one (VIII). V, VI and VIII are all products of ring opening reactions. When the reaction was conducted under anaerobic conditions, the substrate was oxidized but no ring-cleaved products were detected. During the oxidation of I, 4 atoms of ¹⁸O from ¹⁸O₂ were incorporated into the lactol product VIII.     

Spatial relationship between the nucleotide-binding site, Lys-61 and Cys-374 in actin and a conformational change induced by myosin subfragment-1 binding

The spatial relationship between Lys-61, the nucleotide binding site and Cys-374 was studied. Lys-61 was labelled with fluorescein-5-isothiocyanate as a resonance energy acceptor, the nucleotide-binding site was labelled with the fluorescent ATP analogues epsilon ATP or formycin-A 5'-triphosphate (FTP) and Cys-374 was labelled with 5-(2-[(iodoacetyl)amino]ethyl)aminonaphthalene-1-sulfonic acid (1,5-IAEDANS) as a resonance energy donor. The distances between the nucleotide binding site and Lys-61 or between Lys-61 and Cys-374 were calculated to be 3.5 +/- 0.3 nm and 4.60 +/- 0.03 nm, respectively. (The assumption has been made in calculating these distances that the energy donor and acceptor rotate rapidly relative to the fluorescence lifetime.) On the other hand, when doubly-labelled actin with 1,5-IAEDANS at Cys-374 and FITC at Lys-61 was polymerized in the presence of a twofold molar excess of phalloidin [Miki, M. (1987) Eur. J. Biochem. 164, 229-235], the fluorescence of 1,5-IAEDANS bound to actin was quenched significantly. This could be attributed to inter-monomer energy transfer. The inter-monomer distance between FITC attached to Lys-61 in a monomer and 1,5-IAEDANS attached to Cys-374 in its nearest-neighbour monomer in an F-actin filament was calculated to be 3.34 +/- 0.06 nm, assuming that the likely change in the intra-monomer distance does not change during polymerization by more than 0.4 nm. One possible spatial relationship between Lys-61, Cys-374 and the nucleotide binding site in an F-actin filament is proposed. The effect of myosin subfragment-1 (S1) binding on the energy transfer efficiency was studied. The fluorescence intensity of AEDANS-FITC-actin decreased by 30% upon interaction with S1. The fluorescence intensity of AEDANS-FITC-actin polymer in the presence of phalloidin increased by 21% upon interaction with S1. The addition of ATP led to the fluorescence intensity returning to the initial level. Assuming that the change of fluorescence intensity can be attributed to conformational change in the actin molecule induced by S1 binding, the intra-monomer distance was reduced by 0.4 nm and the inter-monomer distance was increased by 0.2 nm.     

Reversible interconversion between primitive endoderm- and parietal endoderm-like F9 cells demonstrated by mRNAs expression

The differentiation of retinoic acid-treated F9 cells (primitive endoderm-like F9 cells) into parietal endoderm-like F9 cells induced by dibutyryl cAMP was studied as a culture model of the morphogenesis of early mouse embryo. For this purpose, 6 cDNA clones coding for mRNAs specifically expressed in parietal endoderm-like F9 cells were selected. Northern hybridization of RNA extracted from variously treated F9 cells to nick-translated plasmid DNA of these clones demonstrated the reversible expression of many mRNAs depending on the presence of dibutyryl cAMP in the culture medium. This result suggested that the differentiated state of parietal endoderm, which is formed from primitive endoderm at a position adjacent to the trophectoderm in mouse embryo, can be reversed if the local signal is removed. One of the selected clones, pLAM, hybridized to an mRNA of 6.3 kb and selected mRNA producing a laminin B subunit in an in vitro translation system. This clone has an inserted sequence of 3.1 kb. Among the restriction sites in this sequence, six were consistent with those in a 1.7 kb inserted sequence of pPE 49 and pPE 386, which were isolated by Barlow et al. as laminin B1 clones. An XbaI site found in both pPE 49 and pPE 386 was, however, not found at the corresponding position of pLAM. Dot hybridization of RNA with pLAM showed that expression of laminin B in F9 cells is stimulated more than 100-fold during differentiation of F9 stem cells into parietal endoderm-like F9 cells.