Effect of selected natural antimicrobials on Baker''s yeast activity

AIMS: To evaluate the responses of Baker's yeast (Saccharomyces cerevisiae) activity to the natural antimicrobials acetic acid, calcium lactate, a lactate-containing cocktail and lactic acid compared to calcium propionate. METHODS AND RESULTS: A dough fermentometer test was used to measure Baker's yeast activity in the presence of these natural antimicrobials and calcium propionate. Yeast activity generally decreased as a function of increasing antimicrobial concentrations, but the lactate-containing cocktail showed no relationship between concentration and yeast activity reduction. At in situ concentrations, calcium propionate resulted in the highest yeast activity reduction, followed by calcium lactate, acetic acid, the lactate-containing cocktail and lactic acid in decreasing order. CONCLUSION: Based on yeast activity reduction, all natural antimicrobials tested showed potential as possible replacements for calcium propionate. SIGNIFICANCE AND IMPACT OF THE STUDY: This has practical implications since calcium propionate inhibits Baker's yeast activity and attracts negative consumer perceptions as a chemical bread preservative.     

IncP-1-beta plasmid pGNB1 isolated from a bacterial community from a wastewater treatment plant mediates decolorization of triphenylmethane dyes

Plasmid pGNB1 was isolated from bacteria residing in the activated sludge compartment of a wastewater treatment plant by using a transformation-based approach. This 60-kb plasmid confers resistance to the triphenylmethane dye crystal violet and enables its host bacterium to decolorize crystal violet. Partial sequencing of pGNB1 revealed that its backbone is very similar to that of previously sequenced IncP-1beta plasmids. The two accessory regions of the plasmid, one located downstream of the replication initiation gene trfA and the other located between the conjugative transfer modules Tra and Trb, were completely sequenced. Accessory region L1 contains a transposon related to Tn5501 and a gene encoding a Cupin 2 conserved barrel protein with an unknown function. The triphenylmethane reductase gene tmr and a truncated dihydrolipoamide dehydrogenase gene that is flanked by IS1071 and another putative insertion element were identified in accessory region L2. Subcloning of the pGNB1 tmr gene demonstrated that this gene is responsible for the observed crystal violet resistance phenotype and mediates decolorization of the triphenylmethane dyes crystal violet, malachite green, and basic fuchsin. Plasmid pGNB1 and the associated phenotype are transferable to the alpha-proteobacterium Sinorhizobium meliloti and the gamma-proteobacterium Escherichia coli. This is the first report of a promiscuous IncP-1beta plasmid isolated from the bacterial community from a wastewater treatment plant that harbors a triphenylmethane reductase gene. The pGNB1-encoded enzyme activity is discussed with respect to bioremediation of sewage polluted with triphenylmethane dyes.     

Benzopyrans in <Emphasis Type="Italic">Hypericum polyanthemum</Emphasis> Klotzsch ex Reichardt cultured in vitro

Hypericum polyanthemum Klotzsch ex Reichardt, an endemic species of Southern Brazil, was micropropagated on MS medium supplemented with 1.78 μM BAP. Shoot proliferation and rooting was achieved on hormone-free medium and plantlets survived acclimatization. The bioactive compounds: 6-isobutyryl-5,7-dimethoxy-2,2-dimethyl-benzopyran (HP1), 7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethyl-benzopyran (HP2) and 5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethyl-benzopyran (HP3) were quantified in the leaves, stems and roots of propagated and acclimatized plantlets and compared with the field-grown plants. The HPLC analysis revealed that the three benzopyrans are accumulated in the aerial parts and the concentration varied with the age of the plant whereas the roots were capable of accumulating only HP3. Greatest yield of HP1 (7.12 mg/g DW) was quantified in the leaves of the acclimatized plantlets, whereas the flowers of the plants from natural habitat displayed higher amounts of HP2 (11.04 mg/g DW) and HP3 (13.99 mg/g DW).     

Expression of PACAP and glutamate transporter proteins in satellite oligodendrocytes of the human CNS

White matter oligodendrocytes have been shown to actively regulate extracellular glutamate levels in the CNS. Such function has yet not been examined in satellite oligodendrocytes of gray matter. Similar to those in white matter, satellite oligodendrocytes are involved in myelination. In addition, they modulate the activity of surrounding neurons. This study examined whether satellite oligodendrocytes express PACAP and glutamate transporter proteins and whether this expression is influenced by global ischemia. We demonstrated expression of PACAP27 and PACAP38 in a major fraction of satellite oligodendrocytes in normal neocortex and hippocampus of human brain tissues obtained post-mortem. All three glutamate transporters EAAT1, EAAT2 and EAAT3 were expressed in satellite oligodendrocytes from these tissues. Thus, satellite oligodendrocytes may participate in the perineuronal glutamate homeostasis. Following transient global ischemia, the total number of satellite oligodendrocytes expressing PACAP or glutamate transporter proteins was significantly decreased in cerebral neocortex and hippocampus. However, alterations of PACAP and glutamate transporter protein expression were region and time specific. In satellite oligodendrocytes of CA1 an early strong reduction of PACAP and glutamate transporter expression was observed. This contrasted with late reduction of PACAP27, PACAP38 and glutamate transporters EAAT1, EAAT2 and EAAT3 in satellite oligodendrocytes of neocortex. Further studies should clarify whether these alterations in protein expression are primary or secondary to neuronal cell death.     

A "gold cluster-linked immunosorbent assay": optical near-field biosensor chip for the detection of allergenic beta-lactoglobulin in processed milk matrices

A new optical biosensor based on the resonance enhanced absorption (REA) effect is described. REA effects are observed when noble metal nanoclusters are deposited at a nanometric distance from a highly reflective mirror. The aim of our study was to adopt the REA effect for the rapid testing of proteins in a direct immunoassay format on chip and to adjust a conventional enzyme-linked immunosorbent assay (ELISA) to a cluster-linked immunosorbent assay (CLISA) by labelling the read-out antibody with monodisperse colloidal gold clusters. For generation of a strong REA signal 30 min of coating of the target protein was sufficient. To evaluate our approach we used the milk allergen β-lactoglobulin (β-LG) as analyte, and β-LG-isolations of processed milk products to prove the applicability of our method to the analysis of proteins in complex matrices at even the trace level. For validating the specificity of the CLISA biosensor we used the non-functionalised cluster reagent without antibody and a non-immunoreactive milk matrix as controls. As expected, very weak background signals were obtained with the controls, whereas the purified food samples clearly showed that β-LG was present and detectable. In conclusion, we were able to describe the successful development of a new biosensor chip for assaying proteins using the REA effect.     

Nitrous oxide emissions from drained organic forest soils––an up-scaling based on C:N ratios

Total emissions of N₂O from drained organic forest soils in Sweden were estimated using an equation linking the C:N ratio of the soil to N₂O emissions. Information on soil C:N ratios was derived from a national database. It was estimated that the emissions from Histosols amount to 2,820 tonnes N₂O a⁻¹. This is almost five times the value calculated for the same soils using the method suggested by the Intergovernmental Panel on Climate Change: 580 tonnes N₂O a⁻¹. The higher value in the present study can mainly be explained by improved accuracy of estimates of N₂O emissions from nutrient-rich soils, including former agricultural soils. In Sweden, in addition to 0.94 Mha of drained Histosols, there are 0.55 Mha of other types of drained organic soils. The annual emissions from these soils were estimated to amount to 1,890 tonnes of N₂O. The total emission value calculated for drained organic forest soils was thus 4,700 tonnes N₂O a⁻¹, which, if added, would increase the current estimate of the Swedish anthropogenic N₂O source strength by 18%. Of these emissions, 88% occur from sites with C:N ratios lower than 25. The exponential relationship between C:N ratio and N₂O emissions, in combination with a scarcity of data, resulted in large confidence intervals around the estimates. However, by using the C:N ratio-based method, N₂O emission estimates can be calculated from a variable that is readily available in databases. Also, the recent findings that there are exceptionally large emissions of N₂O from the most nitrogen-rich drained organic forest soils are taken into account.     

An on-line method for the reduction of fouling of spin-filters for animal cell perfusion cultures

The main limitation in the use of spin-filters during perfusion cultures of animal cells was revealed to be filter fouling. This phenomenon involves cell-sieve interactions as well as cell attachment to, and growth on, the filter surface. The cell attachment effect has been analysed in the present study during long-term perfusion simulations with CHO animal cells. It was demonstrated that at low filter acceleration, below 6.2 m/s2, a high perfusion rate of 25 cm/h induced rapid filter pore clogging within 3 days, whereas increasing the filter acceleration to 25 m/s2 increased filter longevity from 3 to 25 days, for filters with a pore size of 8.5 microm. Increasing the filter pore size to 14.5 microm improved filter longevity by 84% with less viable and dead cell deposits on the filter surface. However, it was demonstrated that filter longevity was not necessarily dependent on the amount of cell deposit on the filter surface. In the second part of this study, ultrasonic technology was used to reduce filter fouling. Filter vibration, induced by a piezo actuator, improved filter longevity by 113% during CHO cells perfusion cultures.     

Proteome dynamics during plastid differentiation in rice

We have analyzed proteome dynamics during light-induced development of rice (Oryza sativa) chloroplasts from etioplasts using quantitative two-dimensional gel electrophoresis and tandem mass spectrometry protein identification. In the dark, the etioplast allocates the main proportion of total protein mass to carbohydrate and amino acid metabolism and a surprisingly high number of proteins to the regulation and expression of plastid genes. Chaperones, proteins for photosynthetic energy metabolism, and enzymes of the tetrapyrrole pathway were identified among the most abundant etioplast proteins. The detection of 13 N-terminal acetylated peptides allowed us to map the exact localization of the transit peptide cleavage site, demonstrating good agreement with the prediction for most proteins. Based on the quantitative etioplast proteome map, we examined early light-induced changes during chloroplast development. The transition from heterotrophic metabolism to photosynthesis-supported autotrophic metabolism was already detectable 2 h after illumination and affected most essential metabolic modules. Enzymes in carbohydrate metabolism, photosynthesis, and gene expression were up-regulated, whereas enzymes in amino acid and fatty acid metabolism were significantly decreased in relative abundance. Enzymes involved in nucleotide metabolism, tetrapyrrole biosynthesis, and redox regulation remained unchanged. Phosphoprotein-specific staining at different time points during chloroplast development revealed light-induced phosphorylation of a nuclear-encoded plastid RNA-binding protein, consistent with changes in plastid RNA metabolism. Quantitative information about all identified proteins and their regulation by light is available in plprot, the plastid proteome database (http://www.plprot.ethz.ch).