Iceberg lettuce as suggested source of a nationwide outbreak caused by two Salmonella serotypes, Newport and Reading, in Finland in 2008

A nationwide outbreak of Salmonella enterica serotypes Newport and Reading occurred between 17 October and 28 November 2008 in Finland. A total of 77 culture-confirmed Salmonella Newport and 30 Salmonella Reading cases, including one case with a double infection, were reported. All strains isolated from the patients were subtyped using serotyping, microbial resistance profiling, and pulsed-field gel electrophoresis (PFGE). Here, the PFGE patterns of the studied Salmonella Newport strains were identical, whereas four different PFGE profiles were found among the Salmonella Reading strains. Two elderly patients died within 2 weeks of the onset of symptoms. Three geographical clusters of cases with an epidemiological link were identified. The traceback investigation suggested that the factor connecting the cases was ready-chopped iceberg lettuce available for mass catering use. However, none of the tested food, environmental samples, or the samples taken from the staff of the processing plant contained Salmonella bacteria. Tracing back to outbreak sources with a short shelf life can be complex.     

Filtration Efficiency of Functionalized Ceramic Foam Filters for Aluminum Melt Filtration

Metallurgical and Materials Transactions B - The influence of filter surface chemistry on the filtration efficiency of cast aluminum alloys was evaluated for four different filter coating...     

C-terminal truncations of a thermostable Bacillus stearothermophilus {alpha}-amylase

A series of truncated proteins from a thermostable Bacillusstearothermophilus -amylase was prepared to study the importanceof the extension in the C-terminus compared with other liquefyingBacillus -amylases. The mutations introducing new translationtermination sites shortened the 515 amino acid residue-longwild type enzyme by 17, 32, 47, 73 or 93 residues. The longerthe truncation, the lower the specific activity of the enzyme.Only the two longest mutant proteins were active: the specificactivity of the 498 residue variant was 97% and protein 483was 36% that of the parental enzyme. The K_m values of starchhydrolysis changed from 1.09 for wild type enzyme to 0.35 and0.21 for mutants 498 and 483, respectively, indicating alteredsubstrate binding. The mutant enzymes had almost identical pHand temperature optima with the wild type amylase, but enhancedthermal stability and altered end product profile. The consequencesof the truncation to the structure and function of the enzymeswere explored with molecular modeling. The liquefying amylasesseem to require {small tilde}480 residues to be active, whereasthe C-terminal end of B.stearothermophilus amylase is requiredfor increased activity.     

Stereochemistry of the hydroperoxides formed during autoxidation of CLA methyl ester in the presence of α-tocopherol

The initial steps in the autoxidation of CLA methyl ester are poorly understood. The aim of this study was to determine the stereochemistry of the hydroperoxides formed during autoxidation of CLA methyl ester in the presence of a good hydrogen atom donor. For this purpose, 9-cis, 11-trans CLA methyl ester was autoxidized in the presence of α-tocopherol under atmospheric oxygen at 40°C in the dark. The CLA methyl ester hydroperoxides were isolated, reduced to the corresponding hydroxy derivatives, and separated by HPLC. The stereochemistry of seven hydroxy-CLA methyl esters was investigated. The position of the hydroxy group was determined by GC-MS. The geometry as well as the position of the double bonds in the alkyl chain was determined by NMR. In addition, the ¹³C NMR spectra of six hydroxy-CLA methyl esters were assigned using COSY, gradient heteronuclear multiple bond correlation, gradient heteronuclear single quantum correlation, and total correlation spectroscopy experiments. The autoxidation of 9-cis, 11-trans CLA methyl ester in the presence of a good hydrogen atom donor is stereoselective in favor of one geometric isomer, namely the 13-(R,S)-hydroperoxy-9-cis, 11-trans-octadecadienoic acid methyl ester. Three types of conjugated diene hydroperoxides are formed as primary hydroperoxides: trans,trans hydroperoxides (12-OOH-8t,10t and 9-OOH-10t,12t), a cis,trans hydroperoxide with the trans double bond adjacent to the hydroperoxide-bearing carbon atom (13-OOH-9c,11t), and a new type of cis,trans lipid hydroperoxide with the cis double bond adjacent to the hydroperoxide-bearing carbon atom (8-OOH-9c,11t). In addition, three nonkinetic hydroperoxides (13-OOH-9t,11t, 8-OOH-9t,11t, and 9-OOH-10t,12c) are formed. This study supports the theory that CLA methyl ester autoxidizes at least partly through an autocatalytic free radical reaction. The complexity of the hydroperoxide mixture is due to formation of two different pentadienyl radicals. Moreover, the stereoslectivity in favor of one geometric isomer can be explained by the selectivity of the two previous steps: the preferential formation of a W-conformer of the pentadienyl radical over the Z-conformer, and regioselectivity of the oxygen addition to the pentadienyl radical.     

Leaf and root litter of a legume tree as nitrogen sources for cacaos with different root colonisation by arbuscular mycorrhizae

Traditionally cacao (Theobroma cacao L.) is cultivated under legume shade trees, which produce N-rich litter that improves soil organic matter content, microbial activity, and recycles N to the crop. Arbuscular mycorrhiza forming fungi (AMF) are known to play an important role in plant nutrient uptake, yet their role in plant N uptake from organic residues in tropical agroforestry systems is not clear. We studied root and leaf litter of the legume shade tree Inga edulis Mart. as a source of N for cacao and the importance of AMF colonisation in the uptake of litter N under controlled conditions. Leaf and root litter of I. edulis enriched with ¹⁵N was added to cacao pots filled with field soil. Half of the cacao saplings were AMF-inoculated and the soil of non-inoculated saplings was treated with fungicide to suppress AMF. During the 10-week experiment, young cacao leaves were sampled for ¹⁵N analyses and at the end of the experiment whole plants were harvested. Microbial populations in the soil were determined using phospholipid fatty acid (PLFA) analysis, and AMF structures in the roots were quantified. Fungicide treatment decreased AMF structures in roots and increased bacterial populations, but did not affect the decomposition rate of either litter type. Inoculated and non-inoculated cacao saplings used 2.6 and 2.1%, respectively, of N added to the pots in leaf litter and 12.1 and 7.1% of N available in root litter indicating that root litter of I. edulis may be a more efficient N source than leaf litter for cacao. Although the fungicide treatment did not completely suppress AMF in non-inoculated pots, it created sufficient contrast in root AMF colonisation for concluding that AMF significantly enhanced cacao N use from both litter types. The role of root litter of shade trees as a N source in agroforestry should not be neglected.     

Use of near-infrared radiation for oxygenic photosynthesis via photon up-conversion

Radiation between 400 and 700 nm, used for oxygenic photosynthesis by cyanobacteria, algae and plants, represents only 44% of total solar energy while the range above 700 nm comprises 52%. An ability to use near infrared (NIR, 700–1200 nm) radiation would greatly improve the efficiency of photosynthesis, but NIR photons have too low energy to excite the photosystems of oxygenic photosynthesis. Here we show that a mechanism called photon up-conversion can turn NIR radiation into an energy source for photosynthesis. In the future, it may be possible to up-convert the NIR part of the solar energy flux to visible light for use in photo-induced biohydrogen production by oxygenic photosynthesis.     

On the effectiveness of EDTA in prolonging the shelf life of fresh fish

Summary The purpose of this investigation was to ascertain whether EDTA might be useful in prolonging the keeping quality of fresh fish. The criteria of quality used were: the total bacterial count, the content of volatile basic nitrogen and trimethylamine, the degree of dephosphorylation of the nucleotides, the level of the hypoxanthine, and the organoleptic properties. The material consisted of rainbow trout (Salmo irideus) and Baltic herring (Clupea harengus var. membranus).The results showed that EDTA had a markedly favorable effect on the keeping quality of fish. Although the effect on the total bacterial count was only slight, a chemical and organoleptical comparison with control material revealed that spoilage in the EDTA-treated samples was definitely slower. In the case of fillets of rainbow trout, judged by the organoleptical method, the controls became unacceptable after storage for 18–20 days at +4°C, whereas after the same storage time the EDTA-treated samples were still free of off-odors and had a fair taste. Similarly, the values of volatile basic nitrogen, trimethylamine, and hypoxanthine increased at a slower rate, and the dephosphorylation of nucleotides proceeded less rapidly in the EDTA-treated fillets than in the controls. In the case of fillets of Baltic herring, sensory evaluation brought out the positive effect of the EDTA treatment. A corresponding difference was noted in the volatile basic nitrogen and trimethylamine values, and a slight difference in the hypoxanthine values. In this fish, the dephosphorylation of the nucleotides was rapid, and between the samples subjected to EDTA treatment and the control material there appeared only a small difference. With regard to the round Baltic herring, again, the differences between the two categories were less conspicuous; the chief difference was noted in the volatile basic nitrogen, but in the sensory evaluation the difference was not fully consistent.

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Zusammenfassung Das Ziel dieser Untersuchung war aufzufinden, ob EDTA (die Äthylen-diamin-Tetraessigsäure) zur Verlängerung der Haltbarkeit von frischem Fisch nützlich wäre. Die verwendeten Qualitätskriterien waren die gesamte Bakterienzahl, die Gehalte an flüchtigem basischem Stickstoff und Trimethylamin, der Grad der Dephosphorylierung der Nucleotide, die Menge des Hypoxanthins, und die organoleptischen Eigenschaften. Das Material bestand aus Regenbogenforelle (Salmo irideus) und Ostseehering (Clupea harengus var. membranus).Die Resultate zeigten, daß EDTA einen beachtlich günstigen Einfluß auf die Haltbarkeit der Fische ausübte. Obgleich der Einfluß auf die gesamte Bakterienzahl nur geringfügig war, zeigte der chemische und organoleptische Vergleich mit Kontrollproben, daß das Verderben bei den mit EDTA behandelten Proben deutlich langsamer verlief. Bei der Regenbogenforelle waren die Kontrollen nach Aufbewahrung von 18–20 Tagen bei 4°C, nicht mehr akzeptabel, aber die mit EDTA behandelten Proben waren nach derselben Zeit noch frei von Fehlgeruch und hatten einen annehmbaren Geschmack. Gleicherweise zeigten die Werte von flüchtigem basischem Stickstoff, Trimethylamin und Hypoxanthin eine langsamere Steigerung, und die Dephosphorylierung der Nucleotide war langsamer bei Behandlung mit EDTA als bei den Kontrollen. Im Falle der Filets von Ostseehering stellte sich die positiveWirkung der EDTA-Behandlung bei der organoleptischen Beurteilung heraus. Ein entsprechender Unterschied wurde in den Werten von flüchtigem basischem Stickstoff und Trimethylamin festgestellt, und eine kleinere Wirkung in den Werten von Hypoxanthin. Bei diesem Fisch war die Dephosphorylierung der Nucleotide schnell, und zwischen den mit EDTA behandelten und den Kontrollproben bestand hier nur ein kleiner Unterschied. Beim runden (ungereinigten) Ostseehering wieder waren die Unterschiede zwischen behandelten und Kontrollfischen weniger bedeutend; der hauptsächlichste Unterschied wurde im flüchtigen basischen Stickstoff wahrgenommen, bei der organoleptischen Beurteilung aber war der Unterschied nicht völlig eindeutig.

     

Yersinia pseudotuberculosis with limited genetic diversity is a common finding in tonsils of fattening pigs

A total of 425 pig tonsils, including 210 tonsils from fattening pigs and 215 from sows, from seven different abattoirs in Finland were studied for the occurrence of Yersinia pseudotuberculosis from 1999 to 2000. The mean prevalence of Y. pseudotuberculosis in fattening pig tonsils was 4%, varying from 0 to 10% between slaughterhouses. Y. pseudotuberculosis was not recovered from sow tonsils. All 30 Y. pseudotuberculosis isolates from eight pig tonsils were recovered after cold enrichment. Seventeen isolates from seven tonsils were found after cold enrichment for 14 days, followed by alkali treatment. Y. pseudotuberculosis was not isolated after direct plating, overnight enrichment, or selective enrichment. All 30 isolates belonged to bioserotype 2/0:3 and carried the virF gene in the virulence plasmid. The isolates exhibited calcium dependence and Congo red absorption. The pyrazinamidase test gave variable results. All isolates were characterized with pulsed-field gel electrophoresis (PFGE). Using SpeI, NotI, and XbaI enzymes, seven, five, and two different PFGE patterns were obtained, respectively. A total of 11 genotypes, gI to gXI, identified by a combination of the various SpeI, NotI, and XbaI profiles, were detected. Three pigs were found to carry more than one genotype. Overall, variations between PFGE patterns were small, indicating genetic homogeneity among pig strains of bioserotype 2/0:3.