Numerical taxonomy of psychrotrophic lactic acid bacteria from prepacked meat and meat products

Ninety-four strains of lactic acid bateria isolated from refrigerated, prepacked meat and meat products were together with 59 reference strains of Brochothrix, Lactobacillus, Leuconostoc, Pediococcus and Streptococcus phenotypically classfied, using 96 unit characters. Data were examined using Simple Matching (S_SM) or Jaccard coefficient (S_J), and unweighted pair group algorithm with arithmetic averages. Twenty-three clusters with two or more members were defined at the 84% S_SM-similarity level which corresponded to the S_J-similarity level of 61%. Based on S_SM, most field strains were included in nine clusters, and with three unsignificant exceptions these contained no reference strains. The field clusters were designated Carnobacterium piscicola (cluster 1; 5% of field isolates), Carnobacterium divergens(cluster 2; 9% of field isolates), Leuconostoc (cluster 9; 18% of field isolates) and Lactobacillus (cluster 4, 10, 11, 12, 13 and 14; together 60% of field isolates). The Lactobacillus clusters had many features in common with cluster II of Shaw & Harding (1984). Phenotypical characteristics of major clusters are given. The S_SM and S_J based classifications basically coincided for the field strains; the exception was cluster 4 which now were split in two parts. Fourteen clusters were made up of mainly reference strains (S_SM). Most of them included more than one type strain on species level; exceptions were Brochothrix thermosphacta (cluster 3), Lactobacillus salivarius (cluster 17) and Leuconostoc mesenteroides (cluster 18). Several rearrangements were seen amongst the clusters of the reference strains when S_J, instead of S_SM, was used for clustering.     

On the absolute configuration of 19′-hexanoyloxyfucoxanthin

The esterifying C₆-acid in 19′-hexanoyloxyfucoxanthin has been identified as n-hexanoic acid by GLC of the methyl ester. Ozonolysis of 19′-n-hexanoyloxyfucoxanthin 3-benzoate provided the n-hexanoyloxy derivative of the allenic ketone produced from fucoxanthin 3-benzoate. NMR and CD correlation of the ozonolysis products and NMR of the native carotenoids provided the basis for assignment of the same absolute configuration of the 19′-n-hexanoyloxy derivative (3S, 5R, 6S, 3′S, 5′R, 6′S) as for fucoxanthin. Biosynthetic implications are considered. CD data for 19′-n-hexanoyloxyfucoxanthin, fucoxanthin and some derivatives thereof are reported. Previously unreported minor carotenoids in Coccolithus huxleyi were diadinoxanthin and 3′-desacetyl 19′-n-hexanoyloxy-fucoxanthin.     

pH dependence of heme electrochemistry in cytochromes investigated by multiconformation continuum electrostatic calculations

Cytochromes belong to a diverse family of heme-containing redox proteins that function as intermediaries in electron transfer chains. They can be soluble, extrinsic, or intrinsic membrane proteins, and are found in different structural motifs (globin, 4-helix bundles, alpha beta roll, beta sandwich). Measured electrochemical midpoint potentials vary over a wide range even though the basic redox reaction at the heme is the same for all cytochromes. The perturbation of the heme electrochemistry is induced by the protein structure. Also, the pH dependence varies since it depends on the strength of interaction between the heme and surrounding residues as well as the ionization states of these groups. Multiconformation continuum electrostatics (MCCE) has been used to investigate the pH dependence of heme electrochemistry in cytochromes with different folds. Often propionates are the primary contributors for pH dependence especially if they are partially protonated in the reduced heme as it is shown for globin cytochrome c551 P. aeruginosa and cytochrome b5 R. norvegicus (alpha beta roll). However, if the propionates are already fully ionized at a certain pH they do not contribute to the pH dependence even if they have big interaction with the heme. At pH 7 there is no propionate contribution for cytochrome f C. reinhardtii (beta sandwich) and the 4-helix bundle c' R. palustris. Other residues can also change their ionization significantly during heme oxidation and therefore be involved in proton release and pH dependence. These residues have been identified for different cytochrome types.     

Development of a Combined Selection and Enrichment PCR Procedure for Clostridium botulinum Types B, E, and F and Its Use To Determine Prevalence in Fecal Samples from Slaughtered Pigs

A specific and sensitive combined selection and enrichment PCR procedure was developed for the detection of Clostridium botulinum types B, E, and F in fecal samples from slaughtered pigs. Two enrichment PCR assays, using the DNA polymerase rTth, were constructed. One assay was specific for the type B neurotoxin gene, and the other assay was specific for the type E and F neurotoxin genes. Based on examination of 29 strains of C. botulinum, 16 strains of other Clostridium spp., and 48 non-Clostridium strains, it was concluded that the two PCR assays detect C. botulinum types B, E, and F specifically. Sample preparation prior to the PCR was based on heat treatment of feces homogenate at 70°C for 10 min, enrichment in tryptone-peptone-glucose-yeast extract broth at 30°C for 18 h, and DNA extraction. The detection limits after sample preparation were established as being 10 spores per g of fecal sample for nonproteolytic type B, and 3.0 × 10³ spores per g of fecal sample for type E and nonproteolytic type F with a detection probability of 95%. Seventy-eight pig fecal samples collected from slaughter houses were analyzed according to the combined selection and enrichment PCR procedure, and 62% were found to be PCR positive with respect to the type B neurotoxin gene. No samples were positive regarding the type E and F neurotoxin genes, indicating a prevalence of less than 1.3%. Thirty-four (71%) of the positive fecal samples had a spore load of less than 4 spores per g. Statistical analysis showed that both rearing conditions (outdoors and indoors) and seasonal variation (summer and winter) had significant effects on the prevalence of C. botulinum type B, whereas the effects of geographical location (southern and central Sweden) were less significant.     

Production of IL-1Ra by human mononuclear blood cells in vitro: influence of serum factors

In vitro cell culture models that measure cytokine production can be of great value when analyzing regulatory mechanisms underlying various pathological conditions. However, testing the function of peripheral blood cells has to take into consideration that serum factors are likely to be of importance in maintaining their function. Interleukin-1 receptor antagonist (IL-1Ra) is a cytokine of key importance in immune regulation and is believed to be involved in numerous pathological processes, such as autoimmunity and cancer. We investigated the influence of normal, human serum on spontaneous production of IL-1Ra by human peripheral blood mononuclear cells (PBMC) in vitro. IL-1Ra production in vitro spanned over a wide range of concentrations, which could be attributed to a combined effect of both cellular parameters and properties of the serum used. The production of IL-1Ra in vitro could be correlated to the level of immobilized IgG, especially IgG1 and IgG3, which is adsorbed from the serum and bound to the tissue culture wells during culture. However, the amount of serum IgG adsorbed to the tissue culture wells could not necessarily be predicted based on the serum concentration of IgG.     

Conductance measurements for data generation in predictive modeling

Summary The electrical resistance of a growth medium inoculated with bacteria may be automatically recorded throughout an incubation period without the necessity for sampling. The rate of change in conductance is dependent on the bacteria studied, the medium composition and the prevailing growth conditions.The effect of growth medium composition, growth conditions and inoculum level on the conductance response was studied forYersinia enterocolitica O:3. A large number of combinations of factors affecting the growth/activity of the bacteria could be studied simultaneously due to the large instrumental capacity of the Malthus 2000. A polynomial model based on conductance measurements was developed forY. enterocolitica describing the effect of temperature, pH andl-lactate level on conductance response curve parameters. The model was used for predicting growth rates. Growth rates calculated from bacterial counts ofY. enterocolitica growing in minced pork corresponded to growth rates predicted using the polynomial conductance models.