Bacterial disinfectant resistance—a challenge for the food industry

The focus on hygiene in the food industry has resulted in an increasing use of chemical disinfection and it has been speculated that this will impose a selective pressure and contribute to the emergence of disinfectant-resistant microorganisms. The frequency of strains with a low-level resistance to quaternary ammonium compounds (QAC) is relatively high for Listeria monocytogenes (10%), Staphylococcus spp. (13%) and Pseudomonas spp. (30%) and lower for lactic acid bacteria (1.5%) and coliforms (1%) isolated from food and food processing industry. In general, bacteria isolated after disinfection are more resistant and represent a potential food safety or food spoilage problem. Adaptation to disinfectants may be accompanied by cross-resistance to related disinfectants. We have recently found a genetic linkage between resistance to QAC and antibiotics in food associated staphylococci, and there is a growing concern about cross-resistance between antibiotics and disinfectants.Disinfectant resistance can in most cases be prevented by effective cleaning and disinfection procedures. More effort should be made to avoid build-up of resistance in food production environments.     

Characterization of PR-10 genes from eight Betula species and detection of Bet v 1 isoforms in birch pollen

Background  

Bet v 1 is an important cause of hay fever in northern Europe. Bet v 1 isoforms from the European white birch (Betula pendula) have been investigated extensively, but the allergenic potency of other birch species is unknown. The presence of Bet v 1 and closely related PR-10 genes in the genome was established by amplification and sequencing of alleles from eight birch species that represent the four subgenera within the genus Betula. Q-TOF LC-MS^E was applied to identify which PR-10/Bet v 1 genes are actually expressed in pollen and to determine the relative abundances of individual isoforms in the pollen proteome.     

Paradoxical effects of maternal stress on fetal steroids and postnatal reproductive traits in female mice from different intrauterine positions

We examined effects of maternal stress on prenatal serum concentrations of testosterone and estradiol and on postnatal reproductive traits in female mice from different intrauterine positions. On Day 18 of fetal life, control females positioned in utero between two male fetuses (2M females) had higher concentrations of testosterone and lower concentrations of estradiol in serum than control female fetuses located between two females (0M females). Control females positioned between a male and a female fetus (1M females) had intermediate levels of both hormones. Prior intrauterine position in control females accounted for differences in genital morphology (length of the anogenital separation) at birth and length of estrous cycles during adulthood. Maternal stress eliminated these postnatal differences due to prior intrauterine position: all 0M, 1M, and 2M female offspring of stressed mothers exhibited postnatal traits that were indistinguishable from those of control 2M females. Maternal stress resulted in an increase of over 1 ng/ml in serum testosterone in all female fetuses; the magnitude of the increase was similar for 0M, 1M, and 2M females. There was no effect of maternal stress on serum concentrations of estradiol in 0M and 2M female fetuses. Maternal stress resulted in a dramatic change in the postnatal traits of 0M females, whereas 2M females showed no change. Since the effect of maternal stress on sex steroids was similar among fetuses from different intrauterine positions but postnatal response to maternal stress varied by intrauterine position, other components of the endocrine system may mediate effects of maternal stress on these postnatal characteristics.     

Molecular evolution of P transposable elements in the genus Drosophila. III. The melanogaster species group

Phylogenetic relationships were determined for 76 partial P-element sequences from 14 species of the melanogaster species group within the Drosophila subgenus Sophophora. These results are examined in the context of the phylogeny of the species from which the sequences were isolated. Sequences from the P-element family fall into distinct subfamilies, or clades, which are often characteristic for particular species subgroups. When examined locally among closely related species, the evolution of P elements is characterized by vertical transmission, whereby the P-element phylogeny traces the species phylogeny. On a broader scale, however, the P-element phylogeny is not congruent with the species phylogeny. One feature of P-element evolution in the melanogaster group is the presence of more than one P-element subfamily, differing by as much as 36%, in the genomes of some species. Thus, P elements from several individual species are not monophyletic, and a likely explanation for the incongruence between P-element and species phylogenies is provided by the comparison of paralogous sequences. In certain instances, horizontal transfer seems to be a valid alternative explanation for lack of congruence between species and P-element phylogenies. The canonical P-element subfamily, which represents the active, autonomous transposable element, is restricted to D. melanogaster. Thus, its origin clearly lies outside of the melanogaster species group, consistent with the earlier conclusion of recent horizontal transfer.      

Choosing the right sigmoid growth function using the unified‐models approach

Growth of the young is an important part of the life history in birds. However, modelling methods have paid little attention to the choice of regression model used to describe its pattern. The aim of this study was to evaluate whether a single sigmoid model with an upper asymptote could describe avian growth adequately. We compared unified versions of five growth models of the Richards family (the four‐parameter U‐Richards and the three‐parameter U‐logistic, U‐Gompertz, U‐Bertalanffy and U4‐models) for three traits (body mass, tarsus‐length and wing‐length) for 50 passerine species, including species with varied morphologies and life histories. The U‐family models exhibit a unified set of parameters for all models. The four‐parameter U‐Richards model proved a good choice for fitting growth curves to various traits – its extra d‐parameter allows for a flexible placement of the inflection point. Which of the three‐parameter U‐models was the best performing varied greatly between species and between traits, as each three‐parameter model had a different fixed relative inflection value (fraction of the upper asymptote), implying a different growth pattern. Fixing the asymptotes to averages for adult trait value generally shifted the model preference towards one with lower relative inflection values. Our results illustrate an overlooked difficulty in the analysis of organismal growth, namely, that a single traditional three‐parameter model does not suit all growth data. This is mostly due to differences in inflection placement. Moreover, some biometric traits require more attention when estimating growth rates and other growth‐curve characteristics. We recommend fitting either several three‐parameter models from the U‐family, where the parameters are comparable between models, or only the U‐Richards model.     

Evolution of the Group 1 late embryogenesis abundant (Lea) genes: analysis of the Lea B19 gene family in barley

The highly conserved Group 1 late embryogenesis abundant (Lea) genes are present in the genome of most plants as a gene family. Family members are conserved along the entire coding region, especially within the extremely hydrophilic internal 20 amino acid motif, which may be repeated. Cloning of Lea Group 1 genes from barley resulted in the characterization of four family members named B19.1, B19.1b, B19.3 and B19.4 after the presence of this motif 1, 1, 3 and 4 times in each gene, respectively. We present here the results of comparative and evolutionary analyses of the barley Group 1 Lea gene family (B19). The most important findings resulting from this work are (1) the tandem clustering of B19.3 and B19.4, (2) the spatial conservation of putative regulatory elements between the four B19 gene promoters, (3) the determination of the relative age of the gene family members and (4) the chimeric nature of B19.3 and B19.4, reflecting a cross-over or gene-conversion event in their common ancestor. We also show evidence for the presence of one or two additional expressed B19 genes in the barley genome. Based on our results, we present a model for the evolution of the family in barley, including the 20 amino acid motif. Comparisons of the relatedness between the barley family and all other known Group 1 Lea genes using maximum parsimony (PAUP) analysis provide evidence for the time of divergence between the barley genes containing the internal motif as a single copy and as a repeat. The PAUP analyses also provide evidence for independent duplications of Group 1 genes containing the internal motif as a repeat in both monocots and dicots.     

Glutamate Synthase: Properties of the Reduced Nicotinamide Adenine Dinucleotide-Dependent Enzyme from Saccharomyces cerevisiae

A reduced nicotinamide adenine dinucleotide (NADH)-dependent glutamate synthase has been detected and partially purified from crude extracts of Saccharomyces cerevisiae. The enzyme is specific for NADH, glutamine, and alpha-ketoglutarate (K(m) values of 2.6 muM, 1.0 mM, and 140 muM, respectively) and has a pH optimum between 7.1 and 7.7. The stoichiometry of the reaction has been determined as 2 mol of glutamate synthesized per mol of glutamine consumed. Glutamate synthase can be distinguished from either of the glutamate dehydrogenases of yeast on the basis of its substrate requirements and behavior during agarose gel and ion exchange chromatography. Variations in the specific activity of glutamate synthase, which occur in response to changes in the growth medium, are similar in character to those observed with the nicotinamide adenine dinucleotide phosphate-dependent (anabolic) glutamate dehydrogenase.     

The nuclear-coded chloroplast 22-kDa heat-shock protein of Chlamydomonas. Evidence for translocation into the organelle without a processing step

A cDNA clone, pCHS62, was isolated using poly(A)-rich RNA from heat-shocked Chlamydomonas reinhardtii cells. The clone has a length of 1.1 kb and codes for the complete heat-shock protein which was reported to be associated with the grana region of the thylakoid membranes and ascribes protection against photoinhibition during heat-shock. An expression vector prepared in the pUC19 plasmid was used to obtain a fusion protein against which rabbit polyclonal antibodies have been raised. The antibodies react specifically with the heat-shock protein of 22 kDa synthesized in vivo during heat-shock, which is localized in the grana thylakoids, with the in vitro translated product using poly(A)-rich RNA from heat-treated cells as well as with the hybrid release translation product of the pCHS62 clone. The clone was sequenced. It contains a 5' region consisting of 85 nucleotides, an open reading frame of 471 nucleotides and a non-coding 3' region of 600 nucleotides. Northern hybridization indicates a length of 1.7 kb for the messenger RNA of heat-shock protein 22. Analysis of similarity between the derived amino acid sequence of this protein and other heat-shock proteins demonstrates that this protein belongs to the small-molecular-mass plant heat-shock protein family and also shows similarities with animal heat-shock proteins including the presence of a short region possessing similarity with bovine alpha-crystalline as reported for other heat-shock proteins. The molecular mass of the protein as determined from the sequence is 16.8 kDa. Despite its localization in the chloroplast membranes, it does not seem to include a transit peptide sequence, in agreement with previous data. The sequence contains only a short hydrophobic region compatible with its previously reported localization as a thylakoid extrinsic protein.