Autochthonous fungi are central components in microbial community structure in raw fermented sausages

Raw meat sausage represents a unique ecological niche rich in nutrients for microbial consumption, making it particularly vulnerable to microbial spoilage. Starter cultures are applied to improve product stability and safety as well as flavour characteristics. However, the influence of starter cultures on microbial community assembly and succession throughout the fermentation process is largely unknown. In particular the effect on the fungal community has not yet been explored. We evaluate the microbiological status of four different raw meat sausages using high-throughput 16S rRNA gene and ITS2 gene sequencing. The objective was to study temporal changes of microbial composition during the fermentation process and to identify potential keystone species that play an important role within the microbial community. Our results suggest that fungi assigned to the species Debaryomyces hansenii and Alternaria alternata play a key role in microbial community dynamics during fermentation. In addition, bacteria related to the starter culture Lactobacillus sakei and the spoilage-associated genera Acinetobacter, Pseudomonas and Psychrobacter are central components of the microbial ecosystem in raw fermented sausages. Elucidating the exact role and interactions of these microorganisms has the potential to have direct impacts on the quality and safety of fermented foods.     

Correlation of changes in transglutaminase activity and polyamine content of neoplastic tissue during the metastatic process

Transglutaminase activity and the levels of the polyamines putrescine, spermidine and spermine were measured in two transplantable rat sarcomata: P₈ which metastasises consistently to the lung, and P₇ which metastasises infrequently. With the P₇ sarcoma no metastases were detected following implantation; similarly, no significant changes occurred in the levels of transglutaminase activity, putrescine, spermidine or spermine during tumour growth. However, with the P₈ sarcoma at approx. 30 days after implantation there was a marked decrease in transglutaminase activity, mirrored exactly by a 20-fold increase in the levels of acid-soluble putrescine. Measurement of covalently-bound polyamines in the P₈ sarcoma indicated a significant and corresponding decrease in the levels of bound putrescine. The timing of these changes coincided with the time at which the P₈ sarcoma was shown to have metastasised, and suggests that the changes observed may be related to this phenomenon.     

Deoxyribonucleases of non-pathogenic corynebacteria

Fourteen species of non-pathogenic corynebacteria have been examined for the presence of DNases. Seven of the species were found to be DNase positive when assayed in Toluidine Blue-DNA-containing agar whereas only one, Corynebacterium callunae, could be detectable as DNase positive when the test was performed in DNA-methyl green-containing agar. Electrophoretic patterns obtained from sodium dodecyl sulfate-polyacrylamide gels containing DNA showed the presence of one or two bands of nucleolytic activity in two species of Brevibacterium and of several bands in C. callunae. Degradation of DNases by cellular proteases seem to occur in this species.     

Synaptic destabilization by neuronal Nogo-A

Formation and maintenance of a neuronal network is based on a balance between plasticity and stability of synaptic connections. Several molecules have been found to regulate the maintenance of excitatory synapses but nothing is known about the molecular mechanisms involved in synaptic stabilization versus disassembly at inhibitory synapses. Here, we demonstrate that Nogo-A, which is well known to be present in myelin and inhibit growth in the adult CNS, is present in inhibitory presynaptic terminals in cerebellar Purkinje cells at the time of Purkinje cell-Deep Cerebellar Nuclei (DCN) inhibitory synapse formation and is then downregulated during synapse maturation. We addressed the role of neuronal Nogo-A in synapse maturation by generating several mouse lines overexpressing Nogo-A, starting at postnatal ages and throughout adult life, specifically in cerebellar Purkinje cells and their terminals. The overexpression of Nogo-A induced a progressive disassembly, retraction and loss of the inhibitory Purkinje cell terminals. This led to deficits in motor learning and coordination in the transgenic mice. Prior to synapse disassembly, the overexpression of neuronal Nogo-A led to the downregulation of the synaptic scaffold proteins spectrin, spectrin-E and β-catenin in the postsynaptic neurons. Our data suggest that neuronal Nogo-A might play a role in the maintenance of inhibitory synapses by modulating the expression of synaptic anchoring molecules. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cloning and sequencing of a human liver carboxylesterase isoenzyme

A human liver lambda gt11 library was screened with antibodies raised to a purified rat liver carboxylesterase, and several clones were isolated and sequenced. The longest cDNA contained an open reading frame of 507 amino acids that represented 92% of the sequence of a mature carboxylesterase protein. This sequence possessed many structural features that are highly conserved among rabbit and rat liver carboxylesterase proteins, including Ser, His, and Asp residues that comprise the active site, two pairs of Cys residues that may participate in disulfide bond formation, and one Asn-Xxx-Thr site for N-linked carbohydrate addition. When the clone was used to probe human liver genomic DNA that had been digested with various restriction enzymes, many hybridizing bands of differing intensities were observed. The results suggest that the carboxylesterases exist as several isoenzymes in humans, and that they are encoded by multiple genes.     

The Susceptibility of Pseudomonas aeruginosa Strains from Cystic Fibrosis Patients to Bacteriophages

Phage therapy may become a complement to antibiotics in the treatment of chronic Pseudomonas aeruginosa infection. To design efficient therapeutic cocktails, the genetic diversity of the species and the spectrum of susceptibility to bacteriophages must be investigated. Bacterial strains showing high levels of phage resistance need to be identified in order to decipher the underlying mechanisms. Here we have selected genetically diverse P. aeruginosa strains from cystic fibrosis patients and tested their susceptibility to a large collection of phages. Based on plaque morphology and restriction profiles, six different phages were purified from “pyophage”, a commercial cocktail directed against five different bacterial species, including P. aeruginosa. Characterization of these phages by electron microscopy and sequencing of genome fragments showed that they belong to 4 different genera. Among 47 P. aeruginosa strains, 13 were not lysed by any of the isolated phages individually or by pyophage. We isolated two new phages that could lyse some of these strains, and their genomes were sequenced. The presence/absence of a CRISPR-Cas system (Clustered Regularly Interspaced Short Palindromic Repeats and Crisper associated genes) was investigated to evaluate the role of the system in phage resistance. Altogether, the results show that some P. aeruginosa strains cannot support the growth of any of the tested phages belonging to 5 different genera, and suggest that the CRISPR-Cas system is not a major defence mechanism against these lytic phages.     

A new genus of Syllidae (Polychaeta) from Western Australia

During a study carried out on the subfamily Exogoninae (Syllidae) from Australia, several specimens of a new genus and species were found in samples of dead coral substrate from Western Australia. They have long palps, fused except for a terminal notch, long median and two short lateral antennae, a single pair of short tentacular cirri, and short dorsal cirri, somewhat longer than the parapodial lobes. These characters resemble those of the genus Exogone Örsted, 1845. However, all these appendages are articulated. The chaetae are very similar to those of several species of Syllis Lamarck, 1818, having coarse spines on the margin of compound chaetal blades and truncated dorsal simple chaetae. Furthermore, the pharynx begins in chaetiger 3, posterior to the peristomium, as in many species of the genus Syllis; this condition does not occur in any described species of Exogone. The new genus is provisionally proposed to belong to the subfamily Syllinae, although it has some characters typical of the Exogoninae. Examination under the SEM shows another peculiar feature, the nuchal organs are distinctly laterally located. Within the Syllinae, only Paratyposyllis Hartmann-Schröder, 1962 has a single pair of tentacular cirri, but in that genus, the palps are only basally fused.     

The alternative aerobic ribonucleotide reductase of Escherichia coli, NrdEF, is a manganese-dependent enzyme that enables cell replication during periods of iron starvation

The genome of Escherichia coli encodes two class I ribonucleotide reductases. The first, NrdAB, is a well-studied iron-dependent enzyme that is essential for aerobic growth. The second, NrdEF, is not functional under routine conditions, and its role is obscure. Recent studies demonstrated that NrdEF can be activated in vitro by manganese as well as iron. Since iron enzymes are potential targets for hydrogen peroxide, and since the nrdHIEF operon is induced during H(2) O(2) stress, we hypothesized that H(2) O(2) might inactivate NrdAB and that NrdEF might be induced to compensate. This idea was tested using E. coli mutants that are chronically stressed by H(2) O(2) . Contrary to expectation, NrdAB remained active. Its resistance to H(2) O(2) depended upon YfaE, which helps to activate NrdB. The induction of NrdEF during H(2) O(2) stress was mediated by the inactivation of Fur, an iron-dependent repressor. This regulatory arrangement implied that NrdEF has a physiological role during periods of iron starvation. Indeed, NrdEF supported cell replication in iron-depleted cells. Iron bound to NrdF when it was expressed in iron-rich cells, but NrdEF was functional only in cells that were both iron-depleted and manganese-rich. Thus NrdEF supports DNA replication when iron is unavailable to activate the housekeeping NrdAB enzyme.     

Hybrids of sugars and aromatics: A Pd-catalyzed modular approach to chromans and isochromans

Herein we describe the synthesis of highly substituted chromans and isochromans using carbohydrates as starting materials. The key step of our synthetic approach is the annelation of the benzene moiety via a highly efficient Pd-catalyzed domino reaction. This powerful approach led to a small library of highly substituted chromans and isochromans by making use of a variety of different diynes and bromoglycals. We investigated several Pd-catalysts in order to improve the yields and to enlarge the scope of the domino reaction. Furthermore, we elucidated the mechanistic picture of the reaction with isotope-labelling experiments. Most probably the reaction proceeds via an oxidative addition followed by two carbopalladation steps and a final cyclization reaction.