Key Factors Determining the Behavior of Pathogens in Dry-Cured Ham after High Pressure Processing

High pressure processing (HPP) inactivates pathogens and increases the safety of ready-to-eat meat products. The high-pressure lethality and the behavior of the surviving cells after HPP depends on process parameters (pressure and time), microorganism and matrix characteristics. The aim of the present study was to quantify the impact of pressure level, water activity (aw), and fat content on the behavior of Salmonella spp. and Listeria monocytogenes during refrigerated storage of dry-cured ham after high-pressure processing. Salmonella enterica serotype London CTC1003 and L. monocytogenes CTC1034 were inoculated at ca. 7 log cfu/g in dry-cured ham of different aw (0.87–0.98), vacuum packaged, pressurized from 300 to 852 MPa for 5 min, and stored at 7 °C for up to 2 months. Salmonella and L. monocytogenes populations were monitored by plate count during the storage of the hams. The gamma concept was used to quantify the individual effects of aw and storage temperature on the pathogen growth/no-growth behavior in pressurized dry-cured ham. The Weibull (inactivation) or Logistic (growth) primary models were fitted to the log change of pathogen levels during storage of dry-cured ham after pressurization. According to the gamma approach, the refrigeration temperature and aw were the main factors limiting the growth of Salmonella and L. monocytogenes, respectively, in dry-cured ham. Under conditions not allowing growth, the effect of increasing pressures on the microbial inactivation depended on the aw of dry-cured ham and the pathogen; dry-cured ham with high fat content with an aw ≥ 0.95 enhanced the inactivation of Salmonella whereas it reduced that of L. monocytogenes. Under conditions allowing growth of L. monocytogenes, the increase in aw from 0.96 to 0.98 reduced the lag time with no apparent impact on the growth rate.info:eu-repo/semantics/publishedVersio

Flowering poration – a synergistic multi-mode antibacterial mechanism by a bacteriocin fold

Bacteriocins are a distinct family of antimicrobial proteins postulated to porate bacterial membranes. However, direct experimental evidence of pore formation by these proteins is lacking. Here we report a multi-mode poration mechanism induced by four-helix bacteriocins, epidermicin NI01 and aureocin A53. Using a combination of crystallography, spectroscopy, bioassays and nanoscale imaging, we established that individual two-helix segments of epidermicin retain antibacterial activity but each of these segments adopts a particular poration mode. In the intact protein these segments act synergistically to balance out antibacterial and hemolytic activities. The study sets a precedent of multi-mode membrane disruption advancing the current understanding of structure-activity relationships in pore-forming proteins

Silver nanoparticle embedded copper oxide as an efficient core–shell for the catalytic reduction of 4-nitrophenol and antibacterial activity improvement

International audienc

Different Dose-Dependent Modes of Action of C-Type Natriuretic Peptide on Pseudomonas aeruginosa Biofilm Formation.

We have previously shown that the C-type Natriuretic Peptide (CNP), a peptide produced by lungs, is able to impact Pseudomonasaeruginosa physiology. In the present work, the effect of CNP at different concentrations on P. aeruginosa biofilm formation was studied and the mechanisms of action of this human hormone on P. aeruginosa were deciphered. CNP was shown to inhibit dynamic biofilm formation in a dose-dependent manner without affecting the bacterial growth at any tested concentrations. The most effective concentrations were 1 and 0.1 µM. At 0.1 µM, the biofilm formation inhibition was fully dependent on the CNP sensor protein AmiC, whereas it was only partially AmiC-dependent at 1 µM, revealing the existence of a second AmiC-independent mode of action of CNP on P. aeruginosa. At 1 µM, CNP reduced both P. aeruginosa adhesion on glass and di-rhamnolipid production and also increased the bacterial membrane fluidity. The various effects of CNP at 1 µM and 0.1 µM on P. aeruginosa shown here should have major consequences to design drugs for biofilm treatment or prevention

Rational design and characterization of bioplastics from Hermetia illucens prepupae proteins

In this study proteins extracted from prepupae of Hermetia illucens, also known as black soldier fly,are investigated as promising base for a new type of bioplastics for agricultural purposes. Designof experiments techniques are employed to perform a rational study on the effects of differentcombination of glycerol as plasticizer, citric acid as cross-linking agent and distilled water as solventon the capability of proteins to form a free-standing film through casting technique, keeping asfixed the quantity of proteins. Glycerol shows interesting properties as plasticizer contributing tothe formation of homogenous and free-standing film. Moreover, mechanical and thermalcharacterizations are performed to estimate the effect of increasing amounts of proteins on thefinal properties and thickness of the specimens. Proteins derived from H. illucens can be success-fully employed as base for bioplastics to be employed for agricultural purposes

Pseudomonas aeruginosa Biofilm Dispersion by the Human Atrial Natriuretic Peptide

This is the final version. Available on open access from Wiley via the DOI in this recordData Availability Statement: The data that support the findings of this study are available from the corresponding author upon reasonable request.Pseudomonas aeruginosa biofilms cause chronic, antibiotic tolerant infections in wounds and lungs. Numerous recent studies demonstrate that bacteria can detect human communication compounds through specific sensor/receptor tools that modulate bacterial physiology. Consequently, interfering with these mechanisms offers an exciting opportunity to directly affect the infection process. It is shown that the human hormone Atrial Natriuretic Peptide (hANP) both prevents the formation of P. aeruginosa biofilms and strongly disperses established P. aeruginosa biofilms. This hANP action is dose-dependent with a strong effect at low nanomolar concentrations and takes effect in 30-120 min. Furthermore, although hANP has no antimicrobial effect, it acts as an antibiotic adjuvant. hANP enhances the antibiofilm action of antibiotics with diverse modes of action, allowing almost full biofilm eradication. The hANP effect requires the presence of the P. aeruginosa sensor AmiC and the AmiR antiterminator regulator, indicating a specific mode of action. These data establish the activation of the ami pathway as a potential mechanism for P. aeruginosa biofilm dispersion. hANP appears to be devoid of toxicity, does not enhance bacterial pathogenicity, and acts synergistically with antibiotics. These data show that hANP is a promising powerful antibiofilm weapon against established P. aeruginosa biofilms in chronic infections.Normandy RegionFrench Ministry of Research (MRE

Ancient DNA analysis identifies marine mollusc shells as new metagenomic archives of the past.

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Marine mollusc shells enclose a wealth of information on coastal organisms and their environment. Their life history traits as well as (palaeo-) environmental conditions, including temperature, food availability, salinity and pollution, can be traced through the analysis of their shell (micro-) structure and biogeochemical composition. Adding to this list, the DNA entrapped in shell carbonate biominerals potentially offers a novel and complementary proxy both for reconstructing palaeoenvironments and tracking mollusc evolutionary trajectories. Here, we assess this potential by applying DNA extraction, high-throughput shotgun DNA sequencing and metagenomic analyses to marine mollusc shells spanning the last ~7,000 years. We report successful DNA extraction from shells, including a variety of ancient specimens, and find that DNA recovery is highly dependent on their biomineral structure, carbonate layer preservation and disease state. We demonstrate positive taxonomic identification of mollusc species using a combination of mitochondrial DNA genomes, barcodes, genome-scale data and metagenomic approaches. We also find shell biominerals to contain a diversity of microbial DNA from the marine environment. Finally, we reconstruct genomic sequences of organisms closely related to the Vibrio tapetis bacteria from Manila clam shells previously diagnosed with Brown Ring Disease. Our results reveal marine mollusc shells as novel genetic archives of the past, which opens new perspectives in ancient DNA research, with the potential to reconstruct the evolutionary history of molluscs, microbial communities and pathogens in the face of environmental changes. Other future applications include conservation of endangered mollusc species and aquaculture management.We thank Tom Schiøtte and Martin Vinther Sørensen at the Zoological Museum of Copenhagen for providing historical shell samples from the Invertebrate Collection. We thank Adeline Bidault for Vibrio DNA extraction, Kristian Hanghøj for technical assistance, Mikkel Schubert and Gabriel Renaud for fruitful discussions, the PALEOMIX group and the staff of the Danish National High-Throughput DNA Sequencing Centre for support. This work was supported by the Danish Council for Independent Research, Natural Sciences (FNU, 4002-00152B); the Danish National Research Foundation (DNRF94); the EPT PROXACHEOBIO from Université Européenne de Bretagne (2010–2012); the APEGE initiative PaleoCOO of the Centre National de la Recherche Scientifique; the cluster of excellence LabexMER (ANR-10-LABX-19; METHOMOL) under the program “Investissements d'Avenir”; the UK Natural Environment Research Council (NE/H023356/1); the EU Marie Curie ARAMACC Initial Training Network (FP7-PEOPLE-2013-ITN 604802); the “Chaires d'Attractivité 2014” IDEX, University of Toulouse, France (OURASI)

Bacteriocin as Weapons in the Marine Animal-Associated Bacteria Warfare: Inventory and Potential Applications as an Aquaculture Probiotic

As the association of marine animals with bacteria has become more commonly recognized, researchers have increasingly questioned whether these animals actually produce many of the bioactive compounds originally isolated from them. Bacteriocins, ribosomally synthesized antibiotic peptides, constitute one of the most potent weapons to fight against pathogen infections. Indeed, bacteriocinogenic bacteria may prevent pathogen dissemination by occupying the same ecological niche. Bacteriocinogenic strains associated with marine animals are a relevant source for isolation of probiotics. This review draws up an inventory of the marine bacteriocinogenic strains isolated from animal-associated microbial communities, known to date. Bacteriocin-like inhibitory substances (BLIS) and fully-characterized bacteriocins are described. Finally, their applications as probiotics in aquaculture are discussed

Antimicrobial Peptides from Marine Proteobacteria

After years of inadequate use and the emergence of multidrug resistant (MDR) strains, the efficiency of “classical” antibiotics has decreased significantly. New drugs to fight MDR strains are urgently needed. Bacteria hold much promise as a source of unusual bioactive metabolites. However, the potential of marine bacteria, except for Actinomycetes and Cyanobacteria, has been largely underexplored. In the past two decades, the structures of several antimicrobial compounds have been elucidated in marine Proteobacteria. Of these compounds, polyketides (PKs), synthesised by condensation of malonyl-coenzyme A and/or acetyl-coenzyme A, and non-ribosomal peptides (NRPs), obtained through the linkage of (unusual) amino acids, have recently generated particular interest. NRPs are good examples of naturally modified peptides. Here, we review and compile the data on the antimicrobial peptides isolated from marine Proteobacteria, especially NRPs