Occurrence and Dynamism of Lactic Acid Bacteria in Distinct Ecological Niches: A Multifaceted Functional Health Perspective

Lactic acid bacteria (LAB) are representative members of multiple ecosystems on earth, displaying dynamic interactions within animal and plant kingdoms in respect with other microbes. This highly heterogeneous phylogenetic group has coevolved with plants, invertebrates, and vertebrates, establishing either mutualism, symbiosis, commensalism, or even parasitism-like behavior with their hosts. Depending on their location and environment conditions, LAB can be dominant or sometimes in minority within ecosystems. Whatever their origins and relative abundance in specific anatomic sites, LAB exhibit multifaceted ecological and functional properties. While some resident LAB permanently inhabit distinct animal mucosal cavities, others are provided by food and may transiently occupy the gastrointestinal tract. It is admitted that the overall gut microbiome has a deep impact on health and diseases. Here, we examined the presence and the physiological role of LAB in the healthy human and several animal microbiome. Moreover, we also highlighted some dysbiotic states and related consequences for health, considering both the resident and the so-called “transionts” microorganisms. Whether LAB-related health effects act collectively or follow a strain-specificity dogma is also addressed. Besides the highly suggested contribution of LAB to interplay with immune, metabolic, and even brain-axis regulation, the possible involvement of LAB in xenobiotic detoxification processes and metal equilibrium is also tackled. Recent technological developments such as functional metagenomics, metabolomics, high-content screening and design in vitro and in vivo experimental models now open new horizons for LAB as markers applied for disease diagnosis, susceptibility, and follow-up. Moreover, identification of general and more specific molecular mechanisms based on antioxidant, antimicrobial, anti-inflammatory, and detoxifying properties of LAB currently extends their selection and promising use, either as probiotics, in traditional and functional foods, for dedicated treatments and mostly for maintenance of normobiosis and homeostasis

Complete Chromosome Sequence of Carnobacterium maltaromaticum LMA 28

Within the lactic acid bacterium genus Carnobacterium, Carnobacterium maltaromaticum is one of the most frequently isolated species from natural environments and food. It potentially plays a major role in food product biopreservation. We report here on the 3.649-Mb chromosome sequence of C. maltaromaticum LMA 28, which was isolated from ripened soft cheese

Recombinant pediocin in Lactococcus lactis:increased production by propeptide fusion and improved potency by co-production with PedC

We describe the impact of two propeptides and PedC on the production yield and the potency of recombinant pediocins produced in Lactococcus lactis. On the one hand, the sequences encoding the propeptides SD or LEISSTCDA were inserted between the sequence encoding the signal peptide of Usp45 and the structural gene of the mature pediocin PA-1. On the other hand, the putative thiol-disulfide oxidoreductase PedC was coexpressed with pediocin. The concentration of recombinant pediocins produced in supernatants was determined by enzyme-linked immunosorbent assay. The potency of recombinant pediocins was investigated by measuring the minimal inhibitory concentration by agar well diffusion assay. The results show that propeptides SD or LEISSTCDA lead to an improved secretion of recombinant pediocins with apparently no effect on the antibacterial potency and that PedC increases the potency of recombinant pediocin. To our knowledge, this study reveals for the first time that pediocin tolerates fusions at the N-terminal end. Furthermore, it reveals that only expressing the pediocin structural gene in a heterologous host is not sufficient to get an optimal potency and requires the accessory protein PedC. In addition, it can be speculated that PedC catalyses the correct formation of disulfide bonds in pediocin.</p

Variations in the Membrane Fatty Acid Composition of Resistant or Susceptible Leuconostoc or Weissella Strains in the Presence or Absence of Mesenterocin 52A and Mesenterocin 52B Produced by Leuconostoc mesenteroides subsp. mesenteroides FR52

Mesenterocins 52A (Mes52A) and 52B (Mes52B) are antimicrobial peptides produced by Leuconostoc mesenteroides subsp. mesenteroides FR 52. Mes52A is a class IIa bacteriocin of lactic acid bacteria with a broad spectrum of activity. Mes52B is an atypical class II bacteriocin with a narrow spectrum of activity. Four Leuconostoc and Weissella wild-type strains were selected for their susceptibility or insensitivity to these mesenterocins. Four strains resistant to Mes52A or Mes52B were generated from the three susceptible wild-type strains by increasing bacteriocin concentrations in culture media. These resistant strains were at least 30 times more resistant than the wild-type strains. No cross-resistance to Mes52A and Mes52B was observed in these strains. No significant differences in membrane fatty acid composition were observed among the three susceptible wild-type strains and the four resistant strains cultured in MRS broth. Thus, the mesenterocin resistance is unlikely to be due to changes in membrane fatty acid composition. When cultured with Mes52A or Mes52B, the membranes of insensitive and resistant strains contained more saturated fatty acids (1 to 10% more) and less unsaturated fatty acids (3 to 6% less), resulting in a more rigid membrane. Thus, the presence of mesenterocin in the culture media of insensitive or resistant strains induced a significant increase in saturated fatty acid contents and a decrease in unsaturated fatty acid contents. Weissella paramesenteroides DSM 20288BR, resistant to Mes52B, responded atypically, probably due to the production of an inhibitor

Optimization of the production and purification processes of carnobacteriocins Cbn BM1 and Cbn B2 from Carnobacterium maltaromaticum CP5 by heterologous expression in Escherichia coli

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Microflora of fresh and ice-stored sardines (Sardina pilchardus) from the Moroccan Atlantic coast

 Sardines (Sardina pilchardus) caught on the Moroccan Atlantic coast (off El Jadida) were examined fresh (February, May and July trials) and after 10 days of storage in ice (July trial). From fresh fish, a total of 193 strains were isolated from the muscle with skin, gills and viscera, whereas from ice-stored fish, 122 strains were isolated from the muscle. Gram-negative bacteria always predominated among the initial flora in all trials. The predominant Gram-negative microflora of the fresh fish consisted of Moraxellaceae (Moraxella sp., Acinetobacter sp., Psychrobacter sp.), Enterobacteriaceae, Pseudomonadaceae (Pseudomonas sp.), and the genera Shewanella and Flavobacterium. The Gram-positive flora was identified as Staphylococcus sp., Micrococcus sp. and coryneform bacteria. Significant seasonal variation in initial flora was not noted. Ice storage allowed the growth of Gramnegative bacteria, with Pseudomonas as the dominant microflora, followed by Shewanella putrefaciens. The present study indicates that Pseudomonas sp. probably contribute to the spoilage of sardines caught in the Atlantic Ocean

Laccase-catalysed functionalisation of chitosan by ferulic acid and ethyl ferulate: Evaluation of physicochemical and biofunctional properties

International audienceChitosan and its derivatives functionalized by laccase-catalyzed oxidation of ferulic acid (FA) and ethyl ferulate (EF) were characterised for their physico-chemical, antioxidant and antibacterial properties. The enzymatic grafting of oxidised phenols led to FA-coloured and EF-colourless chitosan derivatives with good stability of colour and grafted phenols towards the chemical treatment by organic solvents. The efficiency of FA-products grafting onto chitosan was higher than that of EF-products. Moreover, the enzymatic grafting of phenols onto chitosan changed its morphological surface, increased its molecular weight and its viscosity. Furthermore, the chitosan derivatives presented improved antioxidant properties especially for FA-chitosan derivative when compared with chitosan with good antioxidant stability towards thermal treatment (100 degrees C/1 h). Chitosan and its derivatives showed also similar antibacterial activities and more precisely bactericidal activities. This enzymatic procedure provided chitosan derivatives with improved properties such as antioxidant activity, thermal antioxidant stability as well as the preservation of initial antibacterial activity of chitosan

Diffusion of Fluorescently Labeled Bacteriocin from Edible Nanomaterials and Embedded Nano-Bioactive Coatings

Application of nano-biotechnology to improve the controlled release of drugs or functional agents is widely anticipated to transform the biomedical, pharmaceutical, and food safety trends. The purpose of the current study was to assess and compare the release rates of fluorescently labeled antimicrobial peptide nisin (lantibiotic/biopreservative) from liposomal nanocarriers. The elevated temperature, high electrostatic attraction between anionic bilayers and cationic nisin, larger size, and higher encapsulation efficiency resulted in rapid and elevated release through pore formation. However, acidic pH and optimal ethanol concentration in food simulating liquid (FSL) improved the stability and retention capacity of loaded drug. Thus, controlling various factors had provided partition coefficient <i>K</i> values from 0.23 to 8.78 indicating variation in nisin affinity toward encapsulating macromolecule or FSL. Interaction between nisin and nanoscale bilayer systems by atomic force (AFM) and transmission electron microscopy demonstrated membrane activity of nisin from adsorption and aggregation to pore formation. Novel nanoactive films with preloaded nanoliposomes embedded in biodegradable polymer revealed improved morphological, topographic, and roughness parameters studied by confocal microscopy and AFM. Pre-encapsulated nanoactive biopolymer demonstrated excellent retention capacity as drug carriers by decreasing the partition coefficient value from 1.8 to 0.66 (∼30%) due to improved stability of nanoliposomes embedded in biopolymer network

Dynamique et propriétés d’acidification de communautés bactériennes du lait cru lors de fermentations séquentielles

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