Microbiological food safety assessment of high hydrostatic pressure processing: A review

Author: Rendueles, E.; Omer, M.K.; Alvseike, O.; Alonso-Calleja, C.; Capita, R.; Prieto, M. Description: High hydrostatic pressure (HHP) processing as a novel non-thermal method has shown great potential in producing microbiologically safer products while maintaining the natural characteristics of the food items. Scientific research of the process and its industrial applications has been widespread in the past two decades with many scientific publications describing its uses, advantages and limitations. The review describes the effect of HHP on foodborne pathogenic microorganisms, their structures and adaptive mechanisms, the intrinsic and extrinsic factors…

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Bacteriophage resistance mechanisms

Author: Labrie, Simon J.; Samson, Julie E.; Moineau, Sylvain Description: Phages are now acknowledged as the most abundant microorganisms on the planet and are also possibly the most diversified. This diversity is mostly driven by their dynamic adaptation when facing selective pressure such as phage resistance mechanisms, which are widespread in bacterial hosts. When infecting bacterial cells, phages face a range of antiviral mechanisms, and they have evolved multiple tactics to avoid, circumvent or subvert these mechanisms in order to thrive in most environments. In this Review, we highlight the…

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Geographical patterns of the standing and active human gut microbiome in health and IBD

Author: Rehman, A.; Rausch, P.; Wang, J.; Skieceviciene, J.; Kiudelis, G.; Bhagalia, K.; Amarapurkar, D.; Kupcinskas, L.; Schreiber, S.; Rosenstiel, P.; Baines, J.F.; Ott, S. Description: OBJECTIVE: A global increase of IBD has been reported, especially in countries that previously had low incidence rates. Also, the knowledge of the human gut microbiome is steadily increasing, however, limited information regarding its variation on a global scale is available. In the light of the microbial involvement in IBDs, we aimed to (1) identify shared and distinct IBD-associated mucosal microbiota patterns from different…

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The isolation, identification, and bioassay of the antifungal metabolites produced by Monocillium nordinii

Author: Ayer, W.A.; Lee, S.P.; Tsuneda, A.; Hiratsuka, Y. Description: The metabolites produced when Monocillium nordinii (Bourchier) W. Gams, a destructive mycoparasite of pine stem rusts, is grown in liquid culture have been separated and identified. The metabolites include the known compound monorden (1) and five new substances, monocillin I (2), monocillin II (4), monocillin III (3), monocillin IV (5), and monocillin V (6). Structural assignments and chemical correlations of the five new compounds are reported and the absolute configuration of monorden is assigned. The antifungal spectra of the three…

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Serratia marcescens quinoprotein glucose dehydrogenase activity mediates medium acidification and inhibition of prodigiosin production by glucose

Author: Fender, James E.; Bender, Cody M.; Stella, Nicholas A.; Lahr, Roni M.; Kalivoda, Eric J.; Shanks, Robert M. Q. Description: Serratia marcescens is a model organism for the study of secondary metabolites. The biologically active pigment prodigiosin (2-methyl-3-pentyl-6-methoxyprodiginine), like many other secondary metabolites, is inhibited by growth in glucose-rich medium. Whereas previous studies indicated that this inhibitory effect was pH dependent and did not require cyclic AMP (cAMP), there is no information on the genes involved in mediating this phenomenon. Here we used transposon mutagenesis to identify genes involved…

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Biosynthesis of the red antibiotic, prodigiosin, in Serratia: identification of a novel 2-methyl-3-n-amyl-pyrrole (MAP) assembly pathway, definition of the terminal condensing enzyme, and implications for undecylprodigiosin biosynthesis in Streptomyces

Author: Williamson, Neil R.; Simonsen, Henrik T.; Ahmed, Raef A. A.; Goldet, Gabrielle; Slater, Holly; Woodley, Louise; Leeper, Finian J.; Salmond, George P. C. Description: The biosynthetic pathway of the red-pigmented antibiotic, prodigiosin, produced by Serratia sp. is known to involve separate pathways for the production of the monopyrrole, 2-methyl-3-n-amyl-pyrrole (MAP) and the bipyrrole, 4-methoxy-2,2′-bipyrrole-5-carbaldehyde (MBC) which are then coupled in the final condensation step. We have previously reported the cloning, sequencing and heterologous expression of the pig cluster responsible for prodigiosin biosynthesis in two Serratia sp. In this article…

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Phosphate availability regulates biosynthesis of two antibiotics, prodigiosin and carbapenem, in Serratia via both quorum-sensing-dependent and -independent pathways

Author: Slater, Holly; Crow, Matthew; Everson, Lee; Salmond, George P. C. Description: Serratia sp. ATCC 39006 produces two secondary metabolite antibiotics, 1-carbapen-2-em-3-carboxylic acid (Car) and the red pigment, prodigiosin (Pig). We have previously reported that production of Pig and Car is controlled by N-acyl homoserine lactone (N-AHL) quorum sensing, with synthesis of N-AHLs directed by the LuxI homologue SmaI, and is also regulated by Rap, a member of the SlyA family. We now describe further characterization of the SmaI quorum-sensing system and its connection with other regulatory mechanisms. We show…

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Metagenomic analysis of the microbial community in kefir grains

Author: Nalbantoglu, Ufuk; Cakar, Atilla; Dogan, Haluk; Abaci, Neslihan; Ustek, Duran; Sayood, Khalid; Can, Handan Description: Kefir grains as a probiotic have been subject to microbial community identification using culture-dependent and independent methods that target specific strains in the community, or that are based on limited 16S rRNA analysis. We performed whole genome shotgun pyrosequencing using two Turkish Kefir grains. Sequencing generated 3,682,455 high quality reads for a total of 1.6 Gbp of data assembled into 6151 contigs with a total length of 24 Mbp. Species identification mapped 88.16% and…

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Soil microbiomes and climate change

Author: Jansson, Janet K.; Hofmockel, Kirsten S. Description: The soil microbiome governs biogeochemical cycling of macronutrients, micronutrients and other elements vital for the growth of plants and animal life. Understanding and predicting the impact of climate change on soil microbiomes and the ecosystem services they provide present a grand challenge and major opportunity as we direct our research efforts towards one of the most pressing problems facing our planet. In this Review, we explore the current state of knowledge about the impacts of climate change on soil microorganisms in different…

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An ideR mutant of Mycobacterium smegmatis has derepressed siderophore production and an altered oxidative-stress response

Author: Dussurget, O.; Rodriguez, M.; Smith, I. Description: The mycobacterial ideR protein is a homologue of the diphtheria-toxin repressor DtxR. We have previously demonstrated that Mycobacterium tuberculosis ideR, like DtxR, represses transcription of Corynebacterium diphtheriae iron-regulated promoters in vivo and binds to C. diphtheriae operators in a metal-dependent manner in vitro. We show here that ideR mutants of M. smegmatis, constructed by allelic replacement, were defective in their ability to repress siderophore biosynthesis in the presence of iron. They were also more sensitive to hydrogen peroxide and had decreased levels…

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