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发布于:2018-6-22 12:43:09  访问:4 次 回复:0 篇
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An Warfare vs Alisertib And The Ways To Dominate It
, 2005; Rieu-Lesme et?al., GSK J4 supplier 2005), whereas bacteria are distributed in about 800�C1000 species (Macfarlane & Macfarlane, 2004; Backhed et?al., 2005). Cloning and comparative analysis of 16S rRNA gene sequence obtained from fecal samples pointed out the importance of two dominant phyla, Bacteroidetes and Firmicutes (Eckburg et?al., 2005; Hayashi et?al., 2005; Dethlefsen et?al., 2007). The relationship between the intestinal bacteria and their host was initially defined as commensal, but it is now well established that it is mutualistic, with benefits for both partners (Hooper & Gordon, 2001). The positive impact of the microbiota on the host can be measured at several levels. For example, the microbiota is involved in different metabolic reactions, such as degradation of indigestible fibers, biotransformation of conjugated biliary salts or synthesis of vitamins, especially B12 and K (Guarner & Malagelada, 2003; Gill et?al., 2006; Hooper, check details 2009). It also has a tropic effect on the intestinal epithelium by favoring the development of microvilli and is involved in the maturation of the immune response (Cebra, 1999; Nicholson et?al., 2005). One of the most important roles of the intestinal microbiota is colonization-resistance against pathogenic microorganisms. Among the different mechanisms that can be involved in this barrier effect, the capability to produce antimicrobial compounds like bacteriocins is crucial. Bacteriocins are ribosomally synthesized proteinaceous molecules generally active against CP 673451 closely related species. They constitute one of the most diverse and abundant group of antimicrobials, and are synthesized by all lineages of bacteria and Archaea. Frequently, the genes responsible for their biosynthesis are linked to mobile genetic elements like plasmids or transposons. The first key used to classify bacteriocins is the Gram-staining of the producer strain. Bacteriocins synthesized by Gram-positive bacteria, especially those produced by lactic acid bacteria, have been extensively studied over the past decade, and their classification regularly revised since the proposition of Klaenhammer (Klaenhammer, 1993). Even if debatable, it was proposed to distinguish four main groups (Heng et?al., 2007). Class I lantibiotics are post-translationally modified, heat-stable, low molecular mass peptides (<5?kDa) harboring unusual lanthionine or ��-methyllanthionine amino acid residues. Class II bacteriocins are small (<10?kDa) heat-stable, nonmodified peptides. Class III bacteriocins are large heat-labile proteins exhibiting a bacteriolytic activity (class IIIA) or nonlytic antimicrobial proteins (class IIIB). Finally, class IV bacteriocins group are cyclic peptides with covalently linked N- and C-termini. More recently, the identification of distinct groups and subgroups was proposed on the basis of consensus sequence motif (Zouhir et?al., 2010).
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