文献抄读10.27

• 第二个产品是EcoShield™，喷洒于研磨制成汉 堡包 前的红肉上，以杀死大肠杆菌O157:H7，美国每年 发生的62,000例食源性疾病皆由此菌引起。来自不 同动物身上的原料肉混在一起成为肉馅时，只 要一 头动物有细菌就可以感染大批量的肉。Sulakvelidze 证实，在与政府研究人员所进行的研究中， EcoShield在5分钟内可杀死 95~100％的大肠杆菌 O157:H7。 • 第三个产品SalmoFresh™，专门针对禽类及其它食品 中的沙门氏菌，正等待美国食品和药物管理局的批 准。Intralytix公司正在开发用于伤口愈合、兽医保 健和口腔卫生的其它噬菌体疗法。
• A biofilm is any group of microorganisms in which cells stick to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS). Biofilm extracellular polymeric substance, which is also referred to as slime (although not everything described as slime is a biofilm), is a polymeric conglomeration generally composed of extracellular DNA, proteins, and polysaccharides.
• Biofim formation is akin to a developmental pathway. • Initial attachment of bacteria to a surface is often mediated by fiaments that extend from the bacteria. • These proteinaceous appendages can serve as anchors, transiently fiing the bacteria on location. Once attached to the surface, biofim-associated bacteria initiate the synthesis of an extracellular matrix, which generally signifis their commitment to a sedentary existence. • Thus, during biofim formation, the milieu at or near the surface of bacteria undergoes dramatic alterations.
• Some bacteria do not fi this mold;they are able to form robust biofims,yet they do not produce exopolysaccharides as part of biofim formation.Such is the case with mycobacteria • no proteinaceous extensions from these bacteria have been identifid in initial surface attachment, and no exopolysaccharide components of their extracellular matrices are known.
• The discovery of this new role for the GroEL1 chaperone in mycolic-acid synthesis stemmed from the observation of an unexpected phenotype in a strain of lysogenphage is integrated at the 3′ end of the groEL1 gene. This led the investigators to test a ∆groEL1 mycobacterial mutant for biofim formation.
• A mycobacterial mutant lacking GroEL1 was unable to develop architecturally complex biofims and was also defective in the production of mycolic acids • This suggests that GroEL1 has a specifi role in the synthesis of the C56–C68 mycolic acids and that its absence has striking consequences for the development of mature biofims.
• In this issue of Cell, Ojha et al. (2005) identify an apparently new class of fatty acids that plays an important role in the development of biofim architecture in M. smegmatis. Intriguingly, their results indicate that the synthesis of these fatty acids during biofim development specifially involves GroEL1, a member of the Hsp60 family of chaperone proteins found in mycobacteria
噬菌体鸡尾酒
• Intralytix ListShield™是第一个被FDA批准作为食品添 加剂的噬菌体产品，针对即食肉类和禽类食品（如 熟肉制品和法兰克福香肠）中的单核细胞增生性李 斯特 氏菌。该微生物还会污染奶制品及原料，即便 在冷冻食品也会生长，并导致名为李斯特氏菌病的 严重感染，其致死率约为20％。 • 消灭来自食品加工厂的细菌十分困难。“尽管经过 食品 加工机的高强度清洗，单核细胞增生性李斯特 氏菌仍无处不在，十分顽固，”Sulakvelidze说。 ListShield被喷洒在肉类产品，以及食品加 工厂的上 下水道、地板、冷却器和可能携带李斯特氏菌的其 它表面。据Sulakvelidze说，该产品通常会使单核细 胞增生性李斯特氏菌污染降低95％甚 或更多。
• During their examination of the interaction of mycobacteriophages with biofims, the authors noted that mycobacterial strains that harbored the Bxb1 prophage grew well on solid media and in liquid cultures but were unable to develop the typical architecture of mature pellicles characteristic of the biofims of the parent mycobacterial strain.
• Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial and hospital settings. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which, by contrast, are single-cells that may float or swim in a liquid medium.
Five stages of biofilm development: (1) Initial attachment, (2) Irreversible attachment, (3) Maturation I, (4) Maturation II, and (5) Dispersion. Each stage of development in the diagram is paired with a photomicrograph of a developing P. aeruginosa biofilm. All photomicrographs are shown to same scale.
• The mycobacterial cell envelope has an extremely unusual structure One of its most striking features is the presence of very long-chain (C70–C90) fatty acids, known as mycolic acids, that are usually anchored to the envelope through covalent linkage to arabinogalactan(阿拉 伯半乳聚糖）.
Mycobacterial Biofims: A Greasy Way to Hold It Together
Lecturer : Yan He October. 27.2015
• Microorganisms growing on surfaces can form biofims under certain conditions. In this issue of Cell, Ojha et al. (2005) investigate biofim formation in mycobacteria. They identify new cellwall components that are required for the formation of architecturally complex mature biofims in these bacteria and the surprising involvement of a chaperone protein in this process.