细菌的特殊结构7.pptx

Wall-less forms of Bacteria（L Forms）nWhen bacteria are treated with 1)enzymes that have solution for the cell wall 2)antibiotics that interfere with biosynthesis of peptidoglycan L Forms of G+-protoplasts L Forms of G-spheroplasts1.lacking a rigid cell wall-pleiomorphy2.Difficult to cultivate,require a medium with soft agar and the high osmotic strength3.Chromaticity usually register as G-4.Some can revert to the normal5.L-forms can produce chronic infection Characteristics of L-forms Colonies of L-formsStaphylococcusL form of Staphylococcus2.Cell membrane a typical“unit membrane”,which composed of aphospholipid bilayer and proteins similar to that in eukaryotic cells,but do not contain sterols.A model of cell membrane structureFunctionSelective permeability and active transport Energy generation Synthesis of precursors of the cell wallSecretion of hydrolytic enzymes and toxinsImportant protein on the cell membrane1、Penicillin-binding protein(PBP)2、Protein-secreting system3、Two-component signal transduction systemProtein-secreting systemTwo-component signal transduction systemMesosomeA specialized structures formed by convoluted inveigh-nations of cytoplasmic membrane Be divided into septal and lateral mesosome.MesosomeCompartmenting of DNA at cell division providing a membranous support for respiratory enzymesmesosome3.CytoplasmRibosomes Being the site of protein synthesisStreptomycin GentamicinErythromycin ChloramphenicolPlasmidsExtra-chromosomal,closed double-stranded circular DNA molecules metachromatic grandules of Diphtheria bacillus Inclusion granulesMetachromatic Granules Having distinguishable significant 4.Nucleoid（nuclear material）nLacking nuclear membrane,absence of nucleoli,hence known as nucleic material or nucleoid,one to several per bacterium.1.Capsule2.Flagellum3.Pilus or Fimbria4.Spore Special structure of bacteriaCapsule-Surrounding the outside of the cell envelope-Wide enough(0.2m or more)-Development dependent on favorable environmental condition1.Concept2.Chemical compositionPolysaccharide or polypeptide3.Function-Protect the cell wall against attack by various kinds of antibacterial agents-play a role in the adherence of bacteria to human tissues-play a very important part in determining the antigenic specificity of bacteria4.ExaminationFlagellum1.ConceptlSome bacterial species are mobile and possess locomotory organelles-flagella.lThe diameter of a flagellum is thin,and long lBacteria can have one or more flagella arranged in clumps or spread all over the positionStructure basal body hook filament Flagella consist of a number of proteins including flagellin4.FunctionMotility of bacteriaPathogenesis Identification of Bacteria5.ExaminationThe flagella stainObserve directly by EMObserve the motility of bacteria Inoculating on the semisolid agar Pilus/fimbriae1.Concept-Many G-bacteria and few G+bacteria possess-rigid surface appendages-shorter and straighter than flagella position subunits of a protein-pilin3.classes and functionOrdinary pili-Adherence of pathogenic bacteria to host cells-Being the site of the major surface antigenSex pili-only appear in a few gram-negative bacteria-having 14 being borne per cell-Sex pili are coded by F plasmid-Inducing bacterial conjugation-acting as receptor sites for certain bacteriophages4.ExaminationObserved through the EM1.ConceptSpore/endospores-Spore formation occurs when nutrients are depleted-forming insides the cell-A highly resistant resting phaseSpore芽芽胞胞囊囊2.Forming of spore 3.Structure of spore 外壁外壁皮质皮质内膜内膜4.Characteristics-containing necessary components for bacterial life-resistance of the spore may be mediated by dipicolinic acid-having no progenitive activity and remaining dormant for many years5.significance in differentiation6.Significance in medical science-Having extraordinary resistance to heat and chemicals,being standard of thorough sterilizing-can cause diseases through germination-Having significance in differentiation7.ExaminationThe spore stain