2、细菌的特殊结构（7）

nullWall-less forms of Bacteria（L Forms）Wall-less forms of Bacteria（L Forms）When 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- ---- spheroplasts Characteristics of L-forms lacking a rigid cell wall-- pleiomorphy 2. Difficult to cultivate , require a medium with soft agar and the high osmotic strength 3. Chromaticity usually register as G- 4. Some can revert to the normal 5. L-forms can produce chronic infection Characteristics of L-forms null Colonies of L-formsnullStaphylococcusL form of Staphylococcus2. Cell membrane2. Cell membrane a typical “unit membrane”, which composed of a phospholipid bilayer and proteins similar to that in eukaryotic cells, but do not contain sterols.A model of cell membrane structurenullFunctionSelective permeability and active transport Energy generation Synthesis of precursors of the cell wall Secretion of hydrolytic enzymes and toxinsnullImportant protein on the cell membrane1、Penicillin-binding protein (PBP) 2 、Protein-secreting system 3 、Two-component signal transduction systemProtein-secreting systemProtein-secreting systemTwo-component signal transduction system Two-component signal transduction system nullMesosomeA specialized structures formed by convoluted inveigh-nations of cytoplasmic membrane Be divided into septal and lateral mesosome.nullMesosomeCompartmenting of DNA at cell division providing a membranous support for respiratory enzymesnull3. CytoplasmRibosomes Being the site of protein synthesisnullPlasmidsExtra-chromosomal , closed double- stranded circular DNA molecules Inclusion granulesmetachromatic grandules of Diphtheria bacillus Inclusion granulesMetachromatic Granules Having distinguishable significant null4. Nucleoid （nuclear material） Lacking nuclear membrane, absence of nucleoli, hence known as nucleic material or nucleoid, one to several per bacterium. null1. Capsule 2. Flagellum 3. Pilus or Fimbria 4. Spore Special structure of bacterianullCapsule--- Surrounding the outside of the cell envelope --- Wide enough ( 0.2μm or more ) --- Development dependent on favorable environmental condition1. Concept2. Chemical compositionPolysaccharide or polypeptidenullnull3. 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 bacterianull4. ExaminationnullFlagellum1. ConceptSome bacterial species are mobile and possess locomotory organelles - flagella. The diameter of a flagellum is thin, and long Bacteria can have one or more flagella arranged in clumps or spread all over the cell.null2. classesnull3. compositionStructure basal body hook filament Flagella consist of a number of proteins including flagellinnullnull4. FunctionMotility of bacteria Pathogenesis Identification of Bacterianull5. ExaminationThe flagella stain Observe directly by EM Observe the motility of bacteria Inoculating on the semisolid agar nullnullPilus / fimbriae1. Concept--- Many G-bacteria and few G+ bacteria possess --- rigid surface appendages --- shorter and straighter than flagella 2. composition subunits of a protein----pilinnull3. classes and functionOrdinary pili --- Adherence of pathogenic bacteria to host cells --- Being the site of the major surface antigennullSex pili --- only appear in a few gram-negative bacteria --- having 1~4 being borne per cell --- Sex pili are coded by F plasmid --- Inducing bacterial conjugation --- acting as receptor sites for certain bacteriophagesnull4. ExaminationObserved through the EMnull1. ConceptSpore/ endospores --- Spore formation occurs when nutrients are depleted--- forming insides the cell --- A highly resistant resting phasenullnull2. Forming of spore null3. Structure of spore null4. 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 yearsnull5. significance in differentiationnull6. Significance in medical science--- Having extraordinary resistance to heat and chemicals, being standard of thorough sterilizing --- can cause diseases through germination --- Having significance in differentiationnull7. ExaminationThe spore stain