Chapter 3-1 bacteria

nullChapter 3 The ProkaryotesChapter 3 The ProkaryotesKey points Key points Differences between G+ and G- bacteria, the principle of gram stain Structure and components of cytoplastic membrane characteristics of endospore The differences between the prokaryotic and eukaryotic cellsWorking glossaryWorking glossaryCytoplasm（细胞质） cell wall （细胞壁） nucleoid （拟核） ribosome （核糖体） cytoplasmic membrane（细胞膜） Organelle (细胞器) Nucleic acid (核酸) Prokaryote (原核生物) Eukaryote(真核生物) Nucleus (细胞核) chemotaxis(化学向性) endospore (内生芽孢) flagellum (鞭毛) Gram-positive （negative）革兰氏阳性（阴性） Periplasmic space (周质空间) coccus （球菌) spirillum（螺旋菌） spirochete (螺旋体) Bacillum （杆菌） histone (组蛋白) diplococci（二联球菌） streptococci （链球菌）tetrads（四联球菌） Vibrios（弧菌） sarcinae（八叠球菌） phospholipid bilayer（磷脂双分子层） Glyceral (甘油) fatty acid (脂肪酸) sterol(固醇、甾酮) and hopanoid（藿类） Ether(醚键) monolayer (单层) Gram stain（革兰氏染色） peptidoglycan(肽聚糖) teichoic acids（磷壁酸） N-acetylglucosamine (NAG，N-乙酰葡萄糖胺) and N-acetylmuramic acid (NAM，N-乙酰胞壁酸), tetrapeptide side chain (四肽侧链) peptide interbridge (肽间桥)nullChapter Outline1 Bacteria 2 Actinomycetes 3 Cyanobacteria 4 Archaeobacteria 5 Other prokaryotesnullMicroorganisms are too small to be seen without the use of a microscope. The techniques-such as sterilization and the use of culture medium are required to isolate and grow these microbes.ConceptsConceptsBacteria may be spherical (cocci), rod-shaped (bacilli), spiral, or filamentous. Most bacteria can be divided into gram-positive and gram-negative groups based on their cell wall structure and response to the Gram stain. Bacteria such as mycoplasmas lack a cell wall.1 Bacteria1 Bacterianull1.1 Size, Shape, and Arrangement of Bacterial CellsThey have a few basic shapes-spherical coccus (cocci, meaning berries), rod-shaped bacillus (bacilli, meaning little staffs), and spiral.Most bacteria fall within a range from 0.2 to 2.0 μm in diameter and from 2 to 8μm in length.nullnullArrangement of Spherical Bacterial CellsnullArrangements of Cocci nullnull Tetrad Arrangement nullSarcina ArrangementnullRod-shaped bacteria Bacilli divide only across their short axis, so there are fewer groupings of bacilli than of cocci. nullSingle bacillusDiplobacillistreptobacilliCoccobacillusnullSingle Rod (Bacillus) nullScanning Electron Micrograph of Pseudomonas aeruginosa nullnullStreptobacillus ArrangementnullClostridium botulinus C. butyricum C. aceticum C. tetani C. putrificumBacillus subtilis, B. mycoides B. megaterium B. thuringiensis B. anthracis B. cereus Spore-forming rod shaped bacteria Almost all Spore-forming bacteria are Gram+Clostridium – AnaerobicBacillus – AerobicnullNonspore - forming rod shaped bacteria Most nonspore – forming rod shaped bacteria are Gram -Representatives: Escherchia coli Alcaligenes Proteus Flavobacteria Pseudomonas Rhizobium AzotobacternullVibrio, Spirillum and SpirocheteSome bacteria are shaped like long rods twisted into spirals or helices; they are called vibrios, spirilla and spirochetes.vibriospirillumspirochetenullnullElectron Micrograph of Vibrio choleraeCaption:-- Vibrio cholerae - Gram- negative, facultatively anaerobic, curved (vibrio-shaped), rod prokaryote; causes Asiatic cholera.nullnullBdello vibrionullHelicobacter pylorinullLeptospira interrogans nullnull柄细菌、肾形菌、臂微菌、网格硫细菌、贝日阿托氏菌(丝状) 等是特殊形态的细菌。细菌特殊形态null方形细菌 　　 星形细菌细菌特殊形态nullSize of Bacteria nullThiomargarita namibiensisColony charactersColony characters形状：圆形或不规则形状； 质地：粘稠、透明或干燥； 颜色：白色或有颜色； 表面：光滑或粗糙或有突起； 边缘：整齐或有缺刻； 大小：大或小 Colony charactersColony characters球菌 　小、圆、隆起 杆菌 　大、圆、隆起或扁平 产鞭毛 很大、不规则 产芽孢 透明度差，皮肤状皱褶 产荚膜 透明度高，鼻涕状，菌落大1.2 Construction of Bacterial Cell1.2 Construction of Bacterial CellnullOverview of the structure of microbial cells Procaryotic cell wall Cytoplasmic membrane Cellular genetic information Ribosome and Inclusions Components external to the cell wall Bacterial endospores Comparison of the prokaryotic and eukaryotic cellSector OutlinenullProcaryotic cellEucaryotic cell ① An Overview of Cell Structurenullnull3. Their cell wall almost always contain the complex polysaccharide peptidoglycanThe Prokaryotic Cell1. Their genetic material (DNA) is not enclosed within a membrane and they lack other membrane-bounded organelles2. Their DNA is not associated with histidine4. They are very smallnull②. Prokaryotic Cell WallCell WallnullThe cell wall of the bacterial cell is a complex, semi-rigid structure that is responsible for the characteristic shape of the cell. The cell wall surrounds the fragile plasma (cytoplasmic) membrane and protects it and internal parts of the cell from adverse changes in the surrounding environment. Almost all prokaryotes have cell walls.null细胞壁的功能： （1）固定细胞外形和提高机械强度； （2）为细胞的生长、分裂和鞭毛运动所必需； （3）渗透屏障，阻拦酶蛋白和某些抗生素等大分子物质（分子量大于800）进入细胞，保护细胞免受溶菌酶、消化酶和青霉素等有害物质的损伤； （4）细菌特定的抗原性、致病性以及对抗生素和噬菌体的敏感性的物质基础。nullSchematic diagram of bacterial cell wallsBacteria can be divided into two major groups, called gram-positive and gram-negative. The original distinction between G+ and G- was based on a special staining procedure, the Gram stain. nullnullThis method is named after its inventor, the Danish scientist Hans Christian Gram (1853–1938), who developed the technique in 1882 and published it in 1884 to discriminate between two types of bacteria with similar clinical symptoms: Streptococcus pneumoniae (also known as the pneumococcus) and Klebsiella pneumoniae bacteria The word Gram is always spelled with a capital, referring to the name of the inventor of the Gram staining.null He entered medical school in 1878 and graduated in 1883. He traveled throughout Europe between 1878 and 1885. In Berlin, in 1884, he developed a method for distinguishing between two major classes of bacteria. This technique, the Gram Stain, continues to be a standard procedure in medical microbiology. In 1891, Gram became a lecturer in pharmacology, and later that year was appointed professor at the University of Copenhagen. In 1900 he resigned his Chair in Pharmacology to become Professor of MedicineHans Christian Joachim Gram (1853 - 1938) was a Danish bacteriologist. Gram studied botany at the University of Copenhagen and was an assistant in botany. His plants introduced him to the basis of pharmacology and the use of the microscope.nullThe Gram-positive cell wall has a peptidoglycan （肽聚糖）layer that is relatively thick (20-80 nm) and comprises approximately 90% of the cell wall. The cell walls of most Gram-positive eubacteria also have teichoic acids（磷壁酸）.Gram-positive Cell WallnullStructure of the Repeating Unit in PeptidoglycanPeptidoglycan is composed of two sugar derivatives, N-acetylglucosamine (N－乙酰葡糖胺，NAG) and N-acetylmuramic acid (N－乙酰胞壁酸，NAM), and a small group of amino acids consisting of L-alanine(丙氨酸), D-alanine, D-glutamic acid（谷氨酸）, and either lysine （赖氨酸） or diaminopimelic acid (二氨基庚二酸 ，DAP). nullThese constituents are connected to form a repeating structure, the glycan tetrapeptide.nullStructure of one of the repeating units of the peptidoglycan cell wall structure, the glycan tetrapetidenullnullnullPeptide and glycan units are connected in formation of the peptidoglycan sheetnullGram-positive Bacteria frequently have acidic polysaccharides called teichoic acids attached to their cell wall. The term teichoic acids includes glycerophosphate（甘油磷酸） or ribitol phosphate residues（核醣醇磷酸）. Teichoic AcidsnullTeichoic acids and lipoteichoic acids（脂磷壁酸） are arranged in the overall wall structure of gram-positive Bacteria .Teichoic acidLipoteichoic acidnullGram-negative Cell WallnullThe outer membrane contains lipopolysaccharide (脂多糖，LPS) on its outer surface and phospholipid（磷脂） on its inner surface. The space between the outer membrane and the cytoplasmic membrane is called the periplasmic space（周质空间）. Teichoic acids do not occur in Gram-negative bacterial cell walls.. nullnullO side chainCore polysaccharideLipid AChemical Structure of LipopolysaccharidenullnullMolecular Model of E.coli LipopolysaccharidenullG+与G-菌的细胞壁的特征比较 nullnullThe bonds between the carbohydrates in pseudopeptidoglycan are β 1-3 instead of'β1- 4 as in peptidoglycan. Cell Walls of ArchaebacteriaThe archaebacteria do not contain peptidoglycan in their cell walls as occurs in eubacteria.N-acetylmuramic acid and D-amino acids are not found in the cell walls of archaebacteria. ( Differences from eubacteria )nullSome archaebacteria have walls composed of pseudopeptidoglycan, which resembles the peptidoglycan of eubacteria but contains N-acetyltalosaminuronic acid（N－乙酰塔罗糖胺糖醛酸） instead of N-acetylmuramic acid and L-amino acids instead of the D-amino acids in eubacterial cell walls.nullAre there any bacteria without cell walls?nullL-form of bacteria Mycoplasma(支原体) cell wall deficient bacterianullProtoplast Formation Peptidoglycancan be destroyed by certain agents for instance lysozyme, that breaks the 1,4-glycosidic bonds between N-acetylglucosamine and N-acetylmuramic acid in the molecule. null原生质体（protoplast）： 在人为条件下，用溶菌酶处理或在含青霉素的培养基中培养而抑制新生细胞壁合成而形成的仅由一层细胞膜包裹的，圆球形、对渗透压变化敏感的细胞，一般由革兰氏阳性细菌形成。 原生质球 (sphaeroplast) ，又称球状体 采用上述同样方法，针对革兰氏阴性细菌处理后而获得的残留部分细胞壁（外壁层）的球形体。与原生质体相比，它对外界环境具有一定的抗性，可在普通培养基上生长。 null特点： 对环境条件变化敏感，低渗透压、振荡、离心甚至通气等都易引起其破裂； 有的原生质体具有鞭毛，但不能运动，也不被相应噬菌体所感染； 在适宜条件（如高渗培养基）可生长繁殖、形成菌落，形成芽孢。及恢复成有细胞壁的正常结构。 比正常有细胞壁的细菌更易导入外源遗传物质，是研究遗传规律和进行原生质体育种的良好实验材料。 nullThe difference between gram-positive and gram-negative bacteria is due to the physical nature of their cell walls. If the cell wall is removed from gram-positive bacteria, they become gram negative. nullThe peptidoglycan seems to act as a permeable barrier preventing loss of crystal violet. Gram-negative peptidoglycan is very thin, not as highly cross-linked, and has larger pores. Alcohol treatment also may extract enough lipid from the gram negative wall to further increase its porosity. For these reasons, alcohol more readily removes the purple crystal violet-iodine complex from gram-negative bacteria.The Mechanism of Gram Stainingnull Procedures of Gram Stainingnullnull③. Cytoplasmic MembraneMembranenullB. Colorized electron micrograph of 'the cytoplasmic membrane (CM) of the bacterium Bacillus subtilis reveals the characteristic railroad track appearance of this lipid bilayer. Structure of Cytoplasmic MembraneIt is a typical UNIT MEMBRANE !A. The typical cytoplasmic membrane of prokaryotic and eukaryotic cells is a lipid bilayer, as illustrated here showing the orientations of the hydrophilic (tan spheres) and hydrophobic (black) ends of phospholipids that make up this structure. nullThe typical cytoplasmic membrane of prokaryotic and eukaryotic cells is a phospholipid bilayer.Structure of a phospholipid bilayer (8nm thick, 8000 lipid layers thickness= thickness of a piece of paper)Structure of a phospholipid bilayer (8nm thick, 8000 lipid layers thickness= thickness of a piece of paper)It is a typical UNIT MEMBRANE !nullThe cytoplasmic membrane Electron micrograph pf photosynthetic membrane stacks derived from cytoplasmic membrane in the phototrophic bacterium Halorhodospira halochloris. Note the distinct lipid bilayers Enlarged schematic view of a single unit membrane nullThe cytoplasmic membrane, a highly selective barrier, is constructed principally of lipid, within which certain proteins are embedded.Membranes contain both lipids and proteins.What else does the cytoplasmic membrane contain besides the phospholipid? What about the proportion of lipid and protein in cytoplasmic membrane? Are they same in different organisms?The exact proportions of lipid and protein vary widely.nullThe diagram of the structure of cytoplasmic membraneMembrane strengthening agents: sterol(固醇、甾酮) and hopanoid（藿类）Membrane strengthening agents: sterol(固醇、甾酮) and hopanoid（藿类）Sterols are rigid， planar molecules, found in eukaryotic membrane to strengthen the membrabe. They are absent from prokaryotes (methanotrophic bacteria and mycoplasm支原体 are exceptions). Hopanoids in bacteria membrane played the same role as sterols in eukaryotes. Hopanoids not present in Archaea.nullArchaeal membraneArchaeal membraneChemically unique Ether(醚键) linkage between glyceral and their hydrophobic side chain. Lack fatty acids instead have sides chains composed of repeating units of the five-carbon isoprene Some archaea have momolayer other than bilayer of lipid.nullnullnullThe cytoplasmic membrane, a highly selective barrier, is constructed principally of lipid, within which certain proteins are embedded.Membranes contain both lipids and proteins, although the exact proportions of lipid and protein vary widely.null Diagram of the structure of cytoplasmic membranenull3. Energy conservation site of generation and use of the proton motive force. Function of Membrane1. Permeability barrier prevents leakage and function as gate way for transport of nutrients into and out of the cell.2. Protein anchor site of many proteins involved in transport, bioenergetics, and chemotaxis.nullComparative permeability of membrane molecules to various nullIntracellular Membrane SystemBacteria cells don’t contain membrane-enclosed organelles. However, bacteria may have specialized invaginations of the cytoplasmic membrane. Their function may be to provide a larger membrane surface for greater metabolic activity.nullStructure of MesosomeMesosome may be involved in wall formation during division or play a role in chromosome replication and distribution to daughter cells. It may also be involved in secretory processesnull④. Cellular Genetic InformationNucleoidnullBacterial Chromosome Supercoiling and chromosome structure Chromosomal copy number PlasmidsnullMicrograph of a bacterium showing the nucleoid region (green) within the cytoplasm where the bacterial chromosome occursnullThe bacterial chromosome is a circular DNA macromolecule except in Streptomyces(链霉菌属) where it is linear and Rhodobacter（红细菌属） sphaeroides, which has two separate chromosomes. Bacterial ChromosomeThe bacterial chromosome is usually a single covalently closed circular molecule.The term nucleoid is used to describe aggregated DNA in the prokaryotic cell.nullRange of genome sizes in virious groups of organisms and the organelles of eukaryotesnullnullC值 基因组DNA全部碱基（对）数。C值是物种的一个重要特性常数。 乙肝病毒基因组C值 3.2×103 bp 痘病毒基因组C值 3.0×105 bp 人类基因组C值 3.3×109 bp C value paradox C值悖论：生物体的进化程度与基因组大小（ C值）之间不完全成比例的现象。 nullThe bacterial chromosome and supercoiling:nullExample of E. coli cellThere are over 50 supercoiled domain in the E.coli chromosome. The total amount of DNA is about 4600 kb. If the total DNA is opened and linearized, it would be 1 mm in length. The the cell is only about 2-3 μm long. So to package this much DNA into the cell requires that the DNA be highly supercoiled.nullElectron micrograph of an isolated nucleoid released from E. coli. nullChromosome copy number Bacteria that reproduce asexually are typically haploid in genetic complement. Rapidly growing cells contain more than 1 copy of the chromosome, and only when cell growth has ceased does the chromosome number approach one per cell.nullReproduction of a bacterial cell requires the replication of the bacterial chromosome. The micrograph shows the sequence of synthesis of new circular loops of double helical DNA.nullBacteria normally reproduce by binary fission. The inward growth of the septum divides the parent cell to produce two equal-sized progeny cells.null PlasmidProkaryotic cells have small extra-chromosomal genetic elements called plasmids.null Plasmids don’t contain the genetic information for the essential metabolic activities of the cell. They generally do contain genetic information for special features. nullResistant plasmids Col plasmids Conjugative plasmids Metabolic plasmids Major Types of Plasmidsnull⑤. Cytoplasmic Matrix Ribosome and InclusionsRibosome Carbon storage polymers - PHB and glycogen Phosphate polymers Sulfur Granules Gas VacuolesnullAll eucaryotic and procaryotic cells contain ribosomes, which function as the sites of protein synthesis. Ribosomes are composed of two subunits Procaryotic ribosomes are called 70S ribosomes, and those of eucaryotic cells are known as 80S ribosomes RibosomesThe letter S refers to Svedberg units, which indicate the relative rate of sedimentation during ultra-high-speed centrifugationnullnullnullnull Within the cytoplasm of procaryotic (and eucaryotic) cells are several kinds of reserve deposits, known as inclusions. Some inclusions are common to a wide variety of bacteria, whereas others are limited to a small number of species and therefore serve as a basis for identification. Among the more prominent bacterial inclusions are the following:Inclusion Carbon storage polymers – PHB and glycogen Phosphate polymers Sulfur Granules Gas VacuolesnullPolyhydroxybutyric acid (PHB)PHB is a lipidlike compound - one of the most common inclusion bodies in prokaryotic organisms. PHB is commonly found as a storage material and unique to bacteria. A Vibrio speciesnullGlycogen is a starchlike polymer of glucose subunits. Glycogen granules are usually smaller than PHB granules.nullMany microorganisms accumulate granules of polyphosphate, which are large reserves of inorganic phosphates that can be used in the synthesis of ATPPolyphosphate granule in a bacterial cellA Pseudomonas speciesnullThe sulfur globules inside the cells of purple sulfur bacteriumChromatium buderiSome bacteria, including many photosynthetic bacteria, accumulate elemental sulfur granules as a result of their metabolism.nullGas vacuoles (blue) and storage granules (red) in the cyanobacterium MicrocystisThe formation of gas vacuoles by aquatic bacteria provides a mechanism for adjusting the buoyancy of the cell. Many aquatic cyanobacteria use their gas vacuoles to move up and down in the water column.nullMegnetosomenullCrystalnull⑥ Components external to the cell wall Flagella Fimbriae and pili Capsules and slime layersnullFlagellanullMotility allows the cell to reach different regions of its environment. In the struggle for survival, movement to a new location may mean the difference between survival and death of the cell. But, as in any physical process, cell movement is closely tied to an energy expenditure, and the movement of flagella is no exception. Many prokaryotes are motile, and this ability to move independently is usually due to a special structure, the flagellum (plural, flagella). nullnullFour basic types of flagellar arrangementsa. monotrichousb. amphitrichousc. lophotrichousd. peritrichousnullFlagella are arranged differently on different bacteria. In polar flagellation the flagella are attached at one or both ends of the cell. Occasionally a tuft (group) of flagella may arise at one end of the cell, an arrangement called lophotrichous. In peritrichous flagellation the flagella are inserted at many places around the cell surface (peri means "around"). The type of flagellation, polar or peritrichous, is often used as a characteristic in the classification of bacteria.null The flagellum of a Gram-negative bacteriumnullThe filament of bacterial flagella is composed of subunits of a protein called flagellin. The base of the flagellum is different in structure from that of the filament. There is a wider region at the base of the flagellum called the hook. The hook consists of a single type of protein and functions to connect the filament to the motor portion of the flagellum. nullThe basal body is anchored in the cytoplasmic membrane and cell wall. The basal body consists of a small central rod that passes through a system of rings.In gram-negative Bacteria, an outer ring is anchored in the lipopolysaccharide layer and another in the peptidoglycan layer of the cell wall, and an inner ring is located within the cytoplasmic membrane.null In gram-positive Bacter