微生物学英语教学讲义.docx

Introduction to Microbiology 1. What is the unique features of Microorganisms?1.1 Small size, Simple structure Antoni Van Leeuwenhock: The word microorganism is used to describe an organism that is so small that, normally, it can not be seen without use of microscopy. The living organisms of microscopic size Most microorganisms are unicellular Some of them are non-cellular structure1.2 High diversityspecies. Bacteria ( actinomyce, algae, cyanobacteria)archaeafungi ( yeast, mold )protozoaviruse1.3 Widely distributed in various environment with large numberssoil. 109 CFU/gwaterairplants, animals, human bodyextreme environment, e.g. hot springs1.4 Fast growing, easy cultivation generation time, min.- hr.1.5 Easy mutation2. The place of microorganisms in the living world2.1 whittakers five kingdom concept (1969) Kingdom plantae Kingdom animalia Kingdom fungi Kingdom protista Kingdom monera This classification system was based on nutrition, photosynthesis, absorption and ingestion.2.2 Woeses three domains ( kingdoms) Domain bacteria Domain Archaea Domain eucarya3. The scope of microbiology Microbiology is the study of living organisms of microscopic size, which include bacteria, fungi, algae, protozoa and viruses. It is concerned with their morphology, reproduction, physiology, metabolism, genetics and classification. It includes the study of their distribution and function in nature, their relationship to each other and to other living organisms, their effects on human beings, animals and plants.4. Why do we study microbiology?Microorganisms affect the well-being of people in a great many ways. They occur in large numbers in most natural environments. Some of them are beneficial and others are detrimental.4.1 The beneficial aspects In Agriculture Microbial fertilizer Biological control SCP Microbial energy: methane gas for rural consumption In food production yogurt, cheese, wine(alcohol fermentation) food ingredients In environment protection treatment of waste materials to decompose materials: pesticides, herbicides In Biochemical industry Antibiotics enzymes Amino acides organic acids in medicine Vaccine Antibiotics penicillin The potential applied areas of Microbiology GMO Recombinant DNA technology Microbial plastics Microbial pesticides Microbiosensor M传感器 Microbial fuel cells 微生物燃料电池 Microbial DNA chip 微生物DNA芯片 Exploitation of microorganisms in extreme environments4.2 The detrimental aspects Cause diseases: human beings animals Plants spoil food deteriorate materials: iron pipes, wood, clothObjectives: make full use and exploitation of the beneficial aspects; avoid and control the detrimental aspects  Chapter 1 The Morphology and Fine Structure of Microorganisms 1. Procaryotic Microorganisms1.1 Features distinquishing procaryotic from Eucaryotic cells featureProkaryotic cellsBacteria ( archaea)Eucaryotic cells(fungi, protozoa, plant, animal)Cell wallCell membrane    Cytoplasmic structuresMesosomeRibosomeMitochondriaChloroplastGolgi structureEndoplosmic reticulumnucleusPeptidoglycan as componentGenerally do not contain sterol; contain part of respiratory and, in some, photosynthetic machinery invagination Present70SAbsentAbsentAbsentAbsentNot bounded by nuclearmembrane; one circularchromosome,Chromosome does notContain histones; no mitotic divirsionNucleolus absentAbsente of peptidoglycanSterols present; do not carry out respiratory and photosynthesis  non absent80SpresentpresentpresentpresentBounded by nuclear membrane;More than one chromosome Chromosomes have histones;Mitotic nuclear division Nucleolus present 1.2 Bacteria1.2.1 The size, shape and arrangement of bacterial cell sphierical cocci, coccus um; diameterA: diplococci B: streptococciC: tetradsD: staphylococciE: Sarcinae straight rods: widnth x Length um, bacilli, bacillus, Lactobacillus helically curved rods: spirilla, spirillum width x Length um (No. of curve) filament: hyphae, hypha myceliumdiameter of hypha mActinoinyces: streptomyces species some are not constant, but pleomorphic shape1.2.2 Simple staining techniqueThe coloration of bacterial cell by applying a single solution of stain to a fixed smear is termed simple staining.Steps: Smear bacterial cells on a slide dry and fix The fixed smear is flooded with a dye solution for a specified period of time Wash off with H2O and dry the clide exame the size. Shape and arrangement of bacterial cells under microscope1.2.3 The structures and functions of bacterial cells1.2.3.1 Structures external to the cell wallA. Flagella, Flagellum Bacterial flagella are hairlike, helical appendages that protrude through the cell wall and are responsible for swimming motility. chemical composition: protein subunits: flagellin Location: polar: at one or both ends of the bacterium Lateral: alone the sides of the bacterium function: swimming motility gliding motility: some bacteria are motile when they are in contact with a solid surface. As they glide they exhibit a sinuous, flexing motion. This kind of movement is comparatively slow, only a few um per second. Bacterial chemotaxismany, perhaps most, bacteria are capable of directed swimming toward or away from various chemical compoundsa phemomenon called bacterial chemotaxis Bacterial phototaxis phototrophic bacteria move towards increasing light intensities. Pili, pilus( fimbriae) Pili are nonhelical, filamentous appendages that are thinner, shorter, and more numerous than flagella. The well known is the F pilus ( or sex pilus), it serves as the port of entry of genetic material during bacterial mating.B. Capsules Some bacterial cells are surrounded by a viscous substance forming a covering layer or envelope around the cell wall. If this layer can be visualized by light microscopy using special staining method, it it termed a capsule. If it is too thin to be seen by light microscopy, it is termed microcapsule. If is so abundant that many cells are embedded in a common matrix, the material is called slime.  The conditions that some bacteria produce capsule High carbon content in media, low nitrogen The chemical composition of capsule polysaccharides polypeptides The functions of capsule They may provide protection against temporary drying by binding water molecules They may block attachment of bacterophages They may promote attachment of bacteria to surfaces, e.g. Streptococcus mutans, a bacterium associated with producing dental caries, firmly adheres to the smooth surfaces of teeth because of its secretion of a water-insoluble capsular polysaccharide.C. spore and cyst defination: under the undesirable growth conditions,e.g. Lack of nutrients, too acid, temperiture is too high, Some species of bacteria produce thick-walled structure which is metabolically dormant and can undergo germination and outgrowth to form a vegetative cell. This special structure is termed spore which is either within the cell (endospore) or external to the cell (exospore). shapes:  function: spores are extremely resistant to desiccation, staining, disinfecting chemicals, radiation, and heat. Some of sproes can resist boiling for several hours, most of spores can resist heat treatment at 80 for at least 10 minutes. Dormant structure. Cyst: cyst resembles endospore, especially desiccation-resistant. But it does not resist to heat treatment. Genus Azotobacter cyst1.2.3.2 The cell wall defination: A very rigid layer external to the cytoplasmic membrane. The main function is to give shape to the cell and prevent the cell from expanding and eventually bursting because of uptake of water. peptidoglycan: an insoluble, porous, cross-linked polymer of enormous strength and rigidity. Differential staining: staining procedures that make visible the differences between bacterial cells or parts of a bacterial cell are termed differential staining technique. The cells may be exposed to more than one dye solution or staining reagent. Gram staining: one of the most important and widely used differential staining techniques in microbiology is Gram staining. This technique was introduced by Christian Gram in 1884. In this process the fixed bacterial smear is subjected to the following reagents in the order listed: crystal violet, iodine solution, 95% alcohol (decolorizing agent), and safranin or some other suitable counterstain. Bacteria stained by the gram method fall into two groups: Gram positive bacteria (G+), which retain the crystal violet and hence appear deep violet in color; and Gram negative bacteria (G-), which lose the crystal violet, are counterstained by safranin, and hence appear red in color. Why does this proceduce stain some bacteria purple-violet and others red?  The wall of Gram positive bacteria the structure and chamical composition  The wall of Gram negative bacteria The structure and chemical composition  1.2.3.3 The cytoplasmic MembraneImmediately beneath the cell wall is the cytoplasmic membrane. This structure is approximately 7.5nm thick and is composed mainly of phospholipids (2030%) and proteins (6070%). Mesosomemany bacteria, especially G+ bacteria, possess membrane invaginations in the form of convoluted and vesicals termed mesosome. Functions of mesosome: DNA replication cell division export of exocellular enzyme The functions of cytoplasmic membrane the CM is a barrier to penetration by most molecules; specific proteins in the memtrane allow and facilitate the passage of small molecules (e.g. nutrients, waste products); The CM contains various enzymes involved in respiratory metabolism and phtosynthesis. CM is the site of ATP generation, synthesis of capsular and cell wall components.1.2.3.4 The cytoplasm RibosomeIn the cytoplasmic area, granular in appearance and rich in the macromolecular RNA-protein bodies known as Ribosomes, on which proteins are synthesized. In the prokaryotic cells, the sedimentation coefficient of ribosome is 70S. PHB: polyhydroxybutyrate1.2.3.5 The genetic materials The nucleus not bounded by nuclear membrane one circular chromosome chromosome does not contain histones nucleolus absent Plasmid In addition to the normal DNA chromosome, extrachromosomal genetic elements are offen found in bacteria. These elements are called plasmids, and are capable of autonomous replication in the cytoplasm in the bacterial cell. Plasmids are circular pieces of DNA that are extra genes.1.2.2 Bacterial Reproduction and colony1.2.2.1 Reproduction Transverse Binary Fission The most common mode of bacterial cell division in the usual growth cycle of bacterial populations is transverse binary fission, in which a single cell divides into two cells after developing a transverse septum. Transverse binary fission is an asexual reproductive process.   Buddingsome bacteria reproduce by budding, a process in which a small protuberance ( bud ) develops at one end of the cell. This enlarges and eventually develops into a new cell which separates from the parent.   FragmentationBacteria that produce extensive filaments, such as Nocardia species, reproduce by fragmentation of the filaments into small bacillary or coccoid cells, each of which gives rise to a new cell.   Formation of conidiospores or sporangiosporesSpecies of the genes streptomyces and related bacteria produce many spores by developing crosswalls (septation) at the hyphal tips. Each spore gives rise to a new cell.  1.2.2.2 Colony formation Colony: visible aggregate of bacterial growth on a solid culture medium. It is a important characteriastics for identifying a certain bacterial species. Colony-forming unit: aggregate of cells gives rise to a single colony in the platecount technique. Abbreviation:cfu1.2.3 Actinomycetes1.2.3.1 The characteristics of Actinomyctes G+ bacteria Filamentous substrate myceliumhyphaemycelium aerial mycelium conidiospores forming spores sporangiospores Reproduction Fragmentation Formation of spores colony Size small, round shape, tight, dry, diverse color, smell soil. nutrient and environmental factors required for growth chemoorganotroph aerobe neutral pH optimal growth temperature: 23375065 They are distributed mainly in soils. They can grow in soils which have less water content than that needed for most other bacteria, because of their spores that can survive well in dry soil. denifination:Actinomycetes: Gram positive bacteria that are characterized by the formation of branching filaments and spores.1.2.3.2 The roles of Actinomycetes in nature Many actinomycetes, such as, streptomycetes, can degrade polymeric organic substances in soil that are refractory to being decomposed by many other microorganism, e.g., starch, pectin, chitin produce antibiotics, antifungal antibiotics Fix N2: Frankia, These group of bacteria are highly efficient microaerophilic N2fixers that occur within the root nodules of plants. Unlike Rhizobium spcies, however, they infect nonleguminous woody plants, such as alders. some species are pathogenic to plants and humans.1.2.4 Cyanobacteria prokaryotic oxygenic photolithotrophs containing chlorophyll a and phycobilins Algae: phototrophic eukaryotic microorganisms1.3 ArchaeaAn evolutionarily distinct domain of prokaryotes consisting of the methanogens, most extreme halophiles and hyperthermorphiles, and Thermoplasma.  2. Eucaryotic Microorganisms2.1 Features distinguishing Eucaryotic fro prokaryotic cells, see 1.12.2 FungiMolds and yeasts2.2.1 Characteristics of fingi2.2.1.1 Morphology2.2.1.1.1 Yeastyeast cells are larger than most bacteria. Yeasts vary considerably in size, ranging from 15 m in width and from 530m or more in length. They are commonly eggshaped, but some are spherical. Each species has a characteristic shape, but even in pure culture there is considerable variation in size and shape of individual cells, depending on age and environment.2.2.1.1.2 MoldThe thallus of a mold consists essentially of two parts: the mycelium (mycelia) and the spores ( resistant, dormant cells) The mycelium T