일반미생물 강의 1장 미생물과 미생물학(출처:연세대학교 생명공학과)

Chapter 1: Microorganisms and Microbiology 1.1 Microbiology and You (1) Microbiology: The study of very small living organisms. ● Micro: very small, bio: the living organisms. ology: the study of ● The microbiology thus includes the study of prokaryotic microorganisms (bacteria and Archaea), eukaryotic microorganisms (protozoa, fungi, algae), and viruses. (2) Fields of Microbiology: ● Basic biological Sciences: Bacteriology, Phycology (study of various types of algae), Mycology (study of fungi), Protozoology (study of protozoa and their activities), Virology, General Microbiology, Medical Microbiology, Veterinary Microbiology, Industrial Microbiology ●Applied biological sciences 1.2 Microorganisms as cells ● The living cell is a nonequilibrium system (open system) ● Cells: fundamental unit of all living matter consisted of cell membrane (separate the inside of the cell from the outside), nucleus or nuclear region (store genetic information), and the cytoplasm (contain the machinery for cell growth and function). ● Components of cells: proteins, nucleic acids, lipids, and polysaccharides. ● The hallmarks of cellular life (Fig. 1.3) (1) Metabolism (2) Reproduction (3) Differentiation (4) Communication (5) Evolution ● Two views of a cell: (Fig. 1.4) -Machines carrying out metabolic reactions, which are catalyzed by enzymes (functional proteins with catalytic activities) -Coding devises: passage and translation of genetic information ● What is the enzyme? Functional proteins composed of 20 types of amino acids. The amino sequences of enzyme determine its structure as well as its catalytic specificity. ● The genetic information is stored as a genetic code in deoxyribonucleic acid, DNA. Each amino acid is coded by a sequence of three bases, triplet code. ● The genetic code is copied or replicated and translated into the amino acids. Transcription - formation of messenger RNA containing a copy of the information of DNA. Translation -occurs on ribosomes composed of protein and ribonucleic acid (rRNAs and and mRNA templates) -E. coli DNA 4,600 kilobases (kb) &agrave; about 4,300 genes (assuming one gene is about 1.1 kb): protein expression‎ level is controlled at the transcription and translation levels 1.3 Elements of Cells and Viral Structure ● Elements of cells and viral structure (Fig. 1.5) Cell wall (most microorganisms and plant but not on animal cells) Cell membrane Cytoplasm (contains water, macromolecules, ribosomes required for protein synthesis, small organic molecules, and various inorganic ions) ● Prokaryotic and Eukaryotic Cells Prokaryote (bacteria) and eukaryote (algae, fungi, and protozoa, all higher life forms such as plants and animals) Size of microorganisms: 1-2 mm long, thus invisible to the naked eye Arrangement of DNA in Prokaryotic and Eukaryotic cells and the Genetic Potential of the Cell (1) Prokaryotic cells Bacterial chromosomes -single copy in circular and double stranded form -aggregate to form a visible mass in the electron microscope called the nucleoid. Plasmids: small size extra chromosomal DNA in a circular form (2) In eukaryotes -Several chromosomes in a liner form ● Viruses: -not cells -infect all kinds of living organisms -have their genetic elements (DNA or RNA) -use host translation apparatus for protein synthesis. 1.4 Evolutionary Relationships among Living Organisms ● A single cell grows in size and divides into two cells. During copying of DNA, mutations can occur by mistakes, which often result in a formation of defective proteins and enzymes. Natural selection (the process of evolution) might one of reasons responsible for the diversity of microorganisms and higher organisms ● Phylogenetic relationships between microorganisms: by sequence comparision of 16S and 18S ribosomal RNA (structural RNA of the ribosome) ● Fig. 1.8: three domains of life Bacteria: microbial and prokaryotic Archaea: microbial and prokaryotic Eukaryotic: microorganisms (Algae, fungi, protozoa), macroorganisms (plant and animals) ● The Prokaryotic cells Cell wall: a rigid structure outside of the cell membrane providing support and protection of cell from environment. Cell membrane: barrier separating inside from outside of the cell. Ribosomes: small particles composed of protein and RNA Nuclear region: chromosome present within the cell in a more or less free state (compare with nucleus in eukaryotic cells) (other genetic material: plasmids-small circular DNA) Flagella: many, but not all, prokaryotic cells have proteins attached on the cells (coiled tube shape) allowing cells to move by propelling the cells by the rotation of flagella. Size and shape of prokaryotes -0.1 mm-5 mm in diameter -coccus (spherical or egg-shaped, pl: cocci) -rod or bacillus (cylindrical shape) -spirilla (curved rod) -coiled (like spirochetes) -appendaged bacteria (possessing extensions of their cells as long tubes or stalks) Bacterial endospores The spore forming bacteria can form endospores under certain conditions such as starvation of nutrients, which causes growth arrest. The dormant and inactive form of bacteria is resistant to heat and cannot be killed easily. The endospores start normal growth by spore germination under proper conditions. ● The Eukaryotic Cell Eukaryotic cells are larger and more complex in structure and function than prokaryotic cells. Eukaryotes contain true nuclei and organelles with distinct structures. Nucleus: a special membrane-surrounded structure containing chromosomal DNA (chromosome). By mitosis, each daughter cell receives a nucleus with an identical set of chromosomes. Organelles: Mitochondria (energy-generating function), chloroplast (algae use light energy for photosynthesis) Mobility in eukaryotes: Flagella: long filamentous structures, composed of two central protein fibers Cilia: shorter than flagella and more numerous (1) Algae Algae contain chlorophyll, a green pigment in the chloroplast, where photosynthesis occurs. Algae can be either unicellular or colonial (end-to-end filamentous structure or complicated branched filaments, resulting in large masses as aggregates which can be seen in small ponds or streams or even fish tanks. (2) Fungi: molds, yeast, and mushrooms -contain no chlorophylls. -larger than bacteria and can be observed easily by the ordinary light microscope. -Three major groups of fungi: molds, yeasts, and mushrooms Molds -filamentous fungi (seen on stale bread, cheese, or fruit) consisted of a hypha (pl: hyphae). -Hyphae usually grow together to form rather complex tufts, called a mycelium, which can be seen without a microscope. -Aerial hyphae is extended from the surface of the mat-like mycelium, and conidia (spores) with round structures (open pigmented: black, blue-green, red, or brown). -reproduced by asexual or sexual spores. Yeasts -unicellular fungi -spherical, oval, or cylindrical shape -reproduced by budding -do not form filaments or a mycelium but remain as a collection of single cells. -Some yeasts are reproduced by mating between two yeast cells to form a zygote from which spores are generated. Mushrooms -group of filamentous fungi that form complicated structures called fruiting bodies (often called the mushrooms) -Simple mycelium form &agrave; formation of button-shaped structure underground, then expanding into the full-grown fruiting body above the ground (under favorable environmental conditions) &agrave; formation of sexual spores, basidiospores (on flat plate of gills or within deep pores; some mushrooms, puff balls, produce their spores within spherical fruiting bodies). (3) Protozoa -unicellular and motile eukaryotic microorganisms lacking cell walls and chlorophyll. -uptake other organisms or organic particles by swallowing them through gullet. -The amoebae move by amoeboid locomotion; flows of the cytoplasm forward a pseudopodium (false foot) on a solid surface. -the flagellates move by use of flagella attached at one end of the cell. -The typanosomes causing African sleeping sickness and a number of other diseases of human and animals move by flagella. -The ciliates move by the action of cilia, a large number of smaller appendages. -The nonmotile sporozoans (do not form true spores as indicated by the name), consisting of Plasmodium vivax causing malaria, absorb dissolved food materials directly through their membranes. ●Classification and Nomenclature -Genus - species in italics -Escherichia coli or E. coli 1.5 Microbial Populations, Communities, and Ecology ● Prokaryotes (eubacteria and archaebacteria: now Archaea is grouped separately) and eukaryotes (plants and animals, and three major microorganisms such as algae, fungi, and protozoa) ● Populations, Communities, and Ecosystems Summary of terminology: Habitat: the location in the environment where a population lives Ecology: study of living organisms in the natural environments Community: populations of cells living in association with other populations of cells Ecosystem: the living organisms together with the physical and chemical constituents of the environment Biosphere: the global ecosystem, the earth as a whole as an ecosystem consisted of the atmosphere and the lithosphere 1.6 Laboratory Culture of Microorganisms ● Microscopic examination and pure culture procedures are two basic techniques for the study of the structure and function of microorganisms. ●The Culture of Microorganisms -Pure culture: a culture consisting of only one kind of microorganism without contaminants (unwanted organism) -Culture media: aqueous solution containing nutrients required for microbial growth. -Petri dish: solid culture media, which can be used for single colony isolation -Aseptic techniques 1.7 The Impact of Microorganisms on Human Affairs: Fig. 1.14 1.8 The Historical Roots of Microbiology: van Leeuwenhoek, Pasteur, and Koch ● Spontaneous generation vs germ theory -Pasture’s experiments with the swan-necked flask: supporting the idea that the germs are from the air but not from nonliving materials (Fig. 1.18). -Koch and germ theory of disease: Koch’s postulates: experiments with Bacillus anthracis and Mycobacterium tuberculosis (Fig. 1.19) 1.9 Transition into the Twentieth Century ● Enrichment culture: by Martinus Beijerinck ● Table 1.1 ● 21st Century: Metabolic engineering, Use of unculturable organisms, DNA microarray, Genomics and Proteomics