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Lecturer Mr. Zivuku .M Classification of Microorganisms Lecturer: Mr Zivuku M 1 Phylogeny: The Study of Evolutionary Relationships of Living Organisms Over 1.5 million different organisms have been identified to date. Many similarities among living organisms: Made up of cells surrounded by a plasma membrane. Use ATP as energy source. Store genetic information as DNA. Ribosomes are the site of protein synthesis. Both differences and similarities among organisms are caused by natural selection (Darwin, 1858). Organisms can be classified into taxonomic categories (taxa), Lecturer: basedMr on the differences and Zivuku M similarities among them. 2 Phylogeny: The Study of Evolutionary Relationships of Living Organisms Ancient Greeks classified all living organisms into two groups Kingdom Plantae Kingdom Animalia In 1850s bacteria and fungi were incorrectly placed in the Plant Kingdom. In 1860s Kingdom Protista was proposed to include bacteria, fungi, algae, and protozoa, but many scientists still classified bacteria and fungi as plants. Intense disagreement over classification of Lecturer: Mr Zivuku M bacteria and fungi persisted over 100 years. 3 Phylogeny: The Study of Evolutionary Relationships of Living Organisms In 1930s electron microscopy made it clear that bacterial cells lacked a nucleus. The term procaryote was introduced in 1937. In 1959 Kingdom Fungi was established. In 1961 the current definition of the term procaryote was established. In 1968 the Kingdom Procaryotae was accepted by biologists. In 1969 Robert Whitaker proposed a fivekingdom system of biological classification for Lecturer: Mr Zivuku M 4 all living organisms. Differences Between Eucaryotic and Procaryotic Cells Procaryotes Cell size 0.2-2 um in diameter Nucleus Absent Membranous Organelles Absent Cell Wall Chemically complex Ribosomes Smaller (70S) DNA Single circular chromosome Cell Division Binary fission Eucaryotes 10-100 um in diameter Present Present When present, simple Larger (80S) in cell 70S in organelles Multiple linear chromosomes (histones) Mitosis Lecturer: Mr Zivuku M 5 Procaryotes: Lack Nucleus and Membrane-Bound Organelles Lecturer: Mr Zivuku M 6 Lecturer: Mr Zivuku M 7 Prokaryotes: Bacteria and Archaea Unicellular and lack nuclei Much smaller than eukaryotes Found everywhere there is sufficient moisture; some found in extreme environments Reproduce asexually Lecturer: Mr Zivuku M 8 Prokaryotes: Bacteria and Archaea Two kinds – Bacteria – cell walls contain peptidoglycan; some lack cell walls; most do not cause disease and some are beneficial – Archaea – cell walls composed of polymers other than peptidoglycan Lecturer: Mr Zivuku M 9 The Six Kingdom Classification of organism Taxonomy is the branch of biology that names and groups organisms according to their characteristics and history. Lecturer: Mr Zivuku M 10 Kingdoms Archaebacteria Eubacteria Protista Fungi Plantae Animalia Lecturer: Mr Zivuku M 11 Kingdom Archaebacteria The members of the kingdom Archaebacteria (AHR-KEE-bak-TIR-eeuh) are unicellular prokaryotes. They differ from other forms of life by having distinctive cell membranes and different genetic and chemical properties. Autotrophic species of archaebacteria produce food by chemosynthesis Lecturer: Mr Zivuku M 12 Kingdom Archaebacteria Some members produce flammable gases, such as methane, as waste products. Archaebacteria are known to live in harsh environments such as sulfurous hot springs, very salty lakes, and oxygen deprived environments such as the intestines of animals. Lecturer: Mr Zivuku M 13 Kingdom Eubacteria Eubacteria (YOO-bac-TEER-ee-uh) are one-celled prokaryotes. You are in constant contact with these types of bacteria for they are responsible for such things as tooth decay, changing milk into yogurt, and some types of food poisoning. Most species of eubacteria use oxygen but there are a few species that are anaerobic. Lecturer: Mr Zivuku M 14 Kingdom Eubacteria They both reproduce primarily by binary fission. However, some have ways to recombine genes, allowing organisms with different characteristics to develop. It is this recombination of genes that accounts for the remarkably fast development of antibiotic-resistant bacteria. Lecturer: Mr Zivuku M 15 Kingdom Protista The kingdom Protista (pro-TIS-tuh) has a variety of eukaryotic organisms. Most are single-celled organisms but there are a few multicellular types such as giant kelp. Because protists are eukaryotic, they have a membrane-bound nucleus and membranebound organelles. Lecturer: Mr Zivuku M 16 Protozoa Single-celled eukaryotes Similar to animals in their nutritional needs and cellular structure Typically live freely in water; some live inside animal hosts Most reproduce asexually; some reproduce sexually Lecturer: Mr Zivuku M 17 Protozoa Most are capable of locomotion by -Pseudopodia – cell extensions that flow in direction of travel -Cilia – numerous, short, hairlike protrusions that propel organisms through environment -Flagella – extensions of a cell that are fewer, longer, and more whiplike than cilia Lecturer: Mr Zivuku M 18 Examples of Protozoa Lecturer: Mr Zivuku M 19 Examples of Protozoa Lecturer: Mr Zivuku M 20 Examples of Protozoa Lecturer: Mr Zivuku M 21 Algae Unicellular or multicellular Photosythetic Simple reproductive structures Categorised on the basis of pigmentation, storage products and composition of cell walls Lecturer: Mr Zivuku M 22 Examples of algae Lecturer: Mr Zivuku M 23 Examples of algae Lecturer: Mr Zivuku M 24 Fungi Eukaryotic (have membrane-bound nucleus) Obtain food from other organisms Possess cell walls Composed of: – Molds – multicellular; have hyphae; reproduce by sexual and asexual spores – Yeasts – unicellular; reproduce asexually by budding; some produce sexual spores Lecturer: Mr Zivuku M 25 Mycology, Fungi Widely distributed, found where moisture is present Exist in the form of filamentous hyphae Fungi digest insoluble organic matter by secreting exoenzymes, then absorbing the soluble nutrients 2 reproductive structure occur Lecturer: Mr Zivuku M 26 Fungi 1 . sporangia form asexual spores 2. gametangia form sexual gametes The zygospores have resting structures called zygospores (cells in which zygotes are formed) The ascomycetes form zygote within the club shaped structure and results in the production of ascospores Lecturer: Mr Zivuku M 27 Nutrition and Metabolism Grow best in dark moist habitat Are saprophytic Chemoheterophs + use organic material as source of carbon, electrons and energy Optimum pH5.5 some can grow at pH 2-9 Optimum temperature 20-35 deg C, pathogenic spp have a higher temp range Usually aerobic, some yeasts are facultative Lecturer: Mr Zivuku M 28 anaerobic Reproduction of Fungi Either sexual or asexual Asexual reproduction, no union or nuclei, sex cell or sex organs can be accomplished in several ways 1. A parent cell can divide into two daughter cells by central constriction and formation of new cell wall Lecturer: Mr Zivuku M 29 Reproduction of fungi 2. A hyphae can fragment to form cells that behaves as spores, called athrophores. If the cells are surrounded by thick wall before separation, they are called chlamydospores 3. Somatic vegetative cells or spores may bud to produce new organism (common in yeast) 4. Fungi can directly produce spores Lecturer: Mr Zivuku M 30 Examples of Fungi Lecturer: Mr Zivuku M 31 Examples of Fungi Lecturer: Mr Zivuku M 32 Kingdom Plantae The kingdom Plantae (PLAN-tee) is made up of multicellular plants. Most forms are Autotrophic and use photosynthesis as their source of energy. However, a few parasitic forms exist. Over 350,000 species of plants have been identified, most of whom live on land. Included in the kingdom Plantae are Lecturer: Mr Zivuku M mosses, ferns, conifers, and flowering plants. 33 Kingdom Animalia Eukaryotic, multicellular heterotrophic organisms make up the kingdom Animalia. Most animals have a symmetrical body organization and are mobile. Almost all animals reproduce through meiosis. Lecturer: Mr Zivuku M 34 VIROLOGY Virus means toxins This word came about before people actually found the causative agent of viral disease They presumed poisonous substance caused the disease present Viruses constitute the largest heterogeneous group of infecting agents Lecturer: Mr Zivuku M 35 Properties of Viruses They are obligate intracellular parasites for the cells of their specific hosts,. Viruses are the smallest infectious agents and are 20-30nm in size, These can only be seen by an electron microscope. Viruses contain either DNA or RNA as their genetic material, never both Viruses are not sensitive to antibiotics Lecturer: Mr Zivuku M 36 Morphology, Contains DNA or RNA coated by a protein coat Lecturer: Mr Zivuku M 37 BACTERIOPHAGES These are bacteria viruses which can only multiply inside a specific bacteria which they eventually lyses. A typical phage T4 can attack a bacteria where it exact its effect on the chromosome Adsorption, leading to either integration into the chromosome (lysogenic pathway) or replication of phage DNA(lytic pathway) Lecturer: Mr Zivuku M 38 Structure of phage, T4 Lecturer: Mr Zivuku M 39 Phagetyping Bacteriophages can be used in epidemiology to type microorganisms e.g. Salmonella spp and Staphylococcus spp in order to trace the source of infection. PHAGETYPING; is performed by growing the unknown bacterial culture, isolated from a patient on agar plate. Known phages are systematically spotted Lecturer: Mr Zivuku M 40 Phagetyping Spotted onto the confluent growth of bacteria After a suitable incubation period the zones or areas of lyses clearing called plaques appear if the particular bacteria is present From the phages that produce plaques, the bacteria host can be identified Used identification Salmonella typhi and Staphylococcus Lecturer: aureus (food poisoning) Mr Zivuku M 41 Classification of Organisms Scientific Nomenclature Scientific nomenclature: Universal system for naming and classifying living organisms. Initially developed in the 18th century by Carl Linnaeus. Binomial nomenclature: Each organism (species) has a two part name. Names are either italicized or underlined. Genus name: Always capitalized, always a noun. May use initial. species name: Always lower case, usually an adjective. Names are usually derived from Latin (or Greek) or may have latinized endings. Examples: Homo sapiens (H. sapiens): Human Penicillium notatum (P. notatum): Mold that produces penicillin Lecturer: Mr Zivuku M Canis familiaris (C. familiaris): Domestic dog 42 Taxonomic Categories Division (Bacteria) Lecturer: Mr Zivuku M 43 Classification of Organisms Hierarchy of Taxonomic Categories DOMAIN Kingdom Phylum or Division (Bacteria) Class Order Family Genus species Lecturer: Mr Zivuku M 44 Examples Streptococcus (strep throat) Staphylococci aureus(responsible for "staph" infections and gangrene) Escherichia coli or E.coli (found in the intestines of mammals) Salmonella typhi (causes typhoid fever and food poisoning) Lecturer: Mr Zivuku M 45