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INTRODUCTION TO MICROBIOLOGY LEARNING OBJECTIVES • At the end of the session the student should be able to: • Define Microbiology • Briefly describe the different fields of microbiology and their role in Diagnosis of infectious diseases. • Differentiate between Eukaryote and Prokaryote cells and the importance of the morphological difference in disease and dignosis of infections. Micro-organisms and Microbiology • Microbiology is the study of microorganisms; including bacteria, parasites,fungi and viruses • Microscopic, single cell, cluster, chains carry out life processes independently as single cells • Viruses- microscopic, non-cellular, RNA or DNA Branches of study within microbiology • • • • • Immunology Public health microbiology & epidemiology Food, dairy and aquatic microbiology Biotechnology Genetic engineering & recombinant DNA technology History of Microbiology: Antoj van Leeuwenhoek 1623-1723 1-Spontaneous generation 2-Germ theory of disease AGENTS • • • • • The agents of human infectious diseases belong to five major group of organisms: 1) Bacteria (prokaryote kingdom) 2)The fungi (yeasts and molds) (eukaryotes) 3) Protozoa (protists) Helminths (worms) (animal kingdom) Viruses (acellular) EUKARYOTES and PROKARYOTES • Cells have evolved into two fundamentally different types, eukaryotes and prokaryotes. which can be distinguished on the basis of their structure and the complexity of their organization. • Fungi and the protozoa are eukaryotic where as bacteria are prokaryotic 3 domains • Eubacteria -true bacteria, peptidoglycan • Archaea –odd bacteria that live in extreme environments, high salt, heat, etc • Eukarya- have a nucleus, & organelles Naming micoorganisms • Binomial (scientific) nomenclature • Gives each microbe 2 names – Genus - noun, always capitalized – species - adjective, lowercase • Both italicized or underlined – Staphylococcus aureus (S. aureus) – Bacillus subtilis (B. subtilis) – Escherichia coli (E. coli) Characteristics of microbes PROKARYOTES Components • • • • • • • • • • Cytoplasm Ribosomes Nuclear Zone DNA Plasmid Cell Membrane Mesosome Cell Wall Capsule (or slime layer) Flagellum • 1) The eukaryotic cell has a true nucleus with multiple chromosomes surrounded by a nuclear membrane and uses a mitotic apparatus to ensure equal allocation of the chromosomes to progeny cells. • 2) The nucleoid of a prokaryotic cell consists of a single circular molecule of loosely organised DNA lacking a nuclear membrane and mitotic apparatus • Prokaryotic cells like bacteria replicate by BINARY FISSION • Eularyotic cells contain organelles such as mitochondia and lysosomes, and larger (80S) ribosomes • Whereas prokaryotic cells contain no organelles and smaller (70S) ribosomes • Most prokaryotes have a rigid external cell wall that contains peptidoglycan a polymer of aminoacids and sugars as its unique structural component. • Eukaryotes do not contain peptidoglycan . They are bounded by a flexible cell membrane • The eukaryotic cell membrane contains sterol where as no prokaryotic cell except the wall less Mycoplasma has sterol in its membrane COMPARISION OF PROKARYOTES • Nucleus is absent. • Nuclear membrane is absent. • Dna is single,closely coiled loop • Chromosome no. Is 1. • Mambrane bound organelles absent • Ribosome size 70s • Dna not associated with histones. • Cell wall contains peptidoglycan. • Cell does not divide by mitosis. EUKARYOTES. • • • • • • • • • Nucleus is present Nuclear membrane is present. Dna is in arranged in multiple chromosomes More than 1 Membrane bound organelles are present. Ribisome size 80 s DNA associated with histones. Cell wall does not contain peptidoglycan. Cell divides by mitosis Hans Christian Gram 1843-1938 Gram (differential) stain – 1884 1. Fix organisms to slide with heat and stain with basic dye (crystal violet ) - then rinse 2. Apply iodine solution to form dye-I2 complex - then rinse 3. Wash with ethyl alcohol or acetone Gram-positive bacteria remain blue 4. Apply red counterstain (safranin) Gram-negative bacteria stained red Gram stain morphology • Shape – cocci (round) – bacilli (rods) – spiral or curved (e.g. spirochetes) • Single or multiple cells – clusters (e.g. staphylococci) – chains (e.g. streptococci) • Gram positive or negative (NON-GRAM STAINING BACTERIA) Viruses • Acellular entities too small to be seen with a light miroscope • Composed of nucleic acid and protein • Bacteriophage: viruses that infect bacteria • Viroids: nucleic acid without a protein coating • Prions: Infectious proteinaeceous particles **********************************