Classification Of Microorganisms Postlab Midterm PDF

CLASSIFICATION OF MICROORGANISMS Microbiology the study of many diverse organisms, including: archaea bacteria protozoa algae fungi acellular entities Domains of Living Organisms Eukarya – contains all members of the living world except for the prokaryotes; includes algae, f...

CLASSIFICATION OF MICROORGANISMS Microbiology the study of many diverse organisms, including: archaea bacteria protozoa algae fungi acellular entities Domains of Living Organisms Eukarya – contains all members of the living world except for the prokaryotes; includes algae, fungi, and protozoa Bacteria – unicellular; generally small in comparison to eukaryotic organisms and very diverse in terms of cell shape, motility, metabolism, and oxygen requirements; most do not cause human disease, but many diseases are due to bacteria Archaea – have the same basic shape, size, and appearance of bacteria but have biochemical differences; tend to inhabit extreme environments of heat, cold, pH , or salt concentration Medically Significant Entities Viruses – lack many of the characteristics of living cells, including the ability to replicate without the assistance of host cell biosynthetic processes Prions – are proteinaceous in nature and yet infections DOMAIN BACTERIA Taxonomy and Nomenclature Bacteria are grouped and named primarily based on: morphologic characteristics biochemical characteristics Bacteria are named using the binomial Linnaean system as a genus and species; some are classified with subspecies or strain designations Staphylococcus aureus Escherichia coli O157:H7 Morphology Morphology is the classification of bacteria by shape and structure Colony morphology – based on the size, color, shape, and texture of colonies that are grown in pure culture on an agar plate Microscopic morphology – describes bacteria base on the size, shape, and arrangement of the cells Morphology Colony characteristics include: Size – colonies range from pinpoint (less than 1 mm) to as large as 5-10 mm in diameter; only well-separated colonies shoudd be measured since they tend to have larger diameter when crowded Margin – the periphery of the colonies may be entire, with rounded projections, notched, threadlike, filamentous, serrated, or lobate Morphology Colony characteristics include: Surface texture – the surface may be smooth (shiny, glisterning); rough (dull, granular); mucoid (slimmy or gummy); wrinkled, concentric, contoured, etc.; the surface texture can serve as indicator of virulence Elevation – the colonies may be flat, raised or convex Consistency – this can be determined by touching the colony with a transfer needle; some may have butyrous (butterlike), viscous, stringy, rubbery, dry, brittle, or powder consistency Morphology Colony characteristics include: Optical features – colonies may be transparent, translucent, or opaque Pigmentation – some bacterial species produce pigmented colonies; examples are: Serratia marcescens – red Staphylococcus aureus – gold Micrococcus luteus - yellow Bacteroides melaninogenicus - black Pseudomonas aeruginosa – blue green Colony Morphology Colony Morphology Colony Morphology Colony Morphology Colony Morphology Staphylococcus aureus Staphylococcus epidermidis Bacterial Shape and Arrangement Cocci Spherical and exist in chains (e.g. Streptococcus species) Pairs/diplococci (e.g. Neisseria gonorrhea) Clusters (e.g. Staphylococcus species) Bacilli cylindrical and rod-shaped organisms (e.g. pseudomonads, Escherichia) Coccobacili short, rounded rods (e.g. Haemophilus) Bacterial Shape and Arrangement Spirochetes and spirilla are helical like a corkscrew (e.g. Treponema pallidum) Vibrios are comma-shaped rods (e.g. Vibrio cholerae) Pleomorphic organisms exist in varied forms (e.g. Legionella, Corynebacterium) Examples of Medically Important Bacteria BACTERIA DISEASE Treponema pallidum Syphilis Neisseria gonorrhea Gonorrhea Salmonella typhosa Typhoid fever Vibrio cholerae Cholera Yersinia pestis Bubonic plague Staphylococcus aureus Boils Clostridium tetani Tetanus Clostridium botulinum Botulism Legionella pneumophila Legionnaire’s disease Microscopic Morphology Staphylococcus aureus Microscopic Morphology Streptococcus pneumoniae Microscopic Morphology Vibrio cholerae Microscopic Morphology Treponema pallidum Microscopic Morphology Bacillus subtilis Microscopic Morphology Escherichia coli Stains Because of their small size and relative transparency, bacteria must be stained to be visible under the light microscope Staining characteristics may be used in classification The major types of staining reactions are: Simple stain Gram stain Acid-fast stain Endospore stain Capsule stain Simple Stain The simple stain uses a single stain to color the cells Examples: methylene blue basic fuchsin crystal violet safranin Gram Stain Gram stain is a differential staining procedure in which the purple stain is retained in the thick peptidoglycan layer of the gram-positive bacteria, whereas the color is removed by an alcohol rinse from the thinner gram-negative walls. The Gram-negative cells are then stained red by the counterstain, safranin.  Characteristic Gram-Positive Gram-Negative Gram reaction Retain crystal Can be violet dye and decolorized to stain blue or accept purple counterstain and stain pink or red Peptidoglycan layer Thick Thin (single- (mutilayered) layered) Teichoic acids Present in many Absent Periplasmic space Granular layer Periplasm Outer membrane Absent Present Lipopolysaccharide Virtually none High (LPS) content  Characteristic Gram-Positive Gram-Negative Lipid and lipoprotein Low (acid-fast High (because of content bacteria have presence of outer lipids linked to membrane) peptidoglycan) Flagellar structure 2 rings in basal 4 rings in basal body body Toxins produced Exotoxins Endotoxin and exotoxins Resistance to High Low Physical Disruption Cell Wall Disruption High Low (requires by Lysozyme pretreatment to destabilize outer membrane)  Characteristic Gram- Gram- Positive Negative Susceptibility to Penicillin High Low and Sulfonamide Susceptibility to Low High Streptomycin, Chloramphenicol, and Tetracycline Inhibition by Basic Dyes High Low Susceptibility to Anionic High Low Detergents Resistance to Sodium High Low Azide Resistance to Drying High Low Gram Stain Staphylococcus aureus Escherichia coli Gram Stain Gram Positive Gram Negative Staphylococcus Escherichia Streptococcus Pesudomonas Bacillus Salmonella Clostridium Shigella Corynebacterium Neisseria Lactobacillus Haemophilus Listeria Acid Fast Stain The acid-fast stain uses a procedure to stain cells that have an outer layer of a waxy lipid (acid-fast, stained red). The waxy layer prevents removal of the stain by an acid rinse. The stain is removed from cells that lack the waxy layer, which are then counterstained blue (non-acid-fast). Staining methods: Zeihl-Neelsen Method Kinyoun Method Endospore Stain The endospore stain involves a procedure that uses heat to help dye enter the endospore. The Schaeffer-Fulton method uses Malachite green and heat to stain the endospore while safranin is used to stain the vegetative portion of the cell. Endospore location can either be central, subterminal, or terminal. Capsule Stain The capsule stain is a colloidal suspension that is excluded from areas occupied by capsule and allows detection of the unstained capsular material. Negative stain – most commonly used method India ink – stain used Organisms that contain capsule: Streptococcus mutans Klebsiella pneumoniae Bacillus anthracis