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INTRODUCTION TO MICROBIOLOGY July 22, 2013 8th Grade Microbiology the study of microscopic organisms, either unicellular, multicellular (cell colony), or acellular Includes the disciplines virology, mycology, parasitology, bacteriology, and so on Microbes Oldest form of life on earth Simple life forms, reproduce rapidly Found everywhere!! Some are pathogenic Some are beneficial Major categories of microbes Bacteria Parasites fungi And algae Viruses Bacteria Morphology There are three basic shapes for bacteria Cocci – round Bacilli – rod shaped Spirochetes – spiral Bacteria Metabolic needs of bacteria 3 different types Obligate aerobes Need oxygen to survive Aerobic respiration Obligate anaerobes Cannot survive in the presence of oxygen Use fermentation Facultative anaerobes Can use both aerobic respiration and fermentation Bacteria Cell Structure Nucleoid Where the DNA is generally found DNA is in the form of a plasmid Is not bound by a membrane, but is a visually distinct region in the cell Cytoplasm Everything enclosed by the plasma membrane About 80% is water Contains nucleic acids, enzymes, amino acids, carbohydrates, lipids, inorganic ions Liquid component is called the cytosol Quick Question What are the three shapes of bacteria? Cocci, bacilli, spirochetes Quick Question What method to obligate aerobes use? Aerobic respiration What about anaerobes? Fermentation Facultative anearobes? Both Bacteria Cell structure Ribosomes Plasma Membrane Look like little granules in the cytoplasm Smaller than the ribosomes in Eukaryotic cells But have a similar function: translating messenger RNA into proteins Lipid bilayer much like the plasma membrane of other cells Has proteins that move within the layer that transport ions, nutrients, and waste Cell Wall Composed of peptidoglycan Maintains overall shape of bacterial cell Mycoplasma Bacteria that have no cell wall = no defined shape Bacteria Cell Structure Pili Hollow, hair-like structures made of protein Allow bacteria to attach to other cells Sex Pilus A special kind of pilus Allows the transfer of material from one bacterial cell to another Flagella Long appendages that rotate by means of a “motor” located just under the plasma membrane For motility Bacteria may have one or many flagella in different positions on the cell flagellum video Gram Staining The layer of peptidoglycan protects the bacterial cell and is often associated with pathogenic bacteria because it serves as a barrier against phagocytosis by white blood cells Quick Question Why does gram staining work? Because of the layer of peptidoglycan This layer differs between various bacteria…so you can test by staining. Thick (significant) layer = gram positive (purple) Holds the stain Thin (insignificant) layer = gram negative (pink) Can’t hold the stain…retains counterstain Virus Is a submicroscopic particle that can infect the cells of a biological organism Are not plants, animals, or bacteria…but are parasites of the living kingdoms Not considered to be living organisms Virus The ultimate parasite Rely on their host for survival Have genetic material (DNA or RNA) but lack ribosomes needed to translate it into proteins Cannot generate or store energy in the form of ATP Have to derive their energy and all other metabolic functions from the host cell They basically take control of the host cell and use it for its needs They also rob the host cell for the basic building materials Amino acids, nucleotides, lipids Viral Genetic Material All viruses have DNA or RNA, but not both It can be single or double stranded This genetic material is then transcribed into proteins using the host cell’s machinery Virus Structure Can be complex (bacteriophage), helical, round, enveloped, or polyhedral in shape Virus Capsid Is the protein shell that encloses the virus Has three functions: Protects the virus from digestion by enzymes Contains special sites on its surface that allow the cell to attach to a host cell Provides proteins that enable the virus to penetrate the host cell membrane Virus Viral envelope Many viruses have a glycoprotein envelope surrounding the capsid Is composed of a phospholipid bilayer, complete with interspersed proteins Major viruses and their diseases varicella zoster virus (chickenpox) Rabies virus (Rabies) Influenza virus (flu) West Nile Virus Dengue virus (dengue fever) Herpes Zoster (shingles) Quick Question Viruses are living organisms FALSE Viruses have RNA but no DNA FALSE Viruses have capsids that protect them and help them attach to host cells TRUE Parasite Is any organism that uses a host to live in for food, shelter, protection, reproduction Major types Protozoa Single celled organisms Helminths Worms Parasite Protozoa Single celled eukaryotes Are motile Are heterotrophic Belong to kingdom protista Can be free- living or parasitic Paramecium Amoeba Euglena Parasite Medically important protozoa: Plasmodium malariae Malaria parasite From mosquitos Interestingly…traits for sickle cell anemia give resistance to Malaria Heterozygotes for the sickle cell gene are resistant to the disease. Cells sickle and are removed from circulation faster, so the virus has less chance to replicate inside the host. Parasite Medically important protozoa Trypanasoma Cruzi Trypanasomiasis: which is transmitted to animals and people by insects and is found only in the Americas Parasite Helminths (worms) A worm or worm-like animal, that can be parasitic Include roundworm, tapeworm, flukes Have intermediate hosts for larval development and definitive host for adult form Parasite Medically important Helminths Tapeworm, Roundworm Flukes flatworm Quick Question Can a virus be a parasite? NO viruses are not living Parasites ARE living Can a parasitic worm infect your eyeball? Obviously. Are protozoa prokaryotic? Nope. Eukaryotic Single-celled eukaryotes Fungi Multi-cellular fungi have networks of long hollow tubes called hyphae The hyphae often aggregate in a dense network known as mycelium The mycelium cluster into a complex structure, known as the fruit Mushroom is often the name given to the fruit Yes…mushrooms are fungi. Fungus is used everyday in foods such as mushrooms, yeast for bread, beer, and drugs Fungi structure Fungi Medically important Fungi Candida Oral albicans and genital infections It actually grows as a yeast, but can switch to a multicellular form which infects humans Called fungal dimorphism Environmental cues Quick Question What is the order of increasing fungal structure? Hyphae Mycelium Fruit (aka mushroom) Algae Chiefly aquatic, eukaryotic plant like organisms without true stems, roots, or leaves Most are autotrophic, photosynthetic, and contain chlorophyll Produce most of the oxygen in the world available to humans (about 70%) a video about algae oil for fuel
