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Have you heard? • Genus Demodex; live exclusively on human • 2 species: D.folliculorum (top) and D.brevis (bottom) http://blogs.discovermagazine.com/notrocketscience/2012/08/31/everythingyou-never-wanted-to-know-about-the-mites-that-eat-crawl-and-have-sex-onyour-face/ Two types of cells: Prokaryote vs. Eukaryote Prokaryote vs. Eukaryote Characteristics Size Prokaryotes: Archaebacteria and Eubacteria 1-10 m Eukaryotes: Protists, Plants, Fungi, Animals 100-1000 m Genetic materials - Circular DNA - DNA in nucleus including plasmids, not bounded by membrane bound by a membrane - No plasmid - Genome made up of - Genome made up of a single chromosome several chromosomes, thus contains many more genes than prokaryotes Cell division Binary fission Mitosis and meiosis Reproduction Asexual is common Sexual is common Prokaryote vs. Eukaryote (cont.) Characteristics Prokaryotes: Archaebacteria and Eubacteria Eukaryotes: Protists, Plants, Fungi, Animals Number of cells Unicellular Most are multicellular Organelles No membrane-bound organelles such as mitochondria, chloroplast etc. No nucleus Membrane-bound organelles present Metabolisms -Many carry out metabolism under no O2 condition -Metabolism processes carried out in the cytoplasm -Most require O2 -Metabolism processes carried out in membranebound organelles such as mitochondria, chloroplast etc. Endosymbiosis Theory How have prokaryotes possibly become eukaryotes? Eukaryotic cells are believed to be the result of a symbiotic union of separate prokaryotic cells Kingdom Archaebacteria and Eubacteria (generally referred as Bacteria) • • • • • Shared characteristics of Archaebacteria and Eubacteria no nucleus All single-celled. no membrane-bound organelles DNA as a single chromosome. Reproduce asexually by binary fission. Kingdom: Archaebacteria • Archae means primitive or early • Often live extreme environments Eg. high salt concentrations, temperature or acidity; • Most live in environments with no oxygen • Hypothesis: all life kingdoms are descended from the ancestors of this group Classification of Kingdom ArchaeaBacteria • By their habitats A. Anaerobic methanogen: those live in O2free places (e.g. gut of animals and produce CH4) B. Halophiles: salt-loving archaea C. Thermophiles: those inhabit hot, acidic environment such as hot springs Kingdom Eubacteria or Bacteria Kingdom Bacteria Classification 1. Shapes 2. Respiration 3. Reaction to staining 4. Reproduction 1. Bacterial shapes http://www.youtube.co m/watch?v=6p9e0ool bmE Classification – Shape Singular Plural coccus cocci bacillus bacilli Shape round rod spirrillum spirrilla spiral Advantages Resists drying out greater surface area = higher nutrient absorption can move through fluids with less resistance Kingdom Bacteria 2. RESPIRATION Classifying bacteria by respiration 1) Obligate aerobes: require oxygen 2) Obligate anaerobes: grow only in absence of oxygen 3) Facultative anaerobes: can survive with or without oxygen Nutrition: vocabulary revision • Autotrophs: make their own food • Heterotrophs: obtain food by breaking down organic molecules from their environment • Chemo- derived from chemical reactions • Photo- derived from sunlight Bacterial Nutrition Mode of nutrition Photoautotroph Energy source Light Carbon source CO2 Inorganic chemicals CO2 Light Organic compounds Organic compounds (e.g. cyanobacteria) Chemoautotroph (e.g. Ferrobacillus ferrooixdans) Photoheterotroph (e.g. Heliobacter polyri) Chemoheterotroph (e.g. Methanococcus jannaschii ) Organic compounds 4. Bacterial reactions to being stained • Gram staining: a staining technique by Hans Christian Gram in 1884 • Divide bacteria into 2 groups: Gram negative Peptidoglycan absent in cell wall Gram positive Peptidoglycan present in cell wall Gram staining procedure BACTERIAL ASEXUAL REPRODUCTION Called “binary fission” • bacterial DNA replicates and divides • a cross wall develops and the two genetically identical cells separate http://www.youtu be.com/watch?v =DY9DNWcqxI4 &feature=related True! Conjugation- not true sexual reproduction • Cell to cell contact is made with a cytoplasmic bridge • Plasmids (small circular DNA); contain genes different from those in the bacterial chromosome • Plasmids are transferred from the donor to the recipient • Recipient now has new genes from donor (ie. Gene for antibiotic resistance) ENDOSPORE FORMATION • Adaptation to survive unfavourable conditions eg. Anthrax forms spores • Cell wall becomes thick • resistant to heat and not easily destroyed • bacterium emerges when suitable conditions return USEFUL BACTERIA • Production of vinegar • fixing nitrogen in soils • dairy products (cheese, yogurt….) • decomposers in nutrient cycles • source of some Antibiotics • Clean up oil spill HARMFUL EFFECTS BACTERIAL DISEASES 1. Leprosy 2. Tetanus 3. Botulism 4. Cholera DEFENSE AGAINST DISEASE • Body provides own defenses (skin, acidic stomach, lysozyme in eyes, immune system) • sterilization/disinfection of surfaces can reduce disease further (wash your hands) • Antibiotics are chemicals that kill bacteria but don’t harm host cells • Bacteria have evolved to resist many of today’s antibiotics Antibiotics and Antiseptics • Joseph Lister created the first antiseptic, an acid to spray on tables and instruments before surgery (1860) • The Discovery of Penicillin (1928) • • • • Alexander Fleming Noticed mold growing on petri dishes Bacteria did not grow where the mold was He isolated the chemical that killed bacteria, but it was not stable • Howard Flory continued the work, later stabilized the chemical • Fleming and Flory received the Nobel Prize in 1945 Bacterial growth: - Zones of inhibition around the disks shows the effectiveness of the antibiotics Antibiotic resistance: Ability of bacteria to grow in the presence of chemicals meant to destroy them What is the zone of inhibition on this agar? Which disk(s) is most effect at inhibiting the growth of bacteria on this agar? Drug screening: Bacteria can be grown on agar plates to check for antibiotic resistance Which Petri disk show more antibiotic resistance? Bonnie Bassler - PrincetonU How Bacteria Talk to each other? •http://www.ted.com/talks/lang/eng/bonnie_bassler_ on_how_bacteria_communicate.html Quorum sensing: the phenomenon whereby the accumulation of signalling molecules enables bacteria to sense their number so they can launch group behaviour (e.g. virulence etc.) Review 1. Label the bacteria by shape dicocci streptococci staphylococci 2. What is a bacteria called that must live in oxygen? • Obligate aerobe 3. How do bacteria reproduce? • Binary fission (asexual) & conjugation 4. Bacteria on a pin. What shape? a.Cocci b.Bacilli c.Spirilla 5. What survival advantage does this shape bring to the bacteria For your interest • Next 2 slides connect with your antibiotic resistance reading articles Drug- resistant Superbugs non-typhoidal salmonella Vancomycin-resistant Staphylococcus aureus Neisseria gonorrhoeae Streptococcus pneumoniae tuberculosis Pseudomonas aeruginosa Get Smart: Know When Antibiotics Work Q. What kinds of infections are caused by viruses and should not be treated with antibiotics? • cold, flu, sore throat (except strep. throat), cough, bronchitis, ear infections are viral infections shouldn’t be cured with antibiotics Q. Can one strain of bacterium become resistance to multiple drugs? • Absolutely YES! E.g. P. aeruginosa causes eye infections, skin rashes, ear infections, after surgery infection, widely spread in hospital Multi drug-resistant Pseudomonas aeruginosa http://www.cdc.gov/getsmart/antibiotic-use/antibiotic-resistance-faqs.html Kingdom Bacteria Kingdom Bacteria