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Transcript
BACTERIA & VIRUSES A. UNIVERSAL COMMON ANCESTOR • 1. First living cells • a. anaerobic • b. heterotrophic • c. bacteria • 2. ancestor of all other living things • 3. U.C.A. B. TRAITS ALL ORGANISMS GOT FROM UCA • 1. DNA = universal genetic material • a. same nucleotides • b. double helix • 2. DNA replication to reproduce • a. semi conservative • b. helicase • c. DNA polymerase • d. topoisomerase C. DOMAINS • 1) Domain Bacteria • Eubacteria • 2) Domain Archaea • Archaeobacteria • 3) Domain Eukarya • Eukarya D. BACTERIA ANCESTRAL TRAITS • 1) no histones • 2) single circular main chromosome E. BACTERIA CELLULAR STRUCTURES • 1. Nucleoid – main chromosome • 2. Plasmid – small circular DNA trading cards • 3. Ribosomes –only organelle • 4. Pili – projections of cell membrane • 5. Capsule – gelatinous coating • 6. Flagella – with NO microtubules/ basal body BACTERIAL REPLICATION http://www.youtube.com/watch?v=7sZ5 Nz8_cfc F. BACTERIAL REPLICATION • 1. Origin duplicated • 2. DNA helicase unwinds DNA • 3. DNA polymerase complex called replisome • 4. 2 replication forks move opposite directions • Topoisomerase cuts DNA to avoid over-coiling G. PROKARYOTIC FISSION • 1. Origins attach • 2. Cell elongates • 3. Cytoplasmic division • 4. No random assortment H. GENETIC VARIATION IN BACTERIA • 1. Lateral genetic exchange • 2. Advantage = rapid dissemination new phenotypes • a.) conjugation – bacteria to bacteria via tube • b.) transduction – virus introduces new DNA • c.) transformation – uptake of DNA through cell membrane (plasmids) • Famous transformation experiment by… • Griffith CONJUGATION • http://highered.mcgrawhill.com/sites/dl/free/0072835125/126997/animation6.ht ml I. BACTERIAL CONJUGATION • 1. Donor cell (F+) gives a plasmid to recipient cell • 2. F+ fertility plasmid directs sex pilus formation • 3. Conjugation tube joins cytoplasm • 4. Relaxase nicks donor plasmid • 5. One strand of plasmid nucleotides moves into recipient cell • 6. Both strands replicated back into double helix J. BACTERIAL MUTATION RATES • 1. Very high due to rapid reproduction rates • 2. chance of any gene mutating each time it is replicated…… • 1 in 10 million • 3. If 2 x 1010 new cells produced each day • 2000 will have new mutations K. IDENTIFYING/CLASSIFYING BACTERIA • 1. Characteristics that are considered • a) Shape • b) Gram staining • c) Metabolism • d) Gene sequencing…. • i. causing re-structuring of classification • ii. shows genetic diverged from all other life shortly after emergence of first cell SHAPE L. SHAPE • 1. cocci = round • 2. bacilli = rod • 3. spirilli = spiral M. CELL ARRANGEMENTS • 1. diplo – pairs • 2. strepto – chains • 3. staphylo - bunches N.GRAM STAINING • 1. Gram positive stain violet – • a. lots of peptidoglycan in cell wall • 2. Gram negative stain red, • a. less peptidoglycan • b. outer membrane • PEPTIDOGLYCAN = SUGARS CROSS-LINKED BY PEPTIDES GRAM POSITIVE FORM ENDOSPORES OUTER MEMBRANE = RESISTANCE TO DRUGS O. METABOLISM • 1. Chemoheterotrophs – • E from bonds, organic C • parasites, saprobes, decomposers • 2. Chemoautotrophs – • E from bonds, C from CO2 • thermophilic bacteria, some of most primitive. energy from iron or sulfur compounds • 3. Photoautotrophs – • E from sun, C from CO2 • cyanobacteria, stromatolites • P. GENE SEQUENCING • 1. Shows bacteria diverged from all other lineages shortly after first cells appeared Q. FLAGELLA • 1. Bacteria • a. ATP powered protein motor, • b. hook & filament • 2. Archaen :same design but • different proteins • 3. Eukaryotic flagella • a. Covered in membrane • b. microtubules • 4. Flagella of 3 domains: • Analogous structures R. RESPONSE TO EXTERNAL SIGNALS • 1. Signal transduction – extra cellular signaling molecule binds to receptor and initiates response • a) taxis - innate behavioral response to move toward or away from directional stimulus • 1. magnetotactic, 2. phototactic, • 3. thermotactic, 4. geotactic • b) kinesis- non-directional change in activity in response to a stimulus. • c) Quorum sensing: intercellular communication S. QUORUM SENSING • 1. Bacteria use signaling molecules to sense bacterial cell density • 2. Signal molecules species specific • 3. Sufficient signal mol. concentration triggers communal response • a. gene expression activated, • b. proteins produced & excreted • warning-video contains more facts than you need to memorize. Just know the slide. • http://www.youtube.com/watch?v=YJWKWYQfSi0 EXTRA VIDEO ON QS IF THERE IS TIME • http://www.youtube.com/watch?v=nw2os1s0Hjw • Start at 3:20 glowing bacteria/squid • QS enables bacteria to co-ordinate their behaviour. As environmental conditions often change rapidly, bacteria need to respond quickly in order to survive. These responses include adaptation to availability of nutrients, defence against other microorganisms which may compete for the same nutrients and the avoidance of toxic compounds potentially dangerous for the bacteria. It is very important for pathogenic bacteria during infection of a host (e.g. humans, other animals or plants) to co-ordinate their virulence in order to escape the immune response of the host in order to be able to establish a successful infection. • Virulence factors are molecules expressed and secreted by pathogens (bacteria, viruses, fungi and protozoa) that enable them to achieve the following: • colonization of a niche in the host (this includes adhesion to cells) for example, Trimeric Autotransporter Adhesins (TAA) • Immunoevasion, evasion of the host's immune response • Immunosuppression, inhibition of the host's immune response • entry into and exit out of cells (if the pathogen is an intracellular one) • obtain nutrition from the host. • Virulence factors are very often responsible for causing disease in the host because they are often responsible for converting non-pathogenic bacteria into dangerous pathogens. In bacteria, virulence factors are often encoded on mobile genetic elements, such as bacteriophages, and can easily be spread through horizontal gene transfer. Some bacteria, such as Escherichia coli O157:H7, gain the majority of their virulence from mobile genetic elements. Strategies to target these specific virulence factors and mobile genetic elements have been proposed • Streptococcus lactis strep throat • Staphylococcus aureas found on skin, responsible for minor infections (like on cuts/scratches) • Bacillus tetani causes tetanus (lockjaw) • Clostridium botulism causes botulism • Yersinia (bacillus) pestis causes Black Plague • Bacillus anthracis anthrax (forms endospores) • Mycoplasmas very very tiny, cause of pneumonia • Rickettsia rickettsi link between bacteria and viruses, can't reproduce outside host, causes Rocky Mountain Spotted Fever • Escherichia coli E. Coli - common bacteria of the • Horizontal gene transfer (HGT) refers to the transfer of genes between organisms in a manner other than traditional reproduction. Also termed lateral gene transfer, it contrasts with vertical transfer, the transmission of genes from the parental generation to offspring via sexual or asexual reproduction. HGT has been shown to be an important factor in the evolution of many organisms, including bacteria, plants and humans. • Horizontal gene transfer is the primary reason for bacterial antibiotic resistance,[1][2][3][4] and plays an important role in the evolution of bacteria that can degrade novel compounds such as human-created pesticides[5] and in the evolution, maintenance, and transmission of virulence.[6] This horizontal gene transfer often involves temperate bacteriophages and plasmids.[7] Genes that are responsible for antibiotic resistance in one species of bacteria can be transferred to another species of bacteria through various mechanisms (e.g., via Fpilus), subsequently arming the antibiotic resistant genes' recipient against antibiotics, which is becoming a medical challenge to deal with. This is the most critical reason that antibiotics must not be consumed and administered to patients without appropriate prescription from a medical physician