Chapter 28 Prokaryotes 2 Conjunction Plasmids may encode advantageous info antibiotic resistance o Are not required for normal function In E coli conjugation is based on the presence of the F plasmid fertility factor o F cells contain the plasmid o F cells do not o F cell produces F pilus that connects it to F cell o Transfer of F plasmid occurs through conjugation bridge o F plasmid copied through rolling circle replication The F plasmid can integrate into the bacterial chromosome o Events similar to crossing over in eukaryotes o Homologous recombination Hfr cell high frequency of recombination o F plasmid integrated into chromosome o Replicated every time host divides The F plasmid can also excise itself by reversing the integration process o An inaccurate excision may occur picking up some chromosomal DNA F plasmid o Virtually any gene can be transferred o Occurs via accidents in the lytic cycle o Viruses bacteriophage package bacterial DNA and transfer it in a subsequent infection Transduction Occurs during infection with bacteriophage Generalized transduction Specialized transduction o Occurs via accidents in the lysogenic cycle o Imprecise excision of prophage DNA o Only a few host genes can be transferred Transformation Natural transformation DNA is taken up by a bacterium o Occurs in many bacterial species including Streptococcus which was studied by Griffith o DNA that is released from a dead cell is picked up by another live cell Artificial transformation o Done in lab o Used to transform bacteria usually E coli for molecular cloning o Eg a human gene for growth hormone can be inserted into a plasmid and then put into E coli transformed many copies of the gene are made when the E coli divides Medical Significance of Gene Transfer R resistance plasmids o Encode antibiotic resistance genes or toxin genes o Important factor in appearance of antibiotic resistant strains of Staphylococcus aureus o Transferred through conjucation Transduction o Bacteriophage can transfer genes for pathogenic traits toxins lysogenic conversion o Cholera Diphtheria Botulism Mutations can arise spontaneously in bacteria as with any organism o Radiation and chemicals increase likelihood Mutations and plasmids can spread rapidly in a population o Methicilin resistant Staphylococcus aureus MRSA o Vancomycin resistant Staphylococcus aureus VRSA Organisms must obtain energy and carbon need to use to build organic molecules to grow and Prokaryotic Metabolism reproduce Prokaryotes have various ways to do this Acquisition of Carbon Autotrophs from inorganic CO2 Photoautotrophs energy from Sun photosynthesis cyanobacteria algae plants Chemolithoautotrophs energy from oxidizing inorganic substances nitrifiers oxidize ammonia or nitrate to produce energy produce nitrates that plants use key factor in ecosystems others oxidize sulfur or hydrogen gas prokaryotes in ocean vents Heterotrophs carbon from organic molecules Photoheterotrophs light as energy source but obtain organic carbon made by other organisms purple and green non sulfur bacteria Chemoheterotroph both carbon atoms and energy from organic molecules Many bacteria Humans animals fungus Type III Secretion System Found in many gram negative bacteria Genes are similar to the bacterial flagella genes Molecular syringe to inject virulence proteins into host cell cytoplasm can transfer toxins into nearby eukaryotic cells Yersinia pestis bubonic plague virulence proteins enter the cytoplasm of macrophages phagocytic cells and disrupts the signal that tells the macrophage to engulf the bacteria Salmonella and Shigella use type III proteins to directly enter the cell and thus avoid the host s immune system Human Bacterial Disease In the early 20th century infectious diseases killed 20 of children before the age of five o Sanitation and antibiotics considerably improved the situation In recent years however many bacterial diseases have appeared and reappeared Emerging and Reemerging Infections Tuberculosis TB Scourge for thousands of years 2007 worldwide 9 27 new cases diagnosed 1 8 mil deaths 1980 s USA resurgence that peaked in the 90 s and has been declining 2007 13 300 cases 2006 13 754 Mycobacterium tuberculosis granulomas form in lungs may be active or inactive Multidrug resistant MDR strains are a major concern Afflicts the respiratory system Easily transferred from person to person through the air Treatmant multiple expensive drugs for 6 12 months patient compliance is difficult Dental caries tooth decay o Plaque consists of bacterial biofilms o Streptococcus sobrinus and S mutans ferment sugar to lactic acid o Tooth enamel degenerates o Gingivitis and periodontal disease is caused by the host s immune response to plaque build up under the gum line Peptic ulcers o Helicobacter pylori is the main cause discovered in 1980 s o Treated with antibiotics although once ulcer has begun it is difficult to cure because the protective barrier of the stomach has been breached STDS Gonorrhea drops Chlamydia o One of the most prevalent communicable diseases in North America o Neisseria gonorrhoeae o Transmitted through exchange of body fluids o Can pass from mom to baby via birth canal blindness newborns are given antibiotic o Chlamydia trachomatis o Silent STD incidence has skyrocketed o Can cause PID also gonorrhea sterility and ectopic pregnancy and heart disease Syphilis o Treponema pallidum o Transmitted through sex or contact with open chancre o Congenital syphilis o Four distinct stages Primary Chancre highly infectious Secondary Rash infectious Tertiary Latency no longer infectious but attacking internal organs Quaternary gummas form throughout the body cardiovascular damage mental and nervous disorders blindness loss of motor function 1 3 of cases o Bacterial STD s can be treated with antibiotics and cured viral STD s HPV HSV HIV cannot Beneficial Prokaryotes Decomposers release a dead organism s atoms to the environment Fixation o Photosynthesizers fix carbon into sugars Ancient cyanobacteria added oxygen to air o Nitrogen fixers reduce N2 to NH3 ammonia Anabaena in aquatic environments Rhizobium in soil Bacteria are used in genetic engineering o Biofactories that produce various chemicals including insulin and antibiotics Bacteria are used for bioremediation o Remove pollutants from water air and soil o Biostimulation adds nutrients to encourage growth of naturally occurring microbes Symbiosis refers to the ecological relationship between different
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