Chapter 27Friday, February 19, 20161:59 PM Chapter 27 - Bacteria and Archaea Prokaryote Origins-First life was prokaryoticoFirst cells earlier than 3.5 billion years agooAnaerobic (low or no Ox) conditionsoMuch horizontal gene transfer between earliest cells-[26.23]oDiverged early into two domains: Bacteria and Archaea-Earliest prokaryotic fossilsoStromatolite formations (~3.5 billion years ago)-Layered mats of prokaryotes and minerals Prokaryotic Structure-Smallest of all cellsoMostly 1-5 um-Mycoplasma is smallest, no cell wall-Largest is marine sulfur bacteria, sulfur, waste material, not metabolizing-Three major cell shapesoRods (bacillus/bacilli)oSpheres (coccus/cocci)oSpiral (spirilla or spirochetes)-F cell becomes F+ cells (w/ F plasmid)oR-plasmids-Hfr cell conjugationoHfr donor's F factor is part of chromosome-Feeds one strand through the bridge, however, it is attached to the chromosome, so it begins to take part of the chromosome with it and takes some genesoPart of F factor and part of chromosome (new alleles) are transferred from Hfr to F- cell-New alleles insert into recipient chromosomeNew recombinant F- bacterium Prokaryote Metabolic and Ecological Diversity-Nutritional Modes-Food WebsoAutotrophs are primary producers-Carbon fixation produces organic molecules-Important base of aquatic food webs-Ex. Chemoautotrophs form base of food web in this hydrothermal vent communityoMany chemoheterotrophs are decomposers-Break down dead material or waste products (feces or urine)-Release CO2 and nutrients (N, P, K - nitrogen, phosphorus, potassium)Most important decomposers on earthAbsorptive heterotrophs-Oxygen and MetabolismoOxygen kills some metabolic pathways-Obligate anaerobes are poisoned by O2Ex. Tetanus bacteriaFirst life, probably dependent on this kind of obligate anaerobe conditionsoUsing O2 generates more ATP-Facultative anaerobes normally use O2 for cellular respiration but switch to anaerobic processes if no O2 is present-Obligate aerobes require O2 for cell respirationMost life today, oxygen is present acts as final receptoroOxygen revolution changed the world's atmosphere (2.55 bya)-Cyanobacteria photosynthesis produced O2-Cyanobacteria today are still a major world O2 source-Nitrogen CycleoNitrogen -Atmosphere is 78% N2-Most cells need N as ammonium (NH4+) or organic N compoundsATP nitrogenous basePeptide, amino acids chained together, have lots of nitrogenoNitrogen fixation converts (only other natural way) N2 to NH4+-Certain N-fixing prokaryotes do this:Cyanobacteria in water and soil(Heterocysts do nitrogen fixation)Other bacteria in soil or symbiotic in plant rootsoNitrogen cycle is completed by other prokaryotes in soilMetabolic CooperationoProkaryotes often grow better together-Ex. Different roles for cells in Nitrogen-fixing cyanobacteria filamentsReceiving sugars from photosynthetic cells around them-Ex. Biofilms form when prokaryotes recruit other cells (on a surface) often several speciesLiving as a communal groupRemoving plaqueSymbiosis= two species living in close relationshipOpposite: free livingParasitism - smaller parasite benefits at expense of other species (host)-Include pathogens (cause disease)Ex. Anthrax, cholera bacteria - can take hold in the communityCommensalism - one species benefits without any impact (good or bad) on other speciesEx. Most bacteria on our skinMutualism - both species benefit from each otherEx. Rhizobium in legume roots get sugar and water; provide fixed N for plant Prokaryotes and Humans-Mutualistic BacteriaoMostly in digestive tract:-Ward off pathogenic bacteria-Produce vitamins (Ex. K), other nutrients-Help activate immune system-Pathogenic BacteriaoInfections produce bacterial toxins-Some toxins attack cell signal receptorsEx. Tetanus, botulismTetanus - anaerobic -Some have a generalized toxic effectEx. Salmonella food poisoningAvoided by good sanitation practicesoSanitation is best defenseoImmunization preps immune system to fight bacterial infectionsoAntibiotics kill bacteria cells but not eukaryotic cells-Ex. Penicillin affects peptidoglycan wall-Human Use of ProkaryotesoBasic research on cells and DNAoDNA technology and genetic engineering-Human growth hormonesoCommercial chemical and drug productionoBioremediation - used to clean up pollution, use prokaryotes to clean up our wasteoFood products: yogurt, cheese, etc. Prokaryote Phylogeny-Comparing the DomainsoReference the tableoRecognize when it comes to the relationships to the three domains, the bacteria is the most closest, basal groups to the universal ancestor-Domain BacteriaoProteobacteria-Gram-negative; diverse metabolism/nutrition-Includes many N-cycle bacteria-Includes common gastrointestinal pathogens ("food poisoning")(Diverse group in terms of metabolism)Escherichia Coli Salmonella Vibrio Choleri causes choleraoChlamydias-Gram negative; all are endoparasites (live within animal cells)Ex. Chlamydia in humans cause STDCause blindness in childrenMost common STD in USAPreventable, curableoSpirochetes-Characteristic spiral shape-Many free-living but include disease-causing pathogens:Ex. Syphilis (STD)Ex. Lyme disease-Bullseye rashoCyanobacteria-Plant-like, O2-generating photosynthesis-Cyano bacteria "blooms" can make toxinsoGram-positive-Include many decomposers in soilsIncludes some sources of antibiotics-Chemicals that kill-Include many pathogensEx. Anthrax, tetanusEx. Staph and MRSA infectionsEx. "strep" throatEx. Tuberculosis (TB) - attacks the lungs, liquid buildupEx. Leprosy-Domain ArchaeaoIncludes extremophiles and methanogens-But also many live in "normal" conditionsoNo human-disease-causing archaeansoExtreme halophiles (salt) thrive in 2x-3x seawater (up to 20% salinity)-Archaeans in Great Salt LakeoExtreme thermophiles thrive at or close to boiling pointoMethanogens produce methane (CH4) as by-product of anaerobic respiration-Greenhouse gas that affects the