Chapter 27 Friday February 19 2016 1 59 PM Chapter 27 Bacteria and Archaea Prokaryote Origins First life was prokaryotic o First cells earlier than 3 5 billion years ago o Anaerobic low or no Ox conditions o Much horizontal gene transfer between earliest cells 26 23 o Diverged early into two domains Bacteria and Archaea Earliest prokaryotic fossils o Stromatolite formations 3 5 billion years ago Layered mats of prokaryotes and minerals Prokaryotic Structure Smallest of all cells o Mostly 1 5 um Mycoplasma is smallest no cell wall Largest is marine sulfur bacteria sulfur waste material not metabolizing Three major cell shapes o Rods bacillus bacilli o Spheres coccus cocci o Spiral spirilla or spirochetes F cell becomes F cells w F plasmid o R plasmids Hfr cell conjugation o Hfr 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 genes o Part 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 Webs o Autotrophs 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 community o Many 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 Metabolism o Oxygen kills some metabolic pathways Obligate anaerobes are poisoned by O2 Ex Tetanus bacteria First life probably dependent on this kind of obligate anaerobe conditions o Using 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 receptor o Oxygen revolution changed the world s atmosphere 2 55 bya Cyanobacteria photosynthesis produced O2 Cyanobacteria today are still a major world O2 source Nitrogen Cycle o Nitrogen Atmosphere is 78 N2 o o o Most cells need N as ammonium NH4 or organic N compounds ATP nitrogenous base Peptide amino acids chained together have lots of nitrogen Nitrogen 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 roots Nitrogen cycle is completed by other prokaryotes in soil Metabolic Cooperation Prokaryotes 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 Bacteria o Mostly in digestive tract Ward off pathogenic bacteria Produce vitamins Ex K other nutrients Help activate immune system Pathogenic Bacteria o Infections 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 practices o Sanitation is best defense o Immunization preps immune system to fight bacterial infections o Antibiotics kill bacteria cells but not eukaryotic cells Ex Penicillin affects peptidoglycan wall Human Use of Prokaryotes o Basic research on cells and DNA o DNA technology and genetic engineering Human growth hormones o Commercial chemical and drug production o Bioremediation used to clean up pollution use prokaryotes to clean up our waste o Food products yogurt cheese etc Prokaryote Phylogeny Comparing the Domains o Reference the table o Recognize when it comes to the relationships to the three domains the bacteria is the most closest basal groups to the universal ancestor Domain Bacteria o Proteobacteria Gram negative diverse metabolism nutrition Includes many N cycle bacteria Includes common gastrointestinal pathogens food poisoning Diverse group in terms of metabolism Escherichia Coli o Salmonella Chlamydias Gram negative all are endoparasites live within animal cells Ex Chlamydia in humans cause STD Cause blindness in children Most common STD in USA Preventable curable o Spirochetes Characteristic spiral shape Many free living but include disease causing pathogens Vibrio Choleri causes cholera Ex Syphilis STD Ex Lyme disease Bullseye rash o Cyanobacteria Plant like O2 generating photosynthesis Cyano bacteria blooms can make toxins o Gram 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 Archaea o Includes extremophiles and methanogens But also many live in normal conditions o No human disease causing archaeans o Extreme halophiles salt thrive in 2x 3x seawater up to 20 salinity Archaeans in Great Salt Lake o Extreme thermophiles thrive at or close to boiling point o Methanogens produce methane CH4 as by product of anaerobic respiration Greenhouse gas that affects the planet