Chapter 27 Bacteria and Archaea Prokaryote Structure Unicellular But some stay joined in groups chains or clusters after fission Size mostly 1 5 nanometers Common Shapes Rods bacillus bacilli Spheres coccus cocci Spiral spirilla spirochete Cell Surface Cell wall outside plasma membrane Prevents cell rupture in hypotonic environments Bacterial walls have peptidoglycan Archaea walls are diverse but do not have peptidoglycan Gram Satin reflects wall type o Gram are bacteria with a thick peptidoglycan layer They show purple under the microscope because the stain is not washed out o Gram are bacteria with a thinner peptidoglycan layer and outer membrane They show pink under the microscope They are often toxic and resistant to drugs Sticky capsule often outside cell wall o Adheres glues cells together and to the surface o Resists attack from immune system o Holds in moisture Hair like Fimbriae o Helps cells stick to surfaces and each other Sex pillus o Pulls two bacteria together for DNA transfer conjugation Forms mating bridge Motility Taxis is the movement toward or away from stimuli Chemotaxis Phototaxis Geotaxis magnetotaxis use metal to orient and move Many move using rotating flagella the best studied method o Not at all like eukaryotic flagella o H ions flow through a protein motor creating a gradient and causing a distortion of proteins This distortion causes rotation Internal organization There are no membrane bound organelles Some have in folded plasma membranes o Used for aerobic cellular respiration and photosynthesis Similar to mitochondria and chloroplasts Nucleoid is the region with DNA o One circular DNA molecule with fewer binding proteins than eukaryotes Plasmids are independent tiny rings of DNA o They add genetic diversity Genetic Diversity Cell Reproduction and Diversity Binary fission yields two identical cells review 12 12 o There is a short generation time o Geometric growth in numbers 1 2 4 8 o Under stress some species divide to form and endospore Resists heat drought etc for years Mutations do in increase genetic diversity o Mutations are rare per division 1 107 o But high rate of cell division leads to many mutations o Each new mutation is passed on cloned o Mutation can change the phenotype Prokaryotes can evolve rapidly o See experiment 27 10 o Began with one strain using good medium o Generations grow on poor medium o Only source of new diversity was mutation This allowed for natural selection Recombination by transformation See Griffith s experiment Fig 16 2 DNA bits from ruptured donor cells absorbed directly be recipient DNA with new homologous alleles transfers into chromosomes recombinant Recombination by Transduction Bacteriophage virus carries DNA from donor to recipient strain Adds new chromosomal alleles to recipient cell recombination Recombination by Conjugation Requires presence of F Factor in the donor o Located in F plasmid in the chromosome o F Factor gene build sex pilus F plasmid conjugation o From F donor to a F recipient o F cell becomes F cell Hfr cell conjugation o High frequency recombination o Donor s F Factor is a part of the chromosome o F cell gets new chromosomal alleles but not the F allele R Plasmid Conjugation o R plasmids carry genes that Confer resistance to antibiotics Build pilli o R plasmid conjugation accounts for rapid spread of resistance Nutritional and Metabolic Diversity Prokaryote Nutritional Modes table 27 1 The carbon source gives organisms biomass Autotrophs carbon source is self reliant but they still need an energy source o Inorganic carbon can be made organic self feeders o Energy source is light or inorganic chemicals very rare Heterotrophs o C source is organic compounds produced by other living things o E source is light very rare or organic compounds Oxygen and Metabolism Obligate aerobes must have oxygen for all respiration Obligate anaerobes are poisoned by oxygen o Ex Tetanus Facultative anaerobes can use oxygen for cellular respiration or switch to anaerobic processes if no oxygen is present Nitrogen and Metabolism Nitrogen is a crucial nutrient in proteins amino acids and DNA nitrogenous bases o 78 of air is N2 gas But it can t be used as a gas by organisms because it is inert Most cells need nitrogen as ammonium NH4 or nitrides or nitrates Nitrogen fixation converts N2 to NH4 o Almost all of life s nitrogen comes from nitrogen fixating prokaryotes no eukaryotes o It also comes from lightning and volcanoes Other prokaryotes convert and cycle nitrogen compounds in the Nitrogen Cycle see 55 14 Metabolic cooperation Better growth together than alone Function as a colony or group better than on their own o Cyanobacteria and heterocyst and photosynthetic cells o Biofilms plaque are made up of multiple species Prokaryote Ecological Roles Food Webs and Nutrient Cycling Primary produces cyanobacteria create most of the biomass o Autotrophs fix CO2 into organic carbon This is an important base for aquatic food webs Decomposers o Heterotrophs break down dead material waste Release carbon dioxide and nutrients N P K The MOST important decomposers on earth are bacteria Symbiosis is two species living in a close relationship Parasitism smaller parasite benefits at the expense of the other species host Commensalism one species benefits without any impact good or bad on another species o Most bacteria on our skin Mutualism both species benefit from each other o Bacteria in our colon make vitamin K o Rhizobium in legume roots get sugar and water and provide nitrogen fixation to the plant o Flashlight fish have a pocket on their cheek for bioluminescent bacteria to live They flash it at predators and use it to attract food Prokaryotes and Humans Pathogenic Bacteria Bacterial toxins o Exotoxins are secreted out from the bacteria They are toxic even the bacteria is dead Botulism bacteria o Endotoxins come from the outer membrane of Gram bacteria Antibiotics kill bacteria cells but not eukaryotic cells o Penicillin Immunization prepares immune system to resist some bacterial diseases o Bacterial Meningitis typhoid Beneficial Uses of prokaryotes Basic research on cells and DNA DNA technology and genetic engineering Commercial chemicals and drug production o Human growth hormone Acetone Bioremediation is the breakdown of wastes i e crude oil cess pool Used in food products like yogurt cheese ect Prokaryote Phylogeny Early Prokaryotes First cells were prokaryotes about 3 5 bya o Anaerobic heterotrophs The 2 domains