Class announcements. Prokaryotic cell structure. Prokaryotic Diversity II - Coming attractions 2/10/11. Prokaryotic cell structure

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1 Class announcements 1. Today no clickers; Friday probably clickers 2. Discuss phylogenetic tree homework in your study group, but write up the HW on your own 3. Friday phylogenetic tree HW due 4. Friday review exercises from the diagnostic exam due 5. Early next week review sessions for first mid-term exam 6. Use your study group to prepare for first mid-term exam 7. Next Wednesday first mid-term exam Prokaryotic Diversity II - Coming attractions Evolutionary origins Basic features Bacteria several major groups Bacteria - pathogenesis Archaea extremophiles Metabolic diversity Bioenergetics redox reactions Bioenergetics - electron transport chains Biogeochemical cycles Copyright 2002 Pearson Education, Inc. Prokaryotic cell structure Prokaryotic cell structure C & R Fig 7.4 Escherichia coli Methanobacterium foricum 1

2 Major characteristics of 3 domains of life Bacteria Archaea Eukarya Nucleus No No Yes Chromosome (C) One circular C with 1 origin of DNA replication One circular C with 1-3 origins Organelles No No Yes Growth forms Most unicellular, some multicellular All unicellular Several to many linear C with multiple origins Many unicellular, many multicellular Reproduction Binary fission Binary fission Often sexual Lipid structure Glycerol bonded to unbranched fatty acids via ester links Glycerol bonded to branched lipids via ether links Cell wall polymers Peptidoglycan Wide variation, no peptidoglycan Histone proteins No Yes Yes Transcription & translation One simple RNA polymerase, start aa - formylmet, 70S ribo Several complex RNA polymerases, start aa - met, 70S ribosomes Glycerol bonded to unbranched fatty acids via ester links If present, chitin or cellulose Several complex RNA polymerases, start aa - met, 80S ribosomes See F Table 28.1 Jeff sez, For best results, why don t you think about using Charlie Darwin s model of a branching tree? Essential features Bacteria Archaea Eukarya Evolution of simple cell structure last common ancestor/ancestral community Evolution of simple information processing Evolution of simplest life Evolution of complex cell structure Evolution of complex information processing The power of tree thinking: organizes important information in evolutionary model reconstructs the traits characterizing each group summarizes an evolutionary story provides explicit testable hypotheses eukaryote-specific characteristics (derived similarity) common A/E ancestor characteristics LUCA/LUCAC characteristics (primitive similarity) predicted characteristics of protolife Coming attractions Evolutionary origins Basic features Bacteria several major groups Bacteria - pathogenesis Archaea extremophiles Metabolic diversity Bioenergetics redox reactions Bioenergetics - electron transport chains Biogeochemical cycles Copyright 2002 Pearson Education, Inc. 2

3 Bacteria - diversity Unicellular shapes Leeuwenhoek s microscope Spheres (cocci) Nester et al. Fig 10.1 >40 major lineages roughly corresponding to kingdoms >98% of known prokaryotic species 10 4 described species, but 10 7 estimated species (or many more!) Almost overwhelming diversity of metabolisms, habitats, growth forms, and lifestyles within the basic prokaryotic framework Poor coupling between phylogeny and physiology (some notable exceptions) WHY? Great ecological significance - biogeochemical cycles, symbiotic relationships Great human significance - biotechnology, medicines, foods, bioremediation, and some major diseases MMP Fig. 1.9 Leeuwenhoek (1684) wee animalcules Rods (bacilli) Helices (spirilla) Copyright 2002 Pearson Education, Inc., Structural diversity - other examples Bacterial cell walls (F. Fig ) Grampositive cells Merismopedia (cyanobacterium) Nostoc (cyanobacterium) Freeman Fig Caulobacter (stalked proteobacterium) Freeman Fig Chondromyces (myxobacterium with fruiting bodies) microvet.arizona.edu/courses/mic205/exams/pleomorphic2.gif Unindentified pleomorphic bacterium Gramnegative cells The Gram stain separates all bacteria into two classes based on major differences in their cell walls. Gram-positive bacteria (colored purple) have simpler cell wall with much peptidoglycan. 3

4 Bacterial cell walls (F. Fig ) Gram-negative bacteria (colored pink) have more complex cell walls producing an outer membrane on the cell wall composed of lipooligosaccharides (LOS). Outer membrane has toxic LOS, inhibits antibiotic entry and resists host defenses. Grampositive cells Gramnegative cells Dan Stein (CBMG) Gram-positive bacteria Gram-positive cell walls - one cell membrane, thick peptidoglycan cell wall Two subgroups - low GC (20-40%) or high GC (60-80%) ratio in DNA base composition Anaerobic, facultative aerobic, and aerobic species Principal metabolic strategy - chemoheterotrophs (energy and carbon from a wide range of organic compounds) - certain species utilize and/or produce specific organic acids (e.g. formic, acetic, lactic, butyric, and propionic acids) Foods - yogurt, pickles, sauerkraut, and swiss cheese Antibiotics - penicillin, streptomysin, erythromycin (Streptomycetes spp.); bacitracin, gramicidin, and polymyxin (Bacillus spp.); insect-specific toxins (B. thuringiensis - Bt toxin) Diseases - anthrax (B. anthracis), tuberculosis (Mycobacterium tuberculosis) MMP Fig Nester et al. Fig Lactobacillus delbreuckii Bacillus anthracis MMP Fig Streptomycetes spp. Proteobacteria Largest group of known bacteria Gram-negative cell walls two membranes with thin peptidoglycan cell wall Five subgroups - alpha, beta, gamma, delta, and epsilon subgroups Anaerobic, facultative aerobic, and aerobic species Greatest diversity of metabolic strategies - photoautotrophs (non-oxygenic photosynthesis - light as energy source), chemoautotrophs (inorganic compounds as energy sources), and chemoheterotrophs (organic compounds as energy sources) Major biological contributors to biogeochemical cycling of important elements, including C, N, P, and S. Escherichia coli - the most studied organism (other than a particular primate species) Intestinal bacteria, such as E. coli, synthesize essential B and K vitamins. Vibrio group - bioluminescent bacteria in the light organs of deep-sea fish Diseases - bubonic plague (Yersinia pestis), cholera (Vibrio cholerae), bacterial meningitis (Neisseria meningitidus), typhoid fever (Salmonella typhi) α-proteobacteria Symbiotic associations with eukaryotic hosts - the camp followers of eukaryotes Rhizobium - nitrogen fixation in legume hosts Agrobacterium - crown gall disease, plant genetic engineering Ricksettia - tiny intracellular parasites in animals An ancient aerobic alpha - original source of eukaryotic mitochondrion more after 1 st mid-term exam MMP Fig Purple sulfur bacteria Nester et al. Fig E. coli Nester et al. Fig Flashlight fish Nester et al. Fig Nester et al. Fig MMP Fig Legume root nodules Crown gall disease Ricksettsia in insect cell 4

5 Cyanobacteria - biology s working class heroes Photoautotroph (oxygenic photosynthesis) with chlorophyll a Use H 2 O as the ultimate electron donor for photosynthetic electron transport, with O 2 as the waste product Wide variety of growth forms - solitary unicells, colonies, filaments, and branching filaments Also gram-negative walls, but no pathogens Profound historical impact on Earth s atmosphere and the distribution of all organisms Evolutionary source of algal and plant chloroplasts Beth Gantt (CBMG) Cellular differentiation in few cyanobacteria MMP Fig Anabaena sp. Small green vegetative cells - photosynthesis Brown heterocysts - nitrogen fixation Large green endospores dormancy Contrast to eukaryotes? MMP Fig Gleothece sp. Oscillatoria sp. Fischerella sp. Intercellular transport MMP Fig Geological history of prokaryotic gas exchange Evolutionary consequences of O 2 production Banded iron formations C & R Fig Kasting Sci. Am What were the evolutionary consequences of O 2 production? 5

6 Evolutionary consequences of O 2 production Banded iron formations C & R Fig Eventually, atmosphere changed from reducing to oxidizing conditions. All the soluble Fe 2+ in the oceans was oxidized to form insoluble Fe 3+ that precipitated to form banded iron formations All anaerobic organisms became restricted to anoxic environments. The formation of ozone (O 3 ) layer restricted mutagenic UV radiation. Allowed for the origin of aerobic prokaryotes and larger eukaryotes Coming attractions Evolutionary origins Basic features Bacteria several major groups Bacteria - pathogenesis Archaea extremophiles Metabolic diversity Bioenergetics redox reactions Bioenergetics - electron transport chains Biogeochemical cycles Copyright 2002 Pearson Education, Inc. Pathogens - disease-causing organisms Prokaryotes only bacteria are pathogenic Dis-ease - host symptoms resulting from microbial colonization Host-pathogen interactions - BSCI 223 Evolutionary perspectives LGT consequences the acquisition of antibiotic resistance from other bacteria the acquisition of pathogenic ability by non-pathogens Antibiotics - bacteria-specific compounds Bubonic plague (black death) Soybean blight Different antibiotics target different structures or processes. 6

7 Transmission of antibiotic resistance via vertical gene transfer antibiotic drug selects for resistant bacterium then its resistant progeny multiply in the presence of the antibiotic Transmission of antibiotic resistance VGT to its progeny (same species) Lateral gene transfer to other species, perhaps pathogens! Nester et al. Fig R. Stewart R. Stewart from Nester et al. Fig Pathogens - disease-causing organisms Prokaryotes only bacteria are pathogenic Dis-ease - host symptoms resulting from microbial colonization Host-pathogen interactions - BSCI 223 Evolutionary perspectives HGT consequences the acquisition of antibiotic resistance from other bacteria the acquisition of pathogenic ability by non-pathogens Pathogenicity islands (PI s) PI - gene clusters that elicit disease responses One PI in many pathogens encodes Type III secretion system (SS) Type III SS - injects toxic proteins into host cells Bubonic plague (black death) Soybean blight Nester et al. Fig

8 Molecular genetics of Type III secretion Plant pathogens" Pseudomonas syringae! Erwinia spp" P. fluorescens R. solanacearum! X. campestris! Burkholderia cepacia! Steve Hutcheson (CBMG) Mammalian pathogens" Yersinia spp bubonic plague" Salmonella spp. typhoid fever" Shigella spp. - dysentery" P. aeruginosa - UTIʼs" B. pertussis whooping cough" Chlamydia spp.- STDʼs" K" L" J" U" C" A" S" R" Flagellar biosynthesis" Filamentous phase assembly" Hrp (hypersensitive response) Central Conserved Region (CCR)" Summary Questions = Learning Objectives 1. Be able to group related traits together, such as all prokaryotic cell features, and then place those grouped traits on the phylogenetic tree of the three domains. 2. Use this tree to identify the major traits of bacteria, archaea, and eukaryotes. 3. Finally, summarize the current hypothesis about the main events in the evolution of the three domains. 4. Be able to relate the features of bacterial cell walls to the evolution of antibiotics and pathogenic abilities in different bacterial groups 5. Identify the key metabolic innovation of cyanobacteria, and discuss its significance for the evolution of life. 6. Evaluate the significance of lateral gene transfer for the dispersal of antibiotic resistance and for the acquisition of pathogenic ability. Be able to distinguish between these two phenomena. 8