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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

C & R Fig 7.4

Prokaryotic cell structure

Escherichia coli Methanobacterium foricum

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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

Several to many linear C with multiple origins

Organelles No No Yes

Growth forms Most unicellular, some multicellular

All unicellular 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

Glycerol bonded to unbranched fatty acids via ester links

Cell wall polymers Peptidoglycan Wide variation, no peptidoglycan

If present, chitin or cellulose

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

Several complex RNA polymerases, start aa - met, 80S ribosomes

Jeff sez, “For best results, why don’t you think about using Charlie Darwin’s model of a branching tree?”

See F Table 28.1

Essential features Bacteria Archaea Eukarya

Evolution of simplest life

Evolution of simple cell structure

Evolution of simple information processing

Evolution of complex cell structure

Evolution of complex information processing

last  common    ancestor/ancestral  

community  

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)

predicted characteristics of protolife

LUCA/LUCAC characteristics (primitive similarity)

common A/E ancestor characteristics

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.

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Bacteria - diversity

•  >40 major lineages roughly corresponding to kingdoms •  >98% of known prokaryotic species •  104 described species, but 107 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

Nester et al. Fig 10.1

Unicellular shapes

Leeuwenhoek’s microscope

Leeuwenhoek (1684) “wee animalcules”

Spheres (cocci)

Rods (bacilli)

Helices (spirilla)

MMP Fig. 1.9 Copyright © 2002 Pearson Education, Inc.,

Structural diversity - other examples

Freeman Fig. 27-19

www.microscopy-uk.org.uk/mag/imagsmall/merismopedia.jpg

Freeman Fig. 27.21

microvet.arizona.edu/Courses/MIC205/Exams/pleomorphic2.gif

Nostoc (cyanobacterium)

Merismopedia (cyanobacterium) Chondromyces (myxobacterium with fruiting bodies)

Caulobacter (stalked proteobacterium)

Unindentified pleomorphic bacterium

Bacterial cell walls (F. Fig. 28.14)

•  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.

Gram-positive cells

Gram-negative cells

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Bacterial cell walls (F. Fig. 28.14)

•  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. Dan Stein (CBMG)

Gram-positive cells

Gram-negative cells

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)

Bacillus anthracis Lactobacillus delbreuckii MMP Fig. 12.55 Nester et al. Fig 11.17

Streptomycetes spp. MMP Fig. 12. 73

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)

Purple sulfur bacteria E. coli

Nester et al. Fig. 3.43 MMP Fig. 12.4 Flashlight fish

Nester et al. Fig. 11.27

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 1st mid-term exam

Legume root nodules Crown gall disease Ricksettsia in insect cell Nester et al. Fig 11.22 Nester et al. Fig 11.21 MMP Fig. 12.29

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Cyanobacteria - “biology’s working class heroes” •  Photoautotroph (oxygenic photosynthesis) with chlorophyll a •  Use H2O as the ultimate electron donor for photosynthetic

electron transport, with O2 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

Gleothece sp. Oscillatoria sp. Fischerella sp. MMP Fig. 12.78

Beth Gantt (CBMG)

Cellular differentiation in few cyanobacteria •  Small green vegetative cells -

photosynthesis •  Brown heterocysts - nitrogen

fixation •  Large green endospores –

dormancy •  Contrast to eukaryotes?

Anabaena sp.

Intercellular transport

MMP Fig. 12.80

MMP Fig. 12.79

Geological history of prokaryotic gas exchange

Kasting Sci. Am. 2004

What were the evolutionary consequences of O2 production?

Banded iron formations

Evolutionary consequences of O2 production

C & R Fig. 26.5

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Banded iron formations

Evolutionary consequences of O2 production

•  Eventually, atmosphere changed from reducing to oxidizing conditions.

•  All the soluble Fe2+ in the oceans was oxidized to form insoluble Fe3+ that precipitated to form banded iron formations

•  All anaerobic organisms became restricted to anoxic environments. •  The formation of ozone (O3) layer restricted mutagenic UV

radiation. •  Allowed for the origin of aerobic prokaryotes and larger eukaryotes

C & R Fig. 26.5

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

http://history.smsu.edu/jchuchiak http://pearl.agcomm.okstate.edu

Bubonic plague (black death) Soybean blight

Antibiotics - bacteria-specific compounds

Different antibiotics target different structures or processes.

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Nester et al. Fig. 21.13 R. Stewart

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

R. Stewart from Nester et al. Fig. 21.13

Transmission of antibiotic resistance

VGT to its progeny (same species)

Lateral gene transfer to other species, perhaps pathogens!

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

http://history.smsu.edu/jchuchiak http://pearl.agcomm.okstate.edu

Bubonic plague (black death) Soybean blight Nester et al. Fig 19.4

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

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L"K" J" U" C" A" S" R"

Hrp (hypersensitive response) Central Conserved Region (CCR)"Flagellar biosynthesis" Filamentous phase assembly"

Plant pathogens" Pseudomonas syringae! Erwinia spp" P. fluorescens R. solanacearum! X. campestris! Burkholderia cepacia!

Mammalian pathogens" Yersinia spp – bubonic plague" Salmonella spp. – typhoid fever" Shigella spp. - dysentery" P. aeruginosa - UTIʼs" B. pertussis – whooping cough" Chlamydia spp.- STDʼs"

Steve Hutcheson (CBMG)

Molecular genetics of Type III secretion

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.