Archaebacteria & Bacteria Classification Eukaryote Prokaryote Old 5 Kingdom system Monera, Protists, Plants, Fungi, Animals New 3 Domain system reflects a greater understanding of evolution & molecular evidence Prokaryote: Bacteria Prokaryote: Archaebacteria Eukaryotes Protists Plants Fungi Animals Archaebacteria & Bacteria

(a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral 1 µm 2 µm Fig. 27-2 1 µm 2 µm 5 µm (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral

Structure and Function 3 basic shapes: spherical (cocci), rods (bacillus) and spiral Cell Wall Peptidoglycan covers cell, anchors attachments Archaea have no peptidoglycan

Gram Staining Gram + : simple walls, lots of PTG Gram - : complex walls with lipopolysaccharides less PTG Medical significance: Gram – lipids are toxic causing fever or shock and are resistant to our defenses Gram –: antibiotic resistance (hard for drugs to penetrate) Antibiotics often target peptidoglycan

Prokaryote Cell Wall Structure peptide side chains cell wall peptidoglycan plasma membrane protein Gram-positive bacteria peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides Gram-negative bacteria peptidoglycan plasma membrane outer outer membrane of lipopolysaccharides cell wall

Fig. 27-4 200 nm Capsule

Capsule vs Fimbriae Sticky and covers entire cell Protection from dehydration and shield from immune system Hair like appendages that stick Ex. Neisseria gonorrhoeae sticks to mucus membranes Shorter and more numerous than sex pilli

Fig. 27-5 Fimbriae 200 nm

Motility for most bacteria propel themselves by flagella that are structurally and functionally different from eukaryotic flagella PROK flagella are 1/10 the width of EUK PROK flagella are not covered by plasma mem

Video: Prokaryotic Flagella (Salmonella typhimurium) Motility Different composition and propulsion The motor of the flagella is the basal apparatus (rings embedded in the cell wall) ATP proton pump generates power by turning hook attached Hook is attached to chains of flagellin In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli Video: Prokaryotic Flagella (Salmonella typhimurium)

Flagellum Filament Cell wall Hook Basal apparatus Plasma membrane Fig. 27-6 Flagellum Filament 50 nm Cell wall Hook Basal apparatus Figure 27.6 Prokaryotic flagellum Plasma membrane

Structure cont No organelles: embedded membranes for metabolism Ribosomes (70s instead of 80s) Tetracycline and erythromyocin attach ribosomes Nucleoid region for chromosome Circular, naked chromosome Plasmids (extra chromosomal)

Fig. 27-8 Chromosome Plasmids 1 µm

Variations in Cell Interior mitochondria cyanobacterium (photosythetic) bacterium aerobic bacterium chloroplast internal membranes for photosynthesis like a chloroplast (thylakoids) internal membranes for respiration like a mitochondrion (cristae)

Reproduction and Adaptation Binary fission in optimal conditions every 1-3 hours (E.coli every 20 min usually 1/24 hr) They are small, repro binary fission and short generation time Endopsores (ability to endure hardship)

0.1 mL (population sample) Fitness relative to ancestor Fig. 27-10 EXPERIMENT Daily serial transfer 0.1 mL (population sample) Old tube (discarded after transfer) New tube (9.9 mL growth medium) RESULTS 1.8 1.6 Figure 27.10 Can prokaryotes evolve rapidly in response to environmental change? Fitness relative to ancestor 1.4 1.2 1.0 5,000 10,000 15,000 20,000 Generation

Rapid Evolution: high genetic diversity 2 strains of E.coli differ in an rRNA gene more than between a human and a platypus Rapid reproduction Mutation Genetic recombination

Mutation Probability of a spontaneous mutation in an E.coli gene is 1 in 10 million/division 2x1010 new E.coli per day About 2000 bacteria will have mutations 4300 genes total in E.coli 4300 x 2000 = 9 million mutation per day in the human intestines

Genetic Recombination Transformation: uptake foreign DNA Ex. Competent cells, pneumonia Transduction: a bacteriophage performs horizontal gene transfer Conjugation Plasmids

Fig. 27-11-4 Phage DNA A+ B+ A+ B+ Donor cell A+ Recombination Figure 27.11 Transduction A+ A– B– Recipient cell A+ B– Recombinant cell

Conjugation and Plasmids Conjugation is the process where genetic material is transferred between bacterial cells Sex pili allow cells to connect and pull together for DNA transfer A piece of DNA called the F factor is required for the production of sex pili The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome

Fig. 27-12 Figure 27.12 Bacterial conjugation 1 µm Sex pilus

The F Factor as a Plasmid Cells containing the F plasmid function as DNA donors during conjugation Cells without the F factor function as DNA recipients during conjugation The F factor is transferable during conjugation

Fig. 27-13 F plasmid Bacterial chromosome F+ cell F+ cell Mating bridge F– cell F+ cell Bacterial chromosome (a) Conjugation and transfer of an F plasmid Recombinant F– bacterium Hfr cell A+ A+ A+ F factor Figure 27.13 Conjugation and recombination in E. coli A+ A– A+ A– A– A+ A– F– cell (b) Conjugation and transfer of part of an Hfr bacterial chromosome

R Plasmids and Antibiotic Resistance R plasmids carry genes for antibiotic resistance Antibiotics select for bacteria with genes that are resistant to the antibiotics Antibiotic resistant strains of bacteria are becoming more common

Bacterial Diversity Major nutritional modes Role of oxygen in metabolism Nitrogen metabolism nitrogen fixation: converting N2 from the atmosphere into ammonia NH3 Metabolic Cooperation colony of cyanobacterium Anabaena (filaments) genes for photosynthesis (most cells) and N fixation)few heterocytes) but one cell cannot perform both Biofilms

Table 27-1 Table 27-1

Photosynthetic cells Heterocyte 20 µm Fig. 27-14 Figure 27.14 Metabolic cooperation in a colonial prokaryote 20 µm

Prokaryotic phylogeny Horizontal gene transfer (ring instead of a tree) Archaea more closely related to eukaryotes than bacteria polyphyletic Eukarya Archaea Bacteria Eukarya Bacteria Archaea

Domain Eukarya Eukaryotes Korarcheotes Euryarchaeotes Domain Archaea Fig. 27-16 Domain Eukarya Eukaryotes Korarcheotes Euryarchaeotes Domain Archaea Crenarchaeotes UNIVERSAL ANCESTOR Nanoarchaeotes Proteobacteria Chlamydias Figure 27.16 A simplified phylogeny of prokaryotes Spirochetes Domain Bacteria Cyanobacteria Gram-positive bacteria

Table 27-2 Table 27.2

Proteobacteria These gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs Some are anaerobic, and others aerobic

Subgroup: Alpha Proteobacteria Fig. 27-18a Subgroup: Alpha Proteobacteria Alpha Beta Gamma Proteobacteria Delta Epsilon 2.5 µm Rhizobium (arrows) inside a root cell of a legume (TEM) Subgroup: Beta Proteobacteria Subgroup: Gamma Proteobacteria 1 µm 0.5 µm Nitrosomonas (colorized TEM) Thiomargarita namibiensis containing sulfur wastes (LM) Figure 27.18 Major groups of bacteria For the Discovery Video Bacteria, go to Animation and Video Files. Subgroup: Delta Proteobacteria Subgroup: Epsilon Proteobacteria B. bacteriophorus 10 µm 5 µm 2 µm Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Bdellovibrio bacteriophorus attacking a larger bacterium (colorized TEM) Helicobacter pylori (colorized TEM)

Subgroup: Alpha Proteobacteria Many species are closely associated with eukaryotic hosts Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis

Example: Rhizobium, which forms root nodules in legumes and fixes atmospheric N2 Arrows in the next slide are Rhizobium Example: Agrobacterium, which produces tumors in plants and is used in genetic engineering

Rhizobium (arrows) inside a root cell of a legume (TEM) Fig. 27-18c 2.5 µm Figure 27.18 Major groups of bacteria—alpha proteobacteria Rhizobium (arrows) inside a root cell of a legume (TEM)

Cyanobacteria These are photoautotrophs that generate O2 Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis Two species of Oscillatoria, filamentous cyanobacteria (LM)

Concept 27.6: Prokaryotes have both harmful and beneficial impacts on humans Some prokaryotes are human pathogens, but others have positive interactions with humans Prokaryotes cause about half of all human diseases Lyme disease is an example

5 µm Fig. 27-21 Figure 27.21 Lyme disease For the Discovery Video Antibiotics, go to Animation and Video Files.

Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins Exotoxins cause disease even if the prokaryotes that produce them are not present Endotoxins are released only when bacteria die and their cell walls break down Many pathogenic bacteria are potential weapons of bioterrorism