TER 26. Preview for 2/6/02 Dr. Kopeny. Bacteria and Archaea: The Prokaryotic Domains. Nitrogen cycle

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1 Preview for 2/6/02 Dr. Kopeny Bacteria and Archaea: The Prokaryotic Domains TER 26 Nitrogen cycle Mycobacterium tuberculosis Color-enhanced images shows rod-shaped bacterium responsible for tuberculosis (Raven et al 2002) Endosymbiotic Theory Structure of a Eukaryotic Animal Cell Structure of a Prokaryotic Cell Prokaryotic cells have a simple interior organization compared to Eukaryotes. -True nucleus lacking -Cytoskeleton lacking-support from rigid cell wall -Membrane-bound organelles lacking (in most) Structure of a Eukaryotic Plant Cell

2 structure and function origins, evolution and diversity ecological function and relationships 1. Prokaryote Phylogeny

3 Genome of the Archaeon Methanococcus jannaschii was sequenced in Sequencing of M. jannashcii confirmed Carl Woese s longstanding hypothesis that life traces back to three main lineages, one of which (Archaea) includes prokaryotes that share a more recent common ancestry with eukaryotes than with the prokaryotic true bacteria Prokaryotic Structure and Function

4 (Keaton 1993) Cyanobacteria 10 um dia. E. coli 1X2 um Mycoplasma um dia. Bacteriophage 0.07X 0.2 um Paramecium 30X 75 um Viroid 0.01 X 0.3 um Lymphocycte 10 um dia. Largest known prokaryote is the marine bacterium Thiomargarita namibiensis; bright white cell in upper left, about.75 mm dia., attached to two dead ones. Fruitfly in picture for size comparison. Sizes of viruses, bacteria and eukaryotes compared Most bacteria are 1-5 um diameter (most Eukaryotic cells are um) Bacillus on the head of a pin Raven et al 2002 Spherical coccus (Enterococcus) Pseudomonas aeruginosa Streptococcus Spirillum volutans Bacterial Form Rod-shaped bacillus (E. coli) Three shapes are especially common among bacteria spheres, rods and spirals Most are unicellular, some aggregate transiently, some form permanent aggregations of identical cells;some show division of labor between two or more specialized cell times Helical spirilla ( Aquaspirillum spirosa)

5 Scanning electron micrograph of a colony of streptomyces, one of the actinomycetes. The actinomycetes have a much more complicated morphology than most other bacteria. (Keaton and Gould 1993) Penicillium chrysogenum Neisseria gonorrhoeae E. coli Most bacterial cell walls contain peptidoglycan (lacking in Archaea) Gram staining is an important technique for identifying bacterial; cells stain differentially based on structure and composition of walls Pathogenesis is related to cell wall structure and composition Many antibiotics act by preventing formation of cell walls, by inhibiting synthesis of cross-links in peptidoglycan Many prokaryotes produce capsules that function in adherance and protection Many prokaryotes have surface appendages called pili that are function in adherance The exterior surfaces of Prokaryotes. Almost all prokaryotes have a cell wall, and in most that wall contains peptidoglycan polymers of modified sugars that are crosslinked by short polypeptides

6 Aquaspirillum sinosum Spirillum volutans Borrelia burgdorferi Lyme disease symptoms, and the disease vector a tick Mechanisms of Motility Many bacteria are motile. Fllagellar action is the most common,but not the only mechanism, for generating movement. Prokaryotic flagella Flagella-like helical filaments Growing gelatinous threads Motility Behavior Kinesis Taxis 0.05 um 1 um Electron micrograph of E. coli shoing long helical flagella.

7 Vibrio cholerae (pathogen responsbible for cholera); the unsheathed core visible at top of photo is composed of a single crystal of the protein flagellin. Bacteria swim by rotating their flagella. In intact flagella, core is surrounded by a flexible sheath. Rotary motion of the motor creates a kind of rotary motion when organism swims. mesosome plasma membrane DNA The mesosome is an infolding of the plasma membrane serves as a point of attachment for DNA in some bacterial cells Exensive folded photosynthetic membranes are visisble in Prochloron cell. The single, circular DNA molecule is located in the clear area in the central region of the cell. various specialized membranes, but lacking extensive compartmentalization by internal membranes ribosomes present but differ from eukaryotic ones in size and composition genomes are smaller and simpler than in eukaryotes; one major chromosome and, in some species, plasmids Processes of DNA replicatin and protein translation are generally similar to eukaryotes Infoldings of plasma membrane, similar in ways to cristae of mitochondria, function in cellular respiration in aerobic bacteria Thylakoid membranes of photosynthetic cyanobacteria Cellular and Genomic Organization The organization of cellular components, including the genome, differs substantially between prokaryotes and eukaryotes

8 Cell division Asexual reproduction by cell division via binary fission Mechanisms of gene transfer -transformation -conjugation -transduction Adaptation short generation time allows favorable mutations and novel genomes arising from gene transfer to spread quickly in rapidly reprducing Growth virtual geometric growth while in environments with unlimited resources Prokaryote Reproduction and Population Growth Prokaryote populations grow and adapt rapidly, through asexual reproduction as well as mechanisms involving gene transfer Sporulating Bacillus cell Dormancy and Endosporulation Some bacteria form highly resistant spores under harsh environmental conditions Antibiotic synthesis Some prokaryotes (and protists and fungi) synthesize and release antibiotic chemicals that inhibit growth of other microbes Bacillus anthracus Adaptations to Harsh Environmental Conditions: Some bacteria are capable of dormancy, endosporulation and antibiotic synthesis