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 .
The Prokaryotic Domains
Mycobacterium tuberculosis Color-enhanced images shows rod-shaped bacterium responsible for tuberculosis (Raven et al 2002)
Structure of a Prokaryotic Cell
Structure of a Eukaryotic Plant Cell
Genome of the Archaeon Methanococcus jannaschii was sequenced in 1996. Sequencing of M. jannashcii confirmed Carl Woese’s long-standing 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”
Cyanobacteria 10 um dia.
E. coli 1X2 um
Mycoplasma 0.3-0.8 um dia.
Bacteriophage 0.07X 0.2 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.
Paramecium 30X 75 um
Sizes of viruses, bacteria and eukaryotes compared Most bacteria are 1-5 um diameter (most Eukaryotic cells are 10-100 um)
Bacillus on the head of a pin
Rod-shaped bacillus(E. coli)
Bacterial FormThree shapes are especially common among bacteria – spheres, rods and spiralsMost 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)
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)
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 cross-linked by short polypeptides
Lyme disease symptoms, and the disease vector – a tick
Electron micrograph of E. coli shoing long helical flagella.
Vibrio cholerae (pathogen responsbible for cholera); the unsheathed core visible at top of photo is composed of a single crystal of the protein flagellin.
In intact flagella, core is surrounded by a flexible sheath. Rotary motion of the motor creates a kind of rotary motion when organism swims.
Bacteria swim by rotating their flagella.
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.
The mesosome is an infolding of the plasma membrane serves as a point of attachment for DNA in some bacterial cells
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
Cell divisionAsexual reproduction by cell division via binary fission
Mechanisms of gene transfer-transformation; genes from environment-conjugation; genes from another prokaryote-transduction genes via a virus
Adaptationshort 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
Dormancy and Endosporulation Some bacteria form highly resistant spores under harsh environmental conditions
Antibiotic synthesisSome prokaryotes (and protists and fungi) synthesize and release antibiotic chemicals that inhibit growth of other microbes
Sporulating Bacillus cell
Adaptations to Harsh Environmental Conditions: Some bacteria are capable of dormancy, endosporulation and antibiotic synthesis
Overview of photosynthesis and respiration
Overview of cellular respiration One (very important!!) example of metabolic pathways by which many species obtain energy for generating ATP by oxidizing reduced organic compounds
Highly reduced molecule, glucose, serves as original electron donor (ie, molecule is oxidized) and highly oxidized molecule, oxygen, serves as final electron acceptor
Overview of Photosynthesis
Many prokaryotes generate ATP by employing electron donors and acceptors other than sugars and oxygen, and produce by-products other than water
Some Electron Donors and Acceptors Used by Bacteria and Archaea
Electron Donor Electron Acceptor Product Metabolic Strategy *
H2 or organic compounds SO42- H2S sulfate-reducers
H2 CO2 CH4 methanogens
CH4 O2 CO2 methanotrophs
S or H2S O2 SO42- sulfur bacteria
organic compounds Fe3+ Fe2+ iron-reducers
NH3 O2 NO2- nitrifiers
organic compounds NO3- N2O, NO or N2 denitrifiers (or nitrate reducers)
NO2- O2 NO3- nitrosifiers
* This column gives the name biologists use to identify species that use a particular metabolic strategy
nitrification: oxidation of ammonia to nitrite and nitrate ions
denitrification: reduction of nitrogen-containing ions to form nitrogen gas and other products
Lateral Gene Transfer. Gray branches show diversification of the three domains. Red branches show movement of genes from species in one part of the tree to species in other parts
Why Three Domains?
General Biology of the Prokaryotes
Prokaryotes in Their Environments
Prokaryote Phylogeny and Diversity
Some prokaryotes play key roles in global nitrogen and sulfur cycles. Nitrogen fixers, nitrifiers, and denitrifiers do so in the nitrogen cycle. Review Figure 26.10