prokaryotes ap biology spring 2011. domains the two domains of prokaryotes describe the unique...
TRANSCRIPT
Prokaryotes
AP BiologySpring 2011
Domains the two domains of prokaryotes
Describe the unique characteristics of prokaryotes and their metabolic diversity
Discuss how prokaryotes reproduce Give examples of positive and
negative impacts of bacteria on humans
Viruses
Read chapter 21.1-21.2 Good refresher on viruses Remember:
StructureViral replication
http://www1.teachertube.com/viewVideo.php?title=Viral_infection_and_replication&video_id=50887
Viroids and Prions
Since the 1970’s about 30 viroids have been identified
A viroid is a small circle of RNA that can affect organisms
Most affect plants; only one viroid known to affect humans
Prions are misfoldings of proteinsAccumulate in nervous system cellsCause cell death and a spongiform
pathology in the brain cell
Prokaryotes- Enduring, Abundant, and Diverse
The earliest cells were prokaryotes, cells with no nucleus
Bacteria:Classified based on shape, cell wall
properties, metabolism, and other properties
Automated gene sequencing has elucidated prokaryote diversity
Shortly after life began there was a branching between bacteria and Archae Which eventually led
to Eukaryote lineage Despite estimates of
millions of species of bacteria, only about 5,000 named
Bacteria are very successful and terms of reproduction
Metabolic diversity is key to reproductive success in bacteria
Metabolic diversity:Photoautotrophs are
photosynthetic Cyanobacteria
Chemoautotrophs use electrons that they strip from inorganic compounds and use that energy to build organic compounds from CO2 and water
Photoheterotrophs use light energy and obtain carbon from organic compounds from their environment
Chemoautotrophs get both their carbon and their energy by breaking down organic compounds This group includes many prokaryotes, some
protists, and all animals and fungi Usually parasites- get butrients from living host
Prokaryotic Structure and Function
Modern prokaryotes include bacteria and archeansThey are unicellular and do not enclose
their DNA in a nucleus All prokaryotes have ribosomes Some have infoldings of their
membrane Nearly all have a cell wall, some have an
external slime coat that helps them adhere to surfaces
Gram staining: can identify many bacteria species by their wall staining properties
Unknown species exposed to purple dye, then iodine, then alcohol wash, and finally a counterstain
Gram-positive: stays purple Gram-negative: loses colour
at first, then counterstain turns it pink
Glycocalyx: sticky mesh, consists of polysaccharides, polypeptides, or both Capsule: when highly organized and
attached firmlySlime layer: when less organized, and
loosely attached
Three basic shapes:Coccus:
Spherical Bacillus:
Rod Cylindrical
Spirillum: Helical
Two kinds of filamentous structures may be attached to the cell wallBacterial flagellum: rotates like a
propeller to pl the cell along Pili: help bacteria attach to another in
conjugation (exchange of DNA), or help them attach to surfaces
Reproductive rates in prokaryotes are high, some species can reproduce every 20 minutes
Some species reproduce using a budding mechanism
More commonly, reproduce with fission that is similar to mitosis
Some bacteria can also pass along genes without reproducing
During conjugation a plasmid, a small, self-replicating circle of DNA containing only a few genes, can be passed to another cell
Some F (fertilty) plasmids allow bacteria to engage in bacterial conjugation in which a pilus joins two prokaryotic cells to permit the transfer of plasmid DNA
Prokaryotic Growth and Reroduction
When a bacterium divides, each daughter cell inherits a single chromosomeCircular double-stranded DNA molecule
Bacteria reproduce by prokaryotic fissionResults in two genetically identical daughter
cellsOnly bacteria and archaens reproduce by
this type of cell division
A plasmid is small, self-replicating circle of DNA containing only a few genes
Some F (fertility) plasmids allow bacteria to engage in bacterial conjugation in which a pilus joins two prokaryotic cells to permit transfer of plasmid DNA
Conjugation
The Bacteria
Thermophiles exist in extreme environments
Members of the genus Aquifex include bacteria that live in volcanic spring, thermal vents, and hot springs
Chloroplast-containing bacteria Anabaena: by means of heterocysts, can
fix nitrogen
Make up largest, most diverse bacterial group (gram negative)
Theiomargarita namibiensis:Chemeoautotroph that lives in marine
environments and gets its energy from striping electrons from sulfur
Rhizobium: fixes nitrogen on roots of legumes
E. Coli & H. Pylori:Live in human digestive system
E. Coli
Some free living, chemoautotrophic proteobacteria exhibit complex behavior Magnetoacteria: attracted by magnetic
fields
Myxobacteria: move as a group and feed on soil bacteria
Gram Positive: Not a monophyletic group
If all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group
Most are chemioheterotrophs with thick cell walls that retain gram stain
Lactobacillus: used in dairy product conversions such as yogurt
L.acidophilus: lowers the pH of skin and vaginal linings
Some form resistant endospores that can survive harsh environmental conditionsEx. Clostridium tetani (tetnus)
Tetnus
Spirochetes: resemble a springResposible for causing Lyme diseaseFree living parasites or symbionts
Clamydias: intracellular parasites that affect animal cellsCannot make DNA, pilfer it from cells
Archaeans
Archaeans: differ in their ribosomal DNA and cell wallsResemble eukaryotic cells
by making histones and sharing the same start codon for transcription
Some may resemble first cells on Earth
Recently this group has been subdivided into 3 major groups
Methane makers Inhabit swamps, mud, sewage, and animal guts Make ATP anaerobically by converting carbon
dioxide and hydrogen to methane Free oxygen kills them
Salt lovers Can tolerate high salt environments
such as brackish ponds, salt lakes, volcanic vents on seafloor, and the like
Most are heterotrophic aerobes, some can switch to a special photosynthesis, using bacteriorhodopsin to produce ATP Light activating pigment embedded in
plasma membrane, when it absorbs sunlight energy, changes shape and pumps H+ out from cell. H+ flows back into it, through ATP synthase and drives ATP formation
Heat lovers Live in hot springs and other very hot
places such as thermal vents of the sea floor where temps exceed 250 degrees C
Use sulfur as source of electrons for ATP formation