Transcript Who is this? - Susquehanna University

THE
PROKARYOTES
Systematics
• Focus on animals and plants
– History limited to 20% of evolutionary time
• How to classify
prokaryotes?
Limited in
morphological
characters
Carl Richard Woese
1928-2012, USA; Developed system based on 16S rRNA in 1977
Carl Woese and George Fox
rRNA
Emile Zuckerkandl (1922-2013);
Austria & USA. Molecular
biology and molecular clock
Linus Carl Pauling (1901-1994)
USA Founder of fields like
quantum chemistry and
molecular biology
Suggested that a tree of life
might be generated by
comparing sequences of
biopolymers like RNA
Zuckerkandl and Pauling
Flow of information in a cell…
• When DNA is
transcribed, the
result is an RNA
molecule
DNA molecule
Gene 1
Gene 2
Gene 3
DNA strand
Transcription
RNA
Translation
Codon
Polypeptide
Amino acid
Figure 10.10
• When DNA is
transcribed, the
result is an RNA
molecule
DNA molecule
Gene 1
Gene 2
Gene 3
• RNA is then
translated into a
sequence of amino
acids
DNA strand
Transcription
RNA
Translation
Codon
Polypeptide
Amino acid
Figure 10.10
Ribosomal Function
A typical prokaryotic cell
may have
10,000+ ribosomes
Where does rRNA enter the
picture?
Ribosomal Structure
Two subunits
Ribosomal subunits=
rRNA molecules + proteins
Prokaryotes
Eukaryotes
What’s the ‘S’?
• Svedberg units: a measure of how
quickly particles sediment in an
ultracentrifuge
What’s the ‘S’?
• Svedberg units: a measure of how
quickly particles sediment in an
ultracentrifuge
• Larger the particle, the greater its S value
• Smaller subunit of a ribosome sinks slower
than the larger subunit
Why then does
5S + 23S = 50S?
Why then does
5S + 23S = 50S?
Shape AND size
determine
sedimentation
rate…
Ribosomal RNA Molecules
• Components of the ribosomes of ALL
ORGANISMS
• Changes in nucleotide sequence indicative of
evolutionary history
• “highly conserved molecules”…
What does this mean?
Ribosomal Function
• PROTEIN SYNTHESIS
• Not much room for error!
• Disruption of ribosome structure likely to
disrupt protein synthesis…
Life threatening!
Practical applications…
• Some antibiotics (e.g. erythromycin and
streptomycin) work by targeting the 70S
ribosomes
• Alter shape and prevent bacteria from
synthesizing proteins needed to survive
• Why are our own ribosomes not affected
by the same drugs???
A modification of Woese from Brock et al. (1994).
Two different supertrees generated by ML methods for
complete genomes of 45 taxa. Daubin et al. 2002
Ciniglia et al. 2004
Lang et al. 2013
Using 24 genes and
3000 taxa
Gram Stain and Structure
Eubacteria
• >9 Kingdoms
• Same type of ribosomes
• Polysaccharide of outer
wall made of murein
• Most groups involved in
global nutrient cycling
• Many of economic
importance
• Disease
• Other functions (e.g.
antibiotic producers)
Proteobacteria
• Disparate functional
groups joined by
molecular sequences
• Likely the source of
mitochondria
Alphaproteobacteria
• Rikettsias (typhus Rocky
Mtn spotted fever
• Rhizobias (N-fixing
bacteria)
• Likely the ancestor of
mitochondria was from this
group
Gammaproteobacteria
• Usually small rods or
cocci
• Causative agents of
Bubonic Plague,
Tuleremia, Legioner’s
Disease, Cholera
• Includes Escherichia coli
Spirochaetae
Spirochaetae
• Spiraled with internal
flagella
• Many are free-living
• Causative agents of
Lyme disease,
syphilis, yaws, and
relapsing fever
Cyanobacteria
Cyanobacteria
•Like free-living chloroplast
•Group from which chloroplasts
appeared
•Form filaments, colonies
•Very large for bacteria
•Some produce toxins
•Many are nuisance algae in overfertilized waters
•Source of most atmospheric
oxygen, especially prior to
eukaryotes
Firmicutae
• Lack second outer
membrane of
Eubacteria
• Gram positive
Aphragmabacteria
• Tiny, smallest
genome of any nonvirus
• No walls
• Obligate parasites
• One causes
pneumonia; many
plant pathogens
Anoxybacteria
• Obligate anaerobes
• Causative agents of
botulism and tetanus
• Botox
• Common in soil and
animal digestive systems
Endosporobacteria
• Produce resistant spores
• Many major human
pathogens, including
anthrax, staph (including
methicillin-resistant
Staphylococcus aureus),
strep
• Includes Lactobacillus
Actinobacteria
• Many are slow-growing and funguslike
• Antibiotic sources (e.g.
streptomycin, actinomycin)
• Causative agents of leprosy and
tuberculosis; diptheria
• Bacteria which cause holes in Swiss
cheese
• Bifida, a necessary commensal in
our lower bowel
Deinococcobacteria
• Thermophiles
• Deinococcus withstands
6,000 rads (and up to
1500 megarads)
• Thermus, found at
Yellowstone, enzymes
used for PCR
Archaea
Differ from the Eubacteria
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Form of ribosomes
No murein
Different lipids
Different RNA polymerase
Crenarchaea
• These are the
hyperthermophiles
• They tend to inhabit
very hot environments
that are rich in sulfur
Euryarchaeota
• Halobacteria
• Methanobacteria
• Thermoplasmobacteria
Viruses
• Non-cellular
• Usually nucleic acid
and protein
• Types
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DNA (ss & ds)
RNA (ss & ds)
DNA RT
RNA RT
Prions
Some Human Viral Diseases
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Herpes
Smallpox
Hepatitis (B, C, D)
Yellow Fever
Dengue fever
West Nile
HIV
Ebola
Rabies
Chicken Pox
/Shingles
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Rubella (German Measles)
Influenza
Polio
Mumps
Measles
Epstein-Barr
Hemorrhagic fever
Rota
Rhinovirus
Transmissible spongiform
encephalopathy (TSE)
Theories on Origin of Viruses
• Regressive Hypothesis: cellular parasites of
larger cells that became simplified
• Cellular Origin Hypothesis: pieces of living cells
that can replicate (e.g. strands of nucleic acids
like plasmids or transposons)
• Coevolution Hypothesis: evolved together with
the first cells as their parasites