Transcript Ch. 27: Bacteria and Archaea

Ch. 27: Bacteria and Archaea
 Modern/regular/eubacteria
 and the ancient methanogens
 Prokaryote  cells with cell membranes,
cytoplasm/cytosol, DNA in the form of
one circular chromosome and many
plasmids, and 70s ribosomes.
 Shapes are cocci, bacilli, spirillum
 May have cell wall, flagella, cilia and
other structures
Adaptations
 Adaptations to extremes of climate from
freezing to boiling to acidic and salty.
(species specific ranges)
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Salt tolerant up to 32%
Hot springs - thermophiles
Near frozen waters at arctic
Acid conditions; 0.03 pH !! – acidophiles
3 million Rads of radiation
Fig. 27-1
Structure and functions
contribute to success
 Unicellular but may aggregate into colonies
 Cell walls; Gram positive and gram negative
based on peptidoglycans and lipids
 Capsules; waxy layer that helps avoid
antibiotics
 Fimbriae (like velcro) and pili (trade plasmids)
 Motility; cilia and flagella and taxis; roughly 50%
are capable of movement – at relatively fast speeds
 Plasmids
Fig. 27-3
Carbohydrate portion
of lipopolysaccharide
Peptidoglycan
Cell
wall
Cell
layer
wall
Outer
membrane
Peptidoglycan
layer
Plasma membrane
Plasma membrane
Protein
Protein
Grampositive
bacteria
(a) Gram-positive: peptidoglycan traps
crystal violet.
Gramnegative
bacteria
20 µm
(b) Gram-negative: crystal violet is easily rinsed away,
revealing red dye.
Internal and Genomic Organization
 Not usually any internal, membrane-bound
structures
 May have specialization built into PLASMA
MEMBRANE
 70s ribosomes; smaller than eukaryotic, solid
(erythromycin and tetracycline)
 Nucleoid region
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One, circular chromosome, hundreds of genes, fills
central portion,
Many plasmids – copies of frequently or currently
used genes
Adaptations of reproduction
 Binary fission – one cell divides into 2 those into
4 those into 8, etc.
 Can occur every hour at optimal conditions,
some species every 20 minutes, typical is 24 hours
 1 bacteria could create a colony outweighing
Earth in 3 days…. Obvious checks and
balances here.
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Nutrient supply
Toxins/ poison selves
Competition
Space - pressure
Bacterial Populations
1. They are very small organisms
2.
3.
4.
5.
6.
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0.5 – 5 mm ( eukaryotic are 10-100 mm)
They reproduce by binary fission
They have very short generation times
ENDOSPORES can survive harsh
conditions and survive for centuries
MSU study looked at 20,000
generations in 8 years – evidence of
evolution
Simpler – but not inferior or primative
On Earth for over 3.5 billion years now
Diversity
 Three events lead to diversity
 Rapid reproduction
 Most variety in sexually reproducing species is
from arrangement/ shuffling of alleles during
meiosis
 Insertions, deletions, base pair substitutions
 Mutations still very RARE, but sheer numbers of
organisms and time per generation means more
are expressed
 Mutation
 More variety in ribosomal RNA between 2 strains
of E.coli than between human and platypus
 Genetic recombination
 Next page
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Genetic Recombination
 Transformation
 Bacteria are able to absorb genetic
information from their surroundings
 Transduction
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Bacterial genes are also spread between
bacteria populations by viruses known as
bacteriophages
 Conjugation
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Pili bridge bacteria and they trade plasmids
F factor and R factor
Fig. 27-11-4
Phage DNA
A+ B+
A+ B+
Donor
cell
A+
Recombination
A+
A– B–
Recipient
cell
A+ B–
Recombinant cell
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
Hfr cell
A+
A+
F factor
F– cell
A+
A+
A–
Recombinant
F– bacterium
A–
A–
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
A+
A–
A+
Metabolic adaptations (table 27.1)
Metabolism
 Oxygen Metabolism
 Obligate aerobes
 Obligate anaerobes
 Facultative anaerobes
 Nitrogen Metabolism
 N is essential for amino acids
 Atmospheric N isn’t highly useable
 Microbes ‘fix’ nitrogen into nitrate, nitrites and
ammonium ions that are useable
 Metabolic Cooperation
 Colonies of cells that fix nitrogen and produce
oxygen so that neighboring area is hospitable
 Ocean floor and dental plaque 
Molecular Systematics
 Previously bacterial classification (systematics)
used motility, shape, nutrition and gram staining
 Molecular systematics has drastically changed
the classification –
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Much more diverse than assumed
6000+ species/strains ID and named
A soil sample could contain over 10,000 species
Horizontal transfers of genes blur “root” for this
region of the tree of life
 Two main branches are Archaea and Bacteria
Groups of Bacteria
Eukarya
Archaea
Bacteria
Fig. 27-18a
Subgroup: Alpha Proteobacteria
Alpha
Beta
Gamma
Proteobacteria
2.5 µm
Delta
Epsilon
Rhizobium (arrows) inside a
root cell of a legume (TEM)
Subgroup: Beta Proteobacteria
0.5 µm
1 µm
Subgroup: Gamma Proteobacteria
Thiomargarita namibiensis
containing sulfur wastes (LM)
Nitrosomonas (colorized TEM)
Subgroup: Delta Proteobacteria
Subgroup: Epsilon Proteobacteria
Fruiting bodies of
Chondromyces crocatus, a
myxobacterium (SEM)
Bdellovibrio bacteriophorus
attacking a larger bacterium
(colorized TEM)
2 µm
5 µm
10 µm
B. bacteriophorus
Helicobacter pylori (colorized TEM)
Fig. 27-18i
SPIROCHETES
Chlamydia (arrows) inside an
animal cell (colorized TEM)
5 µm
2.5 µm
CHLAMYDIAS
Leptospira, a spirochete
(colorized TEM)
Two species of Oscillatoria,
filamentous cyanobacteria (LM)
1 µm
GRAM-POSITIVE BACTERIA
5 µm
50 µm
CYANOBACTERIA
Streptomyces, the source of
many antibiotics (colorized SEM)
Hundreds of mycoplasmas
covering a human fibroblast
cell (colorized SEM)
Positive Roles of Bacteria
 Decomposers
 Symbioses
 Mutualism
 Commensalism – normal flora
 (parasitism – not positive)
 Chemical recycling
 Nitrogen
 Oxygen
 Carbon
 Research and Technology
 Food (cheese) and beverages
 Waste water treatment
 Genetic engineering
Negative Impacts of Bacteria
 Parasitic bacteria that cause disease are
called PATHOGENS
 Opportunistic
 Exotoxins and endotoxins