Ch. 27: Bacteria and Archaea
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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)
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
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.
Nutrient supply
Toxins/ poison selves
Competition
Space - pressure
Bacterial Populations
1. They are very small organisms
2.
3.
4.
5.
6.
7.
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
Genetic Recombination
Transformation
Bacteria are able to absorb genetic
information from their surroundings
Transduction
Bacterial genes are also spread between
bacteria populations by viruses known as
bacteriophages
Conjugation
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 –
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