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
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 - PowerPoint PPT Presentation
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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
(b) Gram-negative: crystal violet is easily rinsed away, revealing red dye.
20 µm
Cellwall
Plasma membrane
Protein
Carbohydrate portionof lipopolysaccharide
Outermembrane
Peptidoglycanlayer
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 Populations1. They are very small organisms
0.5 – 5 m ( eukaryotic are 10-100 m)2. They reproduce by binary fission3. They have very short generation times4. ENDOSPORES can survive harsh
conditions and survive for centuries5. MSU study looked at 20,000
generations in 8 years – evidence of evolution
6. Simpler – but not inferior or primative7. 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
Recombinant cell
Recipientcell
A+ B–
B–
A+
A–
Recombination
A+
Donorcell
A+ B+
A+ B+
Phage DNA
Fig. 27-13
F plasmid
F+ cell
F– cell
Matingbridge
Bacterial chromosome
Bacterialchromosome
(a) Conjugation and transfer of an F plasmid
F+ cell
F+ cell
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
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