1. 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

2. 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

3. Fig. 27-1

4. 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

5. layer Carbohydrate portion of lipopolysaccharide Outer membrane
Fig. 27-3
Carbohydrate portion
of lipopolysaccharide
Outer
membrane
Peptidoglycan
layer
Cell
wall
Cell
wall
Peptidoglycan
layer
Plasma membrane
Plasma membrane
Protein
Protein
Gram-
positive
bacteria
Gram-
negative
bacteria
20 µm
(a) Gram-positive: peptidoglycan traps
crystal violet.
(b) Gram-negative: crystal violet is easily rinsed away,
revealing red dye.

6. 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

7. 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

8. Bacterial Populations
They are very small organisms – 5 mm ( eukaryotic are 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

9. Diversity Three events lead to diversity Rapid reproduction Mutation
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

10. 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

11. Fig
Phage DNA A+ B+ A+ B+
Donor
cell A+
Recombination A+ A– B–
Recipient
cell A+ B–
Recombinant cell

12. Fig
F plasmid
Bacterial chromosome
F+ cell
F+ cell
Mating
bridge
F– cell
F+ cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Recombinant
F– bacterium
Hfr cell A+ A+ A+ A+
F factor A– A+ A– A– A+ A–
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome

13. Metabolic adaptations (table 27.1)

14. Metabolism Oxygen Metabolism Nitrogen Metabolism Metabolic Cooperation
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 

15. 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

16. Groups of Bacteria
Eukarya
Archaea
Bacteria

17. Subgroup: Alpha Proteobacteria
Fig a
Subgroup: Alpha Proteobacteria
Alpha
Beta
Gamma
Proteobacteria
Delta
2.5 µm
Epsilon
Rhizobium (arrows) inside a
root cell of a legume (TEM)
Subgroup: Beta Proteobacteria
Subgroup: Gamma Proteobacteria
1 µm
0.5 µm
Nitrosomonas (colorized TEM)
Thiomargarita namibiensis
containing sulfur wastes (LM)
Subgroup: Delta Proteobacteria
Subgroup: Epsilon Proteobacteria
B. bacteriophorus
10 µm
5 µm
2 µm
Fruiting bodies of
Chondromyces crocatus, a
myxobacterium (SEM)
Bdellovibrio bacteriophorus
attacking a larger bacterium
(colorized TEM)
Helicobacter pylori (colorized TEM)

18. GRAM-POSITIVE BACTERIA
Fig i
CHLAMYDIAS
SPIROCHETES
2.5 µm
5 µm
Chlamydia (arrows) inside an
animal cell (colorized TEM)
Leptospira, a spirochete
(colorized TEM)
CYANOBACTERIA
GRAM-POSITIVE BACTERIA
50 µm
1 µm
5 µm
Hundreds of mycoplasmas
covering a human fibroblast
cell (colorized SEM)
Two species of Oscillatoria,
filamentous cyanobacteria (LM)
Streptomyces, the source of
many antibiotics (colorized SEM)

19. 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

20. Negative Impacts of Bacteria
Parasitic bacteria that cause disease are called PATHOGENS
Opportunistic
Exotoxins and endotoxins