Ch. 27: Bacteria and Archaea

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
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

1. They are very small organisms 0.5
   5 mm ( eukaryotic are 10-100 mm)
2. They reproduce by binary fission
3. They have very short generation times
4. ENDOSPORES can survive harsh conditions and
   survive for centuries
5. MSU study looked at 20,000 generations in 8 years
   evidence of evolution
6. Simpler but not inferior or primative
7. On Earth for over 3.5 billion years now

9
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

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. 27-11-4
Phage DNA
A
B
A
B
Donor cell
A
Recombination
A
A
B
Recipient cell
A
B
Recombinant cell
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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
Recombinant F bacterium
A
Hfr cell
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
• Obligate aerobes
• Obligate anaerobes
• Facultative anaerobes
• Nitrogen Metabolism
• N is essential for amino acids
• Atmospheric N isnt 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
Fig. 27-18a
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
Thiomargarita namibiensis containing sulfur
wastes (LM)
Nitrosomonas (colorized TEM)
Subgroup Delta Proteobacteria
Subgroup Epsilon Proteobacteria
B. bacteriophorus
5 µm
10 µm
2 µm
Fruiting bodies of Chondromyces crocatus,
a myxobacterium (SEM)
Helicobacter pylori (colorized TEM)
Bdellovibrio bacteriophorus attacking a larger
bacterium (colorized TEM)
18
Fig. 27-18i
CHLAMYDIAS
SPIROCHETES
2.5 µm
5 µm
Chlamydia (arrows) inside an animal cell
(colorized TEM)
Leptospira, a spirochete (colorized TEM)
GRAM-POSITIVE BACTERIA
CYANOBACTERIA
1 µm
50 µm
5 µm
Hundreds of mycoplasmas covering a human
fibroblast cell (colorized SEM)
Streptomyces, the source of many antibiotics
(colorized SEM)
Two species of Oscillatoria, filamentous
cyanobacteria (LM)
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