Download LECTURE 13 THE BACTERIA (cont.)

Photosynthetic Bacteria, phylogenetically widespread
LECTURE 13
THE BACTERIA (cont.)
And many Proteobacteria
Photosynthetic Bacteria
> Green Sulfur - Chlorobi
> Green Sulfur
> Green Nonsulfur
> Purple Sulfur
> Green Nonsulfur - Chloroflexi
Anoxygenic
Photosynthesis
> Purple Nonsulfur
> Purple Nonsulfur
> Cyanobacteria
> Purple Sulfur
Proteobacteria
Oxygenic
Photosynthesis
New terms with relation to the cyanobacteria:
1) Trichome = row of bacterial cells in a
filament.
Oscillatoria
2) Akinetes = specialized dormant cells that
are very resistant to desiccation.
3) Heterocysts = special cells where nitrogen
fixation takes place.
Photosystem I still makes ATP, but get rid of PS
II, so no O2 is made.
The O2 would poison the enzyme that fixes the
nitrogen, nitrogenase.
The heterocyst gets nutrients from nearby
vegetative cells and gives them the fixed
nitrogen that it makes.
Other tidbits about cyanobacteria:
> Many disperse via gliding motility…
> Common in almost all waters and soils.
> They are the “algae” half of most
lichens, and many others are symbiotic
with other organisms.
The Chlamydiae and Planctomyces
The Chlamydiae
• obligate intracellular parasites - can’t make
their own ATP!
• very small in size -
Fig. 25.10. C. trachomatis attaching to
fallopian tube mucosal cells
and no peptidoglycan thus not
sensitive to penicillin.
• genus Chlamydia (many human pathogens)
Fig. 11.30. Numbers indicate development
of infectious “elementary bodies”.
Trachoma and genetical chlamydial infections are caused by
different strains of C. trachomatis
Elementary bodies - infectious “spores”
Reticulate bodies - growing cells inside vacuoles of host cells
Planctomyces - large group of aquatic bacteria related
The Spirochaetes
to Chlamydia, but none cause disease. Most have
never been grown in the lab
- No peptidoglycan - cell walls are protein (= S-layer).
- Reproduce by budding
- Have stalks made of protein (no cytoplasm inside).
- All have internal compartments……..
e.g. see “nucleoid” of Gemmata or
“anammoxosome” of Brocadia
The Spirochaetes Fig. 11.27
Spirochaetes live in diverse habitats
> have flexible, helical shape
Usually anaerobic (facultative or obligate)
> Also distinguished by motility - can move
through viscous solutions
Group contains some important pathogens,
but
most are harmless muck dwellers (or e.g. between your teeth)
!Treponema pallidum - Syphilis
> Use unique structure called the axial filament
!Borrelia burgdorferi
- Lyme Disease
!Leptospira interrogans - an aerobic spirochaete!
leptospirosis (kidney infection)
Bacteroides/Flexibacter/Cytophaga (CFB group)
Bacteroides
• anaerobic - hard to culture,
some can be opportunistic
pathogens
• important in rumens and colons -
Bacteroides = dominant genus in the colon 10 billion per gram of human feces
• break down polymeric substrates (e.g. cellulose)
using extracellular enzymes • use gliding motility
Cytophaga and Sporocytophaga
Obligate aerobes - most important aerobic,
bacterial degraders of cellulose in the biosphere..
Extracellular cellulases - see overheads…
.
LECTURE 14
GRAM POSITIVE
BACTERIA
GC content is useful for classifying Bacteria especially Gram +
% G + C = (G + C)/(G + C + A + T) x 100 =
percentage of guanine (G) and cytosine (C) in
the DNA of the organism.
Quick method to group organisms, but two
organisms can have similar %G+C but completely
different DNA sequences.
It is only useful in conjunction with other tests
and for groups that differ by > 10% or so in G+C.
Low G+C Gram Positives
The Mycoplasmas
The Mycoplasmas
•
Clostridia
•
Bacilli
•
Lactic Acid Bacteria
The Clostridia - Clostridium
• obligately anaerobic
• lack cell walls
• pleomorphic -
•
very flexible because no cell walls
• have smallest bacterial genomes
(~500,000 BPs) about 1/8 the size of E. coli
• endospore producers
Some pathogens:
•C. tetani - causative agent of tetanus
• spoil food, even canned foods - food borne
pathogens: C. botulinum and C. perfringens
• most are parasites or commensals
Fig. 11.28. Colonies of Mycoplasma pneumoniae.
Boiling (100°C) won’t kill them; autoclaves or pressure
cookers needed to kill endospores (121°C for 20 min.)
Clostridium can ferment amino acids
remember the Stickland reaction.
The Clostridia - Heliobacteria
• photosynthetic
One amino
acid is
oxidized…
…another
is the
electron
acceptor
to restore
NAD+.
• bacteriochlorophyll g
• some will form endospores
The genus Bacillus
• endospore formers
• chemoheterotrophs
Fig. 11.16. a. Bacillus
anthracis spores form in
middle of cells.
b. Clostridium tetani spores at
the end of cells.
• usually motile
Important Bacillus species:
B. anthracis - causitive agent of anthrax
Organisms studied by Koch - important
agricultural pathogen.
• usually rapid growers
Mail tainted with anthrax spores found recently.
• diverse group - likely to be split into at
least 5 groups
WWII, Brits experimented with B.
anthracis on Gruinard island off
Scotland.
Sheep were placed in pens and bombs filled with
anthrax spores were dropped on the island.
Bacillus thuringiensis - “Bt”
B. sphaericus
The sheep started dying 3 days later.
Both species form a parasporal body - a solid
protein crystal next to their spores.
The island had to be quarantined for 48 years.
These species of bacteria kill insects:
• B. thuringiensis - moth larvae
In 1987, they soaked the island with 280 tons
of formaldehyde in 2800 tons of seawater then
removed the topsoil the island was declared “safe” in 1990, but
there are still few visitors….
(caterpillars)
- beetle larvae
• B. sphaericus mosquito larvae
Genes from Bt have been integrated into several
plant genomes to give plants permanent
resistance to pests: