Download LECTURE 12 THE BACTERIA

LECTURE 12
Let’s look at some of the basal branches of the Bacterial tree….
THE BACTERIA
Aquifex and Thermotoga
Thermotoga has a sheath, like a toga
• oldest branches of the Bacteria
•
hyperthermophiles
• Aquifex spp. are H2 oxidizers and fix CO2 by
running the TCA cycle backwards. One of the
only hyperthermophic aerobes Use of H2 by so many beeply branching
thermophiles suggests H2 was very common on
the early earth
Thermotoga lives near submarine
hydrothermal vents, have a protein sheath
(“toga”). Anaerobic fermentors…..
Deinococcus - Thermus
Deinococcus-Thermus
• 2 main groups:
> Deinococci
> Thermales
• Deinococcus can survive
extremely high levels of UV and
Gamma radiation. Is Gm- but outer
membrane is surrounded by a protein
sheath (S-layer) thus it stains Gm+. Has
several copies of chromosome per cell and
is very efficient at DNA repair…..
The Proteobacteria
• largest cultured group of bacteria - 380
genera & at least 1500 species!
• 5 major groups (“classes”):
!Alphaproteobacteria
!Betaproteobacteria
!Gammaproteobacteria
!Deltaproteobacteria
!Epsilonproteobacteria
ALPHAPROTEOBACTERIA (cont.)
ALPHAPROTEOBACTERIA
Rickettsia
• many important pathogens e.g.
cause Rocky Mountain spotted fever, Typhus…..
• genome sequencing shows that they are
very similar to mitochondria - probably
ancestor of Rickettsia was involved in
endosymbiotic event.
ALPHAPROTEOBACTERIA (cont.)
Caulobacteraceae & Hyphomicrobiaceae
These 2 groups of bacteria have some sort of appendage:
> A prostheca - an extension of the cell that is
narrower than the mature cell
• Some Hyphomicrobium species are
methylotrophs - can use methane or other
1-carbon compounds as energy and carbon
sources
> Reproduction by budding (see lec. 5)
- reproduction via a small protrusion
that enlarges to form a new cell.
Fig. 11.24. Budding in Hyphomicrobium
Fig. 11.23. Caulobacter life cycle
ALPHAPROTEOBACTERIA (cont.)
Rhizobium - symbionts within root nodules of
plants and fix nitrogen
Fig. 11.20. A crown gall -
plant tumor
induced chemically by Agrobacterium
Agrobacterium - does not stimulate root
nodule formation or fix nitrogen.
Instead, these bacteria invade plant
tissues and cause tumors - crown gall
disease.
ALPHAPROTEOBACTERIA (cont.)
Rhizobium is the most intensively studied
symbiotic (mutualistic) bacterium. Very
important agriculturally (think soy beans,
beans, clover & other legumes etc.)
Plant exudes hormone-like flavonoid
compounds to attract Rhizobium
Live intracellularly
Chemotactic to roots
Fig. 30.14 & Fig. 11.21
ALPHAPROTEOBACTERIA (cont.)
BETAPROTEOBACTERIA
Nitrifying Bacteria
Nitrobacter
(Nitrosomonas and others are in other groups of
the proteobacteria)
Purple Nonsulfur Bacteria
• use anoxygenic photosynthesis
• but can sometimes be chemoheterotrophs
Important groups:
• Neisseriales - Neisseria - gonorrhea,
some meningitis
• Bordetella - whooping cough
Other members of this order
(Burkholderiales) have a sheath
GAMMAPROTEOBACTERIA
• largest group of Proteobacteria
• many familiar genera - Escherichia, Salmonella,
Pseudomonas
• incredibly diverse
• Colorless sulfur bacteria - Thiobacillus
GAMMAPROTEOBACTERIA (cont.)
GAMMAPROTEOBACTERIA (cont.)
Purple Sulfur Bacteria
Pseudomonas • motile - polar flagella
• usually anaerobes
• photosynthetic (anoxygenic)
• oxidize H2S to S0 (and sometimes S0 to SO42-)
1) Involved in mineralization - taking
organic compounds back to inorganic
substances.
2) Useful model organisms
e.g. Pseudomonas aeruginosa
(also an opportunistic pathogen, esp. in CF
patients and burn victims see next slide..).
GAMMAPROTEOBACTERIA (cont.)
Vibrios
• some are important pathogens, e.g. Vibrio cholerae
Fig. 26.7
• some Vibrio (and Photobacterium) species are
capable of bioluminescence
These bacteria can live
symbiotically with squid or
fish (Fig. 11.26).
Pseudomonas aeruginosa - plate shows diffusing
green fluorescent pigment (a siderophore). Bottom shows polar,
monotrichous flagellum. Very top is too gross to show in class
- green discolored skin on a burn patient.
Enzyme luciferase is involved
same as in fire flies
GAMMAPROTEOBACTERIA (cont.)
Enterobacteria
(grouped together
because they are found intestines)
• look similar - metabolic properties
are useful in classification - flow
charts
• contains many common bacteria - E.
coli, Salmonella, etc.
DELTAPROTEOBACTERIA Two main groups:
1) Predatory bacteria:
bdellovibrios and myxobacteria
2) Sulfate- and sulfur-reducing
bacteria
The Life Cycle of Bdellovibrio Fig. 11.25
DELTAPROTEOBACTERIA (cont.)
DELTAPROTEOBACTERIA (cont.)
Myxobacteria
Myxospores are dessication resistant - may
survive up to 10 years!
• soil bacteria
• complex life cycle Fig. 11.18
• most are micropredators or scavengers secrete digestive enzymes that lyse cells of
yeast and other bacteria
Communal living may allow them to digest
prey more efficiently (wolf pack as
opposed to lone predator like Bdellovibrio)
• many produce antibiotics
DELTAPROTEOBACTERIA (cont.)
Sulfate- and Sulfur-reducing Bacteria
• use these sulfur compounds as electron
acceptors - anaerobic respiration
EPSILONPROTEOBACTERIA
• Smallest of 5 proteobacteria groups
• 2 important genera:
• Desulfovibrio
> Campylobacter
• Desulfuromonas
> Helicobacter
• Important in sulfur cycle in nature
• Helicobacter pylori cause ulcers (will
discuss more later….
Fig. 30.12
Campylobacter - some are pathogens