Transcript Microbe of the Day

Text Chapter 18 has a nice set of tables with
characteristics of the major prokaryotic groups
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Microbe(s) of the Day: Deep-branching thermophiles
Aquificales and Thermotogales
•They are thought to have diverged from
other bacteria early (thus similar to the
earliest bacteria, perhaps).
•Oxidize (eat) hydrogen, making water in
the process 2H2+O2 =2H20.
•Live at high temperatures (50 to 90oC) in
hot springs, hydrothermal vents, hot
muds, etc.
•Aquifex and Thermatoga species have
acquired MANY of their genes by
horizontal gene transfer from Archea and
other groups of bacteria.
•Recent work by UConn microbiologists
(Ken Noll, Peter Gorgarten and their
students) suggest that Thermatoga
species may not be belong at the base of
the bacterial tree, but with the Firmicutes
instead (Bacillus, Clostridium)
Microbe(s) of the Day: Deep-branching thermophiles
Aquificales and Thermotogales
Toga
Thermotoga maritima
wwwuser.gwdg.de/%7Eappmibio/research_liebl.html
Thermocrinis ruber in a Yellowstone hot spring
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Microbe(s) of the Day: Cyanobacteria
•Grow a single cells, clusters, filament or sheets (see morphology lecture)
•Photosynthetic bacteria (once called “blue-green algae”) that produce O2 as a product of photosynthesis.
Electrons are needed for photosynthesis and they are taken from water:
H2O--> 4H+ + O2. This is called “oxygenic photosynthesis”. And it was the process that originally produced
O2 in Earth’s atmosphere, 2.3 billion years ago (more later in the course).
•Many can convert (fix) atmospheric N2 into NH3. This process in inactivated by O2 (think about the point
above), and is therefore done when O2 is lacking, or in specialized cells called “heterocysts” where the
fixation is protected from O2.
•Cyanobacteria often contain internal compartments (most prokaryotes do not)
-Thylakoid: membrane in which the photosynthetic machinary is embedded
-Carboxysome: a compartment in which CO2 is fixed into carbohydrates
-Lipid bodies that are storage compartments for energy-rich compounds
-Gas bodies that help the bacteria float at the right depth in water, in order to collect light
Microbe(s) of the Day: Cyanobacteria
•Many Cyanobacteria are symbionts with higher organsms such as lichens, plants and sponges:
•Many sponge species have their own specialized Cyanobacterial symbionts that provide fixed carbon and
nitrogen. Sponges are sources of many interesting compounds that have antibacterial and anti-cancer
properties. Many of these are actually made by the sponges cyanobacterial symbionts.
A
Lobaria pulminaria (Lung lichen)
Cross section
C
Lobaria pulminaria (Lung lichen)
D
A. Sponges of the Dysidea group (www.pbase.com)
B. Oscillatoria spongeliae (www. asturnatuar.com)
C. Fish killing cyanobacterial/sponge metabolites
(see Ridley_ChemBiol_2005)
D. Antibacterial cyanobacterial/sponge metabolites
B
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Microbe(s) of the Day:Firmicutes-endospore formers
-Gram+ organisms with low amount of G and C in their genomes (“low GCs”)
-Best know are Bacillus and Clostridium species
•Bacillus can grow aerobically and anaerobically
•Clostridium species are strict anaerobes
-Both types form endospores (resistant spores that form inside the bacteria)
Most famous Bacillus species:
•B. subtilus: model organism for Gram+ bacteria
•B. anthracis: the anthrax bacterium. Purified endospores were used in the
2001 anthrax mailings
•B. thuringiensis (B.t) and B. popilliae: forms crystals of a toxin which kills
many insects larvae. You can buy either to sprinkle on your lawn to take
care of grubs.
B. popilliae spores
for Japanese beetle
control -->
B.t.
Bt toxin crystals
Microbe(s) of the Day:Firmicutes-endospore formers
-Clostridium species are club shaped during spore growth, and are best know for the
diseases they cause:
C. tetani: causes tetanus by making a toxin that causes muscles to seize up (read
about it here : http://en.wikipedia.org/wiki/Tetanus). C. tetani will grow in anaerobic
wounds (like punctures). That’s why you get a tetanus booster shot after such
injuries.
C. botulinum: causes botulism poisoning (and is the source of BoTox). Organisms
grow in anaerobic, non-acidic environments. Canned goods that are non-acidic
(beans) and that not heated to temps high enough to kill the organisms are often the
source of outbreaks. http://en.wikipedia.org/wiki/Botulism
C. difficile: causes severe diarrhea, often when other bacteria in the intestine are
killed during antibiotic treatment.
Microbe(s) of the Day: Non-spore forming Firmicutes
Microbe(s) of the Day: Non-spore forming Firmicutes
-Lactic acid bacteria: Cannot use O2 as an electron
acceptor. They ferment and make a variety of acids
including lactic acid. These bacteria are often used in
making fermented milk products like yogurt and
cheeses.
-Staphylococcus sp. are commonly found on the skin.
These are salt tolerant and many of them are
pathogenic. Some of the most serious infections are
caused by Staphylococcus sp. that are resistant to
almost all antibiotics used to treat them. These are a
serious public health threat.
-Streptococcus sp. are often found in the oral cavity
and can also cause serious disease including strep
throat (not too serious), pneumonia, scarlet fever and
sometimes severe, quickly moving, tissue damage
(necrotizing fasciitis) .
Microbe(s) of the Day:Non-spore forming Firmicutes
-Mollicutes: bacteria that lack a cell wall. Best studied are the Mycoplasmas. These
are small, have some of the smallest genomes known in free-living organisms
(~500 genes). They need few genes because they only live in association with
hosts which provide them with nutrients
•Mycoplasma species can cause disease:
Mycoplasma pneumoniae: “walking pneumonia”, meningitis
Mycoplasma genetalium: discovered in 1980, causes STDs
Microbe(s) of the Day: the proteobacteria ( subgroup)
All proteobacteri are Gram The -prots are a large, well studied and extremely diverse group. They include:
•Photoheterotrophs: bacteria that can
use light for energyand organic
molecule for carbon. Often called
“purple bacteria”
•Pigmented when photosynthesizing.
•Usually photosynthesize when in
anaerobic environments
•Found in water and soils.
•Examples: Rhodobacter,
Rhodopseudomonas
These are growing or were collected where waters
were anaerobic, but still irradiated with light
Microbe(s) of the Day: the proteobacteria ( subgroup)
All proteobacteri are Gram The -prots are a large, well studied and extremely diverse group. They include:
•Methanotrophs: bacteria that can
oxidize 1-carbon compounds such as
methanol or methane. One widely
spread group is the Methylobacterium
genus. These are found in soil, water
and are easily isolated from plant
leaves.
Clover leaf pressed into a
petri plate with methanol as
the carbon source.
Enriched for
Methylobacterium sp.
www.oeb.harvard.edu/faculty/marx/model-system.htm
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