Download Biology 350: Microbial Diversity

Biology 350:
Microbial
Diversity
Microbial Interactions,
Part I: Symbiosis,
Predation, and Antibiosis
Lecture #30
14 November 2007
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Notice handouts and
announcements for today:
•Your usual outline and sample questions
for today’s lecture.
•Updated lecture schedule.
•Review article on anammox!
•Bonus handout on a very, very bad food
poisoning incident involving Salmonella!
•Monday lecture, in honor of Thanksgiving,
will be all about microbiological food
poisoning!
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Fun and work in lab:
•Serratia
marcescens at
room
temperature.
•Serratia
marcescens at
41 degrees C.
•Undomesticated
Serratia
marcescens.
•Fun with pipet
bulbs in lab…
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Exciting (!) news…
Microbiology wrist bands and Tshirts should be here after
Thanksgiving!
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Today’s lecture agenda
•A word or two about FISH and
microbial ecology.
•A few last words about the coolness
and relevance of the nitrogen cycle and
anammox.
•An introduction to classifying microbial
interactions.
•Discussion of symbiosis and eukaryotic
cell evolution.
•Some specific examples of microbial
symbioses with eukaryotes.
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First…
Let’s think a bit more about
microbial ecology…
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The Power of FISH in microbial ecology!
•A bit of biofilm from a
sewage treatment plant.
•Green = ammonia oxidizing
bacteria.
•Red = Nitrospira-like
bacteria (oxidize nitrite).
•Black spots = autoradiography
of cells taking up radiolabeled
pyruvate.
•So…we can identify different
types of microbes by FISH,
and can detect metabolic
activity in situ as well by
combining techniques!
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Use of FISH in UPS research!
•Joel Elliot finds very large filaments
in low oxygen, high sulfide marine
environments. What are those
filaments?
•First FISH is to a “general”
bacterial signature sequence. Cell
fluoresces when DNA in the
bacterium hybridizes to
fluorochrome-labeled probe.
•Second FISH is to a “vacuolated
Thioploca/Beggiatoa” specific
signature sequence. Same
fluorochrome.
•Controls?
•Thus, this demonstrates that the
filaments are indeed bacteria related
to Thioploca/Beggiatoa.
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A simpler diagram of the
nitrogen cycle…
•All of these steps
are essentially
prokaryotic.
•Some are obligately
aerobic (which?).
•Anammox is very,
very interesting and
novel.
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Fun facts about anammox!
•Anaerobic ammonia oxidation.
•NH4+ + NO2- = N2 + 2H2O
•Process involves the production of
hydrazine (highly caustic compound).
•Anammoxosome “organelles” contain the
enzymes that carry out the oxidation.
•Related to Planctomycetes.
•VERY slow growing in culture.
•Responsible for 70% of the nitrogen
cycling in the oceans!
•Application in waste treatment: can
efficiently remove nitrogen from
wastewater to nitrogen gas!
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Now, let’s move onto the
current topic…
Symbiosis, Predation, and
Antibiosis: different forms of
microbial interactions!
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An example of symbiosis here in
Puget Sound
•NOT a “hairy crab”!
•Beggiatoa like bacterial
filaments cover the
crab.
•Found around wood
waste associated
hydrogen sulfide seeps
here in Commencement
Bay.
•Ectosymbionts?
•Reduce hydrogen sulfide
levels?
•Provide food to the
crab?
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Things to think about regarding
“symbiosis” in general…
•“Symbiosis” is NOT always positive for both
partners!
•Association can be obligate or nonobligate.
•Four basic advantages to positive
symbioses: protection, access to new
habitats, signaling, and nutrition.
•Ectosymbionts versus endosymbionts.
•Establishment of symbioses can be vertical
or horizontal.
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Different “kinds” of microbial
interactions with “partners” exist:
•Mutualism:
•Syntrophy
•Commensalism
•Parasitism
•Amensalism
•Competition
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An impressive list of mutualistic symbioses
NOT covered in your textbook
•Associations between
microbes and a wide variety
of eukaryotes here!
•Some associations
nutritional in the
conventional sense.
•Some are directly
syntrophic.
•Some are very unusual!
•All seem very specific and
suggest a long coevolutionary
history!
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Let’s get back to “Margulian” thinking
Figure 19.1
Figure 19.2
•Mitochondria and chloroplasts were
once prokaryotes (alpha
proteobacters and cyanobacteria).
•Both have prokaryotic Central
Dogma machinery.
•Both are firmly integrated into host
genome and biochemistry now.
•Chloroplasts have much larger
genome and many more genes than
mitochondria (later symbiosis?).
•Compare mitochondrion to bacterium
(Rickettsia, in fact).
•Note that ftsZ protein is involved in
chloroplast division!
•Some human genetic diseases due to
mitochondrial mutations!
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What happens during “integration” of
a symbiont?
•Jeon, amoebae,and “X-bacteria.”
•Peripheral to obligate associations develop over
time.
•Gene flow between symbiont and host
(mitochondria and nucleus).
•Nutritional interdependence (sea slug - sea lettuce
example versus more “integrated” associations.
•Intracellular environment VERY different from
outside---so selection pressures change.
•Manipulation of the host is a key to endosymbiont
transmission.
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Example #1: Bacterial endosymbionts of
insects
Figure 19.6
Figure 19.8
•Most insects have symbiotic relationships with
bacteria.
•These endosymbionts are lodged in specialized
cells called bacteriocytes.
•These bacteria cannot be cultured outside the
insect cell.
•Association is often nutritional.
•Buchnera the bacterium (gamma proteobacter)
associated with aphids.
•Buchnera provides the ten amino acids aphids
cannot make. Aphids provide nutrients to
Buchnera in return.
•Genome of Buchnera is small---and reduced.
•Evidence of long coevolution between aphids and
Buchnera.
•Buchnera is transmitted vertically
(tranovarially)
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Something weird: Wolbachia symbioses
•Wolbachia is an obligate endosymbiont of insects,
spiders, mites, and some nematodes.
•It is a rickettsial alpha proteobacter.
•Symbiosis impacts life history of partner in many
ways.
•Four specific phenotypes associated with Wolbachia
infection: male killing, feminization, parthenogenesis,
and cytoplasmic incompatibility.
•Transovarial transmission (vertical).
•Nature of the mutualism (benefit to host) is unknown.
Nematodes require Wolbachia to reproduce!
•Reproductive isolation in insects.
•Promotes its own transfer.
•Can cause disease in nematodes: river blindness,
elephantiasis, and heartworm in part due to Wolbachia,
not just the filarial nematode (host immune response).
Antibiotic treatment?
•Wolbachia has a reduced and streamlined genome.
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Next time…
More examples of microbial
associations (some familiar
players)…
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Summing up today’s lecture
•FISH can be combined with other techniques to gain
insights into microbial ecology.
•Anammox is a recently discovered part of the nitrogen
cycle, prokaryotic in nature, that is of geochemical
importance.
•Symbiosis is not always positive for both members.
•Four advantages to mutualistic symbioses: protection,
habitat access, signaling, and nutrition.
•Interactions include mutualism, syntrophy, commensalism,
parasitism, amensalism, and competition.
•Chloroplast and mitochondria were once bacteria and are
fully integrated into the host genetic and biochemical
system.
•Buchnera is an endosymbiont of insects in a nutritional
symbiosis.
•Wolbachia is another endosymbiont of arthropods and some
worms, but can both cause disease and manipulate its host.
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Topic(s) for next lecture……
Continuing Microbial
Interactions: More About
Symbiosis, Predation, and
Antibiosis
Please re-read Chapter 19 before class!
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