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Biology 350: Microbial Diversity Microbial Interactions, Part I: Symbiosis, Predation, and Antibiosis Lecture #30 14 November 2007 -1- 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! -2- 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… -3- Exciting (!) news… Microbiology wrist bands and Tshirts should be here after Thanksgiving! -4- 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. -5- First… Let’s think a bit more about microbial ecology… -6- 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! -7- 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. -8- 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. -9- 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! -10- Now, let’s move onto the current topic… Symbiosis, Predation, and Antibiosis: different forms of microbial interactions! -11- 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? -12- 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. -13- Different “kinds” of microbial interactions with “partners” exist: •Mutualism: •Syntrophy •Commensalism •Parasitism •Amensalism •Competition A+ A+ A+ A+ O A- B+ B+ O BBB-14- 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! -15- 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! -16- 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. -17- 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) -18- 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. -19- Next time… More examples of microbial associations (some familiar players)… -20- 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. -21- Topic(s) for next lecture…… Continuing Microbial Interactions: More About Symbiosis, Predation, and Antibiosis Please re-read Chapter 19 before class! -22-