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Lecture 9

MICR 2420 Lecture 9: Lecture 9_biodiversity

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MICR 2420
Lucy Mutharia

Lecture 9: Biodiversity Humans Influence Aquatic Microbial Ecosystems Most natural ecosystems teem with diversity Nutrient sources are competed for A delicate ecological balance results with representation of all microbes in the system Pollutants introduced into a system can skew the balance Loss of ecosystem members Eutrophication One transports phosphate but not nitrogen but one transports nitrogen but not phosphate Nutrients flow from soil into the water Eutrophication happens when too many nutrients are in the water The nutrients are food for algae that grow and reproduce quickly The sunlight gets absorbed by the algae, blocks the other plants The plants and algae both start to die from lack of light and nutrients The bacteria eat the dead plants and grow and reproduce The bacteria consume the oxygen quickly turning it anoxic The fish and other animals die in anoxic water Soil Microecology: A Brief Field Guide What is soil? Complex mixture of decaying organic and mineral matter Life support for vast numbers of microbes as well as terrestrial plants In the watersaturated part there is little oxygen There are different organisms in different layers of the soil The soil food web shows that it is not just microbes in the soil Humus is the remaining phenolic material left after primary degradation of lignin Soil has a particular aroma due to Streptomyces Streptomyces: a major genus of soil bacteria, notable for the diversity of antibiotics they make Nematodes: microscopic worms that reside in the top 15 cm of the soil depicted a nematode containing the fluorescent bacterium photorhabdis luminescens; if an insect eats the nematode, the bacteria is passed to the insect, which it kills, creating biomass in the soil for other nematodes to enjoy Soil is one of the most diverse ecosystems on earth! Microbes in the rhizosphere help to protect plants from pathogens May fix nitrogen (diazotrophs) In return they feed off nutrients provided by the plant There is a fungal type that is very dependent on the plant Called endomuchorrhizae that invade root cells forming arbuscules Endophyte grow within plant tissues, usually bacteria can be fungal One specialist endophytic relationship is that of plant roots and rhizobia, a group of specialized bacteria Forms an elaborate partnership whereby the bacterial cells adapt to life within nodules to form a nitrogen fixing organ for the host plant Leguminous plants
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