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Chapter Outline
26.1 Ecology: The Interconnecting Web of Life
A. Microbial Ecology deals with interactions between the environment and
microorganisms
1. Environment
a. biotic-living or once living components
b. abiotic-nonliving components
2. Ecosystems-collections of organisms and its surrounding physical and
chemical factors
B. Ecosystem Organization
1. Biosphere-area of the earth that is inhabited by living things
a. Hydrosphere-water
b. Lithosphere-soil
c. Atmosphere-air
2. Ecosystems
a. Terrestrial(biomes)
b. Aquatic
3. Commumities-contained in biomes, groups of coexisting organimsms
4. Populations-groups of organisms of the same species
5. Individual organismsa. Habitat-space for an organism
b. Niche-role in community dynamics
26.2 Energy and Nutrient Flow
A. Habitat supplies nutrients and energy
B. Food/energy pyramid summarizes relative trophic status between
organisms
C. Producers-bottom, beginning of the chain or pyramid
1. Synthesize large organic molecules from small inorganic molecules
2. Autotrophs- CO2 is carbon source, plants cyanobacteria
3. Lithotrophs-bacteria that make ATP from simple inorganic molecules
D. Consumers-feed on producers
1. Several levels of consumers; primary, secondary, tertiary and
quaternary-with each level the organisms getting larger
E. Decomposers-breakdown and absorb organic material of dead organisms
1. Recycle nutrients and elements into forms for the producersmineralization
2. Mostly bacteria and fungi
F. Bioremediation-decomposing man-made compounds that are harmful to the
environment
1. Communities of prokaryotes known as a consortium
2. Can be exploited by humans to clean up some forms of pollution
G. Bioaccumulation-nondegradable substances are passed through and up the
trophic levels of a food pyramid/chain
1. Mercury and other toxic pollutants can be concentrated by bacteria
26.3 The Natural Recycling of Bioelements
A. Atmospheric cycles-Carbon and Nitrogen
1. Carbon cycle- carbon dioxide, methane and carbonates
a. Carbon is fixed by autotrophs(photosynthesis)
b. Respiration-organic carbon taken in and used by consumersreleases CO2
c. Fermentation
d. Limestone decomposition
e. Methane production
2. Nitrogen cycle-four processes and several types of microbes
a. Nitrogen fixation-nitrogen gas(79% of air) converted to
nitrates, nitrites, and ammonium salts
b. Ammonification-degradation of nitrogenous organic
compounds(proteins, nucleic acids) by bacteria to ammonium
c. Some bacteria can nitrify-ammonia by converting it to nitrite
and nitrate
d. Denitrification-multistep microbial conversion of
differentnitrogen salts back to nitrogen gas
B. Sedimentary Cycles-highlighting sulfur and phosphorus
1. Sulfur cycle
a. Sulfurous compounds are converted into useful substrates and
then returned to the inorganic reserve by microbes
b. Thiobacilli- found in mud, sewage, bogs, brackish springs;
gain energy from oxidizing elemental sulfur, sulfides and
thiosulfate
2. Phosphorus cycle
a. Chief compound is phosphate(PO4)-found in rocks
b. Microbial action on the reservoir makes it available for
organic phosphate forms
c. Fertilizer and potential eutrophication
26.4 Terrestrial Microbiology: The Composition of the Lithosphere
A. Soil Microbiology
1. Dynamic, complex ecosystem; microbes, animals, plants, fungi in
rich organic debris and air spaces
2. Rock decomposition
a. Pockets of water, inorganic molecules and organisms
important parts of nutrient cycles and the food pyramid
b. Pockets have different composition based on envirnonment
and distance from the surface
3. Rhizosphere-zone around the roots of plants containing array of
microorganisms(bacteria, fungi, protists, viruses)
a. Mycorrhizae-fungi attached to roots of plants-plants feed and
the fungi anchor roots and capture water
B. The Microbiology of the Hydrosphere
1. Hydrologic cycle
a. Surface water, atmospheric moisture and groundwater
b. Evaporation and precipitation
c. Living things contribute by respiration and transpiration
2. Water Communities-diverse
a. Established based on sunlight, temperature, aeration and
dissolved nutrients
b. Phytoplankton and zooplankton drift in upper most zone that
supports the aquatic community
3. Water Monitoring
a. Potable water is central to prevention of water-borne disease
b. Survey water for indicator bacteria (E. coli, coliforms and
enterococci) signal fecal contamination
c. Assays include; plate counts on selective and differential
media and membrane filtration to identify and count coliforms