© 2004 Wadsworth – Thomson Learning Chapter 28 Microorganisms and the Environment

© 2004 Wadsworth – Thomson Learning Soil Environments Mineralization –Organic material converted to inorganic form Availability of oxygen –Soil fertility Adequate supply of inorganic molecules Bacteria and Fungi –diverse population –break down plant and animal remains

© 2004 Wadsworth – Thomson Learning Soil Environments Symbiosis –mycorrhizae soil fungi and roots of plants acquire nutrient for plant –rhizosphere area of soil surrounding root specific microorganisms

© 2004 Wadsworth – Thomson Learning Water Environments Extent of microorganisms in water –Almost all aqueous environments –Differences between bodies of water Nutrients –Nutrient poor Oceans –Phytoplankton Freshwater –Clarity and color –Too much nutrient—eutrophic Pathogens –Freshwater is reservoir

© 2004 Wadsworth – Thomson Learning Air Environments No growth in air Passengers of aerosols –Cough –Sneeze –Talk –Agitation of water

© 2004 Wadsworth – Thomson Learning Nitrogen Cycle Nitrogen exists in many forms –nitrogen gas in atmosphere converted to ammonia –Nitrogen fixation by bacteria nonsymbiotic –Cyanobacteria symbiotic –root hairs –infection thread –root nodules –bacteroids

© 2004 Wadsworth – Thomson Learning Nitrogen Cycle –Nitrification ammonia oxidized to nitrate ion –by nitrifying bacteria –Denitrification only prokayrotes supply nitrogen to atmosphere Figure 28.7

© 2004 Wadsworth – Thomson Learning Carbon Cycle Carbon dioxide to organic compounds to carbon dioxide –Photosynthesis conversion of CO 2 to glucose –Respiration and combustion organic compounds to CO 2. –Earth’s CO 2 is increasing

© 2004 Wadsworth – Thomson Learning Carbon Cycle Figure 28.9

© 2004 Wadsworth – Thomson Learning Phosphorus Cycle Phosphorus to inorganic phosphate to organic phosphate and back. –Differs from nitrogen and carbon cycles No gaseous phase phosphorus neither oxidized or reduced –ecological importance phosphates often limiting nutrient –increase in phosphates results in eutrophication removal from sewage important –bacteria convert to polyphosphate granules

© 2004 Wadsworth – Thomson Learning Phosphorous Cycle Figure 28.11

© 2004 Wadsworth – Thomson Learning Sulfur Cycle Reducing sulfate ion to hydrogen sulfide gas –sulfate-reducing bacteria nutrient terminal electron acceptor sulfate rich anaerobic environments –mud flats Reoxidizing to sulfate –sulfur-oxidizing bacteria –nonoxygenic phototrophic bacteria

© 2004 Wadsworth – Thomson Learning Sulfur Cycle Figure 28.12

© 2004 Wadsworth – Thomson Learning Wastewater treatment Sewage treatment –reduce the biochemical oxygen demand (BOD) –Primary treatment solid material is sedimented Figure 28.13

© 2004 Wadsworth – Thomson Learning Wastewater treatment –Secondary treatment liquid from primary biological treatment –aeration –trickling filter –oxygen added bacteria mineralize sewage –floc: mixture of slime and bacteria activated sludge--used to inoculate next batch Figure 28.14

© 2004 Wadsworth – Thomson Learning Wastewater treatment Septic tanks –sludge settles –effluent piped into leach field Figure 28.15

© 2004 Wadsworth – Thomson Learning Drinking Water: Treatment Treatment –filtration beds of sand diatomaceous earth –activated charcoal –disinfection chlorine ozone Fig 28.16

© 2004 Wadsworth – Thomson Learning Drinking Water: Testing Test for coliforms –indicator organisms –more practical than testing for pathogens Two methods –Most probable number (MPN) –Membrane filter (MF) Safe levels –1 coliform/100 ml tested frequently

© 2004 Wadsworth – Thomson Learning Most Probable Number (MPN) Presumptive test –lactose and gas production Confirmed test –plated on EMB agar Completed test –growth in lactose broth and slants. Fig 28.17

© 2004 Wadsworth – Thomson Learning Membrane Filter (MF) 100 ml water –filtered –filter is placed on surface of a media which identifies coliform bacteria –incubation –coliform colonies are counted Fig 28.17