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BIOL 2051 - EXAM 4

BIOL 2051 - EXAM 4 - Chapter 19 Microbial Ecology PART I...

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Chapter 19 Microbial Ecology PART I Microbial Ecosystems 19.1 -19.3 p. 614 – 619 See figure 19.1 Microbial communities consist of guilds of metabolically related organisms Microbial communities and their natural environment make up an ecosystem Microorganisms recycle elements (C, S, N, Fe) in the environment Fig 19.2 The place where the microorganism actually lives is its microenvironment Table 19.1 Growth of microorganisms depends on the resources available and on the growth conditions - Suboptimal growth is due to: o Low supply of nutrients and suboptimal growth conditions o Distribution of nutrients not uniform in habitat o Microbes growing in mixed populations where competition exists Solid surfaces serve as microbial habitats Nutrients adhere to surface Surface itself could be nutritious Fig 19.5 Biofilms are bacterial communities that form on surfaces to: Provide defense by number Allow cells to stay in a favorable niche Allow cells to live in close association (metabolic cooperation b/t species) Biofilms have been implicated in : Cystic fibrosis Periodontal disease Infections from implants (catheter, artificial joints) Pipeline (oil, water) congestion and corrosion Degradation of submerged objects like offshore oil rigs and boats PART II Soil and Freshwater Microbial Habitats 19.4 – 19.5 p. 619 – 624 Fig 19.6 Most microbial growth occurs on the surface of soil particles around plant roots Factors that influence microbial activity: Water availability for surface soil Nutrient availability for deep soil In aquatic ecosystems, the main primary producers are usually phototrophic microorganisms Oxic areas – cyanobacteria and algae Anoxic areas – purple sulfur and green sulfur bacteria Fig 19.10 Levels of organic material and oxygen are inversely related in a body of water High organic content leads to O 2 depletion due to bacterial respiration BOD- biochemical oxygen demand- amount of organic material in water that could be oxidized by microbes PART III Marine Microbiology 19.6 – 19.8 p. 625 – 631 Marine waters are low in nutrients, but substantial numbers of microorganisms exist there Oxygenic phototrophs: Prochlorococcus- relative of cyanobacteria; primary producer Trichodesmium- Nitrogen fixing cyanobacterium; form tufts or filaments 1
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Anoxygenic phototrophs: Bacteria that use pigment proteorhodopsin (like bacteriorhodopsin but in Proteobacteria) for ATP synthesis Aerobic anoxygenic phototrophs ( Erythrobacter and Roseobacter ) Surface to 300m visible light penetrates and phototrophs predominate Beneath the photic zone , from 300m to 1000m, chemoorganotrophic microorgs prevail At deep sea levels, below 1000m, low temperature (2°C), high pressure (400 atm to over 1000 atm), and low nutrient levels must be endured Fig 19.14 Barophiles grow best under high pressure
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BIOL 2051 - EXAM 4 - Chapter 19 Microbial Ecology PART I...

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