Microbes in the environment F2, p. 304

Microbes in ecosystems F.2.1, p. 304

Did you know? Just one gram of soil contains 5000 to 7000 different species of bacteria. – the-soil.html

Good news! You only have to know 5!

Bacteria Play several major roles in different nutrient cycles –Both in land and in water Involved in P, S, C and N cycles

Decomposing Bacteria break down dead organisms Nutrients released –Nutrients return to the environment

Producers Use raw energy (Ex: sunlight) to create organic molecules and nutrients –Used by bacteria and other organisms Includes: –Photosynthetic bacteria (cyanobacteria) –Chemosynthetic bacteria (in the nitrogen cycle)

Nitrogen cycle F.2.2, p. 304

Fig c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria

Nitrogen cycle Nitrogen moves through the environment Major reserves are: –Atmosphere –Living things Nitrogen must go through chemical reactions during the cycle

Nitrogen Comes in two forms: –Pure element, N 2 (gas) –Fixed (as part of a compound)

Atmospheric nitrogen N 2, gas Three covalent bonds between the atoms –Very difficult to break –Not reactive –Very few organisms have the enzyme for breaking the triple bond Cant be used by organisms

Fixed nitrogen Nitrogen as part of a compound –Nitrite (NO 2 - ), nitrate (NO 3 - ), ammonium (NH 4 + ) NO 3 -, nitrate, is essential for all organisms –An important part of DNA and protein

Importance of nitrogen fixing bacteria Where do animals get nitrogen from? –Plants, amino acids, DNA Where do plants get nitrogen from? –NOT the atmosphere –Usually NO 3 -, NH 4 +, which is created by bacteria ALL organisms get fixed nitrogen from bacteria

Nitrogen fixation p

Nitrogen fixation Nitrogen is fixed by: –Lightening –Manufacturing –Microbes

Lightening High temperatures cause N 2 and O 2 to combine A series of reactions creates NO 3 - P. 304

Haber process N 2 and H 2 reacted at high pressure and temperature NH 3 (ammonia) produced Used to manufacture plant fertilizer –Mixed with the soil for plant nutrition

Microbes fixing nitrogen Two examples: –Azotobacter Free-living –Rhizobium Live in plant root nodules

Root nodules Mutualistic relationship –The plant gets fixed nitrogen –The bacteria get an anaerobic environment

Microbial nitrogen fixation N 2 --> NH 3 Requires ATP Azobacter (free living) and Rhizobium (Root nodules) fix nitrogen –Have nitrogenase, the enzyme that fixes N –Breaks the strong N 2 triple bond to produce NH 3

Fig c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria

Nitrification and denitrification F.2.4, p. 305

Nitrification Two steps: –NH 3 --> NO 2 - –Ammonia --> Nitrite Nitrosomonas bacteria –NO > NO 3 - –Nitrite --> Nitrate Nitrobacter bacteria Releases energy Occurs quickly

Fig c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria

NO 3 - uses NO 3 - assimilated by plants –Pumped into root hairs by active transport Passed on to animals/heterotrophs through the food chain Used for amino acids/proteins and DNA

Denitrification NO > N 2 + H 2 O Example: Pseudomonas denitrificans Anaerobic respiration –NO 3 - is the electron receptor instead of O 2 Anaerobic soils encourage denitrification –Bad drainage/flooding causes –Denitrification exacerbates the problem

Fig c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria

Ammonification Also called putrification –Organic matter (feces and dead organisms) are decomposed by bacteria The nitrogen in the organisms is converted into ammonia (NH 3 ) –The NH 3 then goes through nitrification

Fig c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria

Nitrogen Cycle

Name each process: Name the bacteria carrying out each process

Sewage and fertilizer waste F.2.5, p. 305

Sewage Household - Feces, kitchen waste Industrial - chemicals, heavy metals Farm - fertilizers All cause water pollution –Radically change the aquatic environment

Downstream pollution Graph on p. 306

Downstream pollution Table on p. 306

Steps for contamination 1.Waste discharged, eutricifation 2.Algea bloom, then die off 3.Decomposers break down dead algae and use up oxygen. Oxygen levels decrease. 4.Extreme cases: Oxygen levels are too low and fish/aquatic life is killed (hypoxic zone) 5.Dead organisms are broken down, using oxygen and creating a high concentration of nutrients (eutrification) 6.Extreme cases: nutrients cause another algae bloom, cycle repeats

BOD Biochemical oxygen demand The level of oxygen in a water sample is recorded over 5 days Less oxygen = More O 2 demand (BOD) = more microbes = more contamination –The contamination feeds the microbes –The microbes demand oxygen

BOD levels If BOD is too high, fish and other organisms might die –Not enough O2 in the water –oxygen sag Caused by decomposing bacteria –Use up O2

Oxygen Sag

Stopping the cycle When the pollutants are broken down and diluted enough, the river can recover –Several kilometers from source of pollution Key: improving oxygen levels, avoiding fish kills

Sewage treatment F.2.6, p. 307/145

Treating raw sewage Bacteria are used to treat harmful/polluting substances Two kinds: –Trickle filter bed p. 145 SG –Reed bed. 145 SG

Biofuels F.2.7, p. 308

Gasohol Gasoline + ethanol Ethanol comes from yeasts digesting sugar –Sugar from sugar can/sugar beets

Fig c (c)

Biomass Some microbes convert biomass to fuel –Biomass = Total mass of the living material in an area, minus water –Measured in kg/m 2 –Usually refers to plants

Biogas Bacterial fermentation Biomass --> CH 4, methane, natural gas Several species of bacteria used together

Methanognesis F.2.8, p. 308

Acetogenesis Aerobic bacteria break down waste into lipids, proteins, fats Oxygen used up Acetogenic bacteria (anaerobic) produce acetate

METHANOGENESIS Acetate converted into CH 4 Uses methanogens (archaea) –Obligate anaerobes –Occurs in a sealed tub

Advertisements In groups, create illustrated advertisements for the following products: 1.Trickle-filter bed 2.Reed-filter bed 3.Gasohol 4.Biogas/CH 4

Advertisements: Include the following Target audience/demographic A diagram of the process and equipment Important reaction equations involved The bacteria involved in each process –Include specific environment conditions (ex: anaerobic tank) The benefits of the product/process