microbiology 2

biogeochemical cycle

link metabolic processes of organisms for production and degradation of biomass

microbes in biogeochemical cycle

move atoms btwn living organisms and physical environment

allow most life to exist + elements to be recycled

common cycles

nutrient, carbon, nitrogen

macronutrients

C, N, P, S, O, H

element in cycles often experience changes in

oxidation state and physical state of elements

changes in oxidation state

alter physical characteristics

may be metabolically available to cells or not

redox reactions

transfer of electrons btwn chemical elements

Carbon w -4 oxdiation state

methane CH4

c w -2 oxidation state

methanol CH3OH

c w 0 oxdiation state

carbohydrates

c with +2 oxidation state

formic acid HCOOH

c with +4 oxidation state

carbon dioxide, bicarbonate ion

major reservoirs

terrestrial (lithosphere)

aquatic (hydrosphere)

atmospheric (atmosphere)

living (biosphere)

global reservoirs are

interconnected

flux

amount of material flowing through a unit area or volume per unit of time

element movement expressed as

recipient reservoir

sink

receive flux

donor reservoir

source

where flux is from

reservoir is considered to be in

steady state (in equilibrium)

sources and sinks are equal to each other

human activities disrupting equilibrium

land use (deforestation, conversion of natural grasslands)

fossil fuel burning

industrial N2 fixation

increase level of CO2 = greenhouse gas

climate warming

increase biologically available N

greenhouse gas

CO2, CH4, N2O

absorb infrared radiation and re emit it

less heat escapes through the atmosphere to space

important components of cycle

magnitude, major sources and sinks, rates of cycling

carbon cycle magnitude

reservoirs vary on Earth

carbon cycle rates of cycling

can be long term (geological) or short term (biological)

carbon reservoirs

atmospheric CO2

biomass C

soil organism matter

fossil fuels

sedimentary rock deposits

dissolved CO2 in water

Carbon cycle

photosynthesis —> capture atmospheric CO2

exchange of deep ocean carbon w the more rapidly cycling surface water carbon

death of organisms —> carbonate structure sink —> formation of sedimentary carbonate rocks —> rocks drawn to Earth’s crust —> form silicate rocks releasing CO2 which get into atmosphere by volcanic release

CO2 fixation

photosynthesis

chemosynthesis (minor)

oxygenic photosynthesis

higher plants, microalgae, cyanobacteria, lichens, aquatic plants

in terrestrial / aquatic reservoirs

produce organic carbon with light energy

anoxygenic photosynthesis

purple sulfur, green sulfur bacteria

non mixing lakes or habitats with light and e donors

produce organic C with light energy

respiration

occurs both in dark and light

release of CO2 and water

decomposition of organic matter

catabolic

energy yielding reactions

carried out by organotrophs

fixed C into CO2 and CH4

takes a time

net biomass production

positive: photosynthesis rate over respiration rate —> organic accumulates

negative: opposite

reservoir not steady

methanotrophs

capture energy from methane oxidation

obligate aerobes / microaerophilic

CH4 —> CO2 + cells

catalyze methane to methanol in aerobic environment with MMO

live at oxic-anoxic interface

MMO

methane monooxygenase

derive O from O2 and add it to CH4 to form methanol

methanogenesis

prouduction of methane as a byproduct of organic carbon in an anoxic environment by methanogens and their syntrophic partnership

methanotrophy

only a small fraction of produced methane releases into atmosphere

used by methanotrophs

CH4 —> CO2 which can be fixed into organic compounds

methanogens

consist strickly of anaerobic archaea

produce CH4

restricted substrate range

live with other microorganisms as they rely on them to process complex organic materials and provide these with substrates = syntrophic partnership (with H2 producing and fatty acid oxidizing microbes)

some are lithotrophs

others use acetate and methanol

in anoxic environments

provide metabolizable substrates for other anaerobic groups

syntrophic partnership

microorganisms carry out transformation that neither can conduct alone

consortium

interacting community

anoxic decomposition

polymers get hydrolyzed into monomers by primary fermenters

monomers are used by secondary fermenters (homoacetogens) as substrates to produce acetate

produce CH4 and CO2 from acetate and H2

acetotrophic methanogens

use acetate to produce CH4 and CO2

hydrogenotrophic methanogens

use CO2 and H2 to produce CH4 and CO2

prominent characteristic of anoxic habitats

syntropy in consortium

rumen can be

methanogenic ecosystem

diet = grass and corn (cellulose and starch degradation to glucose)

fermentation of glucose to produce acetate

methanogens produce methanes with acetate

in anoxic environment

ruminants

consume grass but do not have cellulase

rely on methanogenic microbes in rumen to degrade grass