Geomicrobiology at the Sevilleta Predicting the metabolic energy available to aqueous microorganisms...
-
Upload
bethany-barber -
Category
Documents
-
view
212 -
download
0
Transcript of Geomicrobiology at the Sevilleta Predicting the metabolic energy available to aqueous microorganisms...
Geomicrobiology at the Sevilleta
Predicting the metabolic energy available to aqueous microorganisms
By Samantha AdelbergMentors: Laura Crossey and Amy Williams
Water
• Sources of Water at the Sevilleta– Rio Grande– Precipitation– Groundwater Wells and Springs
Groundwater• 25 wells and springs• Minimal Knowledge• Some Previous Research
Research Question
• Water chemistries varying dramatically within the Sevilleta due to local geology
• But how much does the varying water chemistry affect the thermodynamics of the different springs and wells?
Thermodynamics• All reactions want to move towards an equilibrium
state• Natural waters such as the ones at the Sevilleta are not
in equilibrium• Energetically favorable for these reactions to move
from one state to another – Spontaneous reactions, - delta G
• But there is no set time limitAffinity = RT ln(K/Q)
Equilibrium constant
Gas constant
Temperature
Role of Microorganisms
• Act as catalysts in these reactions• Speed up the electron transfers• Must spend energy making enzymes that can
perform these reactions• Facilitate these reactions because they gain a
determined amount of energy through each transaction
• Amount of energy gained changes
Chemo-litho-auto-trophChemo-litho-auto-trophChemo-litho-auto-trophChemo-litho-auto-troph
Energy Source:Energy Source:Energy Source:Energy Source:Chemical reactionsChemical reactionsChemical reactionsChemical reactions
Electron Donor: Electron Donor: InorganicInorganic
Electron Donor: Electron Donor: InorganicInorganic
Carbon source: InorganicCarbon source: InorganicCarbon source: InorganicCarbon source: Inorganic
““Eater of”Eater of”““Eater of”Eater of”
Heterotroph PhotoautotrophChemolithoautotroph
Gib
bs F
ree
Ener
gy
Study Area: Sevilleta Springs and Wells
Methods• In the Field
– pH, conductivity , TDS, temp– Bottles for cations, anions, stable
isotopes, nutrients, delta 13C• In the Lab
– Alkalinity (endpoint titrations)– ICP: cations and trace elements– IC: anions– Nutrients
• Analysis– Geochemical modeling software
Phreeqc– Thermodynamics code to
determine electron affinity
PICTURE of LOCAL GEOLOGY
Cibola
San Acacia
Tomasino
Rio Salado Box Springs
Silver Creek
West Mesa
Deeply Derived Waters
San Acacia SpringRio Salado Box Springs
CoCorp Siesmic Line, Lewis and Baldridge 1994
Results
Reactions AFFINITIES (kJ/mol/e)
Electron Acceptor
9Fe2+ + NO2- + 10H2O -> 3Magnetite + NH4+ + 16H+ 108.3213633 Nitrite
2Fe2+ + NO3- + 2H2O -> Hematite + NO2- + 4H+ 65.70072061 Nitrate
Pyrite + NO3- + 2H+ -> 2Sulfur + Fe2+ + NO2- + H2O 42.97850923 Nitrate
Pyrite + 7NO3- + H2O -> Fe2+ + 2SO42- + 7NO2- + 2H+ 37.70280148 Nitrate
S + 3NO3- + H2O -> SO42- + 3NO2- + 2H+ 37.21998924 Nitrate
Top 5 Reactions for all Springs/Wells
What does this show?• What reactions can occur• The potential energy yield of the different
reactions• What niche spaces are available for use• Trends between the geology, water chemistry, and
affinity coefficients
Affinity Trends
• Chloride Dominated Waters (San A-C, RSB12) have nearly identical affinity coefficients
• P value = .94
The Chloride Dominated Waters
San Acacia Spring Rio Salado Box Spring
Affinity Trends• Geographically similar location (SdC1, TW)• Distinct water types– Sulfate Dominated (Cibola Spring)– Mixed Ion Water (Tomasino Well)
• P value = .925
PICTURE of LOCAL GEOLOGY
Cibola
Tomasino
Affinity Trends
• Bicarbonate Dominated Waters (WMW, SC2)• P value = .665
Nutrient Readings
C:N ratios limiting nutrients whose presence
greatly affects the health of a water system
> 14.6 severe N deficiency8.3 –14.6 moderate deficiency<8.3 no deficiencyOnly Tomasino Well does not have a
severe N deficiency
All Springs/Wells have high TOC readings which predict the presence of chemolithoheterotrophs
Spring/Well C:N
Fish & Wildlife Well 4635.96354
San Lorenzo Spring 2 76.86617
McKenzie Well 23.56353
Cibola Spring 426.27735
Canyon Well 25.24335
Gibbs Well 53.93346
Tule Well 1651.51884
Rio Salado (downstream) 1453.10889
Rio Salado Box spring11 293.03585
Rio Salado Box spring12 285.04539
Silver Creek seep 2 189.86399
San Lorenzo Spring 1 158.53682
Tomasino Well 9.65792
San Acacia brine pool 35.35470
Nunn Well 77.92092
West Mesa Well 66.00071
Canyon del Ojito Spring 39.41307
San Acacia spring 170.15187
Discussion• Nitrate is the dominant electron acceptor• Nutrient reading show that all but one
spring/well is deficient in N– This is probably because NO3 is being used nearly
entirely in these metabolic reactions• Surprisingly, in the springs/wells with O2, Nitrate
continues to have a higher energy yield– Perhaps because O2 is so limited that it isn’t optimal
for microorganisms to use this pathway• Feedback effect between microbs and water
Gib
bs F
ree
Ener
gy
Lower than atmos. pCO2 yet saturated with respect to calcite
Higher than atmos. pCO2 yet under saturated with respect to calcite
Higher than atmos. pCO2 and saturated with calcite
Crossey, unpublished
Why use thermodynamic modeling?• Future geomicrobiology research and sampling• Provides explanations• Similarities to Mid Ocean Ridge thermal vents
Rio Grande Rift; Crossey et al., in prep.
Lost City Hydrothermal area, Kelley et al., 2005
Continental spring systemsMarine vent systems
Acknowledgements - Laura Crossey - Amy Williams - Frankie Reyes- All the REU’s! - Jennifer Johnson - Scott Collins- Fish and Wildlife Services- NSF
- Sevilleta LTER- Ara Kooser - Brandi Cron - Amanda Martinez- Cathy!- Mehdi and Kim in the analytical
chemistry lab- Amanda Schaupp, my statistician!
QUESTIONS?