title: The pH and pCO2 dependence of sulfate reduction in shallow-sea hydrothermal CO2 - venting sediments (Milos Island, Greece).
abstract: Microbial sulfate reduction (SR) is a dominant process of organic matter mineralization in sulfate-rich anoxic environments at neutral pH. Recent studies have demonstrated SR in low pH environments, but investigations on the microbial activity at variable pH and CO2 partial pressure are still lacking. In this study, the effect of pH and pCO2 on microbial activity was investigated by incubation experiments with radioactive (35)S targeting SR in sediments from the shallow-sea hydrothermal vent system of Milos, Greece, where pH is naturally decreased by CO2 release. Sediments differed in their physicochemical characteristics with distance from the main site of fluid discharge. Adjacent to the vent site (T ~40-75°C, pH ~5), maximal sulfate reduction rates (SRR) were observed between pH 5 and 6. SR in hydrothermally influenced sediments decreased at neutral pH. Sediments unaffected by hydrothermal venting (T ~26°C, pH ~8) expressed the highest SRR between pH 6 and 7. Further experiments investigating the effect of pCO2 on SR revealed a steep decrease in activity when the partial pressure increased from 2 to 3 bar. Findings suggest that sulfate reducing microbial communities associated with hydrothermal vent system are adapted to low pH and high CO2, while communities at control sites required a higher pH for optimal activity.
authors: Department of Biogeochemistry, Max Planck Institute for Marine Microbiology Bremen, Germany.
authors: Elisa
authors: E
authors: Bayraktarov
authors: Roy E
authors: RE
authors: Price
authors: Timothy G
authors: TG
authors: Ferdelman
authors: Kai
authors: K
authors: Finster
keywords: extreme environment; microbial activity; pCO2 effect; pH effect; shallow-seahydrothermal vents; sulfate reduction; sulfate reduction rate
references: ISME J. 2008 Aug;2(8):815-29
references: 18309360
references: Biochem Biophys Res Commun. 1981 Mar 16;99(1):81-8
references: 7236271
references: Bioresour Technol. 2008 Nov;99(17):8075-81
references: 18467091
references: Trends Microbiol. 2007 Apr;15(4):165-71
references: 17331729
references: Appl Environ Microbiol. 1999 Feb;65(2):626-31
references: 9925592
references: Appl Environ Microbiol. 1999 Sep;65(9):3834-42
references: 10473383
references: Environ Microbiol. 1999 Oct;1(5):457-67
references: 11207766
references: Nat Rev Microbiol. 2008 Jun;6(6):441-54
references: 18461075
references: Appl Environ Microbiol. 1991 Mar;57(3):847-56
references: 16348450
references: Science. 1992 Dec 11;258(5089):1756-7
references: 17831655
references: Microbiol Rev. 1993 Jun;57(2):451-509
references: 8336675
references: Appl Environ Microbiol. 1984 Dec;48(6):1134-9
references: 16346677
references: Environ Microbiol. 2011 Oct;13(10):2633-48
references: 21895907
references: Science. 2009 Sep 18;325(5947):1541-4
references: 19762643
references: Science. 1985 Aug 23;229(4715):717-25
references: 17841485
references: Adv Appl Microbiol. 2009;68:41-98
references: 19426853
references: FEMS Microbiol Ecol. 2008 Jun;64(3):329-42
references: 18445022
references: ISME J. 2013 Jul;7(7):1391-401
references: 23535916