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Near‐neutral surface charge and hydrophilicity prevent mineral encrustation of F e‐oxidizing micro‐organisms
Author(s) -
Saini G.,
Chan C. S.
Publication year - 2013
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12021
Subject(s) - mineralization (soil science) , zeta potential , chemistry , surface charge , oxidizing agent , contact angle , abiotic component , biomineralization , biophysics , chemical engineering , environmental chemistry , ecology , biology , organic chemistry , nanoparticle , nitrogen , engineering
Microbial survival in mineralizing environments depends on the ability to evade surface encrustation by minerals, which could obstruct nutrient uptake and waste output. Some organisms localize mineral precipitation away from the cell; however, cell surface properties – charge and hydrophobicity – must also play a role in preventing surface mineralization. This is especially relevant for iron‐oxidizing bacteria ( F e OB ), which face an encrustation threat from both biotic and abiotic mineralization. We used electron microscopy and surface characterization techniques to study the surfaces of two stalk‐forming neutrophilic F e OB : the marine Z etaproteobacterium Mariprofundus ferrooxydans PV‐1 and the recently isolated freshwater Betaproteobacterium Gallionellales strain R‐1. Both organisms lack detectable iron on cell surfaces. Live and azide‐inhibited M. ferrooxydans PV ‐1 cells had small negative zeta potentials (−0.34 to −2.73 mV), over the pH range 4.2–9.4; G allionellales strain R ‐1 cells exhibited an even smaller zeta potential (−0.10 to −0.19 mV) over pH 4.2–8.8. Cells have hydrophilic surfaces, according to water contact angle measurements and microbial adhesion to hydrocarbons tests. Thermodynamic and extended D erjaguin– L andau– V erwey– O verbeek ( XDLVO ) calculations showed that as low charge causes low electrostatic attraction, hydrophilic repulsion dominates cell–mineral interactions. Therefore, we conclude that surface properties help enable these F e OB to survive in highly mineralizing environments. Given both mineral‐repelling surface properties and the ability to sequester F e(III) biominerals in an organomineral stalk, these two F e OB have a well‐coordinated system to localize both biotic and abiotic mineral distribution.