Neutrophilic Iron-Oxidizing "Zetaproteobacteria" and Mild Steel Corrosion in Nearshore Marine Environments
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
Pagination or Media Count:
Microbiologically influenced corrosion MIC of mild steel in seawater is an expensive and enduring problem. Little attention has been paid to the role of neutrophilic, lithotrophic, iron-oxidizing bacteria FeOB in MIC. The goal of this study was to determine if marine FeOB related to Monprofundus are involved in this process. To examine this, field incubations and laboratory microcosm experiments were conducted. Mild steel samples incubated in nearshore environments were colonized by marine FeOB, as evidenced by the presence of helical iron-encrusted stalks diagnostic of the FeOB Mariprofundus ferrooxydans, a member of the candidate class Zetaproteobacteria. Temporal in situ incubation studies showed a qualitative increase in stalk distribution on mild steel, suggesting progressive colonization by stalk-forming FeOB. We also isolated a novel FeOB, designated Mariprofundus sp. strain GSB2, from an iron oxide mat in a salt marsh. Strain GSB2 enhanced uniform corrosion from mild steel in laboratory microcosm experiments conducted over 4 days. Iron concentrations including precipitates in the medium were used as a measure of corrosion. The corrosion in biotic samples 7.4 - 0.1 mM was significantly higher than that in abiotic controls 5.0 - 0.1 mM. These results have important implications for the role of FeOB in corrosion of steel in nearshore and estuarine environments. In addition, this work shows that the global distribution of Zetaproteobacteria is far greater than previously thought.
- Biological Oceanography
- Properties of Metals and Alloys