|
| |
Center for Biofilm Engineering
Abstract:
"Influence of the Distribution of the Manganese-Oxidizing Bacterium,
Leptothrix Discophora, on Ennoblement of Type 316L Stainless Steel"
04-017 Type 316L (UNS 31603) stainless steel (SS) was ennobled to an open-circuit
potential (OCP) of 323 mV vs saturated calomel electrode (SCE) within a 5-day
period due to the deposition of manganese oxides on the metal surface by a
monospecies biofilm of Leptothrix discophora. However, the same metal
experienced only partial ennoblement, achieving a maximum potential of 143 mVSCE
during the same period when colonized by a three-species biofilm containing L. discophora, and even this level of ennoblement by the mixed-species biofilm was
only transient since the potential decreased to 122 mVSCE shortly
after achieving the maximum potential. The mixed-species biofilm was
significantly thicker (>200 µm) than the L. discophora
monospecies biofilm (120 µm). Using 16s rRNA probes
specific for L. discophora,
fluorescent in-situ hybridization revealed cells to be heterogeneously
distributed throughout the monospecies biofilm. In the three-species biofilm,
16s rRNA probes revealed a homogeneous
layer of L. discophora that resided proximal to the biofilm-bulk solution phase.
At the most distal position from the biofilm-bulk solution phase near the glass-biofilm
interface there existed very few to no L. discophora. Microelectrode studies
revealed the presence of oxygen (3.85 mg/L to 4.35 mg/L) at the monospecies-glass
substratum interface in 50% of the areas of the substratum assayed. No oxygen
was detected at the three-species biofilm-glass interface where the thickness of
the overlying biofilm exceeded 200 µm. The results
suggest that ennoblement of Type 316L SS by L. discophora depends on
oxygen accessibility to cells proximal to the substratum.
Campbell, S., G. Geesey, Z. Lewandowski, and G. Jackson, "Influence of the
Distribution of the Manganese-Oxidizing Bacterium, Leptothrix Discophora,
on Ennoblement of Type 316L Stainless Steel," Corrosion, 60(7):670-680 |
|
sign take you to sites with
content for which the CBE is not responsible.