Enhanced microbial corrosion by Acidithiobacillus ferrooxidans through
the manipulation of substrate oxidation and genetic engineering
Abstract
Acidithiobacillus ferrooxidans cells can oxidize iron and sulfur and are
key members of the microbial biomining communities that are exploited in
the large-scale bioleaching of metal sulfide ores. Some minerals are
recalcitrant to bioleaching due to presence of other inhibitory
materials in the ore bodies. Additives are intentionally included in
processed metals to reduce environmental and microbially influenced
corrosion. We have previously reported a new aerobic corrosion mechanism
where A. ferrooxidans cells combined with pyrite and chloride can
oxidize low grade stainless steel (SS304) with a thiosulfate-mediated
mechanism. Here we explore process conditions and genetic engineering of
the cells to enable corrosion of a higher grade steel (SS316). The
addition of elemental sulfur and an increase in the cell loading
resulted in a 74% increase in the corrosion of SS316 as compared to
sulfur- and cell-free control experiments. The overexpression of the
endogenous rus gene, which is involved in the cellular iron oxidation
pathway, led to further 85% increase in the corrosion of the steel.
Thus, the modification of the culturing conditions and cell line, led to
a more than 3-fold increase in the corrosion of SS316 stainless steel,
such that 15% of the metal coupons was dissolved in just 2 weeks. This
work demonstrates how the engineering of cells and the optimization of
their cultivation conditions can be used to discover conditions that
lead to the corrosion of a complex metal target.