*Article* **Effect of Multispecies Microbial Consortia on Microbially Influenced Corrosion of Carbon Steel**

**Hoang C. Phan 1,\*, Linda L. Blackall 2 and Scott A. Wade 1,\***


**Abstract:** Microbially influenced corrosion (MIC) is responsible for significant damage to major marine infrastructure worldwide. While the microbes responsible for MIC typically exist in the environment in a synergistic combination of different species, the vast majority of laboratory-based MIC experiments are performed with single microbial pure cultures. In this work, marine grade steel was exposed to a single sulfate reducing bacterium (SRB, *Desulfovibrio desulfuricans*) and various combinations of bacteria (both pure cultures and mixed communities), and the steel corrosion studied. Differences in the microbial biofilm composition and succession, steel weight loss and pitting attack were observed for the various test configurations studied. The sulfate reduction phenotype was successfully shown in half-strength marine broth for both single and mixed communities. The highest corrosion according to steel weight loss and pitting, was recorded in the tests with *D. desulfuricans* alone when incubated in a nominally aerobic environment. The multispecies microbial consortia yielded lower general corrosion rates compared to *D. desulfuricans* or for the uninoculated control.

**Keywords:** corrosion; metabarcoding; MIC; multispecies; SRB
