**5. Conclusions**

The aim of this study was to investigate laboratory tests that mimic the complex communities present in real world cases of MIC/ALWC. As part of this work, a model SRB, *D. desulfuricans*, was used throughout an 8-week corrosion study. The general corrosion rates of many of the mixed microbial test configurations were lower than that of an uninoculated control. Despite that the three mixed microbial tests (T2, T4 and T5) were nominally aerobic, it is likely the test solutions became anaerobic due to oxygen use by aerobic microbes in the milieu which may have been responsible for the reduced general/uniform corrosion. Greater localised corrosion was observed for all of the tests that included *D. desulfuricans*. However, the defined mixed community with *D. desulfuricans* did not lead to increased corrosion compared to tests with *D. desulfuricans* alone. The composition of the mixed microbial communities changed over the duration of the test and key differences were observed between the planktonic and biofilm communities. More laboratory-based experimental work is required to determine optimal microbial communities and test conditions for ALWC studies. Finally, the metabolomic or transcriptomic aspects relevant to the microbe/corrosion processes should be considered for a further study. It is likely that such studies would give further useful insights into MIC and ALWC.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/2624-5 558/2/2/8/s1, Table S1: Summary of example MIC studies using defined multispecies microbial consortia (WL—weight loss test method, CR—corrosion rate), Table S2: Putative metabolic activities of microbes present in metabarcoding profiles identified using METAGENassist, Figure S1: XRD scans of products formed on DH36 coupons in six treatments at 8 weeks. The three highest peaks observed match to the Fe component of the carbon steel coupons used.

**Author Contributions:** Conceptualisation, all authors; methodology, all authors; validation, all authors; formal analysis, H.C.P.; investigation, H.C.P.; writing—original draft preparation, H.C.P.; writing—review and editing, all authors; visualization, H.C.P.; supervision, S.A.W. and L.L.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The microbial sequencing data is planned to be deposited in the NCBI database.

**Acknowledgments:** We would like to thank Melanie Thomson (previously of Deakin University) for providing the *D. desulfuricans* used in this study.

**Conflicts of Interest:** The authors declare no conflict of interest.
