Resistance and Resilience of Sulfidogenic Communities in the Face of the Specific Inhibitor Perchlorate.

Magdalena K Stoeva,Yiwei Cheng,John D Coates,Gilbert Nalula,Anna L Engelbrektson,Nicholas Garcia,Hans K Carlson

doi:10.3389/fmicb.2019.00654

Abstract

Hydrogen sulfide is a toxic and corrosive gas, produced by the activity of sulfate-reducing microorganisms (SRM). Owing to the environmental, economic and human-health consequences of sulfide, there is interest in developing specific inhibitors of SRM. Recent studies have identified perchlorate as a promising emerging inhibitor. The aim of this work is to quantitatively dissect the inhibitory dynamics of perchlorate. Sulfidogenic mixed continuous-flow systems were treated with perchlorate. SRM number, sulfide production and community structure were monitored pre-, during and post-treatment. The data generated was compared to a simple mathematical model, where SRM growth slows as a result of inhibition. The experimental data supports the interpretation that perchlorate largely acts to suppress SRM growth rates, rendering planktonic SRM increasingly susceptible to wash-out. Surface-attachment was identified as an important parameter preventing SRM wash-out and thus governing inhibitory dynamics. Our study confirmed the lesser depletion of surface-attached SRM as compared to planktonic SRM during perchlorate treatment. Indirect effects of perchlorate (bio-competitive exclusion of SRM by dissimilatory perchlorate-reducing bacteria, DPRB) were also assayed by amending reactors with DPRB. Indeed, low concentrations of perchlorate coupled with DRPB amendment can drive sulfide concentrations to zero. Further, inhibition in a complex community was compared to that in a pure culture, highlighting similarities and differences between the two scenarios. Finally, we quantified susceptibility to perchlorate across SRM in various culture conditions, showing that prediction of complex behavior in continuous systems from batch results is possible. This study thus provides an overview of the sensitivity of sulfidogenic communities to perchlorate, as well as mechanisms underlying these patterns.

Highlights

Microbial sulfate reduction (SR) by sulfate-reducing microorganisms (SRM) is one of the primary pathways of anaerobic terminal organic matter mineralization, and as such is a determinant of carbon and sulfur cycling in many environments (Hao et al, 1996; Barton and Fauque, 2009; Plugge et al, 2011; Whitman et al, 2014)
To test the inhibitory dynamics of sulfidogenesis in the presence of perchlorate, a mixed sulfidogenic community was inoculated into triplicate chemostats, treated with 50 mM perchlorate (Table 1, initial run)
The initial chemostat experiment confirms that perchlorate at 50 mM is a potent direct inhibitor of SRM

Summary

Introduction

Microbial sulfate reduction (SR) by sulfate-reducing microorganisms (SRM) is one of the primary pathways of anaerobic terminal organic matter mineralization, and as such is a determinant of carbon and sulfur cycling in many environments (Hao et al, 1996; Barton and Fauque, 2009; Plugge et al, 2011; Whitman et al, 2014). Sulfide production has significant economic and environmental consequences owing to its corrosive nature (Hao et al, 1996). As a result of this economic and industrial importance, SR has been studied with a multiplicity of different tools, and in various systems (Widdel and Bak, 1992; Barton and Fauque, 2009; Plugge et al, 2011; Enning and Garrelfs, 2014)

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