Contribution of bacteria to redox potential (E h) measurements in sediments

E R Hunting,A A Kampfraath

doi:10.1007/s13762-012-0080-4

Abstract

Increasing evidence suggests that bacteria are capable of creating specific redox conditions which are visible as species-specific continuous redox potential (Eh) measurements. It has been demonstrated that continuous measurements of Eh are valuable for tracking bacterial metabolic activities of bacterial species in liquid cultures. However, it remains uncertain whether this phenomenon is widespread among bacterial species and whether Eh mea- surements reflect similar mechanisms in more complex systems such as soils and sediments. The purpose of this study is therefore to evaluate whether bacteria that natu- rally occur in sediments have the capacity to control Eh and assess the relative partitioning of biological processes involved in Eh in natural sediments. To this end, continu- ous Eh measurements are linked to growth of bacteria in liquid cultures and bacterial metabolic activity in aquatic sediment microcosms containing the bioturbator Tubifex spp., in which we evaluate bacterial partitioning in microcosms treated with the bacteriocide formalin. The tested bacterial species (Micrococcus luteus, Paracoccus pantotrophus and Aminobacter aminovarans) appeared to have specific stable Eh signals during linear-exponential growth phase, suggesting that these species are capable of exerting an extracellular control on Eh measurements, thereby supporting the notion that species-specific Eh signals may be widespread among bacterial species. For- malin treatment reduced temporal variability of Eh in sediment microcosms. This outcome suggests that bacterial metabolism and inherent relative contributions of members of bacterial community principally determine development of Eh in sediment systems and that quantitation of sediment electrochemical properties may offer a potential indicator that characterizes bacterial processes.

Highlights

Increasing evidence suggests that bacteria are capable of creating redox conditions which are visible as speciesspecific continuous Eh measurements (Brasca et al 2007; Reichart et al 2007; Michelon et al 2010; Ignatova et al 2010; Tachon et al 2010)
Increasing evidence suggests that bacteria are capable of creating specific redox conditions which are visible as species-specific continuous redox potential (Eh) measurements
Continuous Eh measurements are linked to growth of bacteria in liquid cultures and bacterial metabolic activity in aquatic sediment microcosms containing the bioturbator Tubifex spp., in which we evaluate bacterial partitioning in microcosms treated with the bacteriocide formalin

Summary

Introduction

Increasing evidence suggests that bacteria are capable of creating redox conditions which are visible as speciesspecific continuous Eh measurements (Brasca et al 2007; Reichart et al 2007; Michelon et al 2010; Ignatova et al 2010; Tachon et al 2010). Escalante-Minakata et al 2009; Rosu et al 2010), in which mixed bacterial assemblages may generate a composite redox potential where fluctuations reflect changes in relative metabolic activities of the different species within these assemblages (Escalante-Minakata et al 2009; Rosu et al 2010). This suggests the presence of an apparent redox niche, which is supported by the early observation of redox-taxis in a number of bacterial species

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