Abstract
Bacteria have been implicated as both a source and sink of hydrogen peroxide (H2O2), a reactive oxygen species which can both impact microbial growth and participate in the geochemical cycling of trace metals and carbon in natural waters. In this study, simultaneous H2O2 production and decay by twelve species of heterotrophic bacteria were evaluated in both batch and flow-through incubations. While wide species-to-species variability of cell-normalized H2O2 decay rate coefficients [2x10-8 to 5x10-6 hr-1 (cell mL-1)-1] was observed, these rate coefficients were relatively consistent for a given bacterial species. By contrast, observed production rates (below detection limit to 3x102 amol cell-1 hr-1) were more variable even for the same species. Variations based on incubation conditions in some bacterial strains suggest that external conditions may impact extracellular H2O2 levels either through increased extracellular production or leakage of intracellular H2O2. Comparison of H2O2 production rates to previously determined O2- production rates suggests that O2- and H2O2 production are not necessarily linked. Rates measured in this study indicate that bacteria could account for a majority of H2O2 decay observed in aqueous systems but likely only make a modest contribution to dark H2O2 production.
Highlights
Hydrogen peroxide (H2O2) is ubiquitous in natural water systems and contributes to the biogeochemical cycling of trace metals
H2O2 production in natural waters was previously thought to occur primarily through the dismutation of photochemically produced superoxide (O2−) (Cooper et al, 1988; Shaked et al, 2010) but in recent years it has been shown to occur under dark conditions (Vermilyea et al, 2010a and 2010b; Dixon et al, 2013; Marsico et al, 2015; Zhang et al, 2016a), indicating that other production pathways exists
2016b) suggest that biological production may be a strong contributor to overall H2O2 concentrations in natural waters
Summary
Hydrogen peroxide (H2O2) is ubiquitous in natural water systems and contributes to the biogeochemical cycling of trace metals. H2O2 production in natural waters was previously thought to occur primarily through the dismutation of photochemically produced superoxide (O2−) (Cooper et al, 1988; Shaked et al, 2010) but in recent years it has been shown to occur under dark conditions (Vermilyea et al, 2010a and 2010b; Dixon et al, 2013; Marsico et al, 2015; Zhang et al, 2016a), indicating that other production pathways exists. Culture studies on (extracellular) biological H2O2 production by marine biota have, to date, focused on phytoplankton such as raphidophytes (see Marshall et al, 2002), coccolithophores (Palenik et al, 1987), and diatoms (Milne et al, 2009; Waring et al, 2010; Schneider et al, 2016; Cho et al, 2017). Since H2O2 production rates are not necessarily linked to those of O2− (Schneider et al, 2016; Zhang et al, 2016a), known O2− production rates do not allow for estimation of H2O2 production
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