Enriching distinctive microbial communities from marine sediments via an electrochemical-sulfide-oxidizing process on carbon electrodes

Abstract

Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA) were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA) in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte) equipped with carbon-felt electrodes. In both cases, when potentials of +630 or +130 mV (vs. SHE) were applied, currents were consistently higher at +630 then at +130 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter) not well-known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes.

Assessing Marine Microbial Induced Corrosion at Santa Catalina Island, California

“…Lastly, Arcobacter spp. were reported as predominant in enrichments of Port of Los Angeles sediments in an electrochemical sulfide oxidation study (Li and Nealson, 2015), further associating this genus in MIC/ALWC activity near our study site.…”

“…In the current study, relatively higher proportions of Epsilonproteobacteria sequences were recovered from NE-FLOCS ( Figure 6 ) corroborating a potential link between eutrophic conditions and ALWC microbial community profiles. The majority of these sequences are classified as Arcobacter spp., a genus recently enriched from electrochemical sulfide oxidation studies of Port of Los Angeles sediment (Li and Nealson, 2015). We propose that this genus may play a role in the global phenomenon of ALWC and suggest further investigation into the microbiological-electrochemical role played by Arcobacter spp.…”

Using Cathodic Poised Potential Experiments to Investigate Extracellular Electron Transport in the Crustal Deep Biosphere of North Pond, Mid-Atlantic Ridge

“…Current responses with values greater than the fluid only treatments were in basalt or glass wool treatments in the NP11, NP12, and NP14 experiments. While the current responses between the samples and the fluid only treatments only varied by a few µA cm −2 , we note that other environmental cathodic EET experiments have observed similar patterns between biotic and abiotic treatments (Li and Nealson, 2015;Rowe et al, 2015;Jangir et al, 2016;Karbelkar et al, 2016;Lam et al, 2019b). In NP11, which was three basalt replicates from the Hole U1382A downhole incubation (Table 2), there was considerable variation between the signals.…”

Variation in electrode redox potential selects for different microorganisms under cathodic current flow from electrodes in marine sediments

“…The Clostridiales comprised a significant proportion of the communities for all electrode samples, except for the −650 mV versus Ag/AgCl electrode community, which differed the most in overall composition from all other electrode communities. In our laboratory's prior studies of Catalina Harbor, Clostridia comprised a significant amount of the communities in tertiary solid substrate oxidizing enrichments (Rowe et al ., ) and in anodic electrochemical enrichments (Li and Nealson, ). An enrichment of the orders agg27 and 34P16 distinguishes the −650 mV versus Ag/AgCl electrode from all other samples.…”