ICMGP - Conference Presentation

Abstract Information :

The hgcAB gene pair encodes Hg methylation capability in microorganisms spanning a diverse group of metabolic clades. The gene pair can be used to identify microbes capable of methylating Hg. However, hgcAB gene abundance is often a poor indicator of environmental MeHg levels. Rather metabolic activity of Hg-methylating organisms as well as transcription of hgcAB is thought to be a better predictor of in situ Hg methylation. However, few studies have linked Hg methylation rates to microbial activity. Here we explore the relationship between transcriptional activity of hgcA, metabolic activity, and MeHg production by Pseudodesulfovibrio mercurii ND132. For this study, we compared Hg methylation rates by P. mercurii ND132 cultures grown with various substrates (AsIII, AsV, adenosine-2?3?-dialdehyde, methionine) to test for changes in hgcA transcription and/or metabolic activity compared to a control culture. Mercury methylation was measured over time and normalized to biomass (OD, cell counts), metabolic activity (organic acid production, CO2 respiration), hgcA transcription (qPCR), and total filter-passable and unfiltered Hg. We observed differential expression of hgcA between microbial cultures indicating that hgcA may be transcriptionally regulated by an arsR-like regulator. Significant differences in Hg methylation rates were observed between cultures. Differences in biomass and metabolic activity explained some but not all differences in Hg methylation rates between cultures. This indicates that hgcA activity or some other unknown biochemical or molecular mechanism is affecting Hg methylation rates by P. mercurii ND132.