Genomic Insights into Mn(II) Oxidation by the Marine Alphaproteobacterium Aurantimonas sp. Strain SI85-9A1

Abstract

Microbial Mn(II) oxidation has important biogeochemical consequences in marine, freshwater, and terrestrial environments, but many aspects of the physiology and biochemistry of this process remain obscure. Here, we report genomic insights into Mn(II) oxidation by the marine alphaproteobacterium Aurantimonas sp. strain SI85-9A1, isolated from the oxic/anoxic interface of a stratified fjord. The SI85-9A1 genome harbors the genetic potential for metabolic versatility, with genes for organoheterotrophy, methylotrophy, oxidation of sulfur and carbon monoxide, the ability to grow over a wide range of O 2 concentrations (including microaerobic conditions), and the complete Calvin cycle for carbon fixation. Although no growth could be detected under autotrophic conditions with Mn(II) as the sole electron donor, cultures of SI85-9A1 grown on glycerol are dramatically stimulated by addition of Mn(II), suggesting an energetic benefit from Mn(II) oxidation. A putative Mn(II) oxidase is encoded by duplicated multicopper oxidase genes that have a complex evolutionary history including multiple gene duplication, loss, and ancient horizontal transfer events. The Mn(II) oxidase was most abundant in the extracellular fraction, where it cooccurs with a putative hemolysin-type Ca 2؉ -binding peroxidase. Regulatory elements governing the cellular response to Fe and Mn concentration were identified, and 39 targets of these regulators were detected. The putative Mn(II) oxidase genes were not among the predicted targets, indicating that regulation of Mn(II) oxidation is controlled by other factors yet to be identified. Overall, our results provide novel insights into the physiology and biochemistry of Mn(II) oxidation and reveal a genome specialized for life at the oxic/anoxic interface.

Treatment of groundwater containing Mn(II), Fe(II), As(III) and Sb(III) by bioaugmented quartz-sand filters

“…Results also suggest that other Mnoxidizing Pseudomonas may exist in the columns as the cumA gene is frequently found in different Pseudomonas strains (Brouwers et al, 1999;de Vrind-de Jong et al, 2000). The mox genes in columns were similar to those found in genera Aurantimonas and Methylobacterium (Dick et al, 2008;Vuilleumier et al, 2009). …”

The metatranscriptome of a deep-sea hydrothermal plume is dominated by water column methanotrophs and lithotrophs

“…However, several genes showed a markedly higher transcript abundance in the plume environment, including an MGI archaea ammonium transporter (8.6 times increase) and SUP05 genes for the sox sulfur oxidation system (10-20 times increase) (Figure 2). Notably absent from the abundant protein-coding transcripts were genes encoding known Mn-oxidizing enzymes such as the multicopper oxidases MnxG, CumA and MofA (for example, Dick et al, 2008b) or the heme peroxidase MopA (for example, Dick et al, 2008a;Anderson et al, 2009). Although expression of novel multicopper oxidases was observed (mRNA transcript abundance ranks 186, 282, 818 and 856; data not shown in Figure 2), this diverse family of enzymes oxidizes a wide range of substrates (Tebo et al, 2004), thus further investigation is required to evaluate their potential link to Mn oxidation.…”

Metagenomic analysis of rapid gravity sand filter microbial communities suggests novel physiology ofNitrospiraspp.

“…ACM 3067, suggesting a potential capacity for manganese oxidation. Rhizobiales CG3 encoded for two multicopper oxidases with sequence identity (59% to 75% at protein level) related to those found in the manganese oxidizer Aurantimonas manganoxydans SI85-9A1 (Dick et al, 2008). CG3 encoded for cytochrome cbb3-type oxidase and nitrate reductase (narG).…”