Chrysiogenes arsenatis gen. nov., sp. nov., a New Arsenate-Respiring Bacterium Isolated from Gold Mine Wastewater

Chrysiogenes arsenatis is a newly described strictly anaerobic bacterium isolated from gold mine wastewater at Ballarat Goldfields, Australia. This gram-negative, curved rod-shaped organism is physiologically unique among arsenate-reducing bacteria because it can grow using acetate as both the electron donor and carbon source, with arsenate as the terminal electron acceptor. The bacterium reduces arsenate to arsenite, achieving a generation time of 4 hours. C. arsenatis can also utilize other organic compounds including pyruvate, lactate, succinate, malate, and fumarate as electron donors, and can employ nitrate or nitrite as alternative electron acceptors, but cannot grow using sulfate, thiosulfate, or iron oxide. The organism has a DNA G+C content of 49 mol%. Phylogenetic analysis based on 16S rRNA sequences reveals that C. arsenatis represents a deeply branching lineage of bacteria distinct from other known arsenate-reducing strains (MIT-13 and SES-3), sharing only 74.8–81.8% sequence similarity with representatives of major bacterial phyla.

Key findings

• C. arsenatis is the first pure culture bacterium demonstrated to conserve energy through arsenate respiration using acetate as the electron donor, unlike previously known arsenate-reducing bacteria that require lactate
• The organism reduces arsenate to arsenite while maintaining constant total arsenic levels, with a 4-hour doubling time on 5 mM acetate and 5 mM arsenate
• 16S rRNA sequence analysis indicates C. arsenatis represents a phylogenetically unique, deeply branching bacterial lineage separate from all other major bacterial groups
• C. arsenatis can utilize acetate, pyruvate, L- and D-lactate, fumarate, succinate, and malate as electron donors, but cannot use hydrogen, formate, sugars, or most amino acids