Chrysiogenes arsenatis
Jackie Schneider

Researchers in Ballarat, Australia examined the microbial life in arsenic-contaminated mud near the Ballarat Goldfields. They found an organism that was genetically distinct from most others. Analysis of its binary sequence showed that it only shared 74.8-81.8% of its sequence with representatives of major phylogenetic groups within the Bacteria. Because of this, it was assigned a new phylum named Chrysiogenetes. The bacterium, Chrysiogenes arsenatis, is the only known member of this phylum (“Phylum BV. Chrysiogenetes phy. nov.”).

C. arsenatis is a bacterium with curved, rod-shaped cells that are between 1.0 and 2.0 µm in length and 0.50 and 0.75 µm in diameter. It is Gram-negative and strictly anaerobic. The cells are motile through a single polar flagellum. Colonies grow best at a temperature between 25 and 30 °C (“Phylum BV. Chrysiogenetes phy. nov.”).

C. arsenatis respires anaerobically and uses acetate as its electron donor and carbon source and arsenate as its electron acceptor. It oxidizes acetate to carbon dioxide and reduces arsenate to arsenite. Three other known bacterial species reduce arsenate to arsenite during growth. These are Sulfurospirillum arsenophilum MIT-13, Sulfurospirillum barnesii SES-3, and Desulfotomaculum auripigmentum. Other organisms, including Escherichia coli, can reduce arsenate to arsenite but do not conserve energy during the process (“Phylum BV. Chrysiogenetes phy. nov.”).
The closest relative to C. arsenatis is Flexistipes sinusarabici, a thermophilic bacteria isolated from brine water 2000 m deep in the Red Sea. Both bacteria are Gram-negative and strictly anaerobic, but they differ in most other respects (“Phylum BV. Chrysiogenetes phy. nov.”).

C. arsenatis was recently used to develop a test for arsenite-producing bacteria in drinking water. In South Asia, arsenic-contaminated drinking water causes health problems for numerous people. For example, in Bangladesh alone tens of millions of people drink water that contains arsenic. Research on C. arsenatis led to the development of a molecular assay that tests for the presence of arrA, a bacterial gene present in arsenite-producing organisms (“A Simple Test May Save Millions”). This test can evaluate the safety of drinking water and therefore save countless lives. In the future, perhaps C. arsenatis’s unique respiration and binary sequence will further advance industry and medicine.


“A Simple Test May Save Millions.” 2005. La Trobe University. 1 April 2007. <>

Perry, Jerome J., James T. Staley, and Stephen Lory. Microbial Life. Sunderland, Massachusetts: Sinauer Associates, Inc., 2002.

“Phylum BV. Chrysiogenetes phy. nov.” Bergey’s Manual of Systematic Bacteriology, 2nd Edition. Vol. 1. New York: Springer, 2001.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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