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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING SOIL AND NUTRIENT MANAGEMENT SYSTEMS FOR SUSTAINED PRODUCTIVITY AND ENVIRONMENTAL QUALITY

Location: Soil Plant Nutrient Research (SPNR)

Title: Azospira Oryzae (A Selenium Oxyanion-Reducing Bacterium) 16s Rrna Gene Complete Sequence.

Author
item Hunter, William

Submitted to: National Center for Biotechnology Information (NCBI)
Publication Type: Other
Publication Acceptance Date: August 18, 2006
Publication Date: September 1, 2006
Citation: Hunter, W.J. 2006. Azospira oryzae (a selenium oxyanion-reducing bacterium) 16s rrna gene complete sequence. National Center for Biotechnology Information (NCBI).

Interpretive Summary: This study used molecular and classical methods to identify a selenate and selenite reducing bacterium as Azospira oryzae. In the Western United States selenate or selenite are groundwater problems on almost 160,000 sq. miles of land. Agricultural activities on these lands can result in mobilization of soluble selenium compounds, selenate and selenite. The mobilization of these potentially toxic compounds can cause ground and surface water contamination. Also, refinery wastewaters, a consequence of the refining of crude oil, contain large amounts of selenite and are a significant environmental source of selenium. Selenite is one of the most toxic elements in the environment and ingestion of excess amounts can cause damage to the nervous system. Remediation procedures are needed to remove excess selenium compounds from water. The most economical approach for removing these compounds from water employs biological methods that require the use of microorganisms. Thus, it is important that bacteria that are capable of removing selenite and selenate from ground and surface waters be isolated, characterized, and identified.

Technical Abstract: This study used 1535 base pair 16S rRNA gene sequence methods to confirm the identification of a bacterium that reduces selenite to elemental red selenium as Azospira oryzae. Morphological and biochemical characteristics are consistent with the 16S rRNA gene sequence identification of the bacterium. The isolate was obtained from a laboratory scale permeable reactive barrier that contained vegetable oil as an electron donor and that was supplied with water contaminated with selenate. The 16S rRNA gene sequence shows that the strain has a > 99.9% sequence similarity with A. oryzae but that it is also closely related to Dechlorosoma sp. and D. suillum. However, the literature shows that D. suillum and A. oryzae are the same species with D. suillum being a later synonym of A. oryzae. Thus, we consider our isolate to be an Azospira oryzae, an aerobic Proteobacteria often associated with plant roots. This bacterium, or perhaps its enzymes or DNA, might be useful for the remediation of waters contaminated with Se oxyanions. Selenite is one of the most toxic elements in the environment and ingestion of excess amounts can cause damage to the nervous system. Remediation procedures are needed to remove excess selenium compounds from water. The most economical approach for removing these compounds from water employs biological methods that require the use of microorganisms. Thus, it is important that bacteria that are capable of removing selenite and selenate from ground and surface waters be isolated, characterized, and identified. It is also important to know what organisms may accumulate in biobarriers used for remediation.

Last Modified: 4/20/2014
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