NERENBERG RESEARCH GROUP

PERCHLORATE-REDUCING BACTERIA

Funding: Capitalization fund

Project start: 5/2005

Publications and presentations:

· Margaret Dudley, Anna Salamone, and Robert Nerenberg (submitted, 2007). Kinetics of Novel a Chlorate Accumulating, Perchlorate-Reducing Bacterium.

· M. Dudley, S.J. Green, and R. Nerenberg (2007). Determining the Cause of Chlorate Accumulation in Dechlorosoma HCAP-C, a Novel Perchlorate-Reducing Bacterium. ASM General Conference, May 2007, Toronto. (Poster).

· Anna Salamone and Robert Nerenberg (2006). Novel Perchlorate-Reducing Bacteria Accumulate High Levels of Chlorate. Proceedings of ASM General Meeting, Orlando. Poster.

Perchlorate contamination is widespread in the United States (Gullick et al. 2001). It is found at high concentrations (g/L) near the center of perchlorate plumes, and at low concentrations (μg/L) in many drinking water sources (Motzer 2001, USEPA 2002). Perchlorate is harmful to humans and wildlife because it disrupts natural functioning of the thyroid gland (Clark 2000, Wolff 1998). According to the National Academy of Science (NAS), humans can safely consume perchlorate at a rate of 0.7 μg/kg of body weight per day, which translates to a drinking water maximum contaminant level MCL of 24.5 μg/L (Ginsberg et al. 2005). Some states have perchlorate action levels as low as 2 μg/L.

Certain types of bacteria can use perchlorate as an electron acceptor for anaerobic growth. Such bacteria appear to be ubiquitous in the environment, even though perchlorate is almost exclusively released from human activities and has been produced only for around the past 100 years (Urbansky, 1998). Since all identified perchlorate-reducing bacteria also reduce chlorate, they are sometimes referred to as “(per)chlorate”-reducing bacteria to reflect their ability to use both these acceptors.

In the early 1990s, interest in chlorate-reducing bacteria was stimulated by the need to treat perchlorate- or chlorate-containing industrial wastes, such as kraft mill effluent (Malmqvist et al., 1991; Malmqvist and Welander, 1992), match factory wastewater (Stepanyuk et al., 1993), and rocket manufacture wastewaters (Attaway and Smith, 1993). Today, using perchlorate-reducing bacteria are being used as a means to remediate groundwater and drinking water.

We have isolated numerous PCRB, such as Dechloromonas sp. PC1 (shown below), and are characterizing their phylogeny, kinetics, and ecological relationships in mixed cultures. In particular, we are characterizing novel PCRB that accumulate high levels of chlorate, which we call high chlorate accumulating PCRB or HCAP. We are also interested in their use in bioreactors (see MBfR).

SEM Image of Dechloromonas sp. PC1