Isolation from estuarine sediments of a Desulfovibrio strain which can grow on lactate coupled to the reductive dehalogenation of 2,4, 6-tribromophenol

Abstract

Strain TBP-1, an anaerobic bacterium capable of reductively dehalogenating 2,4,6-tribromophenol to phenol, was isolated from estuarine sediments of the Arthur Kill in the New York/New Jersey harbor. It is a gram-negative, motile, vibrio-shaped, obligate anaerobe which grows on lactate, pyruvate, hydrogen, and fumarate when provided sulfate as an electron acceptor. The organism accumulates acetate when grown on lactate and sulfate, contains desulfoviridin, and will not grow in the absence of NaCl. It will not utilize acetate, succinate, propionate, or butyrate for growth via sulfate reduction. When supplied with lactate as an electron donor, strain TBP-1 will utilize sulfate, sulfite, sulfur, and thiosulfate for growth but not nitrate, fumarate, or acrylate. This organism debrominates 2-, 4-, 2,4-, 2,6-, and 2,4,6-bromophenol but not 3- or 2,3-bromophenol or monobrominated benzoates. It will not dehalogenate monochlorinated, fluorinated, or iodinated phenols or chlorinated benzoates. Together with its physiological characteristics, its 16S rRNA gene sequence places it in the genus Desulfovibrio. The average growth yield of strain TBP-1 grown on a defined medium supplemented with lactate and 2,4,6-bromophenol is 3.71 mg of protein/mmol of phenol produced, and the yield was 1.42 mg of protein/mmol of phenol produced when 4-bromophenol was the electron acceptor. Average growth yields (milligrams of protein per millimole of electrons utilized) for Desulfovibrio sp. strain TBP-1 grown with 2,4,6-bromophenol, 4-bromophenol, or sulfate are 0.62, 0.71, and 1.07, respectively. Growth did not occur when either lactate or 2,4,6-bromophenol was omitted from the growth medium. These results indicate that Desulfovibrio sp. strain TBP-1 is capable of growth via halorespiration.

FIG. 1

Dehalogenation of 2,4,6-TBP in enrichments inoculated with Arthur Kill sediments and supplemented with succinate. Closed circles, 2,4,6-TBP; open circles, phenol; squares, 4-BP; triangles, 2,4-DBP. Dotted lines are used to indicate that these lines do not represent actual rates of activity since all of the 2,4,6-TBP was consumed prior to our first sampling point after feeding. Data are the average of triplicates, and error bars represent 1 standard deviation. Arrow indicates time of succinate resupplementation. Sterile controls did not exhibit 2,4,6-TBP loss or phenol production (data not shown).

FIG. 2

Phase-contrast light micrographs of strain TBP-1 grown on lactate and sulfate. Spherical body illustrates morphological transformation that occurs in older cultures. Bar, 5 μm.

FIG. 3

Growth of strain TBP-1 on modified Baar’s medium at 30°C with increasing concentrations of NaCl (indicated for each curve). Data are the averages of duplicates.

FIG. 4

Stoichiometric dehalogenation of 2,4,6-TBP to phenol by strain TBP-1. Dotted line represents the regression line of the average cumulative 2,4,6-TBP consumed by duplicate cultures plotted against the average cumulative phenol produced. Stoichiometric phenol production demonstrates that dehalogenation of 2,4,6-TBP was complete and that no phenol was consumed by or lost from these cultures.

FIG. 5

Phylogenetic tree of strain TBP-1 and other related species based on 16S rRNA gene sequences. Bootstrap values at nodes are the percentages of 100 iterations. Values less than 50% are not included. The scale bar indicates the estimated number of substitutions per 100 positions.