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Description of the novel perchlorate-reducing bacteria Dechlorobacter hydrogenophilus gen. nov., sp. nov.and Propionivibrio militaris, sp. nov.

Thrash JC, Pollock J, Torok T, Coates JD - Appl. Microbiol. Biotechnol. (2010)

Bottom Line: The use of perchlorate and other electron acceptors distinguished strains MP(T) and CR from P. limicola physiologically.Strains LT-1(T) and MP(T) are the first DPRB to be described in the Betaproteobacteria outside of the Dechloromonas and Azospira genera.The names Dechlorobacter hydrogenophilus gen. nov., sp. nov and Propionivibrio militaris sp. nov. are proposed.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
Novel dissimilatory perchlorate-reducing bacteria (DPRB) were isolated from enrichments conducted under conditions different from those of all previously described DPRB. Strain LT-1(T) was enriched using medium buffered at pH 6.6 with 2-(N-morpholino)ethanesulfonic acid (MES) and had only 95% 16S rRNA gene identity with its closest relative, Azonexus caeni. Strain MP(T) was enriched in the cathodic chamber of a perchlorate-reducing bioelectrical reactor (BER) and together with an additional strain, CR (99% 16S rRNA gene identity), had 97% 16S rRNA gene identity with Propionivibrio limicola. The use of perchlorate and other electron acceptors distinguished strains MP(T) and CR from P. limicola physiologically. Strain LT-1(T) had differences in electron donor utilization and optimum growth temperatures from A. caeni. Strains LT-1(T) and MP(T) are the first DPRB to be described in the Betaproteobacteria outside of the Dechloromonas and Azospira genera. On the basis of phylogenetic and physiological features, strain LT-1(T) represents a novel genus in the Rhodocyclaceae; strain MP(T) represents a novel species within the genus Propionivibrio. The names Dechlorobacter hydrogenophilus gen. nov., sp. nov and Propionivibrio militaris sp. nov. are proposed.

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Growth curves of strain MPT (a) and strain LT-1T (b). Cell number increase was monitored with optical density (OD) at 600 nm. Closed circles OD, open squares [ClO4−], open triangles [Cl−], open diamonds, [ClO3−]; all concentrations in millimolar. Error bars represent the standard deviation of triplicate experiments
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Fig3: Growth curves of strain MPT (a) and strain LT-1T (b). Cell number increase was monitored with optical density (OD) at 600 nm. Closed circles OD, open squares [ClO4−], open triangles [Cl−], open diamonds, [ClO3−]; all concentrations in millimolar. Error bars represent the standard deviation of triplicate experiments

Mentions: Strains MPT and CR grew singly as curved rods, approximately 2 µm long × 0.3 µm in diameter (Fig. 1). Strain LT-1T grew as a slightly curved (Fig. 2a) or short, straight rod (Fig. 2b), 0.8–1.6 × 0.3 µm, either singly or in chains. Cells from all three strains were observed by phase-contrast microscopy to be motile when grown on acetate and perchlorate (10 mM). MPT, CR, and LT-1T were strictly respiratory, as judged by their inability to grow in the absence of an electron acceptor either with 10 mM glucose, or in rich media (10 mM glucose, 1 g/L casamino acids, and 1 g/L yeast extract). None of the strains were capable of growth after pasteurization at 80°C and were therefore considered incapable of forming spores. All three strains grew by complete reduction of perchlorate to chloride, and all three strains contained copies of the chlorite dismutase gene (cld) (Bender et al. 2004), previously reported for strains LT-1T and CR and confirmed in this study for strain MPT (data not shown). The cld sequence for strain MPT was most closely related to that of CR. Figure 3 shows typical growth curves for strain MPT (Fig. 3a) and strain LT-1T (Fig. 3b) on 10 mM acetate and perchlorate. Cell density increase was monitored by optical density changes at 600 nm. Strains MPT and CR had maximum growth rates at 30°C of 0.21 and 0.22 h−1, respectively. In addition, for both strains, chlorate accumulated to ∼2 mM (2.1 mM for strain MPT—Fig. 2) when grown on 10 mM perchlorate. In contrast, strain LT-1T showed much less (maximum concentration ∼0.1 mM) and more transient chlorate accumulation (Fig. 3b). Strain LT-1T had a maximum growth rate of 0.28 h−1 at 37°C.Fig. 1


Description of the novel perchlorate-reducing bacteria Dechlorobacter hydrogenophilus gen. nov., sp. nov.and Propionivibrio militaris, sp. nov.

Thrash JC, Pollock J, Torok T, Coates JD - Appl. Microbiol. Biotechnol. (2010)

Growth curves of strain MPT (a) and strain LT-1T (b). Cell number increase was monitored with optical density (OD) at 600 nm. Closed circles OD, open squares [ClO4−], open triangles [Cl−], open diamonds, [ClO3−]; all concentrations in millimolar. Error bars represent the standard deviation of triplicate experiments
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Related In: Results  -  Collection

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Fig3: Growth curves of strain MPT (a) and strain LT-1T (b). Cell number increase was monitored with optical density (OD) at 600 nm. Closed circles OD, open squares [ClO4−], open triangles [Cl−], open diamonds, [ClO3−]; all concentrations in millimolar. Error bars represent the standard deviation of triplicate experiments
Mentions: Strains MPT and CR grew singly as curved rods, approximately 2 µm long × 0.3 µm in diameter (Fig. 1). Strain LT-1T grew as a slightly curved (Fig. 2a) or short, straight rod (Fig. 2b), 0.8–1.6 × 0.3 µm, either singly or in chains. Cells from all three strains were observed by phase-contrast microscopy to be motile when grown on acetate and perchlorate (10 mM). MPT, CR, and LT-1T were strictly respiratory, as judged by their inability to grow in the absence of an electron acceptor either with 10 mM glucose, or in rich media (10 mM glucose, 1 g/L casamino acids, and 1 g/L yeast extract). None of the strains were capable of growth after pasteurization at 80°C and were therefore considered incapable of forming spores. All three strains grew by complete reduction of perchlorate to chloride, and all three strains contained copies of the chlorite dismutase gene (cld) (Bender et al. 2004), previously reported for strains LT-1T and CR and confirmed in this study for strain MPT (data not shown). The cld sequence for strain MPT was most closely related to that of CR. Figure 3 shows typical growth curves for strain MPT (Fig. 3a) and strain LT-1T (Fig. 3b) on 10 mM acetate and perchlorate. Cell density increase was monitored by optical density changes at 600 nm. Strains MPT and CR had maximum growth rates at 30°C of 0.21 and 0.22 h−1, respectively. In addition, for both strains, chlorate accumulated to ∼2 mM (2.1 mM for strain MPT—Fig. 2) when grown on 10 mM perchlorate. In contrast, strain LT-1T showed much less (maximum concentration ∼0.1 mM) and more transient chlorate accumulation (Fig. 3b). Strain LT-1T had a maximum growth rate of 0.28 h−1 at 37°C.Fig. 1

Bottom Line: The use of perchlorate and other electron acceptors distinguished strains MP(T) and CR from P. limicola physiologically.Strains LT-1(T) and MP(T) are the first DPRB to be described in the Betaproteobacteria outside of the Dechloromonas and Azospira genera.The names Dechlorobacter hydrogenophilus gen. nov., sp. nov and Propionivibrio militaris sp. nov. are proposed.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
Novel dissimilatory perchlorate-reducing bacteria (DPRB) were isolated from enrichments conducted under conditions different from those of all previously described DPRB. Strain LT-1(T) was enriched using medium buffered at pH 6.6 with 2-(N-morpholino)ethanesulfonic acid (MES) and had only 95% 16S rRNA gene identity with its closest relative, Azonexus caeni. Strain MP(T) was enriched in the cathodic chamber of a perchlorate-reducing bioelectrical reactor (BER) and together with an additional strain, CR (99% 16S rRNA gene identity), had 97% 16S rRNA gene identity with Propionivibrio limicola. The use of perchlorate and other electron acceptors distinguished strains MP(T) and CR from P. limicola physiologically. Strain LT-1(T) had differences in electron donor utilization and optimum growth temperatures from A. caeni. Strains LT-1(T) and MP(T) are the first DPRB to be described in the Betaproteobacteria outside of the Dechloromonas and Azospira genera. On the basis of phylogenetic and physiological features, strain LT-1(T) represents a novel genus in the Rhodocyclaceae; strain MP(T) represents a novel species within the genus Propionivibrio. The names Dechlorobacter hydrogenophilus gen. nov., sp. nov and Propionivibrio militaris sp. nov. are proposed.

Show MeSH
Related in: MedlinePlus