Variovorax paradoxus is a microorganism of special interest due to its diverse metabolic capabilities, including the biodegradation of both biogenic compounds and anthropogenic contaminants. V. paradoxus also engages in mutually beneficial interactions with both bacteria and plants. The complete genome sequence of V. paradoxus S110 is composed of 6,754,997 bp with 6,279 predicted protein-coding sequences within two circular chromosomes. Genomic analysis has revealed multiple metabolic features for autotrophic and heterotrophic lifestyles. These metabolic diversities enable independent survival, as well as a symbiotic lifestyle. Consequently, S110 appears to have evolved into a superbly adaptable microorganism that is able to survive in ever-changing environmental conditions. Based on our findings, we suggest V. paradoxus S110 as a potential candidate for agrobiotechnological applications, such as biofertilizer and biopesticide. Because it has many associations with other biota, it is also suited to serve as an additional model system for studies of microbeplant and microbe-microbe interactions.Variovorax paradoxus is a metabolically diverse, aerobic bacterium that engages in mutually beneficial interactions with a variety of bacteria and plants. V. paradoxus belongs to the subclass of Proteobacteria and can metabolically utilize natural compounds produced by other biota, such as acyl homoserine lactones (AHLs) (25) and alkyl/aryl-sulfonates (38). This metabolic capacity suggests that Variovorax plays an essential role in the natural cycling of biogenic chemicals. Variovorax species are also able to degrade a variety of contaminants, including pesticides and crude oil-associated S-metabolites (5,19,37,41,42,46,50,51,52), often in synergistic and mutually beneficial interactions with other bacteria. In addition, a close relative of Variovorax was found to be the central, nonphotosynthetic partner within the phototrophic consortium "Chlorochromatium aggregatum" (22). Moreover, V. paradoxus is resistant to various heavy metals, including cadmium and mercury (2).V. paradoxus belongs to a group referred to as plant growthpromoting rhizobacteria (PGPR), which exert beneficial effects on plant growth. As a common plant symbiont found in the rhizosphere (2, 3), the metabolic diversity of V. paradoxus appears to be related to its role as a PGPR. By degrading toxic contaminants, this bacterium can prevent harm otherwise experienced by the plant and thus can promote plant growth. Strains of Variovorax can enhance the host plant's stress tolerance and disease resistance (2, 3) and aid in nutrient availability and uptake (38). The effectiveness of Variovorax as a PGPR is likely to be more potent because it also appears to be a good endophytic symbiont (34,36,39,43,44,45,47) and thus interacts more closely with the host plant. Conversely, endospheric habitats are known to offer microbes the advantage of a more uniform and protective niche compared to the competitive, high-stress environment of the soil (36).The diverse metabol...

We isolated Dehalococcoides mccartyi strain JNA from the JN mixed culture which was enriched and maintained using the highly chlorinated commercial PCB mixture Aroclor 1260 for organohalide respiration. For isolation we grew the culture in minimal liquid medium with 2,2',3,3',6,6'-hexachlorobiphenyl (236-236-CB)(20 μM) as respiratory electron acceptor. We repeatedly carried out serial dilutions to extinction and recovered dechlorination activity from transfers of 10(-7) and 10(-8) dilutions. Fluorescence microscopy, DGGE and RFLP analysis of PCR amplified16S rRNA genes, and multilocus sequence typing of three housekeeping genes confirmed culture purity. No growth occurred on complex media. JNA dechlorinated most hexa- and heptachlorobiphenyls in Aroclor 1260 (50 μg/mL) leading to losses of 51% and 20%, respectively. Dechlorination was predominantly from flanked meta positions of 34-, 234-, 235-, 236-, 245-, 2345-, 2346-, and 2356-chlorophenyl rings, as indicated by the underscores. The major products were 24-24-CB, 24-26-CB, 24-25-CB, and 25-26-CB. We identified 85 distinct PCB dechlorination reactions and 56 different PCB dechlorination pathways catalyzed by JNA. Dechlorination pathways were confirmed by mass balance of substrates and products. This dechlorination pattern matches PCB Dechlorination Process N. JNA is the first pure culture demonstrated to carry out this extensive and environmentally relevant PCB dechlorination pattern.

Pentachlorophenol and other chlorinated phenols are highly toxic ubiquitous environmental pollutants. Using gas chromatographic analysis we determined that Dehalococcoides mccartyi strain JNA in pure culture dechlorinated pentachlorophenol to 3,5-dichlorophenol (DCP) via removal of the ortho and para chlorines in all of the three possible pathways. In addition, JNA dechlorinated 2,3,4,6-tetrachlorophenol via 2,4,6-trichlorophenol (TCP) and 2,4,5-TCP to 2,4-DCP and 3,4-DCP, respectively, and dechlorinated 2,3,6-TCP to 3-chlorophenol (CP) via 2,5-DCP. JNA converted 2,3,4-TCP to 3,4-DCP and 2,4-DCP by ortho and meta dechlorination, respectively. 2,3-DCP was dechlorinated to 3-CP, and, because cultures using it could be transferred with a low inoculum (0.5 to 1.5% vol/vol), it may act as an electron acceptor to support growth. Using PCR amplification with targeted and degenerate primers followed by cloning and sequencing, we determined that JNA harbors at least 19 reductive dehalogenase homologous (rdh) genes including orthologs of pcbA4 and pcbA5, pceA, and mbrA, but not tceA or vcrA. Many of these genes are shared with D. mccartyi strains CBDB1, DCMB5, GT, and CG5. Strain JNA has previously been shown to extensively dechlorinate the commercial polychlorinated biphenyl (PCB) mixture Aroclor 1260. Collectively the data suggest that strain JNA may be well adapted to survive in sites contaminated with chlorinated aromatics and may be useful for in situ bioremediation.

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