Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacterium

Current water treatment methods struggle to remove perchlorate without introducing organic compounds that promote bacterial growth. Hydrogen is a promising energy source for microbial degradation due to its lack of organic residue. Prior research has shown that hydrogen can support microbial metabolism without leaving contaminants. However, the specific mechanisms of perchlorate reduction using hydrogen remain unclear. This gap motivated the search for bacteria capable of using hydrogen for perchlorate removal. No prior work had resolved the potential of hydrogen-oxidizing bacteria in this context. The need for non-organic, sustainable methods has driven exploration of novel microbial strains. This paper introduces a newly isolated bacterium that may offer a solution to this challenge.

The aim of this study was to identify and characterize a bacterium capable of using hydrogen to reduce perchlorate. The specific problem addressed is the lack of non-organic methods for perchlorate removal in water treatment. The motivation stems from the need to avoid organic byproducts in water systems. The researchers sought to isolate a hydrogen-oxidizing bacterium that could grow autotrophically. This approach could lead to safer water treatment technologies. The study focused on a strain isolated from a biofilm reactor treating contaminated groundwater. The goal was to confirm the bacterium's ability to use hydrogen and perchlorate. The findings may contribute to the development of new bioremediation strategies.

The researchers isolated a bacterium from a biofilm reactor treating perchlorate-contaminated groundwater. The strain was identified as a Gram-negative, rod-shaped facultative anaerobe. Growth conditions were tested using hydrogen and perchlorate as electron donor and acceptor. The ability to grow autotrophically was confirmed by measuring carbon content from CO2. Phylogenetic analysis was conducted using 16S rRNA sequencing. The strain's growth was also tested with acetate and various electron acceptors. The maximum doubling time was measured under optimal conditions. The study combined microbiological isolation with biochemical and genetic analysis.

Strain HZ was confirmed to grow autotrophically with CO2 as the sole carbon source. Biomass carbon analysis showed 100.9% derivation from CO2. The bacterium reduced 10 mM perchlorate to chloride completely. Maximum doubling time was 8.9 hours under optimal conditions. The strain also grew using acetate as an electron donor. Chlorate, nitrate, and oxygen were accepted as electron acceptors. Sulphate was not used as an electron acceptor by the strain. Phylogenetic analysis placed the strain in the genus Dechloromonas.

The study confirms the isolation of a novel hydrogen-oxidizing bacterium capable of perchlorate reduction. The bacterium uses CO2 as its sole carbon source, indicating chemolithoautotrophic growth. The findings suggest potential for using this strain in water treatment applications. The ability to couple hydrogen oxidation with perchlorate reduction is a key finding. The strain's growth with acetate and multiple electron acceptors adds to its versatility. The phylogenetic placement in the genus Dechloromonas supports its classification. The study may lead to new technologies for perchlorate removal. The authors propose that further investigation of such bacteria could improve bioremediation strategies.