Some anaerobic bacteria can efficiently eliminate one or more halide atoms from halogenated compounds such as chlorophenols and chloroethenes through reductive dehalogenation. During this process, the bacteria utilize halogenated compounds as the terminal electron acceptors in their anaerobic respiration, called dehalorespiration, to yield energy for growth. Currently the genera of Desulfitobacterium and Dehalococcoides occupy the major part of the dehalorespiring isolates. The former can acquire energy not only by dehalorespiration but also by other respirations utilizing organic compounds and metals. In sharp contrast, the latter is specialized in dehalorespiration and plays a crucial role in the detoxification of chlorinated compounds in nature. From these bacteria, various reductive dehalogenases, which catalyze the dehalogenation reaction, were purified and their corresponding genes were identified. Most reductive dehalogenases exhibit similar features such as the presences of a Tat (twin arginine translocation) signal sequence, two Fe‐S clusters, and a corrinoid cofactor. Some of dehalogenase‐encoding genes are found to be flanked by insertion sequences. Thus, dehalogenase genes act as a catabolic transposon, and genetic rearrangements mediated by transposable elements occur well in dehalorespirers. Moreover, the genome sequences of some dehalorespiring bacteria provide many insights into the mechanism of dehalorespiration and the evolution of a dehalogenase gene. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 1–12; 2008: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20134

Halogenated organic compounds serve as terminal electron acceptors for anaerobic respiration in a diverse range of microorganisms. Here, we report on the widespread distribution and diversity of reductive dehalogenase homologous ( rdhA ) genes in marine subsurface sediments. A total of 32 putative rdhA phylotypes were detected in sediments from the southeast Pacific off Peru, the eastern equatorial Pacific, the Juan de Fuca Ridge flank off Oregon, and the northwest Pacific off Japan, collected at a maximum depth of 358 m below the seafloor. In addition, significant dehalogenation activity involving 2,4,6-tribromophenol and trichloroethene was observed in sediment slurry from the Nankai Trough Forearc Basin. These results suggest that dehalorespiration is an important energy-yielding pathway in the subseafloor microbial ecosystem.

The filamentous fungus Aspergillus kawachii has traditionally been used for brewing the Japanese distilled spirit shochu. A. kawachii characteristically hyperproduces citric acid and a variety of polysaccharide glycoside hydrolases. Here the genome sequence of A. kawachii IFO 4308 was determined and annotated. Analysis of the sequence may provide insight into the properties of this fungus that make it superior for use in shochu production, leading to the further development of A. kawachii for industrial applications.

Copper has been used as an antimicrobial agent for over a century and is now being added to commercial fungicides. Nanomaterials have attracted much attention due to the special properties they have over their bulk form. We studied nanostructured copper (Cu-NPs), investigating the potential for improved antifungal properties derived from its special properties and studied any effect that the oxidation of copper (CuO-NPs) may have. We conducted this research against Colletotrichum gloeoesporioides, a devastating pathogen to plants/crops worldwide. Research on the effects of copper on this fungus are limited. Our studies showed that nanoforms of copper had significant antifungal activities, with Cu-NPs offering the most sustainable efficacy and was more effective than its oxidative form (CuO-NPs). Scanning Electron Microscopy (SEM) images of the treated pathogen show that the hyphae had a swollen appearance, lost their filamentous structure, and the mycelia had a powder-like structure, indicating the probable destruction of the hyphal tubular cell wall. X-ray Difractogram (XRD) outputs showed substantial changes in the physical characteristics of the Cu-NPs after interaction with the fungus. This is the first report to demonstrate chemo-physical changes in the metal compounds, opening new insights for further studies on the mechanism of copper’s antifungal properties.

Marine subsurface sediments on the Pacific margin harbor diverse microbial communities even at depths of several hundreds meters below the seafloor (mbsf) or more. Previous PCR-based molecular analysis showed the presence of diverse reductive dehalogenase gene (rdhA) homologs in marine subsurface sediment, suggesting that anaerobic respiration of organohalides is one of the possible energy-yielding pathways in the organic-rich sedimentary habitat. However, primer-independent molecular characterization of rdhA has remained to be demonstrated. Here, we studied the diversity and frequency of rdhA homologs by metagenomic analysis of five different depth horizons (0.8, 5.1, 18.6, 48.5, and 107.0 mbsf) at Site C9001 off the Shimokita Peninsula of Japan. From all metagenomic pools, remarkably diverse rdhA-homologous sequences, some of which are affiliated with novel clusters, were observed with high frequency. As a comparison, we also examined frequency of dissimilatory sulfite reductase genes (dsrAB), key functional genes for microbial sulfate reduction. The dsrAB were also widely observed in the metagenomic pools whereas the frequency of dsrAB genes was generally smaller than that of rdhA-homologous genes. The phylogenetic composition of rdhA-homologous genes was similar among the five depth horizons. Our metagenomic data revealed that subseafloor rdhA homologs are more diverse than previously identified from PCR-based molecular studies. Spatial distribution of similar rdhA homologs across wide depositional ages indicates that the heterotrophic metabolic processes mediated by the genes can be ecologically important, functioning in the organic-rich subseafloor sedimentary biosphere.