No abstract

The abundance, identities, and degradation abilities of indigenous polychlorinated biphenyl (PCB)-degrading bacteria associated with five species of mature trees growing naturally in a contaminated site were investigated to identify plants that enhance the microbial PCB degradation potential in soil. Culturable PCB degraders were associated with every plant species examined in both the rhizosphere and root zone, which was defined as the bulk soil in which the plant was rooted. Significantly higher numbers of PCB degraders (2.7-to 56.7-fold-higher means) were detected in the root zones of Austrian pine (Pinus nigra) and goat willow (Salix caprea) than in the root zones of other plants or non-root-containing soil in certain seasons and at certain soil depths. The majority of culturable PCB degraders throughout the site and the majority of culturable PCB degraders associated with plants were identified as members of the genus Rhodococcus by 16S rRNA gene sequence analysis. Other taxa of PCB-degrading bacteria included members of the genera Luteibacter and Williamsia, which have not previously been shown to include PCB degraders. PCB degradation assays revealed that some isolates from the site have broad congener specificities; these isolates included one Rhodococcus strain that exhibited degradation abilities similar to those of Burkholderia xenovorans LB400. Isolates with broad congener specificity were widespread at the site, including in the biostimulated root zone of willow. The apparent association of certain plant species with increased abundance of indigenous PCB degraders, including organisms with outstanding degradation abilities, throughout the root zone supports the notion that biostimulation through rhizoremediation is a promising strategy for enhancing PCB degradation in situ.Polychlorinated biphenyls (PCBs) are toxic, persistent pollutants of worldwide concern whose cleanup using conventional methods like incineration or relocation to specialized landfills is often prohibitively expensive. An alternative strategy for in situ PCB removal is biodegradation by microorganisms capable of metabolizing PCBs. Although bioaugmentation of soil with degradative bacteria has been largely unsuccessful in achieving significant aerobic PCB degradation in the field (29), efforts to biostimulate indigenous PCB-degrading bacteria have been promising. Analogue enrichment with biphenyl has been shown to increase the numbers of aerobic PCB-degrading bacteria in soil microcosms (12, 51) and to enhance PCB degradation rates in soils (6, 12) and in situ sediments (18). Unfortunately, as a field remedial strategy, addition of biphenyl is problematic due to the low water solubility of biphenyl, the necessity of repeated application, and concerns about biphenyl toxicity. By capitalizing on the innate ability of plants to alter soil microbial community structure, rhizoremediation offers an attractive and affordable alternative means for long-term biostimulation of aerobic PCB degradation in situ.Rhizostimulation of aromatic poll...

The activity of the biosurfactant produced by Bacillus licheniformis strain JF-2 was quantified using a unit defined as the amount of the acid-precipitated biosurfactant that lowered the surface tension by 10 mN/m. One unit was equivalent to 37 micrograms/ml of the acid-precipitated biosurfactant. Acid precipitation was very effective in the removal of the biosurfactant from the spent medium. Among the solvents tested methanol was the most efficient in extracting the surfactant activity from acid-precipitated material. Thin-layer chromatography of the acid-precipitated biosurfactant revealed four components, two of which contained a lipid moiety and one of which contained an amino group. The methanol-soluble fraction also contained these four components. Studies suggested that all four components were needed for full activity. The lowest interfacial tensions against octane were observed when NaC1 concentrations were 50 g/l or greater. Calcium concentrations greater than 25 g/l significantly increased the interfacial tension.

Phagocytes of the smooth dogfish (Mustelus canis) contain no endogenous peroxidase within their lysosomes and constitute models for cells genetically deficient in lysosomal enzymes such as myeloperoxidase. We have obtained uptake of over 50% of exogenous horseradish peroxidase, provided the enzyme is exhibited to cells after incorporation into liposomes coated with heat-aggregated (620, 10 min), isologous IgM. Trapping of horseradish peroxidase (EC 1.11.1.7) by liposomes was established by chromatographic resolution (Sephadex G-200; Sepharose 2B and 4B) of free enzyme from that associated with liposomes; liposome-associated horseradish peroxidase, together with trapped markers of the aqueous compartment (glucose, CrO4=), were excluded, and free enzyme and markers were retained. Enzyme and marker trapping was not electrostatic, varied with the molar ratio of charged membrane components, and was reversed by detergent lysis (Triton X-100) of liposomes. Uptake at 300 of aggregated IgM-coated liposomes containing trapped horseradish peroxidase exceeded that of free enzyme by 100-fold, and was more efficient than uptake of horseradish peroxidase presented in uncoated liposomes or in liposomes coated with native IgM. After phagocytosis, peroxidaserich liposomes were localized exclusively in lysosomes of the phagocytes by ultrastructural histochemistry; the enzyme displayed over 50% latency to osmotic lysis. This method may prove to be of general use in the provision of exogenous enzymes to phagocytic cells genetically deficient in lysosomal hydrolases.

Component A, the oxygen-sensitive protein fraction of the methyl coenzyme M methylreductase system of Methanobacterium themoautotrophicum, has been stabilized and resolved into three protein fractions and one cofactor that are required to reconstitute component A activity. Component Al is oxygen-stable and contains hydrogen-dependent deazaflavin (coenzyme F4a)-reducing activity. Component A2 is acidic; components A2 and A3 are oxygen sensitive. The specific functions of each component in methyl group reduction are unknown. Resolution of component A revealed a new cofactor requirement of the methylreductase system for FAD. Hydrogen-dependent reduction of methyl coenzyme M to methane and coenzyme M, the terminal step of CO2 reduction by methanogenic bacteria, requires protein components Al, A2, A3, and C in addition to component B, FAD, ATP, and Mg2+.Study of methanogenesis has been inhibited by the extreme and irreversible toxic response of methanogenic cells and extracts to oxygen. In recent years, cultivation of these anaerobes has been facilitated by development of specialized culture techniques that involve use of a pressurized atmosphere of H2 and CO2 (1). Fractionation of cell extracts from methanogens remains a challenge not only for separation of active enzyme fractions but also for maintenance of these fractions in an active state during storage.A significant technical advance in the fractionation of extracts from methanogens was used by Gunsalus and Wolfe (2) to resolve the terminal reaction in methanogenesis, the 2-(methylthio)ethanesulfonate (CH3-S-CoM) methylreductase system, into three fractions-components A, B, and C. Component C has been the most thoroughly studied component. This oxygenstable protein was purified to homogeneity (3). The yellow chromophore of the protein was shown to be factor F4w, the nickel-containing compound found in extracts of methanogens (4) and now known to be a nickel tetrapyrrole (5). Recently, coenzyme M has been found to be associated with isolated factor F4w (6). This discovery as well as previous observations (7) indicate that component C is likely to be the site of methyl group reduction. The oxygen-labile component B has been purified in small amounts to homogeneity (8), but its structure and function are unknown. Component A was known to be oxygen labile and to contain hydrogenase (2).Here we report the resolution of component A into three protein fractions and one cofactor (Al, A2, and A3 and FAD), each of which is required in the reconstituted system for hydrogen-dependent reduction of the methyl group of CH3-S-CoM to methane. MATERIALS AND METHODSGrowth of Cells and Preparation of Extracts. Methanobacterium thernoautotrophicum strain AH (ATCC 29096) was grown and extracts were prepared as described (2, 9). To prepare boiled cell-free extract (BCFE), a slurry [1 g of cells per 1.5 ml of 0.1 M N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (Tes) buffer at pH 7.0] was exposed to a stream of N2 in a boiling water bath for 45 min. The cooled extract...