Localization of cytochromes in the outer membrane of Desulfovibrio vulgaris (Hildenborough) and their role in anaerobic biocorrosion.

A protocol was developed whereby the outer and cytoplasmic membranes of the sulfate-reducing bacterium Desulfovibrio vulgaris (Hildenborough) were isolated and partially characterized. The isolated outer membrane fractions from cultures grown under high (100 ppm) and low (5 ppm) Fe2+ conditions were compared by SDS-PAGE electrophoresis, and showed that several protein bands were derepressed under the low iron conditions, most notably at 50 kDa, and 77.5 kDa. Outer membrane isolated from low iron cultured cells was found to contain two proteins, 77.5 kDa and 62.5 kDa in size, that reacted with a heme-specific stain and were referred to as high molecular weight cytochromes. Studies conducted on the low iron isolated outer membrane by a phosphate/mild steel hydrogen evolution system showed that addition of the membrane fraction caused an immediate acceleration in H2 production. A new model for the anaerobic biocorrosion of mild steel is proposed.

Hydrogenase I of Clostridium pasteurianum functions as a novel selenite reductase.

Clostridium pasteurianum's hydrogenase I, an important constitutive metabolic enzyme, has been shown to function as a 'novel selenite reductase'. Selenite reductase activity was found to co-purify with hydrogenase I activity; the fold purification and specific activities for these two activities paralleled each other throughout the purification steps. The highly purified hydrogenase I apparent K(m) for the selenite substrate was 0.2 mM. The stoichiometry for the enzymatic reduction of SeO3(2-) to Se(0) via H2 oxidation, was determined to be 2.3:1 (H2:Se(0)), very close to the theoretical ratio of 2:1 for this reduction reaction. Known electron carriers required for hydrogenase I activity were also found to couple its selenite reductase activity, the most efficient one being ferredoxin. The purified hydrogenase I not only reduced selenite but also tellurite, and its selenite activity was completely inhibited by O2 and CuSO4, potent inhibitors of hydrogenase I activity.

Regulation of the Periplasmic [Fe] Hydrogenase by Ferrous Iron in Desulfovibrio vulgaris (Hildenborough).

The periplasmic [Fe] hydrogenase from the sulfate-reducing bacterium Desulfovibrio vulgaris (Hildenborough) DSM 8303 was found to be regulated by ferrous iron availability. During growth with 5 ppm of iron, the enzyme derepressed and the specific activity increased approximately fourfold, whereas the presence of 100 ppm of ferrous iron repressed the enzyme. The repression-derepression phenomenon with ferrous iron was found to be operative when the cells were cultured under either hydrogen or nitrogen gas. This is the first reported case showing that the hydrogenase enzyme is regulated by iron, and the implications of this finding relative to the corrosion industry are discussed.

THE MYTH OF THE UNFEELING STRATEGIC THERAPIST.

This paper explores what the authors consider to be a widespread myth: that strategic therapists ignore, avoid, or neglect client feelings in treatment. This myth is promulgated by trainers' admonitions and strategic theorists' injunctions against dealing with client affect. It is also cultivated by omission of this topic in the strategic literature. The myth is destructive in that it misrepresents what strategic practitioners actually do in a therapy session. Seven elements of the myth are delineated and the corresponding fallacies are illustrated.

Effect of hydrogenase and mixed sulfate-reducing bacterial populations on the corrosion of steel.

The importance of hydrogenase activity to corrosion of steel was assessed by using mixed populations of sulfate-reducing bacteria isolated from corroded and noncorroded oil pipelines. Biofilms which developed on the steel studs contained detectable numbers of sulfate-reducing bacteria (10 increasing to 10/0.5 cm). However, the biofilm with active hydrogenase activity (i.e., corrosion pipeline organisms), as measured by a semiquantitative commercial kit, was associated with a significantly higher corrosion rate (7.79 mm/year) relative to noncorrosive biofilm (0.48 mm/year) with 10 sulfate-reducing bacteria per 0.5 cm but no measurable hydrogenase activity. The importance of hydrogenase and the microbial sulfate-reducing bacterial population making up the biofilm are discussed relative to biocorrosion.

Physiological effects of metronidazole on Clostridium pasteurianum.

The physiological effects of metronidazole on the growth, viability, fermentation end-product production and cellular morphology of Clostridium pasteurianum cells growing logarithmically were studied. Metronidazole (a 5-nitroimidazole) was found to be the most potent of the nitroimidazole compounds tested against C. pasteurianum. It inhibited the growth rate of C. pasteurianum cultures by varying degrees over a range of drug concentrations (2.5-10 mg/L). Metronidazole had an immediate bactericidal effect at a concentration of 10 mg/L, killing 99.9% of cells within 5 min of drug addition. The same concentration caused an immediate cessation of fermentation end-product (acetate and butyrate) production in these cultures. These observations may be relevant to a proposed cell lysing mechanism which may form an additional mode of action of this important antibiotic.

Evidence for proton motive force dependent transport of selenite by Clostridium pasteurianum.

The proton motive force mediated the transport of selenite (SeO3(2-)) in Clostridium pasteurianum cells by proton symport. The proton conductor, carbonyl cyanide m-chlorophenylhydrazone, inhibited SeO3(2-) uptake while N,N'-dicyclohexylcarbodiimide prevented SeO3(2-) uptake by presumably inhibiting the unidirectional ATPase. Acid pulse studies and antibiotic experiments with valinomycin suggest that the transmembrane delta pH component of the proton motive force mediated the transport of SeO3(2-) into the cells. The SeO3(2-) porter system in C. pasteurianum was found to be dependent upon energy source, temperature, and medium pH.

Therapeutic compliments: setting the stage for successful therapy.

Compliments are often viewed primarily as a linear event in which one person expresses approval or admiration of another. Far less attention has been given to the circular nature of compliments and the manner in which they enhance the positions of both the giver and the receiver of the compliment. Therapeutic compliments have proven to be highly effective means of motivating clients, while at the same time increasing therapeutic leverage. This article proposes that compliments should be purposefully given, and that the type of compliment should vary with the stage of therapy and the intended response of the client to the compliment.

The role of Thiobacillus albertis glycocalyx in the adhesion of cells to elemental sulfur.

Thiobacillus albertis, a newly characterized acidophilic Thiobacillus sp., was found not to be dependent on physiological conditions such as pH, cellular energy, or peripheral cell envelope sulfhydryl groups for attachment to elemental sulfur (S0). Heat-killed cells or those pretreated with sulfhydryl reagents (iodoacetate or iodoacetamide) were able to adhere to S0 in comparable numbers as assayed by epifluorescence microscopy. In addition, iodoacetate and iodoacetamide were found to be bactericidal, the former more potent than the latter. Sodium lauryl sulfate was found to cause nearly complete detachment of T. albertis cells from glass slides implicating its glycocalyx for this cell-glass attachment. In addition scanning electron microscopy visually revealed T. albertis cellular adhesion to S0 was due to the organism's threadlike glycocalyx material interacting with the sulfur surface. It was concluded that T. albertis glycocalyx plays an important role in the attachment to solid surfaces (glass or S0). In addition T. albertis was shown to colonize S0 surfaces by microcolonies.