Lasers-an effective artificial source of radiation for the cultivation of anoxygenic photosynthetic bacteria.

The laser diode (LD) is a unique light source that can efficiently produce all radiant energy within the narrow wavelength range used most effectively by a photosynthetic microorganism. We have investigated the use of a single type of LD for the cultivation of the well-studied anoxygenic photosynthetic bacterium, Rhodobacter capsulatus (Rb. capsulatus). An array of vertical-cavity surface-emitting lasers (VCSELs) was driven with a current of 25 mA, and delivered radiation at 860 nm with 0.4 nm linewidth. The emitted light was found to be a suitable source of radiant energy for the cultivation of Rb. capsulatus. The dependence of growth rate on incident irradiance was quantified. Despite the unusual nearly monochromatic light source used in these experiments, no significant changes in the pigment composition and in the distribution of bacteriochlorophyll between LHII and LHI-RC were detected in bacterial cells transferred from incandescent light to laser light. We were also able to show that to achieve a given growth rate in a light-limited culture, the VCSEL required only 30% of the electricity needed by an incandescent bulb, which is of great significance for the potential use of laser-devices in biotechnological applications and photobioreactor construction.

Anatomy of the proximal cutaneous perforator vessels of the gracilis muscle.

An anatomic study was performed to analyse the proximal perforator vessels of the gracilis musculocutaneous flap. Twenty-three cadaver legs preserved by the method of Thiel were carefully dissected 24h after the proximal vascular pedicle was injected with a red silicone mass. Nine additional cadaver legs were injected with ink, to visualise the skin area supplied by the proximal perforators, respectively, clarified by a modified Spalteholz technique to demonstrate the anatomic course of the perforators. A considerable variation in numbers and localisation of proximal cutaneous perforators was found. One to four perforators were seen within an area of 6 x 6 cm(2) at the entrance of the main pedicle into the proximal gracilis muscle. Their external diameter ranged from 0.5 to 1.0 mm. The ink-injections showed an oval shaped angiosome with a mean surface of 88 cm(2) at the level of the proximal gracilis pedicle. We conclude from this anatomic study, that a cutaneous flap based on the medial circumflex femoral gracilis perforators can be harvested by experienced hands bearing in mind the unpredictable perforator-anatomy.

Enzymology and molecular biology of prokaryotic sulfite oxidation.

Despite its toxicity, sulfite plays a key role in oxidative sulfur metabolism and there are even some microorganisms which can use it as sole electron source. Sulfite is the main intermediate in the oxidation of sulfur compounds to sulfate, the major product of most dissimilatory sulfur-oxidizing prokaryotes. Two pathways of sulfite oxidation are known: (1) direct oxidation to sulfate catalyzed by a sulfite:acceptor oxidoreductase, which is thought to be a molybdenum-containing enzyme; (2) indirect oxidation under the involvement of the enzymes adenylylsulfate (APS) reductase and ATP sulfurylase and/or adenylylsulfate:phosphate adenylyltransferase with APS as an intermediate. The latter pathway allows substrate phosphorylation and occurs in the bacterial cytoplasm. Direct oxidation appears to have a wider distribution; however, a redundancy of pathways has been described for diverse photo- or chemotrophic, sulfite-oxidizing prokaryotes. In many pro- and also eukaryotes sulfite is formed as a degradative product from molecules containing sulfur as a heteroatom. In these organisms detoxification of sulfite is generally achieved by direct oxidation to sulfate.

Evidence for two pathways of thiosulfate oxidation in Starkeya novella (formerly Thiobacillus novellus).

The pathway of thiosulfate oxidation in the facultatively chemolithotrophic, sulfur-oxidizing bacterium Starkeya novella (formerly Thiobacillus novellus) has not been established beyond doubt. Recently, isolation of the sorAB genes, which encode a soluble sulfite:cytochrome c oxidoreductase, has been reported, indicating that a thiosulfate-oxidizing pathway not involving a multienzyme complex may exist in this organism. Here we report the cloning and sequencing of the soxBCD genes from S. novella, which are closely related to the corresponding genes encoding the thiosulfate-oxidizing multienzyme complex from Paracoccus pantotrophus. These findings suggest two distinct pathways for thiosulfate oxidation in S. novella. The expression of sorAB and soxC in cells grown on thiosulfate- and/or glucose-containing media was studied by Western blot analysis. The results showed that the SorAB protein is synthesized in the presence of thiosulfate irrespective of the presence of glucose. In contrast, the SoxC protein is subject to repression by glucose; the repression, however, appears to be dependent on the relative amounts of glucose and thiosulfate present. The regulatory effects observed for the expression of sorAB are likely to be mediated by an extracytoplasmic function sigma factor encoded by the sigE gene identified upstream of sorAB.

Sulfite:Cytochrome c oxidoreductase from Thiobacillus novellus. Purification, characterization, and molecular biology of a heterodimeric member of the sulfite oxidase family.

Direct oxidation of sulfite to sulfate occurs in various photo- and chemotrophic sulfur oxidizing microorganisms as the final step in the oxidation of reduced sulfur compounds and is catalyzed by sulfite:cytochrome c oxidoreductase (EC ). Here we show that the enzyme from Thiobacillus novellus is a periplasmically located alphabeta heterodimer, consisting of a 40.6-kDa subunit containing a molybdenum cofactor and an 8.8-kDa mono-heme cytochrome c(552) subunit (midpoint redox potential, E(m8.0) = +280 mV). The organic component of the molybdenum cofactor was identified as molybdopterin contained in a 1:1 ratio to the Mo content of the enzyme. Electron paramagnetic resonance spectroscopy revealed the presence of a sulfite-inducible Mo(V) signal characteristic of sulfite:acceptor oxidoreductases. However, pH-dependent changes in the electron paramagnetic resonance signal were not detected. Kinetic studies showed that the enzyme exhibits a ping-pong mechanism involving two reactive sites. K(m) values for sulfite and cytochrome c(550) were determined to be 27 and 4 micrometer, respectively; the enzyme was found to be reversibly inhibited by sulfate and various buffer ions. The sorAB genes, which encode the enzyme, appear to form an operon, which is preceded by a putative extracytoplasmic function-type promoter and contains a hairpin loop termination structure downstream of sorB. While SorA exhibits significant similarities to known sequences of eukaryotic and bacterial sulfite:acceptor oxidoreductases, SorB does not appear to be closely related to any known c-type cytochromes.

Dissimilatory ATP sulfurylase from the hyperthermophilic sulfate reducer Archaeoglobus fulgidus belongs to the group of homo-oligomeric ATP sulfurylases.

In the hyperthermophilic sulfate reducer Archaeoglobus fulgidus DSM 4304T, two open reading frames (sat and ORF2) are located upstream of the aprBA genes encoding adenosine-5'-phosphosulfate (APS) reductase. sat-ORF2-aprBA probably form a transcriptional unit, since sat is preceded by putative promoter sequences and termination signals are found downstream of aprA. While the 117-residue ORF2 product does not show significant similarity to known proteins, the 456-residue, 52.78-kDa, sat-encoded polypeptide exhibits similarity to the homo-oligomeric adenosine triphosphate (ATP) sulfurylases from sulfur-oxidizing bacteria and from sulfate-assimilating bacteria and eukaryotes. Functional overexpression of sat in Escherichia coli proved that the encoded protein acts as an ATP sulfurylase. The recombinant protein was purified to homogeneity and found to be a homo-dimer. Comparison of sulfate and thiosulfate grown A. fulgidus revealed that ATP sulfurylase and APS reductase are constitutive enzymes. Distance matrix analyses allowed insights into the evolution of prokaryotic ATP sulfurylases.