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The transcriptional regulation of three distinct alcohol oxidation systems, alcohol dehydrogenase (ADH)-I, ADH-IIB and ADH-IIG, in Pseudomonas putida HK5 was investigated under various induction conditions. The promoter activities of the genes involved in alcohol oxidation were determined using a transcriptional lacZ fusion promoter-probe vector. Ethanol was the best inducer for the divergent promoters of qedA and qedC, encoding ADH-I and a cytochrome c, respectively. Primary and secondary C3 and C4 alcohols and butyraldehyde specifically induced the divergent promoters of qbdBA and aldA, encoding ADH-IIB and an NAD-dependent aldehyde dehydrogenase, respectively. The qgdA promoter of ADH-IIG responded well to (S)-(+)-1,2-propanediol induction. In addition, the roles of genes encoding the response regulators exaE and agmR, located downstream of qedA, were inferred from the properties of exaE- or agmR-disrupted mutants and gene complementation tests. The gene products of both exaE and agmR were strictly necessary for qedA transcription. The mutation and complementation studies also suggested a role for AgmR, but not ExaE, in the transcriptional regulation of qbdBA (ADH-IIB) and qgdA (AGH-IIG). A hypothetical scheme describing a regulatory network, which directs expression of the three distinct alcohol oxidation systems in P. putida HK5, was derived.

Upstream of the gene for flavin adenine dinucleotide (FAD)-dependent D-sorbitol dehydrogenase (SLDH), sldSLC, a putative transcriptional regulator was found in Gluconobacter frateurii THD32 (NBRC 101656). In this study, the whole sboR gene and the adjacent gene, sboA, were cloned and analyzed, sboR mutation did not affect FAD-SLDH activity in the membrane fractions. The SboA enzyme expressed and purified from an Escherichia coli transformant showed NADPH-dependent L-sorbose reductase (NADPH-SR) activity, and the enzyme was different from the NADPH-SR previously reported for Gluconobacter suboxydans IFO 3291 in molecular size and amino acid sequence. A mutant defective in sboA showed significantly reduced growth on L-sorbose, indicating that the SboA enzyme is required for efficient growth on L-sorbose. The sboR mutant grew on L-sorbose even better than the wild-type strain did, and higher NADPH-SR activity was detected in cytoplasm fractions. Reverse transcription-PCR experiments indicated that sboRA comprises an operon. These data suggest that sboR is involved in the repression of sboA, but not in the induction of sldSLC, on o-sorbitol and that another activator is required for the induction of these genes by D-sorbitol or L-sorbose.

Acetobacter tropicalis SKU 1100 produces a pellicle polysaccharide, consisting of galactose, glucose and rhamnose, which attaches to the cell surface. This strain forms two types of colony on agar plates: a rough-surfaced colony (R strain) and a mucoid smooth-surfaced colony (S strain). The R strain forms a pellicle, allowing it to float on the medium surface in static culture, while the S strain does not. The pellicle is an assemblage of cells which are tightly associated with capsular polysaccharides (CPS) on the cell surface. In this study, a gene required for pellicle formation by the R strain was investigated by transposon mutagenesis using Tn 10. The resulting mutant, designated [Pel.sup.-] , has a smooth-surfaced colony and a defect in pellicle formation, as for the S strain. The mutant produced polysaccharide which was instead secreted into the culture medium as extracellular polysaccharide (EPS). An ORF was identified at the Tn 10 insertion site, designated polE, upstream of which polABCD genes were also found. The deduced amino acid sequences of polABCD showed a high level of homology to those of rfbBACD which are involved in dTDP-rhamnose synthesis, whereas polE had a relatively low level of homology to glycosyltransferase. In this study a polB (rfbA) disruptant was also prepared, which lacked both CPS and EPS production. A plasmid harbouring the polE or polB genes could restore pellicle formation in the [Pel.sup.-] mutant and S strains, and in the [DELTA]polB mutant, respectively. Thus both polE and polB are evidently involved in pellicle formation, most likely by anchoring polysaccharide to the cell surface and through the production of dTDP-rhamnose, respectively. The [Pel.sup.-] and [DELTA]polB mutants were unable to grow in static culture and became more sensitive to acetic acid due to the loss of pellicle formation. Additionally, this study identified the mutation sites of several S strains which were spontaneously isolated from the original culture and found them to be concentrated in a sequence of 7 C residues in the coding sequence of polE, with the deletion or addition of a single C nucleotide.

Acetic acid bacteria are obligate aerobes able to oxidize ethanol, sugar alcohols, and sugars into their corresponding acids. Among them, Acetobacter and Gluconacetobacter species have very high ethanol oxidation capacity, leading to accumulation of vast amounts of acetic acid outside the cell. Since these bacteria are able to grow in media with high concentrations of acetic acid, they must possess a specific mechanism such as an efflux pump by which they can resist the toxic effects of acetic acid. In this study, the efflux pump of Acetobacter aceti IFO 3283 was examined using intact cells and membrane vesicles. The accumulation of acetic acid/acetate in intact cells was increased by the addition of a proton uncoupler and/or cyanide, suggesting the presence of an energy-dependent efflux system. To confirm this, right-side-out and inside-out membrane vesicles were prepared from A. aceti IFO 3283, and the accumulation of acetic acid/acetate in the vesicles was examined. Upon the addition of a respiratory substrate, the accumulation of acetic acid/acetate in the right-side-out vesicles was largely decreased, while its accumulation was very much increased in the inside-out vesicles. These respiration-dependent phenomena observed in both types of membrane vesicles were all sensitive to a proton uncoupler. Acetic acid/acetate uptake in the inside-out membrane vesicles was dependent not on ATP but on the proton motive force. Furthermore, uptake was shown to be rather specific for acetic acid and to be pH dependent, because higher uptake was observed at lower pH. Thus, A. aceti IFO 3283 possesses a proton motive force-dependent efflux pump for acetic acid.

The biosynthesis of pyrroloquinoline quinone (PQQ), a vitamin and redox cofactor of quinoprotein dehydrogenases, is facilitated by an unknown pathway that requires the expression of six genes, pqqA to -F. PqqC, the protein encoded by pqqC, catalyzes the final step in the pathway in a reaction that involves ring cyclization and eight-electron oxidation of 3a-(2-amino-2-carboxyethyl)-4,5-dioxo-4, 5,6,7,8,9-hexahydroquinoline-7,9-dicarboxylic-acid to PQQ. Herein, we describe the crystal structures of PqqC and its complex with PQQ and determine the stoichiometry of [H.sub.2][O.sub.2] formation and [O.sub.2] uptake during the reaction. The PqqC structure(s) reveals a compact seven-helix bundle that provides the scaffold for a positively charged active site cavity. Product binding induces a large conformational change, which results in the active site recruitment of amino acid side chains proposed to play key roles in the catalytic mechanism. PqqC is unusual in that it transfers redox equivalents to molecular oxygen without the assistance of a redox active metal or cofactor. The structure of the enzyme-product complex shows additional electron density next to R179 and C5 of PQQ, which can be modeled as [O.sub.2] or [H.sub.2]v, indicating a site for oxygen binding. We propose a reaction sequence that involves base-catalyzed cyclization and a series of quinone-quinol tautomerizations that are followed by cycles of [O.sub.2]/[H.sub.2][O.sub.2]-mediated oxidations.

A research was conducted to determine the need for pqqA in the biosynthesis of pyrroloquinoline quinone (PQQ) in Methylobacterium extorquens AM1. pqqA is believed to play a role in the production of PQQ as well as the encoding of PQQ's peptide precusor. Results show that the pqqA can be replaced with a different peptide in pqqA mutants. In addition, the normal methanol induction of PQQ synthesis requires methanol oxidation transcriptional regulator gene.

The sequence of pqqC'BA in the genomic region of Methylobacterium extorquens AM1 and the purification of an intermediate of PQQ synthesis were described. Two open reading frames found in the sequenced region of Methylobacterium extorquens were pqqE and pqqC/D. The pqqC mutant produced an intermediate of PQQ biosynthesis which was converted to PQQ using a crude extract of E. coli cells. The intermediate was found in both the culture medium and crude extract.

The structure and behavior of inactive alcohol dehydrogenase (ADH) and the process of physiologically activating inactive ADH in the growing and resting cells of Gluconobacter suboxydans was studied. Active ADH has 10 times more enzyme reactions than inactive ADH. Interconversion between the two forms of ADH was obtained either by changing the pH of the culture medium or by incubating the resting cells in different levels of pH while exposing them to an energy source.

Pseudomonas putida can produce three different types of alcohol dehydrogenase (ADH) depending on the nature of the alcohol used as its major carbon source. The bacterium produces ADH I when grown on ethanol, ADH IIB when grown on 1-butanol and ADH IIG when grown on 1,2-propanediol. Antibodies against the enzymes could distinguish one from another.

The isolation of thermotolerant Gluconobacter strains that provide a new promising option for industrial production of 5-keto-D-gluconic acid (5KGA) at 37 degree Celsius is reported. The results suggested that the activity of pyrroloquinoline quinone (PQQ)-dependent glycerol dehydrogenase which contributes to 5KGA production increased in response to addition of PQQ and Ca[Cl.sub.2] in vitro when cells were grown at 37 degree Celsius.

Research demonstrates that the quinoproteins, D-arabitol dehydrogenase and D-sorbitol dehydrogenase are identical and catalyze D-gluconate oxidation to 5-keto-D-gluconate in Gluconobacter species. In addition, glycerol dehydrogenase has a role of a major polyol dehydrogenase mediating oxidation of sugar alcohols.