Isolation of a thermotolerant bacterium producing medium-chain-length polyhydroxyalkanoate.

AIMS: The aim of this study was to isolate a thermotolerant micro-organism that produces polyhydroxyalkanoates (PHAs) composed of medium-chain-length (mcl) HA units from a biodiesel fuel (BDF) by-product as a carbon source. METHODS AND RESULTS: We successfully isolated a thermotolerant micro-organism, strain SG4502, capable to accumulate mcl-PHA from a BDF by-product as a carbon source at a cultivation temperature of 45°C. The strain could also produce mcl-PHA from acetate, octanoate and dodecanoate as sole carbon sources at cultivation temperatures up to 55°C. Taxonomic studies and 16S rRNA gene sequence analysis revealed that strain SG4502 was phylogenetically affiliated with species of the genus Pseudomonas. This study is the first report of PHA synthesis by a thermotolerant Pseudomonas. CONCLUSIONS: A novel thermotolerant bacterium capable to accumulate mcl-PHA from a BDF by-product was successfully isolated. SIGNIFICANCE AND IMPACT OF THE STUDY: A major issue regarding industrial production of microbial PHAs is their much higher production cost compared with conventional petrochemical-based plastic materials. Especially significant are the cost of a fermentative substrate and the running cost to maintain a temperature suitable for microbial growth. Thus, strain SG4502, isolated in this study, which assimilates BDF by-product and produces PHA at high temperature, would be very useful for practical application in industry.

A novel ATP regeneration system using polyphosphate-AMP phosphotransferase and polyphosphate kinase.

Polyphosphate-AMP phosphotransferase (PAP) and polyphosphate kinase (PPK) were used for designing a novel ATP regeneration system, named the PAP-PPK ATP regeneration system. PAP is an enzyme that catalyzes the phospho-conversion of AMP to ADP, and PPK catalyzes ATP formation from ADP. Both enzymes use inorganic polyphosphate [poly(P)] as a phosphate donor. In the PAP-PPK ATP regeneration system, ATP was continuously synthesized from AMP by the coupling reaction of PAP and PPK using poly(P). Poly(P) is a cheap material compared to acetyl phosphate, phosphoenol pyruvate and creatine phosphate, which are phosphate donors used for conventional ATP regeneration systems. To achieve efficient synthesis of ATP from AMP, an excessive amount of poly(P) should be added to the reaction solution because both PAP and PPK consume poly(P) as a phosphate donor. Using this ATP generation reaction, we constructed the PAP-PPK ATP regeneration system with acetyl-CoA synthase and succeeded in synthesizing acetyl-CoA from CoA, acetate and AMP. Since too much poly(P) may chelate MG2+ and inhibit enzyme activity, the Mg2+ concentration was optimized to 24 mM in the presence of 30 mM poly(P) in the reaction. In this reaction, ATP was regenerated 39.8 times from AMP, and 99.5% of CoA was converted to acetyl-CoA. In addition, since the PAP-PPK ATP regeneration system can regenerate GTP from GMP, it could also be used as a GTP regeneration system.

Cloning and sequencing of the beta-glucosidase gene from Acetobacter xylinum ATCC 23769.

The beta-glucosidase gene (bglxA) was cloned from the genomic DNA of Acetobacter xylinum ATCC 23769 and its nucleotide sequence (2200 bp) was determined. This bglxA gene was present downstream of the cellulose synthase operon and coded for a polypeptide of molecular mass 79 kDa. The overexpression of the beta-glucosidase in A. xylinum caused a tenfold increase in activity compared to the wild-type strain. In addition, the action pattern of the enzyme was identified as G3ase activity. The deduced amino acid sequence of the bglxA gene showed 72.3%, 49.6%, and 45.1% identity with the beta-glucosidases from A. xylinum subsp. sucrofermentans, Cellvibrio gilvus, and Mycobacterium tuberculosis, respectively. Based on amino acid sequence similarities, the beta-glucosidase (BglxA) was assigned to family 3 of the glycosyl hydrolases.

Cloning and sequencing of the levansucrase gene from Acetobacter xylinum NCI 1005.

The levansucrase gene (lsxA) was cloned from the genomic DNA of Acetobacter xylinum NCI 1005, and the nucleotide sequence of the lsxA gene (1,293 bp) was determined. The deduced amino acid sequence of the lsxA gene showed 57.4% and 46.2% identity with the levansucrases from Zymomonas mobilis and Erwinia amylovora, respectively, while only 35.2% identity with that from Acetobacter diazotrophicus. The gene product of lsxA (LsxA) that was overproduced in E. coli coded for a polypeptide of molecular mass 47 kDa. The LsxA released glucose and produced polysaccharide from sucrose, the structure of which was analyzed by nuclear magnetic resonance spectroscopy and determined to be a beta-(2,6)-linked polyfructan.

Involvement of inorganic polyphosphate in expression of SOS genes.

Inorganic polyphosphate (poly(P)) is a linear polymer that has been found in every organism so far examined. To elucidate the functions of poly(P) in the regulation of gene expression, the level of cellular poly(P) in Escherichia coli was reduced to a barely detectable concentration by overproduction of exopolyphosphatase (exopoly(P)ase) with a plasmid encoding yeast exopoly(P)ase (Shiba et al., Proc. Natl. Acad. Sci. USA 94 (1997) 11210-11215). It was found that exopoly(P)ase-overproducing cells were more sensitive to UV or mitomycin C (MMC) than were control cells. Poly(P) accumulation was observed after treatment with MMC, whereas the poly(P) level was below the detectable level in cells that overproduced exopoly(P)ase. When exopoly(P)ase-overproducing cells were transformed again by a multiple copy number plasmid that carries the polyphosphate kinase gene (ppk), the cells accumulated a great amount of poly(P) and restored the UV and MMC sensitivities to the level of control cells. In exopoly(P)ase-overproducing cells, the expression of recA and umuDC were not induced by MMC. In addition, a strain containing multiple copies of ppk accumulated not only a large amount of poly(P) but also recA mRNA. Since recA expression was induced in a recA-deletion strain harboring a plasmid with the ppk gene, poly(P) could be necessary for regulating the expression of SOS genes without depending on the RecA-LexA regulatory network.

The gene for an exopolyphosphatase of Pseudomonas aeruginosa.

In Pseudomonas aeriginosa, a gene, ppx, that encodes exopolyphosphatase [exopoly(P)ase; EC 3.6.1.11] of 506 amino acids (56,419 Da) was found downstream of the gene for polyphosphate kinase, ppk. Since ppx is located in the opposite direction of the ppk gene, they do not constitute an operon. The predicted amino acid sequence of PPX is 41% identical with Escherichia coli PPX. The gene product of ppx (paPPX) was overproduced in E. coli, and its activity was evaluated. Orthophosphate (Pi) is released from polyphosphate [poly(P)], the average chain lengths of which are 79 and 750, respectively. The amount of Pi released matched the amount of poly(P) lost. Thus ppx encodes an enzyme that has exopoly(P)ase activity.

Inorganic polyphosphate and the induction of rpoS expression.

Inorganic polyphosphate [poly(P)] levels in Escherichia coli were reduced to barely detectable concentrations by expression of the plasmid-borne gene for a potent yeast exopolyphosphatase [poly(P)ase]. As a consequence, resistance to H2O2 was greatly diminished, particularly in katG (catalase HPI) mutants, implying a major role for the other catalase, the stationary-phase KatE (HPII), which is rpoS dependent. Resistance was restored to wild-type levels by complementation with plasmids expressing ppk, the gene for PPK [the polyphosphate kinase that generates poly(P)]. Induction of expression of both katE and rpoS (the stationary-phase sigma factor) was prevented in cells in which the poly(P)ase was overproduced. Inasmuch as this inhibition by poly(P)ase did not affect the levels of the stringent-response guanosine nucleotides (pppGpp and ppGpp) and in view of the capacity of additional rpoS expression to suppress the poly(P)ase inhibition of katE expression, a role is proposed for poly(P) in inducing the expression of rpoS.

The production of a new water-soluble polysaccharide by Acetobacter xylinum NCI 1005 and its structural analysis by NMR spectroscopy.

A new water-soluble polysaccharide (WSP) was isolated from a culture of Acetobacter xylinum NCI 1005 grown on sucrose. The structure of the WSP was analysed by nuclear magnetic resonance spectroscopy and determined to be a beta-(2-->6)-linked polyfructan, which is structurally different from the polymer synthesized from glucose instead of sucrose by the same strain. The discovery of this new polysaccharide has revealed that the bacterium is able to synthesize two different kinds of water-soluble polysaccharides.

Chrymutasins: novel-aglycone antitumor antibiotics from a mutant of Streptomyces chartreusis. I. Taxonomy, mutation, fermentation, isolation and biological activities.

Three novel antibiotics, named chrymutasins A, B and C, were isolated from the fermentation products of a mutant strain obtained by NTG (N-methyl-N'-nitro-N-nitrosoguanidine) treatment. The mutant strain produced the chrymutasins, which differed in the aglycone moiety from chartreusin, and related compounds. The production of these compounds needed a characteristically long fermentation period. The antitumor activity of chrymutasin A is better in vivo than that of chartreusin, the cytotoxic activity against cell lines in vitro is equivalent, and the antimicrobial spectrum is narrower.

Chrymutasins: novel-aglycone antitumor antibiotics from a mutant of Streptomyces chartreusis. II. Characterization and structural elucidation.

Chrymutasins A, B and C are glycosidic antibiotics produced by a mutant of the chartreusin producer-organism Streptomyces chartreusis. We report here the structure elucidation of these compounds. The sugar moieties involved were determined by comparison with the related chartreusins. The structure of the aglycone, the same in all three compounds, was elucidated by NMR, incorporation studies of labeled compounds and synthesis of derivatives. The chrymutasin aglycone differs from that of chartreusin by a single carbon and an amino group.

Novel cytocidal compounds, oxopropalines from Streptomyces sp. G324 producing lavendamycin. I. Taxonomy of the producing organism, fermentation, isolation and biological activities.

In the course of our investigation aimed at the discovery of novel antitumor antibiotics from microorganisms, Streptomyces sp. G324 was found to produce the antitumor antibiotic, lavendamycin, and also, to yield the novel beta-carboline compounds, oxopropalines. We isolated five compounds as oxopropalines A, B, D, E and G. Oxopropalines B, D and G showed cytocidal activities against human or murine tumor cell lines in vitro.

Novel cytocidal compounds, oxopropalines from Streptomyces sp. G324 producing lavendamycin. II. Physico-chemical properties and structure elucidations.

Novel cytocidal compounds designated oxopropalines A, B, D, E and G were isolated from the fermentation of an actinomycete named Streptomyces sp. G324, a strain that also produced an antitumor antibiotic, lavendamycin. All these compounds possessed a beta-carboline chromophore. The structures of the oxopropalines were elucidated by several NMR spectral analyses and other spectroscopic experiments.

Novel antitumor antibiotics, saptomycins. I. Taxonomy of the producing organism, fermentation, HPLC analysis and biological activities.

Streptomyces sp. HP530 was found to produce novel antitumor antibiotics, saptomycins, closely related to the pluramycin-group and was further found to mutate frequently. The natural mutant produced several new saptomycins as determined by HPLC analyses. We isolated saptomycins A, B, C1, C2 and F from the parent strain and saptomycins D, E, G and H from the mutant. The saptomycins showed antimicrobial activities and potent antitumor activities against human or murine tumor cell lines in vitro and against Meth A fibrosarcoma in vivo. In particular, saptomycin D was most effective component in vivo of all saptomycins.

Novel antitumor antibiotics, saptomycins. II. Isolation, physico-chemical properties and structure elucidation.

A complex of novel antitumor antibiotics related to the pluramycin-group was isolated from the fermentation of actinomycete, named Streptomyces sp. HP530. The producing strain mutated frequently. The products isolated from the parent strain were designated saptomycins A, B, C1, C2 and F, while those of the mutant were named saptomycins D, E, G and H. These structures were elucidated by several NMR spectral analyses and other spectroscopic experiments.

Double-negative (L3T4-, Lyt2-) thymocytes of autoimmune lpr/lpr mice are resistant to down-regulation of DNA synthesis by a thymic stromal cell product.

The murine autosomal recessive gene, lpr, induces a progressive lymphadenopathy and lupus-like autoimmune syndrome characterized by the accumulation of immature, dull Thy 1.2+, TCR+, L3T4-/Lyt 2- (double-negative, DN) T cells in peripheral lymphoid organs. Previous studies demonstrated that the thymic microenvironment is required for the generation of the abnormal, peripheral DN T cells, while a more recent report linked the lpr gene defect with a failure of thymocytes to express a functional form of the Fas antigen, which mediates apoptosis. Thus, the lpr gene defect apparently prevents lpr thymocytes from responding to the ordered sequence of differentiation and proliferation signals involved in normal thymocyte maturation and selection. We compared the responses of thymocytes from C57BL/6 +/+ (normal) and congenic C57BL/6 lpr/lpr (lpr) mice to a thymic stromal cell product which down-regulates DNA synthesis in vitro. The results indicate that (a) thymic stromal cells from lpr mice produce a factor that can down-regulate DNA synthesis as efficiently as that from normal mice, even at an age when massive lymphadenopathy is present, (b) mitogen-stimulated thymocytes of normal, but not lpr, mice are sensitive to the inhibitory factor, (c) normal DN thymocytes are the cellular target of the inhibitory factor, which acts at some postmembrane receptor-ligand binding event during mitogen-stimulated proliferation, and (d) IL-4-dependent DN thymocyte proliferation seems to be the main target of the inhibitory factor.

Augmentation by transferrin of IL-2-inducible killer activity and perforin production of human CD8+ T cells.

The effects of human transferrin (Tf) on lymphokine (IL-2)-activated killer (LAK) induction from blood lymphocytes of healthy donors was examined. LAK cells were induced by 6-day incubation in medium with recombinant human IL-2 of lymphocytes, and their cytotoxic activity was assessed by measuring 51Cr release from NK-resistant Daudi cells. Tf alone did not induce any LAK activity, but in combination with IL-2, it augmented LAK induction dose- and time-dependently. This augmenting effect was completely abolished by pretreatment with anti-Tf antiserum. Tf augmented the proliferative response of lymphocytes to IL-2 and their expressions of receptors for IL-2 and Tf. CD8+ T cells were isolated from purified blood lymphocytes using antibody-bound magnetic beads. Addition of Tf to cultures of CD8+ cells resulted in significant augmentation of killer cell induction and perforin (PFP) production after 4 days stimulation with IL-2. These results indicate that Tf is important in generation of IL-2-inducible killer properties and PFP activity of human CD8+ T cells.

Enhancement by monocytes of perforin production and its gene expression by human CD8+ T cells stimulated with interleukin-2.

Pore-forming protein (PFP) is an important effector molecule for cytotoxicity mediated by cytotoxic T cells and NK cells. In the present study, the effect of monocytes on PFP production by interleukin-2 (IL-2)-stimulated T lymphocytes was examined. Highly purified lymphocytes (> 99%) and monocytes (> 90%) were isolated by centrifugal elutriation from peripheral blood of healthy donors, and, CD4+ and CD8+ cells were isolated from the purified lymphocytes by using antibody-bound magnetic beads. PFP production was quantitated with a universal microspectrophotometer in combination with immunostaining using anti-PFP antibody. Monocytes did not produce any PFP. High levels of PFP production were observed in CD8+ cells, but not CD4+ cells after incubation for 4 days with IL-2. Addition of monocytes to cultures of CD8+ cells resulted in significant augmentation of PFP production after 3 days' stimulation with IL-2. Monokines (TNF alpha and IL-6) caused a significant increase in PFP production by IL-2-stimulated CD8+ cells. Northern blot analysis revealed that the PFP mRNA levels was enhanced by stimulation with IL-2, and that addition of monocytes to cultures of CD8+ cells plus IL-2 augmented their PFP mRNA expression. These observations suggest that monocytes are important in in situ regulation of the CD8+ T cell-mediated cytotoxic response through production of PFP.