Analysis of the in vitro synergistic effect of 5-fluorouracil and cisplatin on cervical carcinoma cells

5-Fluorouracil (5-FU) is currently being used as an anticancer drug to reduce tumor bulk in order to increase the operability rate and postoperative survival in patients with cervical cancer, which has been combined with cisplatin (CP) because of its superior activities observed in human carcinoma cells. However, the combined anticancer effect of 5-FU and CP in cervical carcinoma cells is poorly understood. Therefore, we conducted a study to investigate whether anticancer drugs 5-FU and CP may exhibit the combined antiproliferative effect in cervical carcinoma cells. Using proteomics analysis, including two-dimensional gel electrophoresis and matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), we investigated the antiproliferative effect-related proteins after treatment with 5-FU and/or CP. Our experiments showed that the combination of 5-FU and CP engaged both the apoptotic pathways: the membrane death receptor-mediated apoptosis pathway and the mitochondrial apoptotic pathway. Moreover, the combination of 5-FU and CP resulted in remarkable increasing susceptibility to apoptosis. We suggest that the combination of 5-FU and CP suppresses the growth of cervical carcinoma cells by synergistic effect with the induction of apoptosis. In vitro synergistic effect of 5-FU and CP supports the basis of the clinical application of the combination chemotherapy to the patients with cervical cancer.

Hypoxia induces epithelial amphiregulin gene expression in a CREB-dependent manner

Hypoxia occurs during a number of conditions in which altered epithelial proliferation is critical, including tumor development. Microarray analysis of colon-derived epithelial cells revealed a hypoxia-dependent increase in the expression of amphiregulin, an EGF receptor (EGFR) ligand that activates epithelial proliferation and has been associated with the development of colonic tumors. Amphiregulin expression was also induced in tissues from mice exposed to whole animal hypoxia. The hypoxic upregulation of amphiregulin was independent of the classic transcriptional response mediated via hypoxia-inducible factor (HIF)-1α. Transfection of HeLa cells with truncated amphiregulin promoter reporter constructs revealed that a 37-bp segment upstream from the TATA box retained hypoxic sensitivity. This sequence contains an evolutionarily conserved cAMP response element (CRE) that constitutively binds the CRE binding protein (CREB). Deletion of the CRE abolished sensitivity to hypoxia. Thus hypoxia promotes intestinal epithelial amphiregulin expression in a CRE-dependent manner, an event that may contribute to increased proliferation. These data also further support a role for CREB as an HIF-independent hypoxia-responsive transcription factor in the regulation of intestinal epithelial gene expression.

Inhibitory effect of mineral ion accumulation on high density growth of the hyperthermophilic archaeon Sulfolobus solfataricus

A fed-batch operation for high density cultivation of Sulfolobus solfataricus (DSM 1617) in a bench-top fermentor using a feed medium composed of glucose and yeast extract was investigated. The highest maximal cell density obtained in controlled fed-batch cultures was 21.7 g/l. Although higher yeast extract concentrations in the medium favored greater cell biomass yield, cell growth ceased with low cell densities. It was observed that large amounts of inorganic ions, such as sulfate, ammonium, potassium and phosphate ions, were accumulated in the culture broth at higher yeast extract concentrations. This was due to either the addition of the titrant or feeding of yeast extract during cultivation. Fed-batch cultures with additional mineral salts in the feed medium showed much lower cell biomass, indicating that accumulation of inorganic ions has a significant inhibitory effect on the growth of S. solfataricus. Inhibition of cell growth by the presence of mineral ions was further confirmed by the batch culture experiments. Some plausible mechanisms which can account for the growth inhibition at higher mineral ion concentrations have been suggested.

Bandwidth control in a hybrid fiber acousto-optic filter

We report a bandwidth variation technique in an acousto-optic filter. Utilizing the adiabatic conversion in both optical and acoustic modes, we obtain a novel hybrid waveguide composed of serial concatenation of single-mode fiber (SMF) and two-mode hollow optical fiber (HOF). On the basis of dissimilarity in the phase-matching conditions and beat-length dispersion in SMF and HOF, the FWHM of the resonant bands is varied from 3.8 to 190 nm near the 1.5-microm region in a single device. Furthermore, we theoretically analyze the acousto-optic coupling among the guided modes in HOF, which shows good agreement with experimental observations.

Prostaglandin E2 stimulates the growth of colon cancer cells via induction of amphiregulin

Prostaglandin E(2) (PGE(2)), a major product of cyclooxygenase enzymes, is implicated in colorectal carcinogenesis and has been shown to stimulate the growth of human colorectal carcinoma cells. Here, we show that PGE(2) activated the cyclic AMP/protein kinase A pathway, which induced the expression of amphiregulin (AR), an epidermal growth factor family member, through activation of a cyclic AMP-responsive element in the AR promoter. AR exerted a mitogenic effect on LS-174 cells and partially mediated the PGE(2)-induced growth stimulation. In addition, PGE(2), in collaboration with transforming growth factor-alpha or K-Ras oncogene, synergistically induced AR expression and activated receptor tyrosine kinase-dependent signaling pathways. Our results provide novel mechanisms for cyclooxygenase-2 pro-oncogenic activity and suggest that PGE(2) may act with major oncogenic pathways in a synergistic fashion to activate the epidermal growth factor receptor signaling system through a ligand-dependent autocrine pathway.

Suspended multiwalled carbon nanotubes as self-aligned evaporation masks

We describe the nanofabrication study of self-aligned electrodes on suspended multiwalled carbon nanotube structures. When metal is deposited on a suspended multiwalled carbon nanotube structure, the nanotube acts as an evaporation mask, resulting in the formation of discontinuous electrodes. The metal deposits on the nanotubes are removed with lift-off. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gapped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Direct observation of localized defect States in semiconductor nanotube junctions

We report scanning tunneling microscopy of semiconductor-semiconductor carbon nanotube junctions with different band gaps. Characteristic features of the wave functions at different energy levels, such as a localized defect state, are clearly exhibited in the atomically resolved scanning tunneling spectroscopy. The peaks of the Van Hove singularity on each side penetrate and decay into the opposite side across the junction over a distance of approximately 2 nm. These experimental features are accounted for, with the help of tight-binding calculation, by the presence of pentagon-heptagon pair defects at the junction.

Carbon onions: carriers of the 217.5 nm interstellar absorption feature

Ultraviolet-visible absorption measurements of high purity and well separated carbon onion samples are reported. The results show that, after purification, absorption features from carbon onions match well with the interstellar UV spectrum. The measurements show that the absorption peak position remains constant at 4.55+/-0.1 microm(-1), and the width varies from 1.2-1.6 microm(-1), a key feature of the interstellar spectrum. The similarities between the experimental and observed absorption spectra indicate that carbon onions are very strong candidates for the origin of the UV interstellar absorption peak at 4.6 microm(-1).

CA125 levels are a weak predictor of optimal cytoreductive surgery in patients with advanced epithelial ovarian cancer

The utility of preoperative CA125 to predict optimal primary tumor cytoreduction in patients with advanced (stages IIIC and IV) epithelial ovarian cancer is controversial. In this paper, we retrospectively review patients with stage IIIC and IV epithelial ovarian cancer who underwent primary cytoreductive surgery from 1989 to 2001. Ninety-nine patients were identified and included in the analysis. All patients had preoperative CA125 levels measured. Operative and pathology reports were reviewed. Optimal cytoreduction was defined as largest volume of residual disease < 1 cm in maximal dimension. Mean values were compared with t-test on a log scale when needed. The optimal cut-point for discriminating between those with vs. without optimal cytoreduction was determined using the receiver operator curve (ROC) method. Optimal cytoreduction was achieved in 73% of patients. Among patients with optimal cytoreductive status the mean CA125 level was 569, while among patients with suboptimal cytoreduction the mean CA125 level was 1520 (P < 0.007). A CA125 level of 912 was identified as the optimal cut-point to distinguish the two groups. Using this CA125 level, the sensitivity of this test in predicting optimal cytoreduction was 58% and the specificity was 54%. The positive predictive value of CA125 for optimal cytoreduction was 78% and the negative predictive value was 31%. We conclude that CA125 level is a weak positive and negative predictor of optimal cytoreductive surgery in patients with advanced epithelial ovarian cancer. The CA125 level should not be used as a primary predictor of the outcome of cytoreductive surgery and should be viewed in the context of all other preoperative features.

[An analysis of Korean women's reproductivity]

An analysis of reproductivity is mainly concerned with the measurement of net force of fertility expressed in terms of a generation rather than in a given year. The present study examined current trends of Korean Women's reproductivity interpreting general reproduction and net reproduction rates, intrinsic rate of natural increase and mean length of gestation. The data used for this analysis were drawn from the national fertility surveys from 1970 through 1990 conducted by the Korea Institute for Population and Health. The figures of the present study revealed that the reproduction rates of Korea during the last 20 years decreased from 2.22 in 1970 to 0.71 in 1990 and net reproduction rates also dropped from 1.9 to 0.69 during the same period of time. Furthermore, from this study, it is noticed that the replacement level of fertility had been reached since the early 1980s. The intrinsic rate of natural increase as measure of population growth under existing conditions of fertility and mortality and free of the influence of the current age distribution, is computed. The level of rate was not much changed and was 0.3 in 1970 compared with 0.25 in 1990, which is still higher than other developed countries. The mean age of mother at the birth of their daughters defined as the length of generation has been slightly changed from 23.9 in 1971 to 25.8 in 1990.

Induction of the interleukin-2/15 receptor beta-chain by the EWS-WT1 translocation product

EWS-WT1 is a chimeric transcription factor resulting from fusion of the N-terminal domain of the Ewing sarcoma gene EWS to the three C-terminal zinc fingers of the Wilms tumor suppressor WT1. This translocation underlies desmoplastic small round cell tumor (DSRCT), which is noted for the abundance of reactive stroma surrounding islets of tumor cells, suggestive of paracrine signals contributing to tumor cell proliferation. Hybridization to high-density oligonucleotide microarrays can be used to identify targets of EWS-WT1. Expression of EWS-WT1 from a tetracycline-regulated promoter leads to the induction of growth-associated genes, of which the most remarkable is the beta-chain of the interleukin-2/15 receptor (IL-2/15Rbeta). Potent transcriptional activation by the chimeric protein maps to two bindings sites within the IL-2/15Rbeta promoter. Analysis of primary DSRCT tumor specimens demonstrates high levels of IL-2/15Rbeta within the tumor cells, along with expression of IL-2 and IL-15 by the abundant hyperplastic endothelial cells within the reactive stroma. Activation of this cytokine signaling pathway is consistent with the nuclear localization of its downstream effectors, phosphorylated STAT3 and STAT5. These observations suggest that the transcriptional induction of a cytokine receptor by a tumor-associated translocation product enables a proliferative response of epithelial cancer cells to ligands secreted by the surrounding stroma.

Typing of clinical isolates of Mycobacterium leprae and their distribution in Korea

Although there is no genetic diversity in isolates of Mycobacterium leprae, the variance of tandem repeats in the rpoT gene was recently demonstrated. We have typed clinical isolates of M. leprae in Korea using difference of the tandem repeats in the rpoT gene. Among 69 patients, 65 Korean isolates (94.2%) demonstrated four copies of the 6 bp tandem repeat (GACATC) in the rpoT gene, and incidences of three copies were found in only two Koreans and two foreigners (2.9%, respectively).

Low-density lipoprotein-antioxidant constituents of Saururus chinensis

A new diarylbutane lignan, saururin A (1), and a known 8-O-4'-type neolignan, machilin D (2), were isolated from a total methanol extract of the underground parts of Saururus chinensis. The structures of 1 and 2 were elucidated by spectroscopic data analysis. Compounds 1, 2, and virolin (3) (the methyl ether of 2) exhibited significant low-density lipoprotein (LDL)-antioxidant activity in the thiobarbituric acid-reactive substance (TBARS) assay with IC(50) values of 8.5, 2.9, and 4.3 microM, respectively.

Modulation of the multisubstrate specificity of Thermus maltogenic amylase by truncation of the N-terminal domain and by a salt-induced shift of the monomer/dimer equilibrium

The relation between the quaternary structure and the substrate specificity of Thermus maltogenic amylase (ThMA) has been investigated. Sedimentation diffusion equilibrium ultracentrifugation and gel filtration analyses, in combination with the crystal structure determined recently, have demonstrated that ThMA existed in a monomer/dimer equilibrium. The truncation of ThMA by removing the N-terminal domain, which is composed of 124 amino acid residues, resulted in the complete monomerization of the enzyme (ThMADelta124) accompanied by a drastic decrease in the activity for beta-cyclodextrin (beta-CD) and a relatively smaller reduction of the activity for starch. Despite the overall low activity of ThMADelta124, the activity was higher toward starch than beta-CD, and the ratio of the specific activities toward these substrates was approximately 100 fold higher than that of wild-type ThMA. Furthermore, the addition of KCl to wild-type ThMA shifted the monomer/dimer equilibrium toward the monomer. In the presence of 1.0 M KCl, the relative activity of ThMA toward beta-CD decreased to 74%, while that for soluble starch increased to 194% compared to the activities in the absence of KCl. Thus, the ThMA monomer and dimer are both inferred to be enzymatically active but with a somewhat different substrate preference. Kinetic parameters of the wild-type and truncated enzymes also are in accordance with the changes in their specific activities. We thus provide evidence in support of a model, which shows that the relative multisubstrate specificity of ThMA is influenced by the monomer/dimer equilibrium of the enzyme.

Destabilization of CHK2 by a missense mutation associated with Li-Fraumeni Syndrome

Li Fraumeni Syndrome (LFS) is a multicancer phenotype, most commonly associated with germ-line mutations in TP53. In a kindred with LFS without an inherited TP53 mutation, we have previously reported a truncating mutation (1100delC) in CHK2, encoding a kinase that phosphorylates p53 on Ser(20). Here, we describe a CHK2 missense mutation (R145W) in another LFS family. This mutation destabilizes the encoded protein, reducing its half-life from >120 min to 30 min. This effect is abrogated by treatment of cells with a proteosome inhibitor, suggesting that CHK2(R145W) is targeted through this degradation pathway. Both 1100delC and R145W germ-line mutations in CHK2 are associated with loss of the wild-type allele in the corresponding tumor specimens, and neither tumor harbors a somatic TP53 mutation. Our observations support the functional significance of CHK2 mutations in rare cases of LFS and suggest that such mutations may substitute for inactivation of TP53.

Dietary hematein ameliorates fatty streak lesions in the rabbit by the possible mechanism of reducing VCAM-1 and MCP-1 expression

Hematein is a compound isolated from Caesalpinia sappan that has been used in oriental medicine as both an analgesic and an anti-inflammatory agent. In this study, we examined the anti-atherogenic potential of hematein using cholesterol-fed New Zealand White (NZW) rabbits. NZW rabbits were divided into a hematein-supplemented (0.05% in diet) group (n=6), a probucol-supplemented (0.25% in diet) group (n=6), and a control group (n=6). After 8 weeks of treatments, the extent of the atherosclerotic lesions was significantly reduced in the hematein-supplemented group and the probucol-supplemented group without changing plasma lipoprotein levels. Hematein and probucol prevented the up-regulation of the vascular cell adhesion molecule-1 (VCAM-1) expression on the descending aorta induced by cholesterol diet. In culture, hematein also significantly inhibited the secretion of soluble VCAM-1 and of monocyte chemotactic protein-1 (MCP-1) respectively induced by tumor necrotic factor alpha (TNF-alpha) and mildly oxidized low density lipoprotein in human umbilical vein endothelial cell (HUVEC) culture. Also, hematein inhibited monocyte adhesion to endothelial cell and the activation of NF-kappaB in HUVECs stimulated with TNF-alpha. The results of the present study suggest that the anti-atherogenic effect of hematein is not related to control of the plasma lipid profile but probably related to the inhibition of VCAM-1 and MCP-1 expression resulting in an amelioration of lesion development in the rabbit.

Trapping of a covalent enzyme intermediate in the reaction of Bacillus macerans cyclomaltodextrin glucanyltransferase with cyclomaltohexaose

The mechanism of catalysis of Bacillus macerans cyclomaltodextrin glucanyltransferase (CGTase, EC 2.4.1.19) was studied by trapping and isolating a covalent-enzyme intermediate. CGTase catalyzes an acceptor or coupling reaction between cyclomaltohexaose and a carbohydrate acceptor such as D-glucose. CGTase was incubated with 3H-labeled cyclomaltohexaose in the absence of any added acceptor. After 30 s of reaction, the enzyme was rapidly denatured and precipitated by the addition of 10% trifluoroacetic acid (TFA). Extensive washing of the precipitated protein showed retention of radioactivity with the protein. The precipitate was dissolved in 0.1 M TFA, containing 6 M urea and passed over a BioGel P-10 column. The protein fraction retained 95% of its original radioactivity. The reaction with [3H]cyclomaltohexaose was also stopped by the addition of TFA to give an inactive enzyme at pH 2.5. The enzyme was separated from unreacted cyclomaltohexaose on a BioGel P-10 column and was shown to be radioactive. When the radioactive protein fraction was rechromatographed on BioGel P-10, it retained 100% of the label. These results demonstrate the formation of a covalent carbohydrate-enzyme intermediate in the reactions catalyzed by CGTase.

Isolation of a novel gene from Schizosaccharomyces pombe: stm1+ encoding a seven-transmembrane loop protein that may couple with the heterotrimeric Galpha 2 protein, Gpa2

A putative seven transmembrane protein gene, stm1(+), which is required for proper recognition of nitrogen starvation signals, was isolated as a multicopy suppressor of a ras1 synthetic lethal mutant in Schizosaccharomyces pombe. Under nitrogen-deficient conditions, transcription of the stm1 gene was induced; deletion of stm1 was associated with early entry into G(1) arrest. Under nutritionally sufficient conditions, overexpression of Stm1 inhibited vegetative cell growth, resulted in decreased intracellular cAMP levels, increased the expression of the meiosis-specific genes ste11, mei2, and mam2, and facilitated sexual development in homothallic cells. However inhibition of vegetative cell growth and reduction of cAMP levels were not observed in a deletion mutant of the heterotrimeric G protein Galpha2 gene, gpa2, that is responsible for regulating intracellular cAMP levels, a key factor in determining the sexual development in S. pombe. Stm1 protein was shown to interact with Gpa2 through its C-terminal transmembrane domains 5-7. Mutation at Lys(199) in the C-terminal domain (stm1(K199A)) abolished the Stm1 overexpression effect on lowering cAMP levels. Induction of ste11, a meiosis-specific gene transcription factor, by Stm1 overexpression was enhanced in gpa2-deleted cells but was absent in a deletion mutant of sty1, a key protein kinase that links mitotic control with environmental signals and induces stress-responsive genes. Moreover, deletion of both stm1 and ras1 caused delayed entry into G(1) arrest in S. pombe when the cells were grown in a nitrogen-deficient medium. Thus we consider that the stm1 gene can function through Gpa2-dependent and/or -independent pathways and may play a role in providing the prerequisite state for entering the pheromone-dependent differentiation cycle in which heterotrimeric Galpha1 protein, Gpa1, and Ras1 play major roles. Stm1 could function as a sentinel molecule sensing the nutritional state of the cells, stopping the proliferative cell cycle, and preparing the cell to enter meiosis under nutritionally deficient conditions.

General pharmacological properties of YJA20379-8, a new H+/K(+)-ATPase inhibitor with anti-ulcer activities

The general pharmacological properties of YJA20379-8 (3-butyryl-4-[(R)-1-methylbenzylamino]-8-ethoxy-1,7-naphthyridine, CAS 187654-40-6), a new H+/K(+)-ATPase inhibitor with anti-ulcer activities, were investigated in mice, rats and guinea pigs. YJA20379-8 at oral doses of 25, 50 and 100 mg/kg did not affect the locomotor activity, hexobarbital hypnosis and motor coordination in mice. The drug did not have analgesic action and anticonvulsant action at the doses of 100 mg/kg p.o. The respiration and blood pressure were not affected at 10 mg/kg i.v. in rats. YJA20379-8 at 2 x 10(-4) g/ml did neither produce any contraction nor relaxation of isolated organs, such as guinea pig ileum, rat fundus, rat uterus and guinea pig vas deferens, and the drug antagonized the contractile responses to several spasmogens, such as acetylcholine, histamine, serotonin, L-phenylephrine, oxytocin and BaCl2. The drug up to 100 mg/kg p.o. did not affect pupil size and the intestinal propulsion of mice. And it did not show an anticarrageenan action at 100 mg/kg. In this general pharmacology study, hypothermic effect in mice, retardation in gastric emptying in rats, decreases in urine excretion in rats at oral doses of 50 and 100 mg/kg of YJA20379-8 and the spasmolytic activity could be found. However, no other effects were exhibited at a high oral dose of 100 mg/kg in animals in this study.

Intrinsic stability of unused and retrieved polyethylene glenoid components

The surface geometry of polyethylene components can be altered by in vivo use. The purpose of this investigation is to document the effects of these changes on the intrinsic stability provided by the glenoid component. We validated a method of measuring the intrinsic stability of glenoid components as indicated by the balance stability angle (the maximal angle between the glenoid centerline and the resultant humeral force before dislocation of the humeral head occurs). We compared observed values with those predicted for unused glenoid components for which the geometry was known. We then applied this method to retrieved glenoid components in which the surface geometry had been altered by in vivo use. The balance stability angles measured in retrieved glenoids were often substantially reduced: 11 of 24 glenoids had diminished balance stability angles of at least 30% in at least one direction. We concluded that the surface geometry of polyethylene glenoid components can be altered by in vivo use in a manner that may compromise their contribution to glenohumeral stability.

Expression of the native cholera toxin B subunit gene and assembly as functional oligomers in transgenic tobacco chloroplasts

The B subunits of enterotoxigenic Escherichia coli (LTB) and cholera toxin of Vibrio cholerae (CTB) are candidate vaccine antigens. Integration of an unmodified CTB-coding sequence into chloroplast genomes (up to 10,000 copies per cell), resulted in the accumulation of up to 4.1 % of total soluble tobacco leaf protein as functional oligomers (410-fold higher expression levels than that of the unmodified LTB gene expressed via the nuclear genome). However, expression levels reported are an underestimation of actual accumulation of CTB in transgenic chloroplasts, due to aggregation of the oligomeric forms in unboiled samples similar to the aggregation observed for purified bacterial antigen. PCR and Southern blot analyses confirmed stable integration of the CTB gene into the chloroplast genome. Western blot analysis showed that the chloroplast- synthesized CTB assembled into oligomers and were antigenically identical with purified native CTB. Also, binding assays confirmed that chloroplast-synthesized CTB binds to the intestinal membrane GM1-ganglioside receptor, indicating correct folding and disulfide bond formation of CTB pentamers within transgenic chloroplasts. In contrast to stunted nuclear transgenic plants, chloroplast transgenic plants were morphologically indistinguishable from untransformed plants, when CTB was constitutively expressed in chloroplasts. Introduced genes were inherited stably in subsequent generations, as confirmed by PCR and Southern blot analyses. Increased production of an efficient transmucosal carrier molecule and delivery system, like CTB, in transgenic chloroplasts makes plant-based oral vaccines and fusion proteins with CTB needing oral administration commercially feasible. Successful expression of foreign genes in transgenic chromoplasts and availability of marker-free chloroplast transformation techniques augurs well for development of vaccines in edible parts of transgenic plants. Furthermore, since the quaternary structure of many proteins is essential for their function, this investigation demonstrates the potential for other foreign multimeric proteins to be properly expressed and assembled in transgenic chloroplasts.

L-pyroglutamate spontaneously formed from L-glutamate inhibits growth of the hyperthermophilic archaeon Sulfolobus solfataricus

Identification of physiological and environmental factors that limit efficient growth of hyperthermophiles is important for practical application of these organisms to the production of useful enzymes or metabolites. During fed-batch cultivation of Sulfolobus solfataricus in medium containing L-glutamate, we observed formation of L-pyroglutamic acid (PGA). PGA formed spontaneously from L-glutamate under culture conditions (78 degrees C and pH 3.0), and the PGA formation rate was much higher at an acidic or alkaline pH than at neutral pH. It was also found that PGA is a potent inhibitor of S. solfataricus growth. The cell growth rate was reduced by one-half by the presence of 5.1 mM PGA, and no growth was observed in the presence of 15.5 mM PGA. On the other hand, the inhibitory effect of PGA on cell growth was alleviated by addition of L-glutamate or L-aspartate to the medium. PGA was also produced from the L-glutamate in yeast extract; the PGA content increased to 8.5% (wt/wt) after 80 h of incubation of a yeast extract solution at 78 degrees C and pH 3.0. In medium supplemented with yeast extract, cell growth was optimal in the presence of 3.0 g of yeast extract per liter, and higher yeast extract concentrations resulted in reduced cell yields. The extents of cell growth inhibition at yeast extract concentrations above the optimal concentration were correlated with the PGA concentration in the culture broth. Although other structural analogues of L-glutamate, such as L-methionine sulfoxide, glutaric acid, succinic acid, and L-glutamic acid gamma-methyl ester, also inhibited the growth of S. solfataricus, the greatest cell growth inhibition was observed with PGA. We also observed that unlike other glutamate analogues, N-acetyl-L-glutamate enhanced the growth of S. solfataricus. This compound was stable under cell culture conditions, and replacement of L-glutamate with N-acetyl-L-glutamate in the medium resulted in increased cell density.

Isolation and characterization of a thermotolerant bacterium Ralstonia sp. strain PHS1 that degrades benzene, toluene, ethylbenzene, and o-xylene

A thermotolerant bacterium, designated as PHS1, was isolated from a hot spring in Pohang, Korea, on the basis of its ability to grow on benzene, toluene, ethylbenzene, and xylenes (BTEX) as a sole carbon source. Strain PHS1 is a gram-negative, rod-shaped aerobe and grows optimally at 42 degrees C and pH 7.2. According to 16 S rDNA analysis, strain PHS1 showed highest similarity to Ralstonia eutropha (previously named Alcaligenes eutrophus). Unlike its closest known Ralstonia species, however, strain PHS1 was able to utilize toluene, ethylbenzene, o-xylene, and both m- and o-cresol. The degradation of o-xylene by strain PHS1 is particularly important, since o-xylene is a compound of considerable environmental interest, owing to its recalcitrance; and very few microorganisms have been reported to utilize o-xylene as a sole carbon source. It was found that strain PHS1 transformed o-xylene to 2,3-dimethylphenol through direct oxygenation of the aromatic ring. The unique properties of strain PHS1, such as thermotolerance and the ability to degrade o-xylene, may have important implications for the treatment of BTEX-contaminated industrial effluents.