Wastewater Treatment in a Packed-Bed Reactor with Immobilized Cells onto a New Ceramic Carrier

A new porous ceramic carrier based on casting sand, sawdust and zeolite was used to immobilize microorganisms for continuous wastewater treatment in a packed-bed bioreactor. Scanning electron microscopy showed that the ceramic carrier has a high porosity with diameters of around 5~300µm. Immobilization capacity of the carrier was 62 mg/ g dry carrier, in terms of mixed liquor volatile suspended solids. When synthetic wastewater (chemical oxygen demand 250 mg/l) as a model feed solution and 30 mg kaolin/l as a suspended solid (SS) were used, the removal efficiency as measured by the total organic carbon and SS were 91% and 71%, respectively, at a hydraulic retention time of 3 h.     

Effects of cytokinin on adventitious root formation in callus cultures ofVigna unguiculata (L.) walp

Summary Yellowish compact callus, induced from cowpea hypocotyls on Murashige and Skoog(MS) medium (1962) containing 0.2 mg/l(0.93 μM) kinetin and 0.4 mg/l (1.81 μM) 2,4-dichlorophenoxyacetic acid (2,4-D), was subcultured on MS medium containing cytokinin alone, auxin alone, or auxins plus cytokinins in order to determine the effect of cytokinins on root organogenesis in callus cultures. The callus actively proliferated on the same medium but did not show any organogenic activity macroscopically as well as microscopically. On medium with N⁶-benzyladenine (BA) and 1-naphthaleneacetic acid (NAA), the yellowish compact callus first changed to pale green compact callus and then many green spots appeared on its surface under light culture. But the yellowsih compact callus remained yellowish and white spots appeared on its surface in dark culture. These spots gradually became white nodular structures. Adventitious root formation from the nodular structures occurred not only on the same medium, but also on medium with either auxin or cytokinin but not both. Yellowish compact callus on medium with auxin alone was transformed to yellowish friable callus, which did not develop adventitious roots. The yellowish friable callus could gain rhizogenic activity only after morphological modification to pale green compact callus on medium with auxin plus cytokinin. The modified callus did not form adventitious roots on medium with auxins but only with cytokinins. Therefore, it is suggested that cytokinins have stimulating effects on root formation from callus that previously did not show rhizogenic activity on medium with auxins alone. In addition, the rhizogenic potential of cowpea callus was discriminated from that of leaf explants, which formed adventitious roots directly on medium with auxin alone.     

An 8 kb Nucleotide Sequence at the 3' Flanking Region of the sspC Gene (184{degrees}) on the Bacillus subtilis 168 Chromosome Containing an Intein and an Intron

As part of the Bacillus subtilis genome sequencing project,we determined the complete nucleotide sequence of an 8000-bpfragment downstream of the sspC gene (184°) of the B. subtilis168 chromosome. The sequence analysis shows that the sspC geneis located inside of the SPß region, which differsfrom the current genetic map of B. subtilis 168. This regioncontains 12 putative ORFs (yojQ through yojZ and sspC). A homologysearch for the deduced products of the ORFs shows signi.cantsimilarities to enzymes involved in deoxyribonucleotide metabolism:ribonucleotide reductase (Nrd) E, NrdF, thioredoxinand dUTPase.Interestingly, this DNA fragment includes two split genes, yojPcontaining conserved motifs of an intein and yojQ and yojS withan 808-bp intervening sequence for a putative intron structure.In addition, the yojR gene includes a putative new DNA replicationterminator.     

Taxonomic relationships in East AsianVicia species with unijugate leaves based on random amplified polymorphic DNA markers

Random amplified polymorphic DNA(RAPD) markers were investigated to clarify the taxonomic positions ofVicia linearifolia andV. bifolia, and to assess the genomic diversity among the 9 populations ofV. unijuga, each of which represents a geographical variation or infraspecific taxa in southern Korea. These species are characterized by unijugate leaves in East Asia and have been controversial as to infra-or interspecific classification. The polymorphic markers among the populations examined were observed for fifteen decamer primers. The degree of band sharing was used to calculate genetic similarity between populations, and a phenogram using UPGMA cluster analysis was generated based on the Dice similarity coefficient. The taxa studied were divided into two main groups and the populations ofV. unijuga were all grouped together in the phenogram. The genetic similarities ofV. unijuga were very high among the populations and did not show distinctions between the infraspecific taxa, although the populations of Mt. Odae and adjacent areas in eastern Korea were different from others of the species.V. linearifolia fell within the range of the genomic variation among the populations ofV. unijuga, whileV. bifolia was grouped withV. venosa var.cuspidata having multijugate leaves rather thanV. unijuga. The result from studying RAPD markers suggested thatV. linearifolia should be integrated intoV. unijuga and that species with unijugate leaves ofV. bifolia andV. unijuga are polyphyletic.     

Enhancement ofcis,cis-muconate productivity by overexpression of catechol 1,2-dioxygenase inPseudomonas putida BCM114

For enhancement ofcis,cis-muconate productivity from benzoate, catechol 1,2-dioxygenase (C12O) which catalyzes the rate-limiting step (catechol conversion tocis,cis-muconate) was cloned and expressed in recombinantPseudomonas putida BCM114. At higher benzoate concentrations (more than 15 mM),cis,cis-muconate productivity gradually decreased and unconverted catechol was accumulated up to 10 mM in the case of wildtypeP. putida BM014, whereascis,cis-muconate productivity continuously increased and catechol was completely transformed tocis,cis-muconate forP. putida BCM114. Specific C12O activity ofP. putida BCM114 was about three times higher than that ofP. putida BM014, and productivity was enhanced more than two times.     

Oxidation-deficient silkworm hemolymph as a medium supplement for insect cell culture

Hemolymph is oxidized and darkens visibly during the collection from silkworms due to the activity of tyrosinase in it. Toxic quinones are produced by the oxidation and consequently inhibit the cell growth. Heat treatment can be used to prevent the oxidation; however, the oxidation may occur during the collection of hemolymph before it is heat-treated. It makes the hemolymph collection difficult especially on a large-scale preparation. Hemolymphs collected from 257 different strains of silkworms were examined to select the slowly oxidized hemolymphs. Hemolymphs collected from mutant strains such as Lemone, TBO, Cre, Y4, and wE^b showed relatively slow color changes. Oxidation rates of the hemolymphs were measured by the absorbance change using a spectrophotometer. The hemolymph of wE^b showed the slowest oxidation. The absorbance of this mutant hemolymph reached the saturation value at 20°C in 450 min, whereas the total oxidation time of the wild-type (Baekokjam) hemolymph at the same temperature was 120 min. We tested if this mutant hemolymph is useful as a medium supplement for insect cell culture. Cell growth rate and final cell concentration in the medium supplemented with the wE^b hemolymph were almost same as those in the medium supplemented with the wild-type hemolymph. Hemolymph is collected on a small scale by clipping the abdominal leg; however, this method is not appropriate for large scale preparation. Centrifugation after chopping the silkworm hemolymph by a blending mixer is a more appropriate procedure for large scale collection. Slowly oxidized wE^b hemolymph resulted in higher cell concentration than the wild-type hemolymph when hemolymph was collected by the large scale preparation method.     

Immunological analysis of methamphetamine antibody and its use for the detection of methamphetamine by capillary electrophoresis with laser-induced fluorescence

An accurate, simple and rapid immunoassay is demonstrated for the detection of methamphetamine in urine by capillary electrophoresis (CE) with laser-induced fluorescence (LIF). An aminobutyl derivative of methamphetamine was conjugated with proteins, and used as an immunogen to produce antibodies for the assay. The methamphetamine derivative was also labeled with fluorescein isothiocyanate (FITC) to compete with free methamphetamine in the sample for the antibody binding site. Levels of free and antibody-bound FITC-labeled methamphetamine were monitored by performing CE–LIF using an untreated fused-silica column. This competitive immunoassay used antiserum instead of purified antibody or antibody fragment, yet was found to have good precision with a sensitivity of lower than 20 ng/ml. Various antibodies were also screened, and cross-reactivity of anti-MA antibody with methamphetamine analogues were also investigated. The results indicate that CE–LIF-based immunoassay is a powerful tool for the screening and characterization of antibody and may have possible applications in the detection of abused drugs in urine.     

Induction of somatic embryos by macrosalt stress from mature zygotic embryos of Panax ginseng

Mature zygotic embryos of ginseng (Panax ginseng C. A. Meyer) were germinated on a Murashige and Skoog medium lacking growth regulators. However, when the zygotic embryos were cultured on MS medium containing increased levels of macrosalts (NH₄NO₃, KNO₃, KH₂PO₄, MgSO₄, or CaCl₂) to result is a mild salt stress, growth of zygotic embryos was strongly suppressed and eventually browning occurred. Somatic embryos or embryogenic calli were formed directly from these abnormal stressed zygotic embryos. Cotyledons were the most competent tissue for somatic embryo production. The highest frequency of somatic embryo formation (56.3%) was observed on medium containing 61.8 mM of NH₄NO₃. The highest frequency of somatic embryo formation by five different macrosalt treatments occurred in the following order: NH₄NO₃> KNO₃> KH₂PO₄> MgSO₄> CaCl₂. Somatic embryos were regenerated into plants with a shoot and root, and the plants survived on soil in the greenhouse. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cortical tissue-specific accumulation of the root-specific ns-LTP transcripts in the bean (Phaseolus vulgaris) seedlings

The characterization of a cDNA clone encoding non-specific lipid transfer protein (PvLTP, formerly named PVR3) in the roots of bean seedlings has been previously reported. In this study, we examined the temporal and spatial accumulation of PvLTP mRNA and the effect of the auxin naphthaleneacetic acid (NAA) on the accumulation of PvLTP mRNA during root development. In situ hybridization showed that accumulation of PvLTP mRNA is highly tissue-specific. Accumulation was detected in the cortical tissue, but not in other tissues of root, including the quiescent center and root cap. Within the cortical tissue, accumulation of PvLTP mRNA was developmentally regulated; accumulation of PvLTP mRNA was high in the cortical tissue of the proximal and ground meristem and declined as cortical tissue developed further. Since the appropriate distribution of auxin is an important factor responsible for the maintenance of root meristem organization. We examined effect of auxin on the accumulation of PvLTP mRNA in relation to the development of cortical tissue. In bean seedlings grown on medium supplemented with 5 M NAA, morphological alternations, including radial root expansion and abnormal tissue organization in the root apical meristem, were observed. Only faint accumulation signals of PvLTP mRNA were observed in the cortical tissue of proximal meristem region, indicating that cortical tissue development was repressed by exogenous NAA. However, our results suggest that the change in accumulation of PvLTP mRNA is not direct regulatory effect but reflective effect of altered development of cortical tissue that was induced by exogenous NAA. The temporal and spatial accumulation of PvLTP mRNA indicates that PvLTP is a useful marker for the development of cortical tissue in the root tip in bean seedlings.     

Genetic sensitivity analysis: Adjusting for genetic confounding in epidemiological associations

Associations between exposures and outcomes reported in epidemiological studies are typically unadjusted for genetic confounding. We propose a two-stage approach for estimating the degree to which such observed associations can be explained by genetic confounding. First, we assess attenuation of exposure effects in regressions controlling for increasingly powerful polygenic scores. Second, we use structural equation models to estimate genetic confounding using heritability estimates derived from both SNP-based and twin-based studies. We examine associations between maternal education and three developmental outcomes – child educational achievement, Body Mass Index, and Attention Deficit Hyperactivity Disorder. Polygenic scores explain between 14.3% and 23.0% of the original associations, while analyses under SNP- and twin-based heritability scenarios indicate that observed associations could be almost entirely explained by genetic confounding. Thus, caution is needed when interpreting associations from non-genetically informed epidemiology studies. Our approach, akin to a genetically informed sensitivity analysis can be applied widely.