Application of numerical modeling for the development of optimized complex medium for D-hydantoinase production from Agrobacterium radiobacter NRRL B 11291

D-Hydantoinases (E.C.3.5.2.2) are commercially valuable enzymes involved in the production of D-amino acids. However, commercial exploitation of the biological process is rare, mainly because sufficient details are not available on the efficient production of these enzymes by microorganisms. In the present study, Agrobacterium radiobacter was used as the source of D-hydantoinase and its production was optimized with inexpensive carbon and nitrogen sources. The four media components selected to study their effect on biomass and/or enzyme activities were molasses, ammonium nitrate, sodium di-hydrogen orthophosphate, and manganese chloride. With the use of an empirical modeling technique (response surface method), we have optimized both biomass and enzyme production in this organism, with a minimal number of batches. Experiments were performed with optimized media components to validate the model. The maximum level of enzyme and biomass obtained was 35 U/mL and 1.69 mg/mL, respectively. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 148-154, 1997.     

DNA repair in higher plants

Numerous studies have demonstrated a requirement in plants for repair of DNA damage arising from either intrinsic or extrinsic sources. Investigations also have revealed a capacity for repair types of DNA damage, and conversely, identified mutants apparently defective in such repair. This article provides a concise overview of nuclear DNA repair mechanisms in higher plants, particularly those processes concerned with the repair of UV-induced lesions, and includes surveys of UV-sensitive mutants and genes implicated in DNA repair.     

Sterol and lipid components of green Thea sinensis

Petrol. extracts of green tea yielded two straight chain alcohols identified as C₃₀ and C₃₂ alcohols by mass spectrometry, and a mixture of sterols identified as α-spinasterol and stigmast-7-ene-3-β-ol. A new saponin has also been isolated from the methanol extract and shown to be α-spinasterol gentiobioside.     

Repellent,antifeedant and toxic effects of Ageratum conyzoides (Linnaeus) (Asteraceae) extract against Helicovepra armigera (Hübner) (Lepidoptera: Noctuidae)

Repellent, antifeedant and toxic effect of crude hexane extract of Ageratum conyzoides were investigated against Helicoverpa armigera. In orientation bioassay, the extract exhibited dose-dependent repellency against neonates. Extract significantly increased the mortality and decreased growth of different larval stages when administrated orally in artificial diet. EC₅₀ value was at 0.11% for larval growth inhibition. Toxicity of the extract was manifested by high mortality of first instar larvae after 7 days of feeding on diet containing 0.05–0.4% of extract with LC₅₀ of 0.17%. Under choice bioassay, extract showed strong antifeedant activity against fifth instar larvae with DI₅₀ of 0.21%. In nutritional bioassay, extract significantly reduced RCR, RGR, ECI and ECD of fifth instar larvae with increased AD. When RGR were plotted against RCR, the growth efficiency of larvae fed on treated diet was significantly lower than the control fed larvae suggesting the antifeedant and toxic effect of extract.     

Developmentally regulated demethylase activity targeting the betaA-globin gene in primary avian erythroid cells

Differential expression of globin genes has provided an interesting model system for better understanding commonly inherited diseases such as thalassemia. In the avian beta-type globin cluster (5'-rho-betaH-betaA-epsilon-3'), silencing of the embryonic rho-globin gene occurs concomitantly with the activation of the adult betaA-globin gene during embryonic development. DNA methylation is a dynamic process that regulates gene expression. We observed a progressive loss of methylation of betaA-globin gene, during avian embryonic development that was concurrent with the expression of the gene. The promoter and exon 1 regions of the template strand were completely demethylated, whereas residual methylation was retained in exons 2 and 3. Using a modified methylation-sensitive single-nucleotide primer extension (MS-SNuPE) assay, we observed stage-specific demethylase activity in the nuclear extracts of chicken red cells; activity in 5-, 8-, and 11-day-old erythroid cell nuclear extracts was 6, 76, and 24%, respectively. The demethylase targeted both hemimethylated and fully methylated substrates. Our findings demonstrate stage-specific demethylase activity in nuclear extracts from primary chicken erythroid cells that could target the fully methylated promoter of a developmentally regulated native gene.     

Grass vs. tree origin of soil organic carbon under different land-use systems in the Brazilian Cerrado

Aims

This study aimed at assessing whether patch type (i.e., under-shrub soil patch and inter-shrub soil patch) has an effect on soil microbes and how different shrub species altered the soil microbes through understanding soil microbial activity, biomass, and community structure.

Methods

We characterized the soil microbes in under-shrub and inter-shrub soil patches in three shrublands (Artemisia ordosica, Salix psammophila, and Caragana microphylla), respectively, in the Mu Us Desert, China, using microbial activity indicators, chloroform fumigation-extraction analysis, and high-throughput 16S rRNA gene sequencing.

Results

Members of the phyla Proteobacteria, Actinobacteria, Acidobacteria, Planctomycetes, Bacteroidetes, Chloroflexi, Firmicutes, and Gemmatimonadetes were dominant. Inter-shrub soil patch differed from under-shrub soil patch in soil bacterial composition, microbial enzyme activity, and biomass, but not in diversity. Soil collected in A. ordosica shrubland exhibited the highest microbial enzyme activity, biomass, and diversity. Shrub species had significant effects on community structure, primarily the relative abundance of Proteobacteria, Actinobacteria, and Bacteroidetes.

Conclusions

The results indicated that both shrub species and patch type had effects on soil microbial communities. In shrub-dominated desert ecosystems, spatial heterogeneity of soil nutrients and moisture might not be the main factors underlying variations in bacterial diversity. The different compositions of microbial communities in various shrublands provide a foundation for further research into the mechanisms of soil organic carbon accumulation.