Long-term biological hydrogen production by agar immobilized Rhodobacter capsulatus in a sequential batch photobioreactor

In this study, agar immobilization technique was employed for biological hydrogen production using Rhodobacter capsulatus DSM 1710 (wild type) and YO3 (hup-mutant) strains in sequential batch process. Different agar and glutamate concentrations were tested with defined nutrient medium. Agar concentration 4% (w/v) and 4 mM glutamate were selected for bacterial immobilization in terms of rate and longevity of hydrogen production. Acetate concentration was increased from 40 to 60—100 and 60 mM gave best results with both bacterial strains immobilized in 4% (w/v) agar. Cell concentration was increased from 2.5 to 5 mg dcw mL⁻¹ agar and it was found that increasing cell concentration of wild-type strain caused decrease in yield and productivity while these parameters improved by increasing cell concentration of mutant strain. Also, the hydrogen production time has extended from 17 days up to 60 days according to the process conditions and parameters. Hydrogen production by immobilized photosynthetic bacteria is a convenient technology for hydrogen production as it enables to produce hydrogen with high organic acid concentrations comparing to suspended cultures. Besides, immobilization increases the stability of the system and allowed sequential batch operation for long-term application.

     

Biochemical and morphological characteristics of selenite-induced apoptosis in human hepatoma hep G2 cells

Selenium is a cellular growth inhibitor in many mammary tumor cells. To comprehend the mechanism for the selenium-induced cell death, we examined the effects of sodium selenite, which has been one of the most extensively investigated selenium compounds, in human hepatoma Hep G2 cells. Cell viability gradually decreased after treatment with sodium selenite within the concentration range of 10–50 μM. Low (10 μM) selenite has shown a high-percentage laddering pattern compared to the high (25 μM) cytotoxic selenium concentration in agarose gel electrophoresis. G₂M-phase enrichment was also concentration dependent. The most consistent transmission electron microscopic finding was the existence of large lysosomes. Based on these data, we hypothesize that sodium selenite predominantly shows its apoptotic effect over hydrogen selenite accumulation.     

Protein degradation in lysosomes from chemically induced malignant rat hepatoma

Hepatocellular carcinomas were induced in rat liver by exposing the animals to diethylnitrosamine and 2-acetylaminofluorene in combination with partial hepatectomy. Light and electron microscopy demonstrated that the general appearance of the tumour tissue was that of highly differentiated malignant hepatocytic cells. Morphometrically there was a difference between normal and malignant cells in that the entire lysosomal apparatus was twice as large in malignant cells as in normal cells. This was mainly due to an increase in the fractional volume of autophagic vacuoles. A total lysosomal fraction (dense bodies and autophagic vacuoles) was isolated and characterized from both control and tumour livers. Marker enzyme analysis showed that the lysosomal enzyme activities were significantly lower in malignant liver tissue. Injection of leupeptin, an inhibitor of cathepsins B, H, and L, into rats did not increase the fractional volume of autophagic vacuoles in tumour tissue as much as in normal liver tissue. The proteolytic rate was lower in the lysosomal fraction from hepatoma cell tissue compared with the lysosomal fraction from normal cell tissue. This could conceivably be due to the lower activities of lysosomal enzymes. However, if the recovery of lysosomes is taken into account no clear-cut difference in lysosomal proteolysis between control and malignant liver tissue was noted. Accordingly, in malignant liver tissue a proteolytic balance is obtained characterized by an increased fractional volume of AVs and lower rate of protein degradation in individual lysosomes.     

Molecular cloning of a Pseudomonas syringae pv. syringae gene cluster that enables Pseudomonas fluorescens to elicit the hypersensitive response in tobacco plants.

A cosmid clone isolated from a genomic library of Pseudomonas syringae pv. syringae 61 restored to all Tn5 mutants of this strain studied the ability to elicit the hypersensitive response (HR) in tobacco. Cosmid pHIR11 also enabled Escherichia coli TB1 to elicit an HR-like reaction when high levels of inoculum (10(9) cells per ml) were infiltrated into tobacco leaves. The cosmid, which contains a 31-kilobase DNA insert, was mobilized by triparental matings into Pseudomonas fluorescens 55 (a nonpathogen that normally causes no plant reactions), P. syringae pv. syringae 226 (a tomato pathogen that causes the HR in tobacco), and P. syringae pv. tabaci (a tobacco pathogen that causes the HR in tomato). The plant reaction phenotypes of all of the transconjugants were altered. P. fluorescens(pHIR11) caused the HR in tobacco and tomato leaves and stimulated an apparent proton influx in suspension-cultured tobacco cells that was indistinguishable from the proton influx caused by incompatible pathogenic pseudomonads. P. syringae pv. tabaci(pHIR11) and P. syringae pv. syringae 226(pHIR11) elicited the HR rather than disease symptoms on their respective hosts and were no longer pathogenic. pHIR11 was mutagenized with TnphoA (Tn5 IS50L::phoA). One randomly chosen mutant, pHIR11-18, no longer conferred the HR phenotype to P. fluorescens. The mutation was marker-exchanged into the genomes of P. syringae pv. syringae strains 61 and 226. The TnphoA insertions in the two pseudomonads abolished their ability to elicit any plant reactions in all plants tested. The results indicate that a relatively small portion of the P. syringae genome is sufficient for the elicitation of plant reactions.     

Isolation and characterization of the Schizosaccharomyces pombe rad3 gene, involved in the DNA damage and DNA synthesis checkpoints.

We have cloned the Schizosaccharomyces pombe rad3 gene which is involved in G2 arrest following DNA damage, and in the dependence of mitosis on the completion of DNA replication. The gene was cloned by complementation of the sensitivity to UV light and gamma rays of the rad3-136 mutant with an Sz. pombe genomic library. Sublocalization of the complementing activity and sequencing of the clone identified an intronless 3210-bp open reading frame capable of encoding a 1070-amino acid protein with an M(r) of 121974. The rad3 gene is a new gene with no homologs in existing sequence databases. The gene is poorly expressed, with a codon bias index of -0.01. A disruption mutant affecting the coding region was only slightly more sensitive to UV light than the original rad3-136 mutant. The rad3 gene was mapped to NotI fragment C on chromosome II.     

Induction of Parthenocarpy in Rosa Canina and Diospyros Lotus by the application of growth regulators

The effect of indole-3-acetic acid (IAA) and gibberellic acid (GA₃) applications on parthenocarpic fruit set in Rosa canina and Diospyros lotus was investigated. GA₃ induced parthenocarpic fruit set in both plants, but IAA only in D. lotus. Maturation of seedless fruits was earlier than the seeded fruits. GA₃ caused a decrease in the fresh mass and size of both fruits. IAA induced an increase in the fresh mass and size in parthenocarpic fruit of D. lotus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Protective effects of the nuclear factor kappa B inhibitor pyrrolidine dithiocarbamate in bladder ischemia–reperfusion injury in rats

The aim of the present study was to evaluate the protective effects of the NF-кB inhibition with pyrrolidine-dithiocarbamate (PDTC) in ischemia–reperfusion (I/R) injury in the rat bladder. Twenty-four Sprague-Dawley male rats were divided into three groups. Group I; (n = 8) control, group II; (n = 8) I/R group; group III (n = 8) I/R and PDTC treatment. Superoxide dismutase (SOD), catalase (CAT), and gluatathione-S-transferase (GST) enzymes was studied in bladder tissue. Lipid peroxidation (as TBARS) levels in tissue homogenate were measured with thiobarbituric acid reaction. All the slides were stained with NF-кB, p53 and HSP60 immunohistochemistry for detection genome destruction and tissue stress, respectively. Our results show that the mean TBARS levels were significantly higher in group II (p < 0.05). The TBARS levels were significantly decreased in group III compared with the group II (p < 0.05). CAT, SOD and GST activities were decreased in group II, but these enzymes levels were significantly increased in group III according to the group II (p < 0.05). Under microscopic evaluation NF-кB expression increased significantly in group II compared to the group I (p < 0.05) and then decreased in group III (p < 0.05). HSP60 and p53 expression in group II was increased significantly compared with group I. Under microscopic evaluation we detected that HSP60 and p53 expression was increased significantly in group II compared with group I. In group III PDTC administration was decreased the HSP60 and p53 expression, this difference was statistically significant (p < 0.05). The results of the present study have demonstrated that NF-кB inhibition with PDTC protects and provides beneficial effects on ischemia/reperfusion stress related bladder tissue destruction.     

Role of pfkA and General Carbohydrate Catabolism in Seed Colonization by Enterobacter cloacae

Enterobacter cloacae A-11 is a transposon mutant of strain 501R3 that was deficient in cucumber spermosphere colonization and in the utilization of certain carbohydrates (D. P. Roberts, C. J. Sheets, and J. S. Hartung, Can. J. Microbiol. 38:1128–1134, 1992). In vitro growth of strain A-11 was reduced or deficient on most carbohydrates that supported growth of strain 501R3 but was unaffected on fructose, glycerol, and all amino acids and organic acids tested. Colonization by strain A-11 was significantly reduced (P ≤ 0.05) for cucumber and radish seeds compared to that of strain 501R3, but colonization of pea, soybean, sunflower, and sweet corn seeds was not reduced. Pea seeds released several orders of magnitude more total carbohydrates and amino acids than cucumber and radish seeds and approximately 4,000-fold more fructose. Fructose was the only carbohydrate detected in the seed exudates which supported wild-type levels of in vitro growth of strain A-11. Soybean, sunflower, and sweet corn seeds also released significantly greater amounts of fructose and total carbohydrates and amino acids than cucumber or radish seeds. The exogenous addition of fructose to cucumber and radish seeds at quantities similar to the total quantity of carbohydrates released from pea seeds over 96 h increased the populations of strain A-11 to levels comparable to those of strain 501R3 in sterile sand. Molecular characterization of strain A-11 indicated that the mini-Tn5 kanamycin transposon was inserted in a region of the genome with significant homology to pfkA, which encodes phosphofructo kinase. A comparison of strain A-11 with Escherichia coli DF456, a known pfkA mutant, indicated that the nutritional loss phenotypes were identical. Furthermore, the pfkA homolog cloned from E. cloacae 501R3 complemented the nutritional loss phenotypes of both E. coli DF456 and E. cloacae A-11 and restored colonization by strain A-11 to near wild-type levels. These genetic and biochemical restoration experiments provide strong evidence that the quantities of reduced carbon sources found in seed exudates and the ability of microbes to use these compounds play important roles in the colonization of the spermosphere.