Genomic structure and promoter analysis of the dsz operon for dibenzothiophene biodesulfurization from Gordonia alkanivorans RIPI90A

The bacterium Gordonia alkanivorans RIPI90A has been previously reported as dibenzothiophene-desulfurizing strain. The present study provides a complete investigation of the dsz operon including dsz promoter analysis from desulfurization competent strain belonging to the genus Gordonia. PCR was used to amplify the dszABC genes and adaptor ligation-based PCR-walking strategy used to isolate the dsz promoter. Unlike the dsz operon of Rhodococcus erythropolis, the operon of RIPI90A was located on chromosome. Despite the remarkably high homology between dsz genes of G. alkanivorans RIPI90A and R. erythropolis IGST8, promoter sequences of the strains were not very similar. The dsz promoter of G. alkanivorans RIPI90A shows only 52.5% homology to that of R. erythropolis IGTS8 and Gordonia nitida. Deletion analysis of the dsz promoter from RIPI90A using luciferase as a reporter gene revealed that the dsz promoter was located in regions from −156 to −50.     

Identities of Epilithic Hydrocarbon-Utilizing Diazotrophic Bacteria from the Arabian Gulf Coasts, and Their Potential for Oil Bioremediation Without Nitrogen Supplementation

Gravel particles from four sites along the Arabian Gulf coast in autumn, winter, and spring were naturally colonized with microbial consortia containing between 7 and 400 × 10² cm⁻² of cultivable oil-utilizing bacteria. The 16S rRNA gene sequences of 70 representatives of oil-utilizing bacteria revealed that they were predominantly affiliated with the Gammaproteobacteria and the Actinobacteria. The Gammaproteobacteria comprised among others, the genera Pseudomonas, Pseudoalteromonas, Shewanella, Marinobacter, Psychrobacter, Idiomarina, Alcanivorax, Cobetia, and others. Actinobacteria comprised the genera Dietzia, Kocuria, Isoptericola, Rhodococcus, Microbacterium, and others. In autumn, Firmicutes members were isolated from bay and nonbay stations while Alphaproteobacteria were detected only during winter from Anjefa bay station. Fingerprinting by denaturing gradient gel electrophoresis of amplified 16S rRNA genes of whole microbial consortia confirmed the culture-based bacterial diversities in the various epilithons in various sites and seasons. Most of the representative oil-utilizing bacteria isolated from the epilithons were diazotrophic and could attenuate oil also in nitrogen-rich (7.9–62%) and nitrogen-free (4–54%) cultures, which, makes the microbial consortia suitable for oil bioremediation in situ, without need for nitrogen supplementation. This was confirmed in bench-scale experiments in which unfertilized oily seawater was bioremediated by epilithon-coated gravel particles.     

DNA end resection by CtIP and exonuclease 1 prevents genomic instability

End resection of DNA-which is essential for the repair of DNA double-strand breaks (DSBs) by homologous recombination-relies first on the partnership between MRE11-RAD50-NBS1 (MRN) and CtIP, followed by a processive step involving helicases and exonucleases such as exonuclease 1 (EXO1). In this study, we show that the localization of EXO1 to DSBs depends on both CtIP and MRN. We also establish that CtIP interacts with EXO1 and restrains its exonucleolytic activity in vitro. Finally, we show that on exposure to camptothecin, depletion of EXO1 in CtIP-deficient cells increases the frequency of DNA-PK-dependent radial chromosome formation. Thus, our study identifies new functions of CtIP and EXO1 in DNA end resection and provides new information on the regulation of DSB repair pathways, which is a key factor in the maintenance of genome integrity.     

In vitro protoscolicidal effects of hypertonic glucose on protoscolices of hydatid cyst

To evaluate the protoscolicidal effects of various concentrations of hypertonic glucose, live protoscolices of sheep were exposed to 10%, 15%, 25% and 50% glucose solutions. Cetrimide (0.5%), silver nitrate (0.5%) and hypertonic saline (20%) were used as positive controls, while physiological saline was used as a negative control. After 1, 2 and 5 min, the protoscolicidal effects were determined by 1% eosin. A 25% glucose solution had no significant protoscolicidal effect. However, a 50% glucose solution revealed higher protoscolicidal effect than 0.5% silver nitrate but weaker effect than 0.5% cetrimide; the effect was comparable with that of 20% hypertonic saline. The results showed that hypertonic glucose solution is highly effective in killing protoscolices of Echinococcus granulosus in vitro.     

Partial and full agonism in endomorphin derivatives: comparison by null and operational model

The partial mu-opioid receptor pool inactivation strategy in isolated mouse vas deferens was used to determine partial agonism of endomorphins and their analogs (endomorphin-1-ol, 2',6'-dimethyltyrosine (Dmt)-endomorphin-1, endomorphin-2-ol and (D-Met2)-endomorphin-2) using morphine, normorphine, morphiceptin, (D-Ala2,MePhe4,Gly5-ol)-enkephalin (DAMGO) and its amide (DAMGA) as reference opioid agonists. Agonist affinities (KA) and efficacies were assessed both by the "null" and the "operational" method. The KA values determined by the two methods correlated significantly with each other and also with the displacing potencies against 3H-naloxone in the receptor binding assay in the presence of Na+. DAMGO and DAMGA were full agonist prototypes, morphine, endomorphin-1, endomorphin-1-ol, Dmt-endomorphin-1, endomorphin-2-ol and (D-Met2)-endomorphin-2 were found by both methods to be partial agonists whereas the parameters for normorphine, morphiceptin and endomorphin-2 were intermediate.     

Biochemical study of the anti-diabetic action of the Egyptian plants Fenugreek and Balanites

Fenugreek and Balanites are two plants commonly used in Egyptian folk medicine as hypoglycemic agents. In the present study, the effects of 21 days oral administration of Fenugreek seed and Balanites fruit extracts (1.5 g/kg bw) on the liver and kidney glycogen content and on some key liver enzymes of carbohydrate metabolism in STZ-diabetic rats were studied. In addition, the effects of these two plant extracts on the intestinal α-amylase activity in vitro and starch digestion and absorption in vivo were also examined. Results indicated that single injection of STZ (50 mg/kg bw) caused 5-folds increase in the blood glucose level, 80% reduction in serum insulin level, 58% decrease in liver glycogen and 7-folds increase in kidney glycogen content as compared to the normal levels. The activity of glucose-6-phosphatase was markedly increased, whereas, the activities of both glucose-6-phosphate dehydrogenase and phospho-fructokinase were significantly decreased in the diabetic rat liver. Administration of Fenugreek extract to STZ-diabetic rats reduced blood glucose level by 58%, restored liver glycogen content and significantly decreased kidney glycogen as well as liver glucose-6-phosphatase activity. Meanwhile, Balanites extract reduced blood glucose level by 24% and significantly decreased liver glucose-6-phosphatase activity in diabetic rats. On the other hand, our results demonstrated that both the Fenugreek and Balanites extracts were able to in vitro inhibit α-amylase activity in dose-dependent manner. Fenugreek was more potent inhibitor than Balanites. This inhibition was reversed by increasing substrate concentration in a pattern which complies well with the effect of competitive inhibitors. Furthermore, this in vitro inhibition was confirmed by in vivo suppression of starch digestion and absorption induced by both plant extracts in normal rats. These findings suggest that the hypoglycemic effect of Fenugreek and Balanites is mediated through insulinomimetic effect as well as inhibition of intestinal α-amylase activity.     

Host protein interactions with enteropathogenic Escherichia coli (EPEC): 14-3-3tau binds Tir and has a role in EPEC-induced actin polymerization

Enteropathogenic Escherichia coli (EPEC) cause infantile diarrhoea and are characterized by their ability to produce attaching and effacing lesions on the surface of intestinal epithelial cells. EPEC employ a filamentous type III secretion system to deliver effector molecules that subvert mammalian cell function to generate actin- and cytokeratin-rich pedestals beneath adherent bacteria. Tir is a major effector protein that is delivered to the plasma membrane of the eukaryotic cell where it acts as the receptor for the bacterial adhesin intimin. Host cell proteins that are recruited to the site of intimate attachment include focal adhesion and cytoskeletal proteins that contribute to pedestal formation. We have used Tir as bait in a yeast two-hybrid screen to identify the protein 14-3-3tau as a binding partner. 14-3-3 proteins are a family of adaptor proteins that modulate protein function in all eukaryotic cells. Here we demonstrate that the tau isoform (also known as theta) of 14-3-3 can bind specifically to Tir in a phosphorylation-independent manner, and that the interaction occurs during the infection process by co-immunoprecipitation of the partners from infected HeLa cell extracts. 14-3-3tau is recruited to the site of the pedestal (3 h after infection) and can decorate attached EPEC in the later stages of the infection process (5-7 h). Pedestal formation can be impaired by depletion of cellular 14-3-3tau using small interfering RNAs. This study indicates a direct functional role for the 14-3-3tau:Tir interaction and is the first to demonstrate the association of a host protein with the surface of EPEC.     

Key components of the fission machinery are interchangeable

Brefeldin-A ADP-ribosylated substrate (BARS) and dynamin function in membrane fission in distinct intracellular transport pathways, but whether their functions are mechanistically similar is unclear. Here, we show that ARFGAP1, a GTPase-activating protein (GAP) for ADP-ribosylation factor 1 (ARF1), couples to either BARS or endophilin B for vesicle formation by the coat protein I (COPI) complex - a finding that reveals an unanticipated mechanistic flexibility in mammalian COPI transport. Because dynamin is coupled to endophilin A in vesicle formation by the clathrin-coat complex, our finding also predicts that dynamin and ARF GAPs are likely to be functional counterparts in membrane fission among different transport pathways that connect intracellular membrane compartments.     

First among equals: competition between genetically identical cells

Competition between genetically identical organisms is considered insignificant in evolutionary theory because it is presumed to have little selective consequence. We argue that competition between genetically identical cells could improve the fitness of a multicellular organism by directing fitter cells to the germ line or by eliminating unfit cells, and that cell-competition mechanisms have been conserved in multicellular organisms. We propose that competition between genetically identical or highly similar units could have similar selective advantages at higher organizational levels, such as societies.