Metagenomic insights into strategies of carbon conservation and unusual sulfur biogeochemistry in a hypersaline Antarctic lake

Organic Lake is a shallow, marine-derived hypersaline lake in the Vestfold Hills, Antarctica that has the highest reported concentration of dimethylsulfide (DMS) in a natural body of water. To determine the composition and functional potential of the microbial community and learn about the unusual sulfur chemistry in Organic Lake, shotgun metagenomics was performed on size-fractionated samples collected along a depth profile. Eucaryal phytoflagellates were the main photosynthetic organisms. Bacteria were dominated by the globally distributed heterotrophic taxa Marinobacter, Roseovarius and Psychroflexus. The dominance of heterotrophic degradation, coupled with low fixation potential, indicates possible net carbon loss. However, abundant marker genes for aerobic anoxygenic phototrophy, sulfur oxidation, rhodopsins and CO oxidation were also linked to the dominant heterotrophic bacteria, and indicate the use of photo- and lithoheterotrophy as mechanisms for conserving organic carbon. Similarly, a high genetic potential for the recycling of nitrogen compounds likely functions to retain fixed nitrogen in the lake. Dimethylsulfoniopropionate (DMSP) lyase genes were abundant, indicating that DMSP is a significant carbon and energy source. Unlike marine environments, DMSP demethylases were less abundant, indicating that DMSP cleavage is the likely source of high DMS concentration. DMSP cleavage, carbon mixotrophy (photoheterotrophy and lithoheterotrophy) and nitrogen remineralization by dominant Organic Lake bacteria are potentially important adaptations to nutrient constraints. In particular, carbon mixotrophy relieves the extent of carbon oxidation for energy production, allowing more carbon to be used for biosynthetic processes. The study sheds light on how the microbial community has adapted to this unique Antarctic lake environment.     

Transient quinonimines and 1,4-benzothiazines of pheomelanogenesis: new pulse radiolytic and spectrophotometric evidence.

Biosynthetic and model in vitro studies have shown that pheomelanins, the distinctive pigments of red human hair, arise by oxidative cyclization of cysteinyldopas mainly 5-S-cysteinyldopa (1) via a critical o-quinonimine intermediate, which rearranges to unstable 1,4-benzothiazines. To get new evidence for these labile species, fast time resolution pulse radiolytic oxidation by dibromide radical anion of a suitable precursor, the dihydro-1,4-benzothiazine-3-carboxylic acid 7 was performed in comparison with that of 1. In the case of 7, dibromide radical anion oxidation leads over a few microseconds (k = 2.1 x 10(9) M(-1) s(-1)) to a phenoxyl radical (lambda(max) 330 nm, epsilon = 6300 M(-1) cm(-1)) which within tens of milliseconds gives rise with second-order kinetics (2k = 2.7 x 10(7) M(-1) s(-1)) to a species exhibiting an absorption maximum at 540 nm (epsilon = 2200 M(-1) cm(-1)). This was formulated as the o-quinonimine 3 arising from disproportionation of the initial radical. The quinonimine chromophore is converted over hundreds of milliseconds (k = 6.0 s(-1)) to a broad maximum at around 330 nm interpreted as due to a 1,4-benzothiazine or a mixture of 1,4-benzothiazines, which as expected are unstable and subsequently decay over a few seconds (k = 0.5 s(-1)). Interestingly, the quinonimine is observed as a labile intermediate also in the alternative reaction route examined, involving cyclization of the o-quinone (lambda(max) 390 nm, epsilon = 6900 M(-1) cm(-1)) arising by disproportionation (2k = 1.7 x 10(8) M(-1) s(-1)) of an o-semiquinone (lambda(max) 320 nm, epsilon = 4700 M(-1) cm(-1)) directly generated by dibromide radical anion oxidation of 1. Structural formulation of the 540 nm species as an o-quinonimine was further supported by rapid scanning diode array spectrophotometric monitoring of the ferricyanide oxidation of a series of model dihydrobenzothiazines.     

Pictet-Spengler condensation of the antiparkinsonian drug L-DOPA with D-glyceraldehyde. Opposite kinetic effects of Fe3+ and Cu2+ ions and possible implications for the origin of therapeutic side effects

In 0.05 M phosphate buffer, pH 7.4, and at 37 degrees C. L-DOPA, a widely used antiparkinsonian drug, reacted smoothly with D-glyceraldehyde to afford diastereoisomeric (1R, 1'S,3S)-3-carboxy-1-(1',2'-dihydroxyethyl)-6,7-dihydroxy-1,2,3,4- tetrahydroisoquinoline (1) and (1S,1'5S,3S)-3-carboxy-1-(1',2'-dihydroxyethyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (2) in an approx. 3:2 ratio. The prevalent formation of 1 over 2 reflects stereoselective cyclisation of a transient Schiff base in accord with the Felkin-Anh model. Fe3+ ions, present at relatively high levels in parkinsonian brains, markedly accelerated formation of 1 and 2, whereas Cu2+ decreased the reaction rate, due apparently to different sites of chelate formation between L-DOPA and the metal ions. Both metal ions markedly decreased the stereoselectivity of the reaction. Product 1 exhibited chelating properties toward metal ions comparable or stronger than those of L-DOPA. These results throw new light on the effects of transition metal ions on the Pictet-Spengler reaction and suggest a possible role of tetrahydroisoquinoline products from L-DOPA and carbohydrate metabolites in the severe side effects of the drug.     

Effects of essential oil formulations on Ceratitis capitata Wied. (Dipt., Tephritidae) adult flies

The effects on adult Ceratitis capitata of the ingestion of formulations containing different concentrations of some essential oils were examined. The bioassays were carried out using groups of C. capitata adults fed for 3 days with formulations containing a known concentration (0.25%, 0.5%, 1.0%) of essential oils. The oils, of different chemical composition, were obtained by steam distillation from aromatic plants collected during the balmy period. The essential oils of Rosmarinus officinalis and Salvia officinalis , which are rich in monoterpenic hydrocarbons and monoterpenic ketones, respectively, showed poor activity, whereas the oils of Cinnamomum zeylanicum and Thymus sp. showed a marked toxic effects (over 90% mortality after 72 h). This could be explained by the activity of cinnamic aldehyde (about 80% of the Cinnamomum oil) and carvacrol (68% of Th. capitatus oil and about 45% of Th. herba barona oil). The first consequence of ingesting even small quantities of essential oils was a depressive effect on the nervous system. Dissection of dead flies showed marked differences compared with the controls and microscopic examination revealed anomalies in the gut region.     

Biocides formulation of essential oils having antimicrobial activity

Essential oils of fennel, peppermint, caraway, eucalyptus, geranium and lemon were tested for their antimicrobial activities against some plant pathogenic micro-organisms (Fusarium oxysporum, Alternaria alternate, Penicilium italicum Penicilium digitatum and Botyritus cinerea). Essential oils of fennel, peppermint, caraway were selected as an active ingredient for the formulation of biocides due to their efficiency in controlling the tested micro-organisms. Successful emulsifiable concentrates (biocides) were prepared from these oils using different emulsifiers (Emulgator B.L.M. Tween20 and Tween80) and different fixed oils (sesame, olive, cotton and soybean oils). Physico-chemical properties of the formulated biocide (spontaneous emulsification, emulsion stability test, cold stability and heat stability tests as well as viscosity, surface tension and pH) were measured. The prepared biocides were ready to be tested for application in a future work as a safe pesticide against different pathogens.     

A correlation between BCL-2 modifying factor,p53 and livin gene expressions in cancer colon patients

Accumulating evidence has revealed that livin gene and BCL-2 modifying factor (BMF) gene are closely associated with the initiation and progression of colon carcinoma by activating or suppressing multiple malignant processes. Those genes that can detect colon - cancer are a promising approach for cancer screening and diagnosis. This study aimed to evaluate correlation between livin, BMF and p53 genes expression in colon cancer tissues of patients included in the study, and their relationship with clinicopathological features and survival outcome in those patients. In this study, 50 pathologically diagnosed early cancer colon patients included and their tissue biopsy with 50 matched adjacent normal tissue, and 50 adenoma tissue specimens were analyzed for livin gene and BMF gene expressions using real time PCR. The relationship of those genes expressions with clinicopathological features, tumor markers, Time to Progression and overall survival for those patients were correlated in cancer colon group. In this study, there was a significant a reciprocal relationship between over expression of livin gene and down regulation of BMF and p53 genes in colon cancer cells. Livin mRNA was significantly higher, while BMF and p53 mRNA were significantly lower in colorectal cancer tissue compared to benign and normal colon tissue specimens (P < 0.001), however, this finding was absent between colon adenomas and normal mucosa. There was a significant association between up regulation of livin and down regulation of BMF and p53 expressions with more aggressive tumor (advanced TNM stage), rapid progression with metastasis and decreased overall survival in cancer colon patients, hence these genes can serve as significant prognostic markers of poor outcome in colon cancer patients. This work highlights the role of livin, BMF and p53 genes in colorectal tumorigenesis and the applicability of using those genes as a diagnostic and prognostic markers in patients with colon carcinoma and as a good target for cancer colon treatment in the future.     

A molecular dynamics study of reovirus attachment protein sigma1 reveals conformational changes in sigma1 structure

Molecular dynamics simulations were performed using the recently determined crystal structure of the reovirus attachment protein, sigma1. These studies were conducted to improve an understanding of two unique features of sigma1 structure: the protonation state of Asp(345), which is buried in the sigma1 trimer interface, and the flexibility of the protein at a defined region below the receptor-binding head domain. Three copies of aspartic acids Asp(345) and Asp(346) cluster in a solvent-inaccessible and hydrophobic region at the sigma1 trimer interface. These residues are hypothesized to mediate conformational changes in sigma1 during viral attachment or cell entry. Our results indicate that protonation of Asp(345) is essential to the integrity of the trimeric structure seen by x-ray crystallography, whereas deprotonation induces structural changes that destabilize the trimer interface. This finding was confirmed by electrostatic calculations using the finite difference Poisson-Boltzmann method. Earlier studies show that sigma1 can exist in retracted and extended conformations on the viral surface. Since protonated Asp(345) is necessary to form a stable, extended trimer, our results suggest that protonation of Asp(345) may allow for a structural transition from a partially detrimerized molecule to the fully formed trimer seen in the crystal structure. Additional studies were conducted to quantify the previously observed flexibility of sigma1 at a defined region below the receptor-binding head domain. Increased mobility was observed for three polar residues (Ser(291), Thr(292), and Ser(293)) located within an insertion between the second and third beta-spiral repeats of the crystallized portion of the sigma1 tail. These amino acids interact with water molecules of the solvent bulk and are responsible for oscillating movement of the head of approximately 50 degrees during 5 ns of simulations. This flexibility may facilitate viral attachment and also function in cell entry and disassembly. These findings provide new insights about the conformational dynamics of sigma1 that likely underlie the initiation of the reovirus infectious cycle.