This paper presents the feasibility of phenol removal from aqueous solutions by using microwaves activated spent coffee grounds.The activation of the coffee grounds made it possible to increase with 75% the quantity eliminated compared to the not activated coffee grounds.The results showed that the adsorption process was favourably fitted with the pseudo-second order kinetic model and the isotherm obeys to Langmuir model.The maximum amount of phenol adsorbed (7.35 mg/g) for optimal conditions was determined using an experimental factorial design 2³.
A bacterium, Pseudomonas aeruginosa (ATTC27853), was investigated for its ability to grow and to degrade phenol as sole carbon source, in aerobic batch culture.The parameters which affect the substrate biodegradation such as the adaptation of bacteria to phenol, the temperature, and the nature of the bacteria were investigated.The results show that for a range of temperature of 30 to 40°C, the best degradation of phenol for a concentration of 100mg/l was observed at 30°C.The regeneration of the bacterium which allows the reactivation of its enzymatic activity, shows that the degradation of 100 mg/ l of substrate at 30° C required approximately 50 hours with revivified bacteria, while it only starts after 72 hours for those no revivified.Adapted to increasing concentrations, allows the bacteria to degrade a substrate concentration of about 400mg/ l in less than 350 hours.A second part was consisted in the determination of a substrate degradation model using the factorial experiment design, as a function of temperature (30-40°C) and of the size of the inoculums (260.88 -521.76mg/l).The results were analyzed statistically using the Student's t-test, analysis of variance, and F-test.The value of R 2 (0.99872) and adjusted R 2 (0.9962) close to 1.0, verifies the good correlation between the observed and the predicted values, and provides the excellent relationship between the independent variables (factors) and the response (the time of the phenol degradation).F-value found above 200, indicates that the considered model is statistically significant.
Photorhabdus luminescens is an insect-pathogenic bacterium that forms a symbiosis with specific entomopathogenic nematodes. In this bacterium, a symbiosis-‘deficient’ phenotypic variant (known as the secondary variant or form II) arises at a low frequency during prolonged incubation. A knock-out mutant was generated of the regulator of a newly identified two-component regulatory system, designated AstR–AstS. Interestingly, this mutation altered the timing of phenotypic switching. Variant cells arose in the mutant strain several days before they did in the wild-type population, suggesting that AstRS is directly or indirectly involved in the genetic mechanism underlying variant cell formation. This mutation also affected motility and antibiotic synthesis. To identify AstRS-regulated genes, a comparative analysis using two-dimensional gel electrophoresis was performed. Seventeen proteins with modified synthesis in stationary phase were identified by mass spectrometry and shown to be involved in electron-transport systems, energy metabolism, iron acquisition and stress responses. The results imply that AstRS is involved in the adaptation of cells to the stationary phase, whilst negatively affecting the competitive advantage of form I cells. The link between AstRS-dependent stationary-phase adaptation and phenotypic variation is discussed.
Abstract Comparison of the proteomes of wild‐type Photorhabdus luminescens and its hcaR derivative, grown in insect hemolymph, showed that hcaR disruption decreased the production of toxins ( tcdA1 , mcf , and pirAB ) and proteins involved in oxidative stress response (SodA, AhpC, Gor). The disruption of hcaR did not affect growth rate in insects, but did delay the virulence of P. luminescens in Bombyx mori and Spodoptera littoralis larvae. This delayed virulence was associated with a lower toxemia rather than delay in bacteremia. The disruption of hcaR also increased bacterial sensitivity to hydrogen peroxide. A sodA mutant and an hcaR mutant had similar phenotypes in terms of sensitivity to hydrogen peroxide, virulence, toxin gene expression, and growth rate in insects. Thus, the two processes affected by hcaR disruption – toxemia and oxidative stress response – appear to be related. Besides, expression of toxin genes tcdA1 , mcf , and pirAB was decreased by paraquat challenge. We provide here the first demonstration of the importance of toxemia for P. luminescens virulence. Our results also highlight the power of proteomic analysis for detecting unexpected links between different, concomitant processes in bacteria.
ABSTRACT Pseudomonas aeruginosa is an opportunistic pathogen in human lungs, where its secretable LasB metalloproteinase can be a virulence factor. The urokinase-type plasminogen activator receptor (uPAR) participates in pericellular proteolysis and the adherence/migration of epithelial cells and leukocytes recruited during infection and shows functional regulation by various proteinases via limited endoproteolysis occurring within its three domains (D1 to D3). We thus examined the proteolytic activity of LasB on uPAR by using recombinant uPAR as well as uPAR-expressing, human monocytic, and bronchial epithelial cell lines. Protein immunoblotting and flow immunocytometry using a panel of domain-specific anti-uPAR antibodies showed that LasB is able to cleave uPAR both within the sequence linking D1 to D2 and at the carboxy terminus of D3. Comparison of LasB-producing and LasB-deficient bacterial strains indicated that LasB is entirely responsible for the uPAR cleavage ability of P. aeruginosa . Based on amino-terminal protein microsequencing and mass spectrometry analysis of the cleavage of peptides mimicking the uPAR sequences targeted by LasB, cleavage sites were determined to be Ala 84 -Val 85 and Thr 86 -Tyr 87 (D1-D2) and Gln 279 -Tyr 280 (D3). Such a dual cleavage of uPAR led to the removal of amino-terminal D1, the generation of a truncated D2D3 species, and the shedding of D2D3 from cells. This proteolytic processing of uPAR was found to (i) drastically reduce the capacity of cells to bind urokinase and (ii) abrogate the interaction between uPAR and the matrix adhesive protein vitronectin. The LasB proteinase is thus endowed with a high potential for the alteration of uPAR expression and functioning on inflammatory cells during infections by P. aeruginosa .
Abstract Following transmission to the vertebrate host, the protozoan parasite Leishmania donovani differentiates into the pathogenic amastigote stage that is adapted for intracellular survival. This developmental transition is induced by environmental factors including elevated temperature and acidic pH and is likely transduced by signaling cascades involving protein kinases and their downstream phosphoprotein substrates. These signaling networks are highly adapted to the specific nutritional and physiological requirements of the organism and thus studying Leishmania phosphorylation may allow important insight into the parasite‐specific biology. We used a gel‐based approach to investigate qualitative and quantitative changes of the phosphoproteome of the major L. donovani life cycle stages. Phosphoproteins were purified by immobilized metal affinity chromatography (IMAC), separated by IEF and SDS‐PAGE using pH 4–7 IPG immobiline strips, revealed by fluorescent multiplex staining, and identified by MALDI‐MS and MS/MS. Our analysis allowed us to establish a first repertoire of the Leishmania phosphoproteome and to identify phosphoproteins implicated in stress‐ and heat shock response, RNA/protein turnover, metabolism, and signaling.
Structures of the UCCG and UGCG tetraloops formed in octamer ribonucleotidic hairpin sequences, i.e., 5'-r[GC(UCCG)GC]-3' and 5'-r[GC(UGCG)GC]-3', have been studied in aqueous solution by methods of optical spectroscopy. UV absorption melting profiles of these short hairpins, containing only two closing GC base pairs in the stem, are consistent with a monophasic, completely reversible order-to-disorder transition and clearly confirm their unusual structural stability (with Tm congruent with 50 degrees C). To establish structural characteristics of these tetraloops, Raman and FTIR spectroscopies have been used and vibrational conformation markers arising from the phosphate backbone and various nucleosides have been analyzed. They have been assigned on the basis of known unambiguous vibrational markers established for DNA and RNA chains. Surprisingly, they are easily transferable to short oligonucleotidic sequences. Intensities and wavenumbers of these conformation markers have been monitored in the 0-70 degrees C temperature range, i.e., in going from an ordered to a disordered structure. The main structural features of the UCCG and UGCG tetraloops are similar to those previously found in the UUCG and UACG tetraloops by means of NMR and vibrational spectroscopies, except those of the second nucleosides of the tetraloops (rC and rG, respectively) which adopt a 3'-endo/anti rather than a 2'-endo/anti conformation.
