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In this study, the biosorption ability of various potentially toxic elements from phosphate-processing effluent (PPE) using the indigenous bacterium Serratia rubidaea NCTC12971 immobilized in Ca-alginate beads was investigated. The experimental data analyzed by the Langmuir isotherm revealed that the optimum dose of 2 g·100 ml

Bioremediation using microorganisms have become innovative efficient tools for detoxifying a wide variety of urban and industrial wastewaters. In this study, we investigated for the first time the ...

Eleven bacterial strains, isolated from various Tunisian biotopes, were characterized for their lignin degradation activities and were screened for Indigo Carmine (IC) decolorization for the first time. Results revealed that these isolated strains were able to decolorize IC. Based on this property, the newly isolates crude filtrates (NICF) showed that eight ones prove the effectiveness for IC degradation (100 mg). More than 80% of IC could be decolorized within 12 h under non-optimised conditions. The UV–Visible absorption spectra and FT-IR analysis of the degradation products showed an IC decolorization and/or transformation, proving the enzyme’s role in dye decolorization. Furthermore, the phytotoxicity and the cytotoxicity using Vero and erythrocyte cells were performed to evaluate the acute toxicity of the treated and untreated dye. The results showed that some NICF can decrease and sometimes detoxify IC. In fact, NICF decolorize the toxic IC into non-toxic products. These NICF, acting as powerful tools, could be effectively used to decolorize and to bioremediate rich-dye-textile effluents and found worthy of investigation for potential applications in restoration work and other biotechnological uses.

Soil contamination by heavy metals through the application of a phosphate fertilizer is a key issue for sustainable agriculture. Among contaminants, cadmium (Cd) is considered the most hazardous to human beings’ health and the surrounding environment. X-ray diffraction (XRD), combined with binocular mineralogical analysis and chemical analysis, was used to determine the C(I) and C(II) layers’ composition. In the C(II) (+71 µm)-size fraction, the presence of carbonate-fluorapatite, illite, and montmorillonite was revealed, whereas in the C(I) (−71 µm)-size fraction, carbonate-fluorapatite, calcite, quartz, sanidine, clinoptilolite, and taramovite were identified. The P2O5 and CaO contents were greater in the C(II) layer than that in the C(I) layer, whereas SiO2, MgO, CO2, Cd, Zn, and COrg were higher in the C(I) layer than that in the C(II) layer. The bioleaching of Cd from phosphate rock samples from the Kef Eddour deposit was investigated using three bacterial strains isolated from the local phosphate environment. A decrease in cell viability was noticed when the phosphate C(I) and C(II) samples showed toxicity in the samples. In addition, the isolated bacteria, which were initially moderately hydrophobic, changed to strongly hydrophobic. The use of the consortium (S1 + S2 + S3) was the most powerful combination to reduce the Cd content, which increased from 13.31% to 29.07% using S3 and the consortium (S1 + S2 + S3), respectively, when the C(II) (+71 µm)-size fraction sample was added to the medium. The same result was shown when the C(I) (−71 µm)-size fraction sample was used. The isolated strains could be used as a biological tool for bioleaching.

Effluents discharged by poultry meat industries are heavily polluted with raw materials, such as fat, blood residues, and proteins. Thus, untreated effluents directly discharged into the environment may constitute a public health threat. This study aims to evaluate the bacterial diversity of three water qualities: industrial poultry wastewater (PWW), tap water (TW), and PWW diluted with TW (50 : 50) (V/V) (TWPWW) by the combination of culture-independent and culture-dependent approaches. The total bacterial DNA was extracted using phenol/chloroform method. The hypervariable 16S rRNA region V3-V5 was amplified by PCR using universal primers. The amplicons were separated by vertical electrophoresis on a polyacrylamide gel of increasing denaturing gradient according to their richness in GC bases. Selected bands were reamplified and sequenced. Pure isolated bacteria from nutrient agar medium were characterized according to their morphological and biochemical characteristics. Genomic DNA from pure strains was extracted by boiling method, and a molecular amplification of the 16S–23S ITS region of the 16S rRNA gene was performed using the universal primers. Selected isolates were identified by sequencing. Results showed a high bacterial load and diversity in PWW in comparison with TW and TWPWW. A collection of 44 strains was obtained, and 25 of them were identified by sequencing. Proteobacteria represented 76% of isolated bacteria Gamma-Proteobacteria was the predominate isolate (68%). Other isolates were Firmicutes (8%), Bacteroidetes (12%), and Actinobacteria (8%). These isolates belong to different genera, namely, Pseudomonas, Acinetobacter, Proteus, Empedobacter, Corynebacterium, Enterobacter, Comamonas, Frondibacter, Leclercia, Staphylococcus, Atlantibacter, Klebsiella, and Microbacterium.

The aim of the present study is to isolate, characterize and identify a novel strain ZC from the Metlaoui phosphate laundries wastewater (MPLW). The chemical characterization of this phosphate rich effluent showed an alkaline pH and is saline, highly turbid and rich in suspended matter and total solids. The MPLW samples were loaded with potentially toxic metals, presented in decreasing order as follows: magnesium (5655 mg L−1), potassium (45 mg L−1), lead (1 mg L−1), iron (0.7 mg L−1), cadmium (0.5 mg L−1), copper (0.3 mg L−1) and zinc (0.1 mg L−1). Due to the high COD/BOD5 ratio, a poorly biodegradable organic load is underlining. The newly isolated strain was identified as Lysinibacillus fusiformis using 16S rDNA sequencing analysis. The viability of this new strain was tested in presence of the zinc, lead, cadmium, manganese and copper at 1, 10 and 100 mM. The L. fusiformis survival, under metallic stress, was inversely proportional to metal ion concentrations, while lead and zinc were the most toxic ones using MTT assay. Then, the newly isolated strain was characterized in terms of enzyme production, proteomic alteration and antibiotic resistance. The strain ZC revealed some modifications in the biochemical and enzymatic profiles by either the appearance or/and the disappearance of some activities. In addition, the increase in metal ions stress and concentrations was proportional to the adherence and to the hydrophobicity. The presence of the metal ions suggested the change of sensitivity to the resistance of this strain towards tobramycin, kanamycin, neomycin, netilmicin and cefoxitin, showing an increase in the MARindex. The strain ZC, used as a biological tool for MPLW treatment, showed a reduction in the metal ion contents. This reduction was due to accumulation and/or adsorption, showing a bioprocessing performance of the newly isolated L. fusiformis.

In this study, we incubated three strains of Shigella (Shigella sonnei (S1), Shigella boydii(S2) and Shigella flexneri (S3)) in seawater microcosms (at room temperature and at 4°C) for eight months and we studied the modification of the proteins secreted, cytosolicand inner membrane profiles and their composition in fatty acids. Plasmid profiles were also investigated. Plasmids profiles analysis showed that S. boydii (S2) and S. flexneri (S3) did not lose any of their plasmids. In addition, fatty acids composition of Shigella under stress conditions was modified. Proteins secreted, cytosolic and inner membrane of stressed bacteria was changed and these modifications were manifested by the appearance and/or disappearance of bands. Key words: Shigella, seawater, starvation, plasmids, proteins, fatty acids.

In this study, an Aeromonas hydrophila identified as a denitrifying bacterium by PCR detection of nitrate reductase (narG) and nitrite reductase (nirK) genes was incubated in seawater microcosms for 8 months at room temperature and at 4 °C. A study of the phenotypic variation demonstrated that A. hydrophila becomes gelatinase-positive after the incubation in sea water. We noted that starved A. hydrophila becomes unable to produce leucine arylamidase, and that the starved strain appears to grow more slowly. Indeed, we also observed a severe decrease in cellular aggregation of Aeromonas after incubation. In addition, atomic force micrographs revealed a reduction in cell size.

Salmonella is an international foodborne pathogen widely disseminated in seawater that regularly causes large outbreaks of food poisoning. In this study, we have investigated the effect of starvation on the ability of Salmonella enterica serovar Typhimurium cells to adhere to polystyrene microplate and Hep2 cells in seawater microcosms after incubation for 3 years. Cell surface hydrophobicity was evaluated. Effect of stress on fatty acids composition was also established. Our results showed that after incubation in seawater, the ability of starved cells to adhere to polystyrene microplate was decreased significantly. However, the adhesion values to Hep2 cells have increased. In addition, cells surface hydrophobicity was decreased. The fatty acids composition of starved cells was modified.

In this study, we incubated four strains of Shigella in seawater microcosms (at room temperature and at 4°C) for eight months and we studied the alteration of their morphologic and outer membranes proteins. The starved cells showed an evolution to the filterable minicells state capable to pass membrane pore size 0.45 µm. In addition, the atomic force micrographs showed a reduction of the cells size and an evolution to coccoid-shapes. Outer membrane proteins patterns of stressed bacteria did not changed too much and these modifications were manifested by the appearance of one new band. Key words: Shigella, seawater, starvation, morphological, outer membrane proteins.

In this study, we incubated four strains of Staphylococcus aureus for 8 months in seawater microcosms. The biofilm formation on microplates and on glass and the surface hydrophobicity of starved cells were investigated. Our results showed that the stressed cells increased their hydrophobicity from 12 to 44% and also their capacity for producing biofilm. Indeed, after 8 months of incubation in seawater microcosms, all strains became slime positive on CRA plates and very adherent to polystyrene microplates or glass wells.

In this study, we investigated the survival, adhesion and the morphology of Shigella after its incubation in various concentrations of salts. Our results showed that, after 48 h of incubation, the rate of cell survival is inversely proportional to the increase of salinity of the medium. In addition to that, the results prove the evidence that the concentration of salt can significantly influence the capacity of Shigella to produce biofilm on Congo red agar and on polystyrene microplate wells. Adherence and invasion assays of Shigella were performed with KB cells line. Indeed, an increase of the salts concentration enhances the ability of Shigella species to attach and to invade the tissue culture cells. The percentage of adherence was increased to 15% and the invasion to 90% at 6% of salt. The atomic force micrographs showed a reduction of the cells’ size after stress.

International audience; Vibrio parahaemolyticus and Vibrio alginolyticus were subjected to γ-irradiation (0.5 kGy) or starvation by incubation for 8 months in seawater to study modifications in their outer membrane protein patterns. After treatment, outer membrane protein profiles of starved or γ-irradiated bacteria were found to be altered when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Altered proteins were identified by mass spectrometry (MS and MS/MS) and analyses revealed that OmpU can be considered a starvation stress-induced protein. In addition, expression of OtnA, OmpW, OmpA and peptidoglycan-associated lipoprotein decreased to non-detectable levels in starved cells. Furthermore, MltA-interacting protein MipA appeared under γ-irradiation or starvation conditions. Thus, it can be considered to be a γ-irradiation, long-term starvation stress protein in some vibrios.

The survival of bacteria in natural environments is of practical importance. In this study, we investigated the effect of starvation on the survival and adhesion ability of Shigella in domestic treatment plant effluent microcosms after incubation at either room temperature or 4°C for 1 month. Our results showed that the number of cells decreased considerably after this period of stress. We also revealed some modifications to the biochemical and enzymatic profiles, and antibiotic susceptibility of stressed cells. Adherence assays to the human oral cavity epidermoid carcinoma (KB) cell line revealed an increase in the number of adherent cells from 0.7 to 1.85% after 1 month of incubation in domestic treatment plant effluent.

Shigella sonnei encounter numerous different stresses during their growth, survival and infection. In this study, the effect of stress response to pH and starvation was investigated. We studied the survival, adhesion and the morphology of Shigella after its incubation in several pH. Our results show that after 2 h of incubation, the rate of cell survival was proportional to the decrease of pH of the medium, but we also noted that the reduction of the cells viability is significant for the normal cells compared to starved cells. In addition to that, the results proved the evidence that the pH can influence significantly the hydrophobicity of S. sonnei (normal and starved) and their capacity to produce biofilm on Congo red agar and on polystyrene microplate wells. The atomic force micrographs showed a reduction of the cells size after stress. Keywords : Shigella sonnei , starvation, pH, survival, adhesion, morphology African Journal of Biotechnology Vol. 12(16), pp. 2034-2040

International audience; Vibrio parahaemolyticus and V. alginolyticus, marine foodborne pathogens, were treated with UVC-radiation (240 J/m(2)) to evaluate alterations in their outer membrane protein profiles. Outer membrane protein patterns of UVC-irradiated bacteria were found altered when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Altered proteins were identified by mass spectrometry (MS and MS/MS) and analysis revealed that OmpW, OmpA, Long-chain fatty acid transport protein, Outer membrane receptor protein, Putative uncharacterized protein VP0167, Maltoporin (lamB), Polar flagellin B/D, Agglutination protein Peptidoglycan-associated lipoprotein and MltA-interacting protein MipA were appeared, thereby they can be considered as UVC-stress proteins in some vibrios. In addition, expression of OmpK decreased to non-detectable level. Furthermore, we observed a decrease or an increase in the expression level of other outer membrane proteins.

The foodborne pathogen Salmonella enterica serovar Typhimurium was subjected to starvation in seawater microcosms for three years to study modifications in its outer membrane and extracellular protein profiles. After incubation, outer membrane proteins and extracellular proteins profiles of stressed bacteria were found to be altered when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). These modifications were shown by the appearance of bands, as well as the level of expression of certain proteins. The expression levels of sopE2, invA, sipA and sopBvirulence genes were also studied by reverse transcriptase polymerase chain reaction. Our findings showed that the expression level of sopE2 was slightly decreased under starvation. Whereas the quantities of sopB mRNA were increased in the two starved strains S1 and S2. The expression of sipA was decreased in strain S1 after starvation, but was significantly increased in strain S2. Key words: Salmonella, starvation, alteration, outer membrane protein, extracellular proteins, virulence gene expression.

In this work, we incubated four Shigella strains for one month at room temperature and at 4°C. Their adhesion capacity to KB cells, biofilm formation on microplate and surface hydrophobicity of starved cells were investigated. Our results showed that the stressed cells exhibited a remarkable increase in their hydrophobicity from 19 to 34 % and in their capacity to produce biofilm. Adherence assays to KB cells showed an increase in the number of adherent cells from 0.7 to 6.7% after one month of incubation in seawater. However, the percentage of invasion was decreased from 34 to 11% under stress condition.

International audience; In this study, Vibrio parahaemolyticus and Vibrio alginolyticus, marine foodborne pathogens, were treated with Ultraviolet-C (UV-C) irradiation (240 J.m(-2)) to evaluate alterations in their virulence genes expression levels. Firstly, we searched for the presence of eight Vibrio cholerae virulence genes, toxR, toxS, toxRS, ctxA, zot, ace, toxT, and virulence pathogenicity island (VPI), in the genome of investigated strains. The expression of toxR and toxS genes in UVC-irradiated bacteria, studied by reverse transcriptase polymerase chain reaction, was found to be altered. These variations were manifested by an increase or a decrease in the expression level of tested virulence genes. Further, the mRNA quantities of VPI and ace genes remained stable after treatment.

In this study, we incubated Vibrio parahaemolyticus and Vibrio alginolyticus (marine food-borne pathogens bacteria) in seawater for 8 months to study their morphologic, proteomic and genetic responses to starvation. The atomic force micrographs of stressed strains showed a reduction of the cells size and an evolution to two coccoid-shape forms whose length is less than 0.4 μm and between 0.5 and 1 μm. Extracellular protein patterns and gelatinase profiles of stressed bacteria were also altered. Indeed, these modifications were manifested by the appearance and/or disappearance of bands as well as in the level of expression of certain proteins. In addition, we also searched for the presence of eight Vibrio cholerae virulence genes: toxR, toxS, toxRS, ctxA, zot,ace, toxT, and Virulence Pathogenicity Island (VPI) in the genome of investigated strains. The expression level of VPI gene studied by reverse transcriptase polymerase chain reaction was decreased, whereas the mRNA quantities of toxR, toxS, and ace in starved Vibrio remained stable. Key words: Vibrio, seawater, alterations, morphology, proteins secreted, virulence gene expression, RT-PCR