Problem statement:This study was conducted to find and determine whether the siderophores of the four environmental Pseudomonas spp. isolates possess a sequestering activity towards essential transition metals (Zn and Mn) other than iron. Approach: Four fluorescent Pseudomonads isolated from various environments, were characterized analytically (Isoelectric focusing), biologically (pyoverdine-mediated uptake) and genetically (16S rDNA sequencing). By means of spectrophotometric measurements, it was possible to establish and compare the levels of pyoverdine production, in two different nutrient-poor media. Results: The strains were assigned, by sequencing, to P. fluorescens, P. aeruginosa, P. putida and P. mosselii isolated, respectively from soil, compost, sea water and waste water treatment plant. These bacterial strains were recognized as producing diver's yellow-green siderophores types, when grown under conditions of iron starvation. The highest metabolite concentration was obtained with PsC132 and PsTp171 strains isolated respectively from compost and waste water treatment plant, in CAA medium. Strains grown in CAA medium exhibit a higher PVD level compared to SM medium. Mn (II) was found to promote pyoverdine biosynthesis, but rather, Zn (II) had no significant effect on siderophore production when compared to control medium. For both strains PsS29 and PsC132, the increase of iron concentration quenched siderophore production especially above 20 µM. Pyoverdine level declined with the high concentration of zinc but increased with Manganese concentration ranging up to 70 µM (in case of PsC132) and 300 µM (in case of PsS29). Conclusion/Recommendations: The ability of fluorescent Pseudomonas, isolated from wastewater treatment plant and from compost, to sequester zinc, point to a unique advantage of these species for divers bioremediation applications.
Constructed wetlands (CWs) have received increasing attention in the last decade due to their high potential for wastewater treatment. The nitrogen removal performance is always the main focus when evaluating the treatment ability of CWs. In this work, we aimed to isolate and identify the heterotrophic bacteria using the 16S rRNA gene sequencing method and to characterize the microbial communities removing nitrogen from wastewater and rhizosphere of constructed wetlands and quantified the heterotrophic nitrification on a microtiter plate by applying a spectrofluorometric assay. A number of 35 isolates within the obtained bacterial collection (380 isolates), were selected for molecular classification based on their genetic patterns after amplification of ITS fragments. Results obtained from the PCR amplification of the 16S-23S rDNA gene followed by the partial sequencing of the 16S rDNA genes confirmed the affiliation of the isolates to γ-Proteobacteria, Firmictes, α-Proteobacteria, Actinobacteria and δ-Proteobacteria. Batch tests were carried out to investigate the capacity for heterotrophic nitrification in the pure culture. The batch test results indicate that nitrifying bacteria can utilize the organic carbon as the source of assimilation when it grows on glucose and ammonium chloride medium accompanying the formation of NO 2-(nitrified products > 80%). Quantification of bacterial biofilms grown on microtiter plate showed that six strains were strongly adhesive to polystyrene microtiter plate with an OD 595 ranging between 3.031 and 4.0368 and only one strain was weak biofilm forming. These bacteria might be used to activate nitrifying bioreactor for a tertiary domestic wastewaters treatment.
A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental biotypes (wastewater, compost, wastewater treatment plant, etc.) were analysed by two polymerase chain reaction (PCR)-based methods, 16S-23S intergenic spacer regions (ITS)-PCR and repetitive extragenic palindromic (BOX)-PCR. These typing techniques were evaluated to assess their usefulness as tool to study the Pseudomonas diversity within this complex group. Genetic analysis using ITS-and BOX-PCR generated respectively 12 and 45 distinct profiles. Phylogenetic relationships within fluorescent pseudomonads were examined by analyzing partial 16S rRNA and rpoB genes sequences. The phylogenetic resolution of the rpoB tree was higher than that of the 16S rRNA tree. Moreover, the sequencing of the rpoB gene has recognized 13 different species and sub-species, while the 16 rRNA gene sequencing differentiated only 9 species.
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