Several studies in recent years have provided evidence that Pseudomonas aeruginosa has a non-clonal population structure punctuated by highly successful epidemic clones or clonal complexes. The role of recombination in the diversification of P. aeruginosa clones has been suggested, but not yet demonstrated using multi-locus sequence typing (MLST). Isolates of P. aeruginosa from five Mediterranean countries (n = 141) were subjected to pulsed-field gel electrophoresis (PFGE), serotyping and PCR targeting the virulence genes exoS and exoU. The occurrence of multi-resistance (≥3 antipseudomonal drugs) was analyzed with disk diffusion according to EUCAST. MLST was performed on a subset of strains (n = 110) most of them had a distinct PFGE variant. MLST data were analyzed with Bionumerics 6.0, using minimal spanning tree (MST) as well as eBURST. Measurement of clonality was assessed by the standardized index of association (IA S). Evidence of recombination was estimated by ClonalFrame as well as SplitsTree4.0. The MST analysis connected 70 sequence types, among which ST235 was by far the most common. ST235 was very frequently associated with the O11 serotype, and frequently displayed multi-resistance and the virulence genotype exoS −/exoU +. ClonalFrame linked several groups previously identified by eBURST and MST, and provided insight to the evolutionary events occurring in the population; the recombination/mutation ratio was found to be 8.4. A Neighbor-Net analysis based on the concatenated sequences revealed a complex network, providing evidence of frequent recombination. The index of association when all the strains were considered indicated a freely recombining population. P. aeruginosa isolates from the Mediterranean countries display an epidemic population structure, particularly dominated by ST235-O11, which has earlier also been coupled to the spread of ß-lactamases in many countries.

A new consortium of four bacterial isolates (Agrobacterium radiobacter; Bacillus spp.; Sphingomonas paucimobilis, and Aeromonas hydrophila)-(CM-4) was used to degrade and to decolorize triphenylmethane dyes. All bacteria were isolated from activated sludge extracted from a wastewater treatment station of a dyeing industry plant. Individual bacterial isolates exhibited a remarkable color-removal capability against crystal violet (50 mg/L) and malachite green (50 mg/L) dyes within 24 h. Interestingly, the microbial consortium CM-4 shows a high decolorizing percentage for crystal violet and malachite green, respectively, 91% and 99% within 2 h. The rate of chemical oxygen demand (COD) removal increases after 24 h, reaching 61.5% and 84.2% for crystal violet and malachite green, respectively. UV-Visible absorption spectra, FTIR analysis and the inspection of bacterial cells growth indicated that color removal by the CM-4 was due to biodegradation. Evaluation of mutagenicity by using Salmonella typhimurium test strains, TA98 and TA100 studies revealed that the degradation of crystal violet and malachite green by CM-4 did not lead to mutagenic products. Altogether, these results demonstrated the usefulness of the bacterial consortium in the treatment of the textile dyes.

-Synthetic dyes are widely used in the textile, cosmetic, printing, drug, and food processing industries. Triphenylmethane dyes belong to the most important group of synthetic dyes. They are generally considered as the xenobiotic compounds, which are very recalcitrant to biodegradation. Bacillus sp., was isolated from the treatment plant effluent of a textile and dyeing industry (SITEX) located in Ksar Hellal, Tunisia, decolorizes crystal violet (500 ppm) within 2.5 h under shaking condition at pH 7 and temperature 30 °C. The effect of dye concentration, temperature and initial pH of the solution were studied. The results obtained from the batch experiments revealed the ability of bacteria in removing dye. UV-Vis spectroscopy and FTIR analysis of samples before and after dye decolorization in culture medium confirmed decolorization of crystal violet. The phytotoxicity and microbial toxicity studies of extracted metabolites suggest the less toxic nature of them.

In this study, Gram negative bacterium, Sphingomonas paucimobilis, was used to test its ability to decolourise two triphenylmethane dyes: malachite green (MG) and crystal violet (CV) in mineral salts medium (MSM). Decolourisation was examined with dye concentrations (2.5, 5, 15, 25, 30 and 50 mg/l), glucose (0, 1.4, 2.8, 4.2, 5.6 and 7 mM) and yeast extract concentrations (0, 0.05, 0.10, 0.15% w/v). Our results showed that Sphingomonas paucimobilis used at 1 OD ( 600 nm), equivalent to 14 x 10 7 CFU/ ml cell concentration, remove MG and CV colour with 35 and 55%, respectively, for 2.5 mg/l dye concentration in MSM. The best removal efficiencies for decolourisation were 93.43% for MG and 71.29% for CV at 50 mg/l dye concentration, obtained with 7 mM of glucose used as source of carbon. Whereas the optimum concentration of yeast extract which allowed high value on decolourisation was determined at 0.1% for MG and 0.05% for CV. We obtained the high percentage of decolourisation which reaches 100% within 10 h. Moreover, at the same conditions the source of nitrogen yeast extract enhanced more rapidly the decolourisation of dyes colour removal by a new natural isolates Sphingomonas paucimobilis which was significantly affected by adding nutrient sources.

The purpose of the present study was to explore the potential behavioural changes of Pseudomonas aeruginosa following growth in different aquatic environmental conditions. To achieve this, P. aeruginosa was cultured in various water microcosms for 12 months under fixed (pH, nutrients and temperature) factors. P. aeruginosa responses to these conditions were investigated using colony morphotype, biochemical and enzymatic characterisation, pyocin typing, serotyping, sensitivity to different classes of antibiotics and molecular identification. Results show that starvation in water microcosms lead to unusual phenotypes. Of interest is that the pyocin changed from 24/n in the wild type to 83/a following culture in the water microcosms, and the serotype changed from O6 in the wild type to O1 in microcosm-cultured P. aeruginosa. Furthermore, the starvation period in various aquatic microcosms enhanced the resistance of P. aeruginosa against beta-lactam antibiotics. Compared to the other aquatic environments, the seawater microcosm produced the greatest amount of variations in P. aeruginosa. Overall, data demonstrated a high adaptability of P. aeruginosa to environmental changes. This may explain the unusual antibiotic-resistant phenotypes belonging to P. aeruginosa species, and their capacity for spreading that leads to human infections.