Allochthonous bioaugmentation in ex situ treatment of crude oil-polluted sediments in the presence of an effective degrading indigenous microbiome.

Oil-polluted sediment bioremediation depends on both physicochemical and biological parameters, but the effect of the latter cannot be evaluated without the optimization of the former. We aimed in optimizing the physicochemical parameters related to biodegradation by applying an ex-situ landfarming set-up combined with biostimulation to oil-polluted sediment, in order to determine the added effect of bioaugmentation by four allochthonous oil-degrading bacterial consortia in relation to the degradation efficiency of the indigenous community. We monitored hydrocarbon degradation, sediment ecotoxicity and hydrolytic activity, bacterial population sizes and bacterial community dynamics, characterizing the dominant taxa through time and at each treatment. We observed no significant differences in total degradation, but increased ecotoxicity between the different treatments receiving both biostimulation and bioaugmentation and the biostimulated-only control. Moreover, the added allochthonous bacteria quickly perished and were rarely detected, their addition inducing minimal shifts in community structure although it altered the distribution of the residual hydrocarbons in two treatments. Therefore, we concluded that biodegradation was mostly performed by the autochthonous populations while bioaugmentation, in contrast to biostimulation, did not enhance the remediation process. Our results indicate that when environmental conditions are optimized, the indigenous microbiome at a polluted site will likely outperform any allochthonous consortium.

Molecular analysis and antimicrobial resistance of Salmonella isolates recovered from raw meat marketed in the area of "Grand Tunis", Tunisia.

A total of 315 samples of chicken (60), beef (144), minced meat (56), lamb meat (33), merguez (10) and fish (12) were collected from various local outlet stores in the area of "Grand Tunis", Tunisia between 2006 and 2008. Salmonella was recovered from 80 samples with the highest occurrence in chicken (48.3%) followed by beef (29.8%), minced meat (10.7%) and lamb (6.0%). No Salmonella were isolated from 12 fish and 10 merguez samples (typical Tunisian sausages). Nine serovars were identified among the isolates with the predominance of Salmonella Typhimurium (n=25) followed by Salmonella Kentucky (n=14), Salmonella Suberu (n=12) and Salmonella Zanzibar (n=11). Isolated Salmonella were characterized by serotyping, pulsed-field gel electrophoresis (PFGE) analysis, plasmid content and antimicrobial resistance profiling. Sixteen (20.0%) Salmonella isolates displayed resistance to ampicillin (13 isolates), streptomycin (five isolates), cefoperazone (two isolates), furazolodine (two isolates), with seven of these isolates displaying multiple resistance to at least two of these antimicriobal agents. PFGE analysis showed homogenous restriction patterns in each serovar. Compiled serotyping, PFGE analysis, plasmid profiling and antimicrobial resistance data provided additional discrimination.

Antimicrobial resistance and molecular analysis of non-typhoidal Salmonella isolates from human in Tunisia.

During the period from 2006 to 2007, a total of 32 clinical isolates of Salmonella enterica were isolated from diarrheagenic stool samples and further examined for their susceptibility to various antibiotics. Sixteen of the human isolates were from the capital Tunis, 11 were from Sousse, four were from Nabeul and one was from Mahdia, Tunisia. The isolates were serotyped and identified at the National Centre of Enteropathogenic Bacteria, Pasteur Institute, Tunis (Centre National de Salmonella, Shigella et Vibrio - Institut pasteur de Tunis); nine distinct serovars were identified: Enteritidis (n=20), Typhimurium (n=4), Zanzibar (n=2), Manhattan (n=1), Bovismorbificans (n=1), Amsterdam (n=1), Saint Paul (n=1), Kentucky (n=1) and Muenster (n=1). Our results showed that 25 Salmonella isolates (78.1 %) were resistant to antibiotics with 20 isolates (62.5 %) displayed resistance to ampicillin. Isolates sharing invA gene, as shown by PCR amplification, were further characterized by the techniques of pulsed-field gel electrophoresis (PFGE) using the restriction enzyme XbaI and plasmid analysis to determine possible genetic relationships among Salmonella enterica clinical isolates and to assess genetic diversity. Plasmid profiling identified seven plasmid profiles (with 1-5 plasmids) among the isolates; four isolates (Salmonella Kentucky, Salmonella Muenster, Salmonella Bovismorbificans and Salmonella Zanzibar) did not carry any plasmid. The isolates were differentiated into 10 distinct XbaI-pulsotypes. Our findings show genetic diversity among the different serovars and cluster analysis of compiled serotyping, PFGE, plasmid profiling and antibiotic resistance data provided additional discrimination.

Esterase as an enzymatic signature of Geodermatophilaceae adaptability to Sahara desert stones and monuments.

AIM: To assess esterase profiling of members of Geodermatophilaceae isolated from desert stones and monuments in Tunisia and Egypt. METHODS AND RESULTS: Members of Geodermatophilaceae family isolated from desert stones and monuments in Tunisia and Egypt were characterized by partial 16S rRNA sequences. Twenty-five strains were clustered in three dissimilar groups of the genera Geodermatophilus (12 strains), Blastococcus (5 strains) and Modestobacter (3 strains). Isolates were also screened and typed based on major groups of esterase hydrolytic activity. Their esterase patterns were determined and compared to those of ten reference strains belonging to Geodermatophilaceae family. Strains exhibited a diverse and complex pattern of electrophoretic esterase bands, and 31 haplotypes were obtained for the 35 investigated strains. Esterases produced by members of Geodermatophilaceae family have an optimal activity around 40 degrees C and at pH 8. Esterases from Geodermatophilus strains display a high resistance to thermal inactivation and alkaline pH and retaining 30 and 20% of activity after heating for 20 min at 120 degrees C and at pH 12, respectively, and were completely inactivated after 30 min at 120 degrees C. Enzyme activity has been strongly activated in the presence of Ca(2+)and Mg(2+) ions and moderately by Zn(2+) and was markedly inhibited by Cu(2+) and Co(2+) ions. CONCLUSIONS: Geodermatophilaceae isolates share a rich and particular pool of esterase activities that could be directly linked to harsh conditions characterizing their ecological habitat including high level of aridity, temperature, ionic strength and low nutrient availability. SIGNIFICANCE AND IMPACT OF THE STUDY: Esterase could be considered as enzymatic signature that outlines adaptability of Geodermatophilaceae in arid area.

Effect of culturing processes and copper addition on laccase production by the white-rot fungus Fomes fomentarius MUCL 35117.

AIM: To produce high laccase activities from the white-rot fungus Fomes fomentarius. METHODS AND RESULTS: Different culturing methods, viz, cell immobilization on stainless steel sponges and plastic material and solid-state fermentation (SSF) using wheat bran as substrate were used for laccase production by the white-rot fungus F. fomentarius. The SSF study expresses the highest laccase activities, nearly to 6400 U l(-1) after 13 days of laboratory flasks cultivation. When the wheat bran medium was supplemented with 2 mmol l(-1) copper sulfate, laccase activity increased by threefold in comparison to control cultures, reaching 27 864 U l(-1). With the medium thus optimized, further experiments were performed in a 3 l fixed-bed bioreactor (working volume 1.5 l) leading to a laccase activity of about 6230 U l(-1) on day 13. CONCLUSIONS: The results obtained clearly showed the superiority of wheat bran for laccase production over stainless steel sponges and plastic material. Supplementing the wheat bran solid medium with 2 mmol l(-1) copper sulfate allowed obtaining high activities at flask scale. The system was scaled to fixed-bed laboratory reactor. SIGNIFICANCE AND IMPACT OF THE STUDY: The high enzyme production along with the low-cost of the substrate, showed the suitability of the system F. fomentarius- SSF for industrial purposes.

Olive oil mill wastewater purification by combination of coagulation- flocculation and biological treatments.

In order to define an efficient pre-treatment of Olive Oil Mill Wastewater (OOMW) to overcome major obstacles to biological treatment, various organic and mineral coagulants have been tested. In particular, the application of quicklime until a pH around 12 - 12.4 was reached, allowed the reduction of almost 37% of the initial COD, and approximately 88% and 71% of the colour and phenolic content of the waste. Hence, further biological treatments with an adapted aerobic consortium (AC) and a white rot fungus (WRF) strain were improved. The WRF Coriolopsis polyzona was more efficient than AC to reduce colour and polyphenols when the waste was prior diluted or pre-treated; however, it was less effective in COD removal. The combined treatment: lime - AC of OOMW having initial COD of 102 g l(-1) led to the elimination of about 77, 91 and 63%, of the COD, phenols and colour, respectively. Interestingly, the opposite combination AC - lime permitted better COD, phenols and colour reduction to respectively, 21, 11 and 11% of the initial values. This latter condition is technically recommended since only one step separation was needed and no pH correction was necessary before undergoing aerobic treatment. Moreover, the process would produce a sludge potentially rich in organic matter, and consequently, useful as an agricultural amendment or/and as an additive in animal nutrition.