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Two of the largest crude oil-polluted areas in the world are the semi-enclosed Mediterranean and Red Seas, but the effect of chronic pollution remains incompletely understood on a large scale. We compared the influence of environmental and geographical constraints and anthropogenic forces (hydrocarbon input) on bacterial communities in eight geographically separated oil-polluted sites along the coastlines of the Mediterranean and Red Seas. The differences in community compositions and their biodegradation potential were primarily associated (P < 0.05) with both temperature and chemical diversity. Furthermore, we observed a link between temperature and chemical and biological diversity that was stronger in chronically polluted sites than in pristine ones where accidental oil spills occurred. We propose that low temperature increases bacterial richness while decreasing catabolic diversity and that chronic pollution promotes catabolic diversification. Our results further suggest that the bacterial populations in chronically polluted sites may respond more promptly in degrading petroleum after accidental oil spills.

Petroleum pollution has become a serious environmental problem, which can cause harmful damage to the environment and human health. This pollutant is introduced into the environment from both natural and anthropogenic sources. Various physicochemical and biological treatments were developed for the cleanup of contaminated environments. However, bioremediation is based on the metabolic capabilities of microorganisms, and it is considered as the most basic and reliable way to eliminate contaminants, particularly petroleum and its recalcitrant compounds. It is more effective alternative comparing to classical remediation techniques. A high diversity of potential hydrocarbon degrader's microorganisms was reported, and bacteria constitute the most abundant group, which has been well studied for hydrocarbon degradation. Several bioremediation approaches through bioaugmentation or/and biostimulation have been successfully applied. The interest on the optimizing of different parameters to achieve successful bioremediation technologies has been increased. In this chapter, we summarize the diversity and the hydrocarbon degradation potential of microorganism involved in the remediation of contaminated environments. We also present an overview of the efficient bioremediation strategies used for the decontamination of polluted marine environments.

The present investigation focused on screening of a new potent strain for laccase production and optimizing the process parameters to achieve the maximum enzymatic decolourization of textile azo dye Congo red. Seven hydrocarbonoclastic bacterial strains were selected as positive in laccase production in solid medium using 2,6 dimethoxyphenol as an enzyme activity indicator. The best enzyme producer Pseudomonas extremorientalis BU118 showed a maximum laccase activity of about 7000 U/L of wheat bran under solid-state conditions. The influence of different concentrations of dye, enzyme, salt and various incubation times on Congo red decolourization was studied using response surface methodology to find the optimum conditions required for maximum decolourization by P. extremorientalis laccase. The enzyme exhibited a remarkable colour removal capability over a wide range of dye and salt concentrations. The above results show the potential use of this bacterial laccase in the biological treatment of the textile effluent.

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28"Oil-polluted sediment bioremediation depends on both physicochemical and 29" biological parameters, but the effect of the latter cannot be evaluated without the optimization 30" of the former. We aimed in optimizing the physicochemical parameters related to 31" biodegradation by applying an ex-situ landfarming set-up combined with biostimulation to 32" oil-polluted sediment, in order to determine the added effect of bioaugmentation by four 33" allochthonous oil-degrading bacterial consortia in relation to the degradation efficiency of the 34" indigenous community. We monitored hydrocarbon degradation, sediment ecotoxicity and 35"hydrolytic activity, bacterial population sizes and bacterial community dynamics, 36"characterizing the dominant taxa through time and at each treatment. We observed no 37" significant differences in total degradation, but increased ecotoxicity between the different 38" treatments receiving both biostimulation and bioaugmentation and the biostimulated-only 39" control. Moreover, the added allochthonous bacteria quickly perished and were rarely 40" detected, their addition inducing minimal shifts in community structure although it altered the 41" distribution of the residual hydrocarbons in two treatments. Therefore, we concluded that 42" biodegradation was mostly performed by the autochthonous populations while 43" bioaugmentation, in contrast to biostimulation, did not enhance the remediation process. Our 44" results indicate that when environmental conditions are optimized, the indigenous 45" microbiome at a polluted site will likely outperform any allochthonous consortium. 46"47"

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