Search

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. [ABSTRACT FROM AUTHOR]

Amination of bulky ketones, particularly in (R)-configuration, is an attractive chemical conversion, however known ω-transaminases (ω-TAs) show insufficient performances. By applying two screening methods we discovered 10 amine transaminases from the class III ω-TAs family, 38-76% identical to homologues. We present examples of such enzymes preferring bulky ketones over keto acids and aldehydes with stringent (S)-selectivity. We also report representatives from the class III ω-TAs capable of converting (R) and (S) amines and bulky ketones, and one converting amines with longer alkyl substituents. The preference for bulky ketones was associated with the presence of a hairpin region proximal to the conserved Arg414 and residues conforming and close to it. The outward orientation of Arg414 additionally favored the conversion of (R)-amines. This configuration was also found to favor the utilization of putrescine as amine donor, so that class III ω-TAs with Arg414 in outward orientation may participate in vivo in the catabolism of putrescine. The positioning of the conserved Ser231 contributes also to the preference of amines with longer alkyl substituents. Optimal temperatures for activity ranged from 45 to 65°C, and a few enzymes retained = 50% of their activity in water-soluble solvents (up to 50% (v/v)). Hence, our results will pave the way to design, in the future, new class III ω-TAs converting bulky ketones and (R)-amines for production of high value products, and screen those converting putrescine. [ABSTRACT FROM AUTHOR]