The variety of halogenated substances and their derivatives widely used as pesticides, herbicides and other industrial products is of great concern due to the hazardous nature of these compounds owing to their toxicity, and persistent environmental pollution. Therefore, from the viewpoint of environmental technology, the need for environmentally relevant enzymes involved in biodegradation of these pollutants has received a great boost. One result of this great deal of attention has been the identification of environmentally relevant bacteria that produce hydrolytic dehalogenases—key enzymes which are considered cost-effective and eco-friendly in the removal and detoxification of these pollutants. These group of enzymes catalyzing the cleavage of the carbon-halogen bond of organohalogen compounds have potential applications in the chemical industry and bioremediation. The dehalogenases make use of fundamentally different strategies with a common mechanism to cleave carbon-halogen bonds whereby, an active-site carboxylate group attacks the substrate C atom bound to the halogen atom to form an ester intermediate and a halide ion with subsequent hydrolysis of the intermediate. Structurally, these dehalogenases have been characterized and shown to use substitution mechanisms that proceed via a covalent aspartyl intermediate. More so, the widest dehalogenation spectrum of electron acceptors tested with bacterial strains which could dehalogenate recalcitrant organohalides has further proven the versatility of bacterial dehalogenators to be considered when determining the fate of halogenated organics at contaminated sites. In this review, the general features of most widely studied bacterial dehalogenases, their structural properties, basis of the degradation of organohalides and their derivatives and how they have been improved for various applications is discussed.

Shiga toxin-producing Escherichia coli O157: H7 (STEC) is a food-borne pathogen that is associated with human illnesses from mild gastroenteritis to severe life-threatening hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Its pathogenesis can be enhanced by the occurrence of certain virulence genes and the ability to produce biofilm. The present study investigates the spectrum of such pathogenesis on the basis of the occurrence of shiga-toxigenic E. coli O157:H7 in raw cow milk obtained from cattle herds. Furthermore, the inhibitory potential of some selected essential oils against their biofilm formation was determined. Results revealed isolated shiga-toxigenic E. coli O157:H7 harboured the stx1 and stx2 virulence genes. Inhibitory assessments of cinnamon, clove, eucalyptus, and tea tree oils also revealed impairment of biofilm formation at 1%, 2% and 3% concentrations, with cinnamon having a higher inhibitory impact. The presence of E. coli 0157:H7 in raw cow milk suggests that they are not restricted to contaminating raw meat only, but can be a contaminant of dairy products as well. The combined effect of stx1, stx2, and biofilm formation is of public health concern as plasmid transfer among strains could result in antimicrobial resistance. Phytochemicals from plants such as cinnamon, clove, eucalyptus, and tea tree could play vital biofilm inhibitory roles in decreasing the virulence of E. coli 0157:H7.