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Oxidation of Benzene to Phenol, Catechol, and 1,2,3-Trihydroxybenzene by Toluene 4-Monooxygenase of Pseudomonas mendocina KR1 and Toluene 3-Monooxygenase of Ralstonia pickettii PKO1. Ying Tao, 2004.Aromatic hydroxylations are important bacterial metabolic processes but are difficult to perform using traditional chemical synthesis, so to use a biological catalyst to convert the priority pollutant benzene into industrially relevant intermediates, benzene oxidation was investigated . It was discovered that toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1, toluene 3-monooxygenase (T3MO) of Ralstonia pickettii PKO1, and toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 convert benzene to phenol, catechol, and 1,2,3-trihydroxybenzene by successive hydroxylations . At a concentration of 165 µM and under the control of a constitutive lac promoter, Escherichia coli TG1/pBS(Kan)T4MO expressing T4MO formed phenol from benzene at 19 ± 1.6 nmol/min/mg of protein, catechol from phenol at 13.6 ± 0.3 nmol/min/mg of protein, and 1,2,3-trihydroxybenzene from catechol at 2.5 ± 0.5nmol/min/mg of protein . The catechol and 1,2,3-trihydroxybenzene products were identified by both high-pressure liquid chromatography and mass spectrometry . When analogous plasmid constructs were used, E . coli TG1/pBS(Kan)T3MO expressing T3MO formed phenol, catechol, and 1,2,3-trihydroxybenzene at rates of 3 ± 1, 3.1 ± 0.3, and 0.26 ± 0.09 nmol/min/mg of protein, respectively, and E . coli TG1/pBS(Kan)TOM expressing TOM formed 1,2,3-trihydroxybenzene at a rate of 1.7 ± 0.3 nmol/min/mg of protein (phenol and catechol formation rates were 0.89 ± 0.07 and 1.5 ± 0.3 nmol/min/mg of protein, respectively) . Hence, the rates of synthesis of catechol by both T3MO and T4MO and the 1,2,3-trihydroxybenzene formation rate by TOM were found to be comparable to the rates of oxidation of the natural substrate toluene for these enzymes (10.0 ± 0.8, 4.0 ± 0.6, and 2.4 ± 0.3 nmol/min/mg of protein for T4MO, T3MO, and TOM, respectively, at a toluene concentration of 165 µM) . Effect of Campylobacter-Specific Maternal Antibodies on Campylobacter jejuni Colonization in Young Chickens. Orhan Sahin, 2003.Using laboratory challenge experiments, we examined whether Campylobacter-specific maternal antibody (MAB) plays a protective role in young chickens, which are usually free of Campylobacter under natural production conditions . Kinetics of C . jejuni colonization were compared by infecting 3-day-old broiler chicks, which were naturally positive for Campylobacter-specific MAB, and 21-day-old broilers, which were negative for Campylobacter-specific MAB . The onset of colonization occurred much sooner in birds challenged at the age of 21 days than it did in the birds inoculated at 3 days of age, which suggested a possible involvement of specific MAB in the delay of colonization . To further examine this possibility, specific-pathogen-free layer chickens were raised under laboratory conditions with or without Campylobacter infection, and their 3-day-old progenies with (MAB+) or without (MAB-) Campylobacter-specific MAB were orally challenged with C . jejuni . Significant decreases in the percentage of colonized chickens were observed in the MAB+ group during the first week compared with the MAB- group . These results indicate that Campylobacter-specific MAB plays a partial role in protecting young chickens against colonization by C . jejuni . Presence of MAB in young chickens did not seem to affect the development of systemic immune response following infection with C . jejuni . However, active immune responses to Campylobacter occurred earlier and more strongly in birds infected at 21 days of age than those infected at 3 days of age . Clearance of Campylobacter infection was also observed in chickens infected at 21 days of age . Taken together, these findings (i) indicate that anti-Campylobacter MAB contributes to the lack of Campylobacter infection in young broiler chickens in natural environments and (ii) provide further evidence supporting the feasibility of development of immunization-based approaches for control of Campylobacter infection in poultry .
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