Lead concentrations in feathers and blood of common blackbirds (Turdus merula) and in earthworms inhabiting unpolluted and moderately polluted urban areas.

Despite the dramatic decrease of atmospheric lead (Pb) concentrations in urban areas of most industrialised countries, we hypothesised that urban common blackbirds (Turdus merula) may still be contaminated by Pb concentrations of toxicological concern due to transfer from soil through the food chain. We sampled blackbirds and earthworms, one of their main preys, in Besançon, a middle-size city of Eastern France (where atmospheric Pb concentrations decreased from 0.5 microg/m(3) in 1987 to nearly 0 in 2002) and in a rural reference site. Lead concentrations were determined in the tissues of the different functional groups of earthworms (anecic, epigeous and endogeous) and in blood, washed and unwashed outermost tail feathers and breast feathers of blackbirds. Fresh masses and an index of individual body condition were measured in the two blackbird populations as biomarkers of possible toxic effects. Lead concentrations in earthworms did not differ among functional groups but were significantly higher in urban individuals than in rural ones. Concentrations in outermost tail feathers, breast feathers and blood were significantly higher in urban blackbirds (7.75+/-4.50, 3.15+/-1.77 and 0.15+/-0.09 microg/g, respectively) than in rural individuals. In urban blackbirds, concentrations in washed and unwashed outermost tail feathers allowed estimating the external contamination (probably due to deposition of dusts and/or to excretion of the uropygial gland) at 37% of the total Pb concentration of the unwashed feathers. Remaining 63% should be linked to food chain transfer of persistent Pb from urban soils. Among the 23 sampled blackbirds, 4 of them (3 in the urban site and 1 in the rural site) exhibited blood Pb concentrations higher than the benchmark value (0.20 microg/g) related to subclinical and physiological effects in birds. Variations in body condition index were not correlated to Pb concentrations in blackbird tissues. Present results suggest that Pb may still be of environmental concern for blackbirds in urban areas because of the persistence of Pb in soils and its transfer through the food chain.

An amplifiable and deletable locus of Streptomyces ambofaciens RP181110 contains a very large gene homologous to polyketide synthase genes.

Streptomyces ambofaciens RP181110 produces the macrolide polyketide spiramycin. Like many other Streptomyces species, the RP181110 strain is prone to genetic instability involving genomic rearrangements (deletions and/or amplifications) in the large unstable region of the genome. It has previously been demonstrated that the amplification of a particular locus (AUD205) affects spiramycin biosynthesis and, conversely, the loss of this amplification is correlated with the restoration of antibiotic production. This report focuses on a 0.93 kb reiterated fragment specific for the AUD205 locus. Sequencing of 3596 bp including this reiteration revealed the presence of an ORF (orfPS) whose potential product was highly homologous to the EryA and Raps proteins, responsible for the biosynthesis of erythromycin in Saccharopolyspora erythraea and rapamycin in Streptomyces hygroscopicus, respectively. orfPS encodes a protein with at least four successive domains: ketoacyl synthase, acyltransferase, ketoreductase and acyl carrier protein. This organization is very similar to most eryA and rap modules. The reiterated sequence corresponds to the acyltransferase domain. orfPS was transcribed during rapid growth and stationary phase in RP181110 and overtranscribed in the amplified mutant. Both these results suggest that the gene encodes a type I polyketide synthase and its reorganization is responsible for the loss of spiramycin production in the amplified strains.