Aims:  To develop a simple, rapid and inexpensive soil DNA extraction protocol. Methods and Results:  The protocol relies on the use of superparamagnetic silica‐magnetite nanoparticles for the isolation and purification of DNA from soil samples. DNA suitable for use in molecular biology applications was obtained from a number of soil samples. Conclusions:  The DNA extracted using the tested method successfully permitted the PCR amplification of a fragment of the bacterial 16S rDNA gene. The extracted DNA could also be restriction endonuclease digested. Significance and Impact of the Study:  The protocol reported here is simple and permits rapid isolation of PCR‐ready soil DNA. The method requires only small quantities of soil sample, is scalable and suitable for automation.

Strains of Bacteroides fragilis isolated from clinical specimens are known to be frequently resistant to penicillins or cephalosporins. The production of beta-lactamases is the major mechanism in this resistance. Up to now at least five types of beta-lactamase enzymes have been described in the Bacteroides fragilis group. The purpose of this study was to evaluate the susceptibility to different antibiotics and the prevalence of the beta-lactamase types among 100 Bacteroides fragilis strains isolated from clinical specimens in Italy. MICs of 11 antibiotics were determined by the reference agar dilution method and by the new E test (AB Biodisk, Sweden). Results showed an acceptable correlation between the MICs determined for most strains, although those obtained by the E test tended to be lower. In the beta-lactam resistant strains the enzyme activity and isoelectric points were determined on crude enzyme extract.

Chloride channel proteins (ClC) are found in living systems where they transport chloride ions across cell membranes. Recently, the structure/function of two prokaryotic ClC has been determined but little is known about the role of these proteins in the microbial metabolism of chlorinated compounds. Here we show that transposon Tn5530 from Burkholderia cepacia strain 2a encodes a ClC protein (BcClC) which is responsible for expelling Cl(-) ions generated during the catabolism of 2,4-dichlorophenoxyacetic acid (a chlorinated herbicide). We found that BcClC has the ability to transport Cl(-) ions across reconstituted proteoliposome membranes. We created two mutants in which the intrachannel glutamate residue of the protein, known to be responsible for opening and closing the channel (i.e. gating), was changed in order to create constitutively open and closed forms. We observed that cells carrying the closed-channel protein accumulated Cl(-) ions intracellularly leading to a decrease in intracellular pH, cell stasis and death. Further, we established that BcClC has the same gating mechanism as that reported for the ClC protein from Salmonella typhimurium. Our results show that the physiological role of ClC is to maintain cellular homeostasis which can be impaired by the catabolism of chlorinated compounds.

The Authors wish to retract the article 'Tn5530 from Burkholderia cepacia strain 2a encodes a chloride channel protein essential for the catabolism of 2,4-dichlorophenoxyacetic acid' on the basis of lack of confidence in certain data therein. Specifically, data relating to chloride ion measurements are currently unsustainable and are being repeated. ReferenceSebastianelli, A. and Bruce, I.J. (2007) Tn5530 from Burkholderia cepacia strain 2a encodes a chloride channel protein essential for the catabolism of 2,4-dichlorophenoxyacetic acid. Environ Microbiol 9: 256-265.