[1] Stockholm Univ, Arrhenius Labs, Dept Biochem & Biophys, SE-10691 Stockholm, Sweden
[2] BioCtr Amsterdam, Dept Microbiol, NL-1081 HV Amsterdam, Netherlands
[3] Ohio State Univ, Dept Chem, Columbus, OH 43210 USA
[4] Iowa State Univ, Dept Microbiol, Ames, IA 50011 USA