Research Product

The substrate specificity of the DNA binding mechanism(s) of bacteria in a Florida reservoir was investigated in short and long term uptake studies with radiolabelled DNA and unlabelled competitors. Thymine oligonucleotides ranging in size from 2 bp to 19-24 bp inhibited DNA binding in 20 min incubations by 43 to 77%. Deoxynucleoside monophosphates, thymidine, and thymine had litte effects on short term DNA binding, although several of these compounds inhibited the uptake of radiolabel from DNA in 4 h incubations. Inorganic phosphate and glucose-1-phosphate inhibited neither short or longterm binding of [3H] or [32PDNA], indicating that DNA was not utilized as a phosphorous source in this reservoir. RNA inhibited both short and long term radiolabelled DNA uptake equally as well as unlabelled DNA. Collectively these results indicate that aquatic bacteria possess a generalized nucleic acid uptake/binding mechanism specific for compounds containing phosphodiester bonds and capable of recognizing oligonucleotides as short as dinucleotides. This binding site is distinct from nucleoside, nucleotide, phosphomonoester, and inorganic phosphate binding sites. Such a nucleic acid binding mechanism may have evolved for the utilization of extracellular DNA (and perhaps RNA) which is abundant in many marine and freshwater environments.