Heat sensitivity of Azotobacter vinelandii genetic transformation.
Heating competent Azotobacter vinelandii at 37 or 42 degrees C resulted in a total loss of competence with no loss of viability. The transformation process was relatively insensitive to heating at either temperature once DNase-resistant DNA binding was nearly complete. Although competent and 42 degrees C-treated cells bound equivalent amounts of [32P]DNA in a DNase-resistant state, no donor DNA marker (nif) or radioactivity was detected in the envelope-free cell lysate of heated cells, suggesting that DNA transport across the cell envelope was a heat-sensitive event. Competence was reacquired in a 42 degrees C-treated culture after 2 h of incubation at 30 degrees C by a process which required RNA and protein syntheses. The release of a surface glycoprotein, required for competence, from cells treated at 42 degrees C occurred in an insufficient amount to account for the total loss of competence. Recovery of competence in 42 degrees C-treated cells and further transformation of competent cells were prevented by the exposure of cells to saturating amounts of transforming DNA. Further DNase-resistant DNA binding, however, still occurred, suggesting that there were two types of receptors for DNase-resistant DNA binding to competent A. vinelandii. DNase-resistant DNA binding was dependent on magnesium ions, and at least one receptor type did not discriminate against heterologous DNA.
D001395:Azotobacter / Q000201:enzymology / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D003851:Deoxyribonucleases; D006358:Hot Temperature; D007700:Kinetics; D009591:Nitrogenase / Q000378:metabolism; D013045:Species Specificity; D014169:Transformation, Bacterial
D004269:DNA, Bacterial; D009591:Nitrogenase; D003851:Deoxyribonucleases