Competent Diplococcus pneumoniae accept both single- and double-stranded deoxyribonucleic acid.

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• Deoxyribonucleic acid (DNA) is the genetic material of organisms.
• Transformation is a process of genetic alteration.
• The role of single-stranded DNA in bacterial transformation was investigated.

Purpose of the Study:

• To determine if pure single strands of Diplococcus pneumoniae DNA possess transforming activity.
• To characterize the nature of the transforming agent in fractionated DNA.

Main Methods:

• Fractionation of Diplococcus pneumoniae DNA.
• Denaturation of DNA in CsCl at pH 11.0.
• Digestion with exonuclease-I.
• Transformation assays with competent bacterial cells.

Main Results:

• Transforming activity was located in fully denatured DNA fractions.
• Exonuclease-I digestion destroyed >99.8% of the transforming activity.
• Pure single strands demonstrated transforming capability.
• The efficiency of single-strand transformation was approximately 0.5% of native DNA.

Conclusions:

• Pure single strands of Diplococcus pneumoniae DNA are capable of transforming competent cells.
• The transforming principle is indeed single-stranded DNA.
• Single-stranded DNA transformation is less efficient than double-stranded DNA transformation.