Studies of Extracellular and Intracellular Bacterial Deoxyribonucleic Acids

Abstract

SUMMARY : Highly polymerized bacterial deoxyribonucleic acids (DNAs) obtained from extracellular and from intracellular locations were analysed. DNAs from two strains (Staphylococcus aureus and S. epidermidis) were of the type having high adenine and thymine contents ; two others (Alcaligenes faecalis and Pseudomonas fluorescens) had a high content of guanine and cytosine. For each micro-organism the composition of extracellular DNA was essentially the same as that of the intracellular DNA. Conditions associated with the extracellular accumulation of DNA in cultures of 3 strains were investigated. S. aureus elaborated a deoxyribonuclease (DNase) which required calcium ion and high pH for activity. In a culture medium of c. pH 6 and insufficient calcium, the DNase was inactive and DNA slime accumulated. In cultures of P . jluorescens a specific ribonuclease-sensitive DNase inhibitor protected slime DNA from depolymerization by culture DNase. In cultures of A . faecalis, also, both a DNA slime and a low concentration of DNase may occur. This enzyme, detected by studying its action against solutions of calf thymus DNA prepared from dried fibres, was activated by various cations within the pH range of cultures. Unlike other DNases, however, it has little capacity to attack the slimelayer DNA, which presumably is more nearly native.

Extracellular DNA in oral microbial biofilms

“…Studies in the 1950's identified eDNA as the major component of the slimy pellicle produced by a variety of different bacteria including Actinomyces viscosus [37,38]. Even at such an early stage, it was speculated that eDNA may play roles in addition to the carriage of genetic information between cells, such as protection against desiccation or radiation, avoiding overcrowding or slowing the movement of cations towards cells [38].…”

Transforming Activities and Base Contents of Deoxyribo-nucleate Preparations from Various Neisseriae

“…Organisms were lysed with sodium dodecylsulphate, as described . The DNA-containing fibrous masses obtained by precipitation with 2 volumes of ethanol were purified by methods (Catlin & Cunningham, 1958; which included two separate steps of deproteinization with sodium dodecylsulphate; each was followed by a step involving centrifugation of the DNA solution (in M-NaCl) for 110 min. (32,OOOg; 3"), and precipitation of DNA fibres with ethanol.…”

Transformation by Extracellular DNA Produced by Pseudomonas aeruginosa

“…In addition, the organism has the unique biological character of producing large amounts of DNA which accumulates extracellularly (7,16). The occurrence of extracellular DNA has also been reported for Neisseria (2), Bacillus subtilis (15), Pseudomonas fluorescens (7), Vibrio parahaemolyticus (7), Staphylococcus aureus (3), Staphylococcus epidermidis (3), and Alcaligenes faecalis (3). Moreover, transformation by extracellular DNA has been demonstrated in Neisseria (2), Streptococcus (12), and B. subtilis (14).…”