Specificity in Deoxyribonucleic Acid Uptake by Transformable Haemophilus influenzae

Abstract

Cells of Haemophilus influenzae strain Rd competent for genetic transformation irreversibly bound approximately five molecular fragments of H. influenzae deoxyribonucleic acid (DNA) per cell; under identical conditions, DNA derived from Escherichia coli B was not taken up (<1 molecule per 50 cells). Similarly, DNA from Xenopus laevis was not taken up by competent H. influenzae. Of the heterologous DNAs tested, only DNA from H. parainfluenzae interfered with the uptake of H. influenzae DNA, as judged by competition experiments employing either DNA binding or genetic transformation as the test system. The extracellular heterologous DNA did not suffer either singleor double-strand breakage upon exposure to competent H. influenzae. The deleterious consequences attending the uptake and integration of heterologous deoxyribonucleic acid (DNA) by transformable Haemophilus influenzae were presented by Steinhart and Herriott (18); their experiments demonstrated that incorporation of H. parainfluenzae DNA into the H. influenzae chromosome was lethal for the majority of the recipient cells. Earlier experiments by Schaeffer et al. had shown that H. parainfluenzae DNA and wildtype H. influenzae DNA were equally effective in competitively inhibiting transformation by genetically marked H. influenzae DNA (15). Preparations of DNA from other genera varied considerably in their competing abilities when freshly made, but lost the ability to compete with H. influenzae DNA upon storage. No explanation of this anomalous instability was offered; this, together with the low competence of the cultures used by Schaeffer, makes the interpretation of these experiments uncertain. More recently, Newman and Stuy showed that certain cultures of H. influenzae could take up (but not integrate) X phage DNA (13). Considerable variation in the extent of uptake of X DNA was observed among different sublines of H. influenzae by these workers, who suggest that the bacteria may possess both extracellular and intracellular systems which are capable of recognizing homologous DNA. The present paper provides evidence demon-'Present address: Children's Hospital of Michigan, Detroit, Mich. 48201.

Characteristics of Helicobacter pylori natural transformation

“…That transformation of strain HPK5 was inhibited by the addition of unmarked DNA from H. pylori or H. bilis , but not from E. coli , suggests a rate‐limiting step in H. pylori transformation that is specific for Helicobacter DNA. These results are similar to those that led to the identification of uptake sequences required for efficient transformation of H. influenzae [21,23]. Whether such uptake sequences are required for H. pylori transformation has yet to be determined.…”

“…1A) and saturation occurred when approximately 6 ng of DNA was added to 10 8 cells. This is similar to the amount of DNA found to reach the maximum DNA uptake in Haemophilus influenzae (5–10 ng per 10 8 cells) [21,22]. The maximum frequency of transformation for the strain of H. pylori tested was approximately 1.3×10 −4 transformants (μg DNA) −1 colony forming units (cfu) −1 .…”

Mosaic-like organization of IgA protease genes in Neisseria gonorrhoeae generated by horizontal genetic exchange in vivo.

“…This assumption is intriguing in the light of several recent observations. N.gonorrhoeae, like few other bacterial species, possesses an efficient natural DNA uptake system that allows high frequency transformation of this species (Sparling, 1966;Scocca et al, 1974;Dougherty et al, 1979), with homologous DNA being rapidly incorporated into the chromosome of transformed cells by homologous recombination. In addition, gonococci tend to undergo spontaneous autolysis (Hebeler and Young, 1975), thus providing DNA that might be taken up by healthy cells.…”

EXTENSIVE VARIATION IN NATURAL COMPETENCE INHAEMOPHILUS INFLUENZAE

“…Competence is regulated in very different ways in different species, and strain-specific variation has also been reported (Pozzi et al 1996;Solomon and Grossman 1996;Martin et al 2006). Second, the DNA provided may have been inappropriate; some bacteria do not efficiently take up circular plasmid DNA or DNA lacking specific uptake sequences (Scocca et al 1974;Stuy and Walter 1986). Third, DNA may have been taken up but not recombined into the chromosome because of cytoplasmic degradation or insufficient sequence similarity (Albritton et al 1984;Majewski and Cohan 1999) (Palchevskiy and Finkel 2006).…”