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The gene encoding a periplasmic deoxyribonuclease from Aeromonas hydrophila
1Department of Microbiology, University of Queensland, Australia.
Abstract:
A gene encoding a deoxyribonuclease, dnsH, was cloned from Aeromonas hydrophila JMP636. The predicted mature protein was very similar to the previously described extracellular Dns from this organism and an N-terminal region corresponding to a large putative signal sequence was predicted for the JMP636 protein. Inactivation of dnsII demonstrated that the DnsH protein was not present extracellularly in this strain. As DnsH degraded plasmid DNA and was believed to have a periplasmic location, a dnsH mutant was constructed to determine whether electroporation of A. hydrophila with plasmid DNA could be achieved. No transformants were detected. From SDS-PAGE studies, at least two additional DNases remain to be characterised from A. hydrophila JMP636.
Insights
Aeromonas hydrophila
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Aeromonas hydrophila possesses multiple deoxyribonucleases (DNases) that influence DNA stability.
- The extracellular DNase (Dns) is well-characterized, but intracellular DNases remain less understood.
Purpose of the Study:
- To clone and characterize the deoxyribonuclease H (DnsH) gene from Aeromonas hydrophila JMP636.
- To investigate the role of DnsH in plasmid DNA degradation and its potential periplasmic localization.
- To assess the impact of DnsH on the transformation efficiency of Aeromonas hydrophila via electroporation.
Main Methods:
- Gene cloning of dnsH from Aeromonas hydrophila JMP636.
- Bioinformatic analysis to predict protein features, including signal sequences.
- Gene inactivation (mutant construction) of dnsH.
- Electroporation experiments to assess transformation efficiency.
- SDS-PAGE analysis to study protein profiles.
Main Results:
- The dnsH gene was successfully cloned, and the predicted DnsH protein showed similarity to known extracellular DNases.
- Inactivation of dnsII indicated that DnsH is not extracellular in this strain, suggesting a periplasmic location.
- A dnsH mutant exhibited no transformants after electroporation with plasmid DNA, indicating DnsH interferes with this process.
- SDS-PAGE revealed at least two other unidentified DNases in Aeromonas hydrophila JMP636.
Conclusions:
- DnsH is likely a periplasmic deoxyribonuclease in Aeromonas hydrophila JMP636 that degrades plasmid DNA.
- The presence and activity of DnsH significantly inhibit the electroporation efficiency of Aeromonas hydrophila.
- Further characterization of remaining DNases in Aeromonas hydrophila is warranted.