RecD Plays an Essential Function During Growth at Low Temperature in the Antarctic Bacterium Pseudomonas syringae Lz4W

• Published in: Genetics (Austin) 2005-08, Vol.170 (4), p.1473-1484
• Main Authors: Regha, K, Satapathy, Ajit K, Ray, Malay K
• Format: Article
• Language: English
• Subjects: Alkylating Agents - pharmacology; Amino Acid Sequence; Antarctic Regions; Apoptosis - drug effects; Apoptosis - radiation effects; Bacteria; Cell Death - drug effects; Cell Death - radiation effects; Cloning, Molecular; Cold Temperature; DNA - analysis; DNA Damage; DNA Transposable Elements; Drug Tolerance; Escherichia coli; Escherichia coli - genetics; Escherichia coli Proteins - chemistry; Gene Expression Regulation, Bacterial; Genes; Genes, Bacterial; Genetic Complementation Test; Investigations; Microbiology; Mitomycin - pharmacology; Molecular biology; Molecular Sequence Data; Monoclonal antibodies; Mutagenesis, Site-Directed; Mutation; Open Reading Frames; Operon; Pseudomonas syringae; Pseudomonas syringae - cytology; Pseudomonas syringae - genetics; Pseudomonas syringae - growth & development; Radiation Tolerance; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Ultraviolet Rays
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1534/genetics.104.038943

The Antarctic psychrotrophic bacterium Pseudomonas syringae Lz4W has been used as a model system to identify genes that are required for growth at low temperature. Transposon mutagenesis was carried out to isolate mutant(s) of the bacterium that are defective for growth at 4 degrees but normal at 22 degrees . In one such cold-sensitive mutant (CS1), the transposon-disrupted gene was identified to be a homolog of the recD gene of several bacteria. Trans-complementation and freshly targeted gene disruption studies reconfirmed that the inactivation of the recD gene leads to a cold-sensitive phenotype. We cloned, sequenced, and analyzed approximately 11.2 kbp of DNA from recD and its flanking region from the bacterium. recD was the last gene of a putative recCBD operon. The RecD ORF was 694 amino acids long and 40% identical (52% similar) to the Escherichia coli protein, and it could complement the E. coli recD mutation. The recD gene of E. coli, however, could not complement the cold-sensitive phenotype of the CS1 mutant. Interestingly, the CS1 strain showed greater sensitivity toward the DNA-damaging agents, mitomycin C and UV. The inactivation of recD in P. syringae also led to cell death and accumulation of DNA fragments of approximately 25-30 kbp in size at low temperature (4 degrees ). We propose that during growth at a very low temperature the Antarctic P. syringae is subjected to DNA damage, which requires direct participation of a unique RecD function. Additional results suggest that a truncated recD encoding the N-terminal segment of (1-576) amino acids is sufficient to support growth of P. syringae at low temperature.