Role of a serine-type D-alanyl-D-alanine carboxypeptidase on the survival of Ochrobactrum sp. 11a under ionic and hyperosmotic stress.
The plant growth-promoting rhizobacterium, Ochrobactrum sp. 11a displays a high intrinsic salinity tolerance and has been used in this work to study the molecular basis of bacterial responses to high concentrations of NaCl. A collection of Ochrobactrum sp. 11a mutants was generated by Tn5-B21 mutagenesis and screened for sensitivity to salinity. One clone, designated PBP and unable to grow on glutamate mannitol salt agar medium supplemented with 300 mM NaCl was selected and further characterized. The PBP mutant carries a single transposon insertion in a gene showing a high degree of identity to the serine-type d-alanyl-d-alanine carboxypeptidase gene of Ochrobactrum anthropi. Interestingly, the expression of this gene was shown to be upregulated by salt in the PBP mutant. Moreover, evidence is presented for the requirement of the gene product for adaptation to high-salt conditions as well as to overcome the toxicity of LiCl, KCl, sucrose, polyethylene glycol (PEG), AlCl(3), CuSO(4), and ZnSO(4). In addition to the altered tolerance to both ionic and osmotic stresses, the PBP mutant exhibited changes in colony and cell morphology, exopolysaccharide production, and an increased sensitivity to detergents.
Príncipe
Analía
A
Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Córdoba, Argentina.
Jofré
Edgardo
E
Alvarez
Florencia
F
Mori
Gladys
G
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response; D007477:Ions / Q000494:pharmacology; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D042041:Ochrobactrum / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D009997:Osmotic Pressure; D046915:Penicillin-Binding Proteins / Q000235:genetics / Q000378:metabolism; D055049:Salt Tolerance; D017422:Sequence Analysis, DNA; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000235:genetics / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology
D001426:Bacterial Proteins; D003470:Culture Media; D004251:DNA Transposable Elements; D007477:Ions; D046915:Penicillin-Binding Proteins; D012965:Sodium Chloride; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase