Characterization of Pseudomonas putida genes responsive to nutrient limitation.
The low bioavailability of nutrients and oxygen in the soil environment has hampered successful expression of biodegradation and biocontrol genes that are driven by promoters highly active during routine laboratory conditions of high availability of nutrients and oxygen. Hence, in the present study, expression of the gus-tagged genes in 12 Tn5-gus mutants of the soil microbe Pseudomonas putida PNL-MK25 were examined under various conditions chosen to mimic the soil environment: low carbon, phosphate, nitrate or oxygen, and in the rhizosphere. Based on their expression profiles, three nutrient-responsive mutant (NRM) strains, NRM5, NRM7 and NRM17, were selected for identification of the tagged genes. In strain NRM5, expression of the glutamate dehydrogenase (gdhA) gene was increased 4.9-26.4-fold under various low-nutrient conditions. In NRM7, expression of the novel NADPH : quinone oxidoreductase-like (nql) gene was consistently amongst the highest and was synergistically upregulated by low-nutrient and anoxic conditions. The cyoD gene in NRM17, which encodes the fourth subunit of the cytochrome o ubiquinol oxidase complex, had decreased expression in low-nutrient conditions but its absolute expression level was still amongst the highest. Additionally, it was independent of oxygen availability, in contrast to that in Escherichia coli.
Syn
Chris K C
CKC
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117 543.
Magnuson
Jon K
JK
Pacific Northwest National Laboratory, Richland, WA, USA.
Kingsley
Mark T
MT
Pacific Northwest National Laboratory, Richland, WA, USA.
Swarup
Sanjay
S
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117 543.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003470:Culture Media / Q000737:chemistry; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry* / Q000382:microbiology; D016958:Pseudomonas putida / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D014908:Triticum / Q000737:chemistry* / Q000382:microbiology
D001426:Bacterial Proteins; D003470:Culture Media; D004251:DNA Transposable Elements; D010088:Oxidoreductases; C432586:ubiquinol oxidase; D005969:Glutamate Dehydrogenase; D016660:NAD(P)H Dehydrogenase (Quinone); D010100:Oxygen