Overexpression of hns in the plant growth-promoting bacterium Enterobacter cloacae UW5 increases root colonization.
OBJECTIVE
Plant growth-promoting rhizobacteria (PGPR) introduced into soil often do not compete effectively with indigenous micro-organisms for plant colonization. The aim of this study was to identify novel genes that are important for root colonization by the PGPR Enterobacter cloacae UW5.


RESULTS
A library of transposon mutants of Ent. cloacae UW5 was screened for mutants with altered ability to colonize canola roots using a thermal asymmetric interlaced (TAIL)-PCR-based approach. A PCR fragment from one mutant was reproducibly amplified at greater levels from genomic DNA extracted from mutant pools recovered from seedling roots 6 days after seed inoculation compared to that from the cognate inoculum cultures. Competition assays confirmed that the purified mutant designated Ent. cloacae J28 outcompetes the wild-type strain on roots but not in liquid cultures. In Ent. cloacae J28, the transposon is inserted upstream of the hns gene. Quantitative RT-PCR showed that transposon insertion increased expression of hns on roots.


CONCLUSIONS
These results indicate that increased expression of hns in Ent. cloacae enhances competitive colonization of roots.


CONCLUSIONS
A better understanding of the genes involved in plant colonization will contribute to the development of PGPR that can compete more effectively in agricultural soils.
English
M M
MM
Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada.
Coulson
T J D
TJ
Horsman
S R
SR
Patten
C L
CL
D001426:Bacterial Proteins / Q000235:genetics*; D001937:Brassica / Q000254:growth & development / Q000382:microbiology*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D016972:Enterobacter cloacae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005798:Genes, Bacterial; D016254:Mutagenesis, Insertional; D009154:Mutation; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012988:Soil Microbiology
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria