Root colonization by Agrobacterium tumefaciens is reduced in cel, attB, attD, and attR mutants.
Root colonization by Agrobacterium tumefaciens was measured by using tomato and Arabidopsis thaliana roots dipped in a bacterial suspension and planted in soil. Wild-type bacteria showed extensive growth on tomato roots; the number of bacteria increased from 10(3) bacteria/cm of root length at the time of inoculation to more than 10(7) bacteria/cm after 10 days. The numbers of cellulose-minus and nonattaching attB, attD, and attR mutant bacteria were less than 1/10,000th the number of wild-type bacteria recovered from tomato roots. On roots of A. thaliana ecotype Landsberg erecta, the numbers of wild-type bacteria increased from about 30 to 8,000 bacteria/cm of root length after 8 days. The numbers of cellulose-minus and nonattaching mutant bacteria were 1/100th to 1/10th the number of wild-type bacteria recovered after 8 days. The attachment of A. tumefaciens to cut A. thaliana roots incubated in 0.4% sucrose and observed with a light microscope was also reduced with cel and att mutants. These results suggest that cellulose synthesis and attachment genes play a role in the ability of the bacteria to colonize roots, as well as in bacterial pathogenesis.
Matthysse
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AG
Department of Biology, University of North Carolina, Chapel Hill 27599-3280, USA. matthysse@unc.edu
McMahan
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S
D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D017360:Arabidopsis / Q000382:microbiology*; D001422:Bacterial Adhesion; D015169:Colony Count, Microbial; D018551:Solanum lycopersicum / Q000382:microbiology*; D009154:Mutation / Q000235:genetics; D018517:Plant Roots / Q000382:microbiology*