Root Colonization by Agrobacterium tumefaciens Is Reduced in cel , attB , attD , and attR Mutants

Abstract

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 103 bacteria/cm of root length at the time of inoculation to more than 107 bacteria/cm after 10 days. The numbers of cellulose-minus and nonattachingattB, 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. thalianaecotype 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 andatt 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.

Screening and Assessment of Potential Plant Growth-promoting Bacteria Associated with <i>Allium cepa</i> Linn.

“…The same procedure was used to isolate strains from bulbs. However, the method of Matthysse and McMahan (1998) was used to isolate rhizosphere and rhizoplane bacteria with slight modifications. Approximately 3.5 cm of the root tip was washed in 9 mL sterile reverse osmosis (RO) water twice, and the two washes were combined as loosely bound bacteria.…”

Attachment of different soil bacteria to arbuscular mycorrhizal fungal extraradical hyphae is determined by hyphal vitality and fungal species

“…The biofilm itself consists of bacteria covered in mucilaginous material and enables anchorage to surfaces for whole bacterial aggregates, but does not necessarily involve direct cell contact between individual bacteria and the surface material. A number of studies have shown that bacteria forming extracellular mucilaginous material are better colonizers of roots and hyphae (Bianciotto et al, 1996b(Bianciotto et al, , 2001Matthysse & McMahan, 1998). For example, Bianciotto et al (1996b) studied the colonization of spores and hyphae of the AM fungus Gigaspora margarita by different strains of Pseudomonas and Rhizobium.…”

Unwounded plants elicit Agrobacterium vir gene induction and T‐DNA transfer: transformed plant cells produce opines yet are tumour free

“…A. tumefaciens , however, is not an obligate pathogen, as it can grow vigorously as a saprophyte. It can also colonize plants without causing any symptoms, forming relatively benign biofilms on roots (Matthysse and Kijne, 1998;Matthysse and McMahan, 1998). These commensal interactions between A. tumefaciens and unwounded plants have received relatively little attention, and are the topic of the present study.…”