Fate of Agrobacterium radiobacter K84 in the environment

Abstract

Agrobacterium radiobacter K84 is an effective, commercially applied, biological control agent for the plant disease crown gall, yet little is known about the survival and dissemination of K84. To trace K84 in the environment, spontaneous antibiotic-resistant mutants were used. Growth rates and phenotypes of streptomycinor rifampin-resistant K84 were similar to those of the parental K84, except the rifampin-resistant mutant produced less agrocin 84 as determined by bioassay. K84 and a strain of Agrobacterium tumefaciens established populations averaging 105 CFU/g in the rhizosphere of cherry and persisted on roots for 2 years. K84 established rhizosphere populations between 104 and 106 CFU/g on cherry, ryegrass, and 11 other herbaceous plants. Populations of K84 declined substantially in fallow soil or water over a 16-week period. K84 was detected in the rhizosphere of ryegrass located up to 40 cm from an inoculum source, indicating lateral dissemination of K84 in soil. In gall tissue on cherry, K84 established populations of 105 CFU/g, about 10to 100-fold less than that of the pathogen. These data demonstrate that K84 persists for up to 2 years in a field environment as a rhizosphere inhabitant or in association with crown gall tissue. Agrobacterium radiobacter (Beijerinck and van Delden) Conn K84 is used commercially to control crown gall, a tumorigenic plant disease caused by a ubiquitous soil-borne pathogen, Agrobacterium tumefaciens (41, 42). Losses due to crown gall can be extensive, particularly in the nursery industry, where each galled plant must be culled. Wounds caused by the routine practice of root pruning may be colonized and infected byA. tumefaciens when seedlings are planted in nursery soils infested with the pathogen. During the infection process, A. tumefaciens transfers the T-DNA region of the tumor-inducing plasmid (pTi) into the plant cell (58). Incorporation of T-DNA into the plant genome results in the formation of a hyperplastic growth called a gall. The gall provides a nutrient-rich environment for further bacterial growth. Galls can weaken, reduce the aesthetic quality, and eventually kill the host plant. There are no effective chemical controls currently available for crown gall. Strain K84 has demonstrated remarkable and widespread success as an agent for the biological control of crown gall (40). K84 has been used commercially for more than a decade in many regions of the world, including Australia,

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

“…Wild-type A. tumefaciens C58 colonized tomato roots in numbers comparable to the numbers observed for colonization of tomato roots by the biocontrol strains Agrobacterium rhizogenes K84 and J73 (15), for colonization of pea roots by A. tumefaciens A723 (8), and for colonization of many root systems by pseudomonads (3,4,11,29). All regions of the root except the root tip were found to be colonized.…”

Exploring Beneficial Properties of the Bacteriocinogenic Enterococcus faecium ST10Bz Strain Isolated from Boza, a Bulgarian Cereal-Based Beverage

“…Thus, in general, E. faecium ST10Bz may possibly attenuate listerial and enterococcal infections under conditions of the upper GIT. Moreover, E. faecium ST10Bz was able to significantly reduce the levels of L. monocytogenes ATCC ® 15313™ and E. faecalis 200A; this may be considered as an example of superior competitiveness [ 79 ]. It could be speculated that under conditions mimicking GIT conditions bacteriocin/s are most probably produced and are able to inhibit the applied test organisms.…”

New Antagonistic Strains of Non‐Pathogenic Agrobacterium vitis to Control Grapevine Crown Gall

“…Penyalver et al (2000) has suggested that the ability of strain K84 to colonize and persist on roots is important in the biological control process. Stockwell et al (1993) reported that K84 established populations averaging 10 5 CFU ⁄ g (fresh weight) on galled root tissue in the rhizosphere of cherry after inoculation with a cell suspension (10 8 CFU ⁄ ml), but the populations dropped to approximately 10 2 CFU ⁄ g of galled root tissue after 22 months. We have reported that colonization of grapevine roots by VAR03-1 remained at approximately 10 6 CFU ⁄ g of root for up to 1 year, then dropped to approximately 10 4 CFU ⁄ g of root after 2 years (Kawaguchi et al 2008b).…”