Multilocus Sequence-Based Analysis Delineates a Clonal Population of Agrobacterium (Rhizobium) radiobacter (Agrobacterium tumefaciens) of Human Origin

Abstract

The genus Agrobacterium includes plant-associated bacteria and opportunistic human pathogens. Taxonomy and nomenclature within the genus remain controversial. In particular, isolates of human origin were all affiliated with the species Agrobacterium (Rhizobium) radiobacter, while phytopathogenic strains were designated under the synonym denomination Agrobacterium tumefaciens. In order to study the relative distribution of Agrobacterium strains according to their origins, we performed a multilocus sequence-based analysis (MLSA) on a large collection of 89 clinical and environmental strains from various origins. We proposed an MLSA scheme based on the partial sequence of 7 housekeeping genes (atpD, zwf, trpE, groEL, dnaK, glnA, and rpoB) present on the circular chromosome of A. tumefaciens C58. Multilocus phylogeny revealed that 88% of the clinical strains belong to genovar A7, which formed a homogeneous population with linkage disequilibrium, suggesting a low rate of recombination. Comparison of genomic fingerprints obtained by pulsed-field gel electrophoresis (PFGE) showed that the strains of genovar A7 were epidemiologically unrelated. We present genetic evidence that genovar A7 may constitute a human-associated population distinct from the environmental population. Also, phenotypic characteristics, such as culture at 42°C, agree with this statement. This human-associated population might represent a potential novel species in the genus Agrobacterium.

Multilocus genetics to reconstruct aeromonad evolution

“…Both the genetic and ST diversity per strain were observed to be exceptionally high in the genus Aeromonas and were much higher than observed for many other environmental bacteria [9,11,34]. Although strains from countries other than France only represented approximately 25% of the total strains of our dataset, the high level of genetic diversity observed validated the non-redundancy and representativeness of our population.…”

“…There is evidence that genetic clusters can correspond to ecologically distinct populations and/or host-adapted populations, even when genes that are not related to virulence are considered [9,11-14]. …”

Slow sand filtration for elimination of phytopathogens in water used in forest nurseries

“…and agrobacteria were found to occur in these postagricultural soils. The agrobacteria group describes tumour and gall forming Rhizobium species: R./Agrobacterium radiobacter (previous classified as Agrobacterium tumefaciens; Sawada et al 1993;Young et al 2001Young et al , 2003Aujoulat et al 2011). R. radiobacter rarely attacks coniferous seedlings and is only sometimes the cause of dying off in plants (Sinclair et al 1987).…”

Agrobacterium arsenijevicii sp. nov., isolated from crown gall tumors on raspberry and cherry plum

“…It is recently reported that Agrobacterium strains may carry symbiotic (Sym) plasmid and have nodulating activity on legume plants [7,41]. They have been also identified as an opportunistic human pathogens responsible for nosocomial infections [2] and are widely used in biotechnology to produce genetically modified plants [36].…”

“…The atpD, glnA and rpoB gene fragments were amplified and sequenced as described by Aujoulat et al [2]. The portion of gyrB gene was amplified according to the protocol described by Martens et al [17], and sequenced by using the same primers as for PCR amplifications.…”