Diversity of root-associated bacteria associated with field-grown canola (Brassica napus L.) and wheat (Triticum aestivum L.)

Abstract

Little is known about the composition and diversity of the bacterial community associated with plant roots. The purpose of this study was to investigate the diversity of bacteria associated with the roots of canola plants grown at three field locations in Saskatchewan, Canada. Over 300 rhizoplane and 220 endophytic bacteria were randomly selected from agar‐solidified trypticase soy broth, and identified using fatty acid methyl ester (FAME) profiles. Based on FAME profiles, 18 bacterial genera were identified with a similarity index >0.3, but 73% of the identified isolates belonged to four genera: Bacillus (29%), Flavobacterium (12%), Micrococcus (20%) and Rathayibacter (12%). The endophytic community had a lower Shannon‐Weaver diversity index (1.35) compared to the rhizoplane (2.15), and a higher proportion of Bacillus, Flavobacterium, Micrococcus and Rathayibacter genera compared to rhizoplane populations. Genera identified in the endophytic isolates were also found in the rhizoplane isolates. Furthermore, principal component analysis indicated three clusters of bacteria regardless of their site of origin, i.e., rhizoplane or endophytic. In addition, the rhizoplane communities of canola and wheat grown at the same site differed significantly. These results indicate that diverse groups of bacteria are associated with field‐grown plants and that endophytes are a subset of the rhizoplane community.

Endophytic root bacteria associated with the natural vegetation growing at the hydrocarbon-contaminated Bitumount Provincial Historic site

“…As previously mentioned, endosphere bacteria are thought to be a subset of the rhizosphere bacteria that are able to colonize the endosphere (Germida et al 1998). Population size of endophytes is highly varied and is influenced largely by bacterial species and host genotype.…”

“…After transferring the colonies 3 times, the pure colonies were grown at 28°C under agitation (150 rev·min −1 ) in ½-strength liquid TSB. Endophytic isolates were then stored at −80°C in a 1:1 mixture of TSB and sterile glycerol (v/v) (Germida et al 1998). …”

Luteibacter rhizovicinus gen. nov., sp. nov., a yellow-pigmented gammaproteobacterium isolated from the rhizosphere of barley (Hordeum vulgare L.)

“…Soil adjacent to plant roots (the rhizosphere) usually supports a larger number and diversity of culturable bacteria than bulk soil (Lilley et al, 1996;Marilley & Aragno, 1999;Johansen & Binnerup, 2002) probably due to release of exudates and sloughed off cells from the root tissue. The culturable rhizosphere bacteria obtained on standard laboratory substrates are usually dominated by copiotrophic bacteria, such as Bacillus species (Germida et al, 1998), Cytophaga-like bacteria (Johansen & Binnerup, 2002), Enterobacter species (Mahaffee & Kloepper, 1997), Pseudomonas species and Xanthomonas species (Lilley et al, 1996).…”

Microbiomics: An Approach to Community Microbiology

“…Different plant species have their own confi guration of exudates and nutrient uptake from soil; different plant species are expected to have different rhizospheric microbiota. Indeed, plant-specifi c microbial communities could be isolated from roots in studies comparing, for example, wheat, ryegrass, bentgrass, and clover (Grayston et al 1998 ), or wheat and canola (Germida et al 1998 ). Further, plant species-specifi c rhizosphere populations could be isolated within a specifi c bacterial group such as fl uorescent Pseudomonas spp., .…”

“…For over 200 years, ever improving microscopy techniques have enabled microbiologists to study the diversity of the microbial world. The fi ndings and discoveries of the botanist Ferdinand Cohn are undoubtedly important, as he classifi ed bacteria and described the life cycle of Bacillus subtilis (Geison 1981 ). Another invention to revolutionize the fi eld of microbiology was the concept of pure culture-developed by Franz Unger in the 1850s-which became the standard bacteriological technique for microbiology (Drews 1999 ;Mazumdar 1995 ).…”