Methylobacterium, a major component of the culturable bacterial endophyte community of wild Brassica seed

Abstract

<jats:sec> <jats:title>Background</jats:title> <jats:p>Plants are commonly colonized by a wide diversity of microbial species and the relationships created can range from mutualistic through to parasitic. Microorganisms that typically form symptomless associations with internal plant tissues are termed endophytes. Endophytes associate with most plant species found in natural and managed ecosystems. They are extremely important plant partners that provide improved stress tolerance to the host compared with plants that lack this symbiosis. Plant domestication has reduced endophyte diversity and therefore the wild relatives of many crop species remain untapped reservoirs of beneficial microbes. <jats:italic>Brassica</jats:italic> species display immense diversity and consequently provide the greatest assortment of products used by humans from a single plant genus important for agriculture, horticulture, bioremediation, medicine, soil conditioners, composting crops, and in the production of edible and industrial oils. Many endophytes are horizontally transmitted, but some can colonize the plant’s reproductive tissues, and this gives these symbionts an efficient mechanism of propagation <jats:italic>via</jats:italic> plant seed (termed vertical transmission).</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>This study surveyed 83 wild and landrace <jats:italic>Brassica</jats:italic> accessions composed of 14 different species with a worldwide distribution for seed-originating bacterial endophytes. Seed was stringently disinfected, sown within sterile tissue culture pots within a sterile environment and incubated. After approximately 1-month, direct isolation techniques were used to recover bacterial endophytes from roots and shoots of symptomless plants. Bacteria were identified based on the PCR amplification of partial 16S rDNA gene sequences and annotated using the BLASTn program against the NCBI rRNA database. A diversity index was used as a quantitative measure to reflect how many different bacterial species there were in the seed-originating microbial community of the <jats:italic>Brassica</jats:italic> accessions sampled.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Bacterial endophytes were recovered from the majority of the <jats:italic>Brassica</jats:italic> accessions screened. 16S rDNA gene sequencing identified 19 different bacterial species belonging to three phyla, namely Actinobacteria, Firmicutes and Proteobacteria with the most frequently isolated species being <jats:italic>Methylobacterium fujisawaense</jats:italic>, <jats:italic>Stenotrophomonas rhizophila</jats:italic> and <jats:italic>Pseudomonas lactis</jats:italic>. <jats:italic>Methylobacterium</jats:italic> was the dominant genus composing 56% of the culturable isolated bacterial community and was common in 77% of accessions possessing culturable bacterial endophytes. Two selected isolates of <jats:italic>Methylobacterium</jats:italic> significantly promoted plant growth when inoculated into a cultivar of oilseed rape and inhibited the growth of the pathogen <jats:italic>Leptosphaeria maculans</jats:italic> in dual culture. This is the first report that investigates the seed-originating endophytic microorganisms of wild <jats:italic>Brassica</jats:italic> species and highlights the <jats:italic>Brassica</jats:italic> microbiome as a resource for plant growth promoting bacteria and biological control agents.</jats:p> </jats:sec>

Comprehensive Comparative Genomics and Phenotyping of Methylobacterium Species

“…These results suggest that all of the studied PPFMs are recognized as non-plant-pathogenic bacteria. This is supported by the fact that PPFMs are abundant endophytic and epiphytic bacteria (Delmotte et al, 2009;Knief et al, 2010;Tani et al, 2012;Roodi et al, 2020). A negative effect of rice leaf bleaching by inoculation with a strain of Mb.…”

Development of Plant–Fungal Endophyte Associations to Suppress Phoma Stem Canker in Brassica

“…Our previous research identified that Methylobacterium was the dominant cultural bacterial genus inhabiting wild Brassica plants [24]. Within the same study, two fungal isolates were also recovered from accessions of wild Brassica, but this was not reported earlier.…”

“…Both accessions were collected as wild material and originated from California, USA. Seeds from these accessions were subsequently screened for the presence of microbial endophytes according to a modified method of Roodi et al [24]. Briefly, seed were surface disinfected and grown under sterile conditions within tissue culture pots containing Murashige & Skoog (MS) basal salts [25] with minimal organics (Sigma-Aldrich, Auckland, New Zealand), plus 3% sucrose and 1.5% agar [26].…”

Potentials, Utilization, and Bioengineering of Plant Growth-Promoting Methylobacterium for Sustainable Agriculture

“…Methylobacterial community composition interacting with plants is influenced by many factors including sites, environments, and plant species. Knief et al [32] studied the influence of the factor site, host plant species, time, and presence of other phyllosphere bacteria on Methylobacterial community composition and population size, finding that nearly half of the variation in the Methylobacterial community composition could be explained by site and species, with some members of the communities being host-plant specific [41]. In the phyllosphere of some temperate trees, evolutionary associations between groups of bacteria and host species were significant, and bacterial community structure was determined mainly by host species [42].…”