Microbial interkingdom interactions in roots promote arabidopsis survival
Durán et al., 2019
Plant roots are associated with highly structured microbial communities
composed of bacteria, fungi, and oomycetes. How these microbes interact
to influence plant health has remained poorly studied. Although it is
generally believed that a balanced soil microbial community is critical,
how different components of the community influence each other and how
they influence plant health are unknown. The study led by Schulze-Lefert
and Stéphane Hacquard investigated microbial community structures of
three natural populations of Arabidopsis from different geographical
locations. They conducted profiling analyses of relative abundance and
operational taxonomic units (OTUs) of root-associated bacteria, fungi,
and oomycetes, and investigated intra- and inter-kingdom relationships
of the communities. These uncovered a striking difference between
inter-kingdom and intra-kingdom interactions. While the bacterial-fungal
interactions were predominantly negative, the bacterial and fungal
intra-kingdom interactions were predominantly positive.
To experimentally determine how the bacterial community interacts with fungal and oomycetal communities, the authors established culture collections covering significant proportions of the observed OTUs of bacteria, fungi, and oomycetes. They then adopted a gnotobiotic system to reconstitute microbial communities, so that they can determine impact of different communities on plant health and influence between different communities. Strikingly, they found that inoculation of sterile soil with a fungal or oomycetal community in the absence of bacteria led to low to zero survival rates of plants, indicating detrimental effects of fungal and oomycetal communities on plant health. In contrast, the addition of bacterial community provided not only positive growth benefits to Arabidopsis plants, but also full protection against fungi and oomycetes. As a large proportion of these fungi and oomycetes are plant pathogens, the results indicate that the plant immune system is unable to defend against these pathogens and that the root-associated bacterial community plays a decisive role in protecting plants from these pathogens. Consistent with observations from natural communities, the synthetic bacterial community had a large negative effect on fungal and oomycetal communities.
Pair-wise interaction analyses of individual bacterial strains on fungal growth showed that Comamonadaceae and Pseudomonadaceae had greatest antagonistic effects against diverse fungal isolates. Depletion of these two groups of bacteria from the synthetic community resulted in reduced protection against fungi. However, this Comamonadaceae- and Pseudomonadaceae-depleted bacterial community still provided profound protection against the fungal community in the gnotobiotic system, indicating that plant health protection against fungal pathogens is a highly redundant function in commensal bacteria. Together, this study advances our understanding of inter-kingdom interactions in root-associated microbial communities and provides much needed insights into the role of microbial community in plant health. The successful application of a gnotobiotic system and synthetic communities opens up new horizons for plant immunity studies and development of better biocontrol agents.
To experimentally determine how the bacterial community interacts with fungal and oomycetal communities, the authors established culture collections covering significant proportions of the observed OTUs of bacteria, fungi, and oomycetes. They then adopted a gnotobiotic system to reconstitute microbial communities, so that they can determine impact of different communities on plant health and influence between different communities. Strikingly, they found that inoculation of sterile soil with a fungal or oomycetal community in the absence of bacteria led to low to zero survival rates of plants, indicating detrimental effects of fungal and oomycetal communities on plant health. In contrast, the addition of bacterial community provided not only positive growth benefits to Arabidopsis plants, but also full protection against fungi and oomycetes. As a large proportion of these fungi and oomycetes are plant pathogens, the results indicate that the plant immune system is unable to defend against these pathogens and that the root-associated bacterial community plays a decisive role in protecting plants from these pathogens. Consistent with observations from natural communities, the synthetic bacterial community had a large negative effect on fungal and oomycetal communities.
Pair-wise interaction analyses of individual bacterial strains on fungal growth showed that Comamonadaceae and Pseudomonadaceae had greatest antagonistic effects against diverse fungal isolates. Depletion of these two groups of bacteria from the synthetic community resulted in reduced protection against fungi. However, this Comamonadaceae- and Pseudomonadaceae-depleted bacterial community still provided profound protection against the fungal community in the gnotobiotic system, indicating that plant health protection against fungal pathogens is a highly redundant function in commensal bacteria. Together, this study advances our understanding of inter-kingdom interactions in root-associated microbial communities and provides much needed insights into the role of microbial community in plant health. The successful application of a gnotobiotic system and synthetic communities opens up new horizons for plant immunity studies and development of better biocontrol agents.
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