Erschienen:
American Society for Microbiology, 2016
Erschienen in:mBio
Sprache:
Englisch
DOI:
10.1128/mbio.01664-16
ISSN:
2161-2129;
2150-7511
Entstehung:
Anmerkungen:
Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Colonization of plant roots by
<jats:named-content content-type="genus-species">Bacillus subtilis</jats:named-content>
is mutually beneficial to plants and bacteria. Plants can secrete up to 30% of their fixed carbon via root exudates, thereby feeding the bacteria, and in return the associated
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
bacteria provide the plant with many growth-promoting traits. Formation of a biofilm on the root by matrix-producing
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
is a well-established requirement for long-term colonization. However, we observed that cells start forming a biofilm only several hours after motile cells first settle on the plant. We also found that intact chemotaxis machinery is required for early root colonization by
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
and for plant protection.
<jats:named-content content-type="genus-species">Arabidopsis thaliana</jats:named-content>
root exudates attract
<jats:italic>B. subtilis in vitro</jats:italic>
, an activity mediated by the two characterized chemoreceptors, McpB and McpC, as well as by the orphan receptor TlpC. Nonetheless, bacteria lacking these chemoreceptors are still able to colonize the root, suggesting that other chemoreceptors might also play a role in this process. These observations suggest that
<jats:italic>A. thaliana</jats:italic>
actively recruits
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
through root-secreted molecules, and our results stress the important roles of
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
chemoreceptors for efficient colonization of plants in natural environments. These results demonstrate a remarkable strategy adapted by beneficial rhizobacteria to utilize carbon-rich root exudates, which may facilitate rhizobacterial colonization and a mutualistic association with the host.
</jats:p>
<jats:p>
<jats:bold>IMPORTANCE</jats:bold>
<jats:named-content content-type="genus-species">Bacillus subtilis</jats:named-content>
is a plant growth-promoting rhizobacterium that establishes robust interactions with roots. Many studies have now demonstrated that biofilm formation is required for long-term colonization. However, we observed that motile
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
mediates the first contact with the roots. These cells differentiate into biofilm-producing cells only several hours after the bacteria first contact the root. Our study reveals that intact chemotaxis machinery is required for the bacteria to reach the root. Many, if not all, of the
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
10 chemoreceptors are involved in the interaction with the plant. These observations stress the importance of root-bacterium interactions in the
<jats:named-content content-type="genus-species">B. subtilis</jats:named-content>
lifestyle.
</jats:p>