Engineering Bacterial Competitiveness and Persistence in the Phytosphere

Abstract

Several tactics exist to improve the survival of an introduced microorganism of interest in the plant environment. One, derived from studies on the Agrobacterium-plant interaction and the role of opines in this interaction, proposes to promote growth of the inoculant in the plant environment via the establishment of a bias in the rhizosphere. It is supported by the occurrence of natural biases, such as those generated by opine-like molecules, by calestegins, or by mimosine. Opine-mediated biases have allowed several investigators to favor the growth of opine-degrading bacteria or communities under sterile or axenic environments or in microcosms mimicking near field conditions. Another way to favor a given microbe consists in impeding growth of competing microorganisms. Experiments performed using detergent or bacteriostatic agents as amendments under field or near field conditions yielded promising results. Research perspectives for engineering plant-microbe interactions also include specific engineering of predation and strategies designed to interfere with some of the signals perceived by the microbes, provided these signals control the expression of functions central to microbial fitness. In this respect, quorum-sensing signal molecules, such as N-acyl-homoserine lactones, may be valuable targets for the development of biocontrol agents and procedures.

A mutant GlnD nitrogen sensor protein leads to a nitrogen-fixing but ineffective Sinorhizobium meliloti symbiosis with alfalfa

“…We suggest that this nitrogen was in compounds that the plant does not have the ability to metabolize and that, after transient localization in the shoots, these were released as root exudates. A model for this type of metabolism could be the production of rhizopines, like 3-Omethyl-scyllo-inosamine, by some strains of S. meliloti (42) or opines, like octopine or nopaline, by Agrobacterium tumefaciens transformed plant gall tissue (43). In the latter case, the nitrogen-rich compounds are released from the plant and catabolized by bacteria at the gall surface.…”

New Approaches for Bioaugmentation as a Remediation Technology

“…161,169,194 Many different bacteria communicate via chemical signals, including amino acids or short peptides (gram-positive bacteria) and fatty acid derivatives (gram-negative bacteria). 253 Communication by gram-negative bacteria via N -acyl-homoserine lactones (AHL) is one of the most characterized systems.…”

Methylotrophic Metabolism Is Advantageous for Methylobacterium extorquens during Colonization of Medicago truncatula under Competitive Conditions

“…Metabolic resources are known to be key determinants of microbial colonization of plants, and microbes compete for utilization of organic compounds released by plants (29,48). Therefore, it appears likely that methylotrophic bacteria profit from their ability to utilize methanol and that methylotrophy provides a selective advantage upon phyllosphere colonization.…”