Figure 7. PG-Cl and PG-Cl₂ function as cell-cell communication signals of P. protegens Pf-5.

(A) Proposed cell-cell communication model. Cell [1] (ΔphlAΔpltM) produces phloroglucinol (PG) and releases it into the environment. PG is taken up by cell [2] (ΔphlAΔphlDΔpltA) and converted into PG-Cl and PG-Cl₂, which are secreted into the environment. PG-Cl and PG-Cl₂ are taken up by cell [1] and induce expression of pyoluteorin biosynthetic genes and production of pyoluteorin by cell [1]. The plt gene cluster is shown. Red font indicates that the gene was deleted. (B) GFP expression from the pure- and co-culture of the ΔphlAΔpltM mutant containing pL-gfp and the ΔphlAΔphlDΔpltA mutant containing pL-gfp on NAGly plate. (C) Antibiosis of the pure- and co-culture of the ΔphlAΔpltM mutant and ΔphlAΔphlDΔpltA mutant against growth of Erwinia amylovora on a NAGly plate. The co-culture was prepared by mixing the two mutants 1:1 and spotting on the plate. The experiment was repeated at least twice, with similar results.

DOI: http://dx.doi.org/10.7554/eLife.22835.026

Figure 7—figure supplement 1. Levels of signaling compounds in cultures of P. protegens Pf-5 of different ages.

Relative levels of signaling compounds that induce pltL expression were determined from extracts of Pf-5 culture supernatants by assessing GFP expressed by P. fluorescens SBW25 containing the reporter construct pRL-gfp. Cultures of wild-type Pf-5 were grown in 5 ml NBGly for different times, as indicated. Data are means of three biological replicates from a representative experiment repeated three times with similar results, and error bars represent the standard deviation of the mean.

DOI: http://dx.doi.org/10.7554/eLife.22835.027

Figure 7—figure supplement 2. Toxicity of pyoluteorin (A) and DAPG (B) to the plant pathogen Erwinia amylovora.

Erwinia amylovora was cultured in NBGly broth for 24 hr in a 96-well plate with or without the tested compounds. The final concentrations of the tested compounds are indicated. The growth of the bacteria was monitored by measuring the value of OD₆₀₀ of the bacterial cultures. Me, negative control composed of a culture amended with the same volume of methanol used in cultures amended with pyoluteorin or DAPG. Data are means of three biological replicates from a representative experiment repeated two times with similar results, and error bars represent the standard deviation of the mean.

DOI: http://dx.doi.org/10.7554/eLife.22835.029