Influence of Environmental Conditions on the Production of Phenazine-1-Carboxamide by Pseudomonas chlororaphis PCL1391

Abstract

Pseudomonas chlororaphis PCL1391 produces the secondary metabolite phenazine-1-carboxamide (PCN), which is an antifungal metabolite required for biocontrol activity of the strain. Identification of conditions involved in PCN production showed that some carbon sources and all amino acids tested promote PCN levels. Decreasing the pH from 7 to 6 or decreasing the growth temperature from 21 to 16 degrees C decreased PCN production dramatically. In contrast, growth at 1% oxygen as well as low magnesium concentrations increased PCN levels. Salt stress, low concentrations of ferric iron, phosphate, sulfate, and ammonium ions reduced PCN levels. Fusaric acid, a secondary metabolite produced by the soilborne Fusarium spp. fungi, also reduced PCN levels. Different nitrogen sources greatly influenced PCN levels. Analysis of autoinducer levels at conditions of high and low PCN production demonstrated that, under all tested conditions, PCN levels correlate with autoinducer levels, indicating that the regulation of PCN production by environmental factors takes place at or before autoinducer production. Moreover, the results show that autoinducer production not only is induced by a high optical density but also can be induced by certain environmental conditions. We discuss our findings in relation to the success of biocontrol in the field.

darR and darS are regulatory genes that modulate 2-hexyl, 5-propyl resorcinol transcription in Pseudomonas chlororaphis PCL1606

“…Salt stress, in the form of high concentrations of NaCl, strongly reduced the HPR biosynthesis in P. chlororaphis PCL1606. In contrast, high osmolality through high glucose (100 mM) did not inhibit HPR biosynthesis (data not shown), suggesting the integration of a mechanism for salt concentration with the regulation of HPR biosynthesis as previously reported for P. chlororaphis PCL1391 (van Rij et al, 2004).…”

Carbon source regulation of antibiotic production

“…However, fructose, sucrose and ribose had negative effects on phenazine 1-carboximide production. 38 Similar results were observed in a mutant of Pseudomonas sp. M18G, in which the greatest production of phenazine 1-carboxylic acid was achieved with glucose and ethanol as carbon sources.…”

“…One of the primary factors governing phenazine production is population density, and in Pseudomonas aeruginosa, this dependency is affected by at least three quorumsensing systems. 38 In several species of Pseudomonas, phenazine production is affected by the carbon source. For example, in Pseudomonas chloraphis, the greatest production of phenazine 1-carboximide was obtained using L-pyroglutamic acid and glucose.…”

Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt

“…Furthermore, DAPG biosynthesis may also have been repressed by specific environmental conditions (Duffy and Défago, 1999) or by fusaric acid ( Figure 5; Notz et al, 2002;Duffy et al, 2004), a phytotoxin produced by pathogenic F. oxysporum and non-pathogenic F. oxysporum strain Fo47 (Schouten et al, 2004). However, given that also phenazine production can be repressed by fusaric acid (Van Rij et al, 2004, it seems unlikely that this phytotoxin played a major role in the multitrophic interactions occurring in the biocontrol assays.…”