Isolation and Partial Characterization of Antagonistic Peptides Produced by Paenibacillus sp. Strain B2 Isolated from the Sorghum Mycorrhizosphere

Abstract

Paenibacillus sp. strain B2, isolated from the mycorrhizosphere of sorghum colonized by Glomus mosseae, produces an antagonistic factor. This factor has a broad spectrum of activity against gram-positive and gram-negative bacteria and also against fungi. The antagonistic factor was isolated from the bacterial culture medium and purified by cation-exchange, reverse-phase, and size exclusion chromatography. The purified factor could be separated into three active compounds following characterization by amino acid analysis and by combined reverse-phase chromatography and mass spectrometry (liquid chromatography-mass spectrometry and mass spectrometry-mass spectrometry). The first compound had the same retention time as polymyxin B 1 , whereas the two other compounds were more hydrophobic. The molecular masses of the latter compounds are 1,184.7 and 1,202.7 Da, respectively, and their structure is similar to that of polymyxin B 1 , with a cyclic heptapeptide moiety attached to a tripeptide side chain and a fatty acyl residue. They both contain threonine, phenylalanine, leucine, and 2,4-diaminobutyric acid residues. The peptide with a molecular mass of 1,184.7 contains a 2,3-didehydrobutyrine residue with a molecular mass of 101 Da replacing a threonine at the A2 position of the polymyxin side chain. This modification could explain the broader range of antagonistic activity of this peptide compared to that of polymyxin B.

Stimulation of Defense Reactions in Medicago truncatula by Antagonistic Lipopeptides from Paenibacillus sp. Strain B2

“…In the present study, we analyzed the possibility of eliciting plant defense responses by paenimyxin, an antagonistic compound isolated from the PGPR Paenibacillus sp. strain B2 (43). For this purpose, M. truncatula cell suspensions were used and a pathosystem between M. truncatula and F. acuminatum was established.…”

“…Bacterial growth conditions and purification of the Paenibacillus sp. strain B2 antagonistic factor (paenimyxin) were as described previously by Selim et al (43) and referred to as Superdex purified material.…”

“…Moreover, we have demonstrated that a mixture of cyclic lipopolypeptides (paenimyxin) isolated from Paenibacillus sp. strain B2 has an antagonistic activity against several plant-pathogenic bacteria and fungi (43). In this study, we investigated the capacity of paenimyxin to stimulate defense responses in M. truncatula, reduce disease symptoms from F. acuminatum, and upregulate transcripts from genes involved in defense mechanisms.…”

Management of rice blast disease (Pyricularia oryzae) using formulated<br>bacterial consortium

“…Development of biocontrol formulation can be successful if microbial agents could survive during storage, as well as competitive and aggressiveness after inoculation process (Beatty and Jensen, 2002;Selim et al, 2005). In this study, although the potential suspension-based formulation showed good effect in blast suppression, but for large scale this formulation is less efficient in terms of packaging and use.…”

The role of the arbuscular mycorrhiza-associated rhizobacteria in the biocontrol of soilborne phytopathogens: a review

“…B2, isolated from the mycorrhizosphere of G. mosseae and identified by phylogenetic comparison of the 16S rRNA gene sequence and analytical profile index (API, analytical profile index) system, was antagonistic against various soilborne pathogens in vitro and reduced tomato root necrosis caused by P. nicotianae (Budi et al, 1999). This isolate displayed cellulolytic, proteolytic, chitinolytic and pectinolytic activities and was shown to liberate the antibiotic polymixin B1 and two other polymyxin-like compounds antagonistic among F. solani and F. acuminatum (Budi et al, 2000;Selim et al, 2005). Moreover, its presence resulted in disorganization of cell walls and/or cell contents of P. nicotianae and F. oxysporum observed by electron microscopy.…”