Abstract
A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental biotypes (wastewater, compost, wastewater treatment plant, etc.) were analysed by two polymerase chain reaction (PCR)-based methods, 16S-23S intergenic spacer regions (ITS)-PCR and repetitive extragenic palindromic (BOX)-PCR. These typing techniques were evaluated to assess their usefulness as tool to study thePseudomonas diversity within this complex group. Genetic analysis using ITS- and BOX-PCR generated respectively 12 and 45 distinct profiles. Phylogenetic relationships within fluorescent pseudomonads were examined by analyzing partial 16S rRNA and rpoBgenes sequences. The phylogenetic resolution of the rpoB tree was higher than that of the 16S rRNA tree. Moreover, the sequencing of the rpoB gene has recognized 13 different species and sub-species, while the 16 rRNA gene sequencing differentiated only 9 species. Key words: Fluorescent pseudomonads, 16S-23S intergenic spacer regions (ITS)-PCR, repetitive extragenic palindromic (BOX)-PCR, 16S rRNA, rpoB.
Highlights
The genus Pseudomonas, firstly described by Migula in 1894, is characterized as straight or slightly bent Gram negative rods with one or more polar flagellae, not forming spores (Fuchs et al, 2001)
A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental biotypes were analysed by two polymerase chain reaction (PCR)-based methods, 16S-23S intergenic spacer regions (ITS)-PCR and repetitive extragenic palindromic (BOX)-PCR
Fifty microliters of an appropriate serial dilution was spread on King's B (KB) and King's A (KA) agar medium (Difco Laboratories), and one of each of the phenotypically different colonies developing a fluorescent halo after 48 h of incubation at 25°C was further purified by streaking it on the same medium (Munsch et al, 2000)
Summary
The genus Pseudomonas, firstly described by Migula in 1894, is characterized as straight or slightly bent Gram negative rods with one or more polar flagellae, not forming spores (Fuchs et al, 2001). Several species of rRNA group I pseudomonads have the ability to produce and excrete, under condition of iron limitation, soluble yellow green pigments that fluorescence under UV light (Bultreys et al, 2003), named pyoverdines (PVDs) or pseudobactins, which act as siderophores for these bacteria (Meyer, 2000). These molecules are thought to be associated with biocontrol of fungal pathogens in the biosphere (Fuchs et al, 2001)
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