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N-Acyl Homoserine Lactone (N-AHL) has been known as the quorum sensing (QS) signals that control phosphate bacteria (PB) activities in enhancing soil phosphorus (P) availability. This study was aimed at determining: 1) the bacteria biochemical characteristics capable of soil P solubilizing, 2) the N-AHL production types and 3) the best plant roots extract as a N-AHL source. The PB species were determined using 16S rRNA analysis. The determination of the organic acids, phosphatase, phytase, N-AHL and dissolved P was carried out using HPLC, para-Nitro Phenyl Phosphate (pNPP), Na-phytate and spectrophotometry methods, respectively. The PB isolates obtained were classified as Pseudomonas trivialis, P. putida and P. fluorescens. The PB secreted citric, lactic, malonic, oxalic and acetic acids amounting to 156.25 mg. kg-1. The PB phosphatase and phytase activities ranged from 12 to 47 mg PO43- dm-3 h-1. The P solubilized in the PB Pikovskaya inoculated was greater with the amounts between 147.66 and 194.61 mg P kg-1 as control compared (31.06 mg P kg-1). The PB inoculation also produced greater mineralized organic P (63.69 mg P kg-1) than the control (23.7 mg P kg-1). The PB secreted N-AHL greatest was butanoyl-AHL (C4-AHL). The 30% of root extract corn seemed to be the best source of N-AHL as it could increase P dissolution even 300% in comparison with control variant. [ABSTRACT FROM AUTHOR]

Virulence and adaptability of many Gram-negative bacterial species are associated with an N-acylhomoserine lactone (AHL) gene regulation mechanism called quorum sensing (QS). The arrangement of quorum sensing genes is variable throughout bacterial genomes, although there are unifying themes that are common among the various topological arrangements. A bioinformatics survey of 1,403 complete bacterial genomes revealed characteristic gene topologies in 152 genomes that could be classified into 16 topological groups. We developed a concise notation for the patterns and show that the sequences of LuxR regulators and LuxI autoinducer synthase proteins cluster according to the topological patterns. The annotated topologies are deposited online with links to sequences and genome annotations at http://bacteria.itk.ppke.hu/QStopologies/.

Members of the Burkholderia genus of Proteobacteria are capable of living freely in the environment and can also colonize human, animal and plant hosts. Certain members are considered to be clinically important from both medical and veterinary perspectives and furthermore may be important modulators of the rhizosphere. Quorum sensing via N-acyl homoserine lactone signals (AHL QS) is present in almost all Burkholderia species and is thought to play important roles in lifestyle changes such as colonization and niche invasion. Here we present a census of AHL QS genes retrieved from public databases and indicate that the local arrangement (topology) of QS genes, their location within chromosomes and their gene neighborhoods show characteristic patterns that differ between the known Burkholderia clades. In sequence phylogenies, AHL QS genes seem to cluster according to the local gene topology rather than according to the species, which suggests that the basic topology types were present prior to the appearance of current Burkholderia species. The data are available at http://net.icgeb.org/burkholderia/. [ABSTRACT FROM AUTHOR]

Virulence and adaptability of many Gram-negative bacterial species are associated with an N-acylhomoserine lactone (AHL) gene regulation mechanism called quorum sensing (QS). The arrangement of quorum sensing genes is variable throughout bacterial genomes, although there are unifying themes that are common among the various topological arrangements. A bioinformatics survey of 1,403 complete bacterial genomes revealed characteristic gene topologies in 152 genomes that could be classified into16 topological groups. We developed a concise notation for the patterns and show that the sequences of LuxR regulators and LuxI autoinducer synthase proteins cluster according to the topological patterns. The annotated topologies are deposited online with links to sequences and genome annotations at http://bacteria.itk.ppke.hu/QStopologies/. [ABSTRACT FROM AUTHOR]