Strain RB38 was recovered from a former dumping area in Malaysia. MALDI-TOF mass spectrometry and genomic analysis identified strain RB-38 as Pandoraea pnomenusa. Various biosensors confirmed its quorum sensing properties. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis was subsequently used to characterize the N-acyl homoserine lactone production profile of P. pnomenusa strain RB38, which validated that this isolate produced N-octanoyl homoserine lactone as a quorum sensing molecule. This is the first report of the production of N-octanoyl homoserine lactone by P. pnomenusa strain RB38.
Aeromonas hydrophila is a quorum-sensing (QS) bacterium that causes diarrhea in humans upon infection. Here, we report the genome of pathogenic Aeromonas hydrophila strain 187, which possesses a QS gene responsible for signaling molecule N-acyl homoserine lactone (AHL) synthesis and has been found to be located at contig 36.
Bacteria communicate by producing quorum sensing molecules called autoinducers, which include autoinducer-1, an N-hexanoyl homoserine lactone (AHL), and autoinducer-2. Bacteria present in the human oral cavity have been shown to produce autoinducer-2, but not AHL. Here, we report the isolation of two AHL-producing Klebsiella pneumoniae strains from the posterior dorsal surface of the tongue of a healthy individual. Spent culture supernatant extracts from K. pneumoniae activated the biosensors Agrobacterium tumefaciens NTL4(pZLR4) and Escherichia coli [pSB401], suggesting the presence of both long and short chain AHLs. High resolution mass spectrometry analyses of these extracts confirmed that both K. pneumoniae isolates produced N-octanoylhomoserine lactone and N-3-dodecanoyl-L-homoserine lactone. To the best of our knowledge, this is the first report of the isolation of K. pneumoniae from the posterior dorsal surface of the human tongue and the production of these AHLs by this bacterium.
Jeotgalibacillus soli, a bacterium capable of degrading N-acyl homoserine lactone, was isolated from a soil sample in Portugal. J. soli constitutes the only Jeotgalibacillus species isolated from a non-marine source. Here, the draft genome, several interesting glycosyl hydrolases, and its putative N-acyl homoserine lactonases are presented.
Quorum sensing (QS) is a term used to describe cell-to-cell communication that enables bacteria to orchestrate group behaviours according to density of bacterial cells. In Gram-negative bacteria, this signalling system is widely known to regulate a variety of different phenotypes such as antibiotic production and biofilm formation. In this study, we report the production of N-acyl homoserine lactones produced by Chromobacterium haemolyticum strain KM2, a bacterium isolated from a river water of a reserved tropical national park. Preliminary screening of QS activity using biosensor reporter assays indicated that C. haemolyticum strain KM2 produces both short- and long-chain AHLs. Analysis with high-resolution liquid chromatography-mass spectrometry (LC-MS/MS) analysis revealed the production of three AHLs by strain KM2: N-octanoyl-L-homoserine lactone (C8-HSL), N-dodecanoyl-L-homoserine lactone (C12-HSL), and N-3-oxo-dodecanoyl-L-homoserine lactone (OC12-HSL). This bacterial isolate also exhibited strong β-haemolytic activity. To the best of our knowledge, this is the first documentation of QS activity and multiple AHLs production by C. haemolyticum strain KM2.
The link between quorum sensing in Vibrio campbellii and its virulence towards tiger grouper (Epinephelus fuscoguttatus) was investigated using V. campbellii wild type and quorum-sensing mutants with inactive quorum sensing or constitutively maximal quorum-sensing activity, and signal molecule synthase mutants. The results showed that wild-type V. campbellii is pathogenic to grouper larvae, causing more than 50% mortality after 4 days of challenge. Furthermore, the mortality of larvae challenged with the mutant with maximally active quorum sensing was significantly higher than that of larvae challenged with the wild type, whereas a higher survival was observed in the larvae challenged to the mutant with a completely inactive quorum-sensing system. Grouper larvae challenged with either the signal molecule synthase triple mutant, the harveyi autoinducer-1 (HAI-1) synthase mutant and the autoinducer-2 (AI-2) synthase mutant showed higher survival than larvae challenged with the wild type. In contrast, larvae challenged with the cholerae autoinducer-1 (CAI-1) synthase mutant showed high mortality. This indicates that HAI-1 and AI-2, but not CAI-1, are required for full virulence of V. campbellii towards grouper larvae. Our data suggest that quorum-sensing inhibition could be an effective strategy to control V. campbellii infections in tiger grouper.
Bacteria realize the ability to communicate by production of quorum sensing (QS) molecules called autoinducers, which regulate the physiological activities in their ecological niches. The oral cavity could be a potential area for the presence of QS bacteria. In this study, we report the isolation of a QS bacterial isolate C10B from dentine caries. Preliminary screening using Chromobacterium violaceum CV026 biosensor showed that isolate C10B was able to produce N-acylhomoserine lactones (AHLs). This bacterium was further identified as a member of Burkholderia, an opportunistic pathogen. The isolated Burkholderia sp. was confirmed to produce N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL), N-decanoyl-L-homoserine lactone (C10-HSL) and N-dodecanoyl-L-homoserine lactone (C12-HSL).
In this study, we sequenced the genome of Pandoraea pnomenusa RB38 using Pacific Biosciences RSII (PacBio) Single Molecule Real Time (SMRT) sequencing technology. A pair of cognate luxI/R homologs was identified where the luxI homolog, ppnI, was found adjacent to a luxR homolog, ppnR1. An additional orphan luxR homolog, ppnR2, was also discovered. Multiple sequence alignment and phylogenetic analysis revealed that ppnI is an N-acyl homoserine lactone (AHL) synthase gene that is distinct from those of the nearest phylogenetic neighbor viz. Burkholderia spp. High resolution tandem mass spectrometry (LC-MS/MS) analysis showed that Escherichia coli BL21 harboring ppnI produced a similar AHL profile (N-octanoylhomoserine lactone, C8-HSL) as P. pnomenusa RB38, the wild-type donor strain, confirming that PpnI directed the synthesis of AHL in P. pnomenusa RB38. To our knowledge, this is the first documentation of the luxI/R homologs of the genus Pandoraea.
N-Acyl homoserine lactone (AHL) serves as signaling molecule for quorum sensing (QS) in Gram-negative bacteria to regulate various physiological activities including pathogenicity. With the aim of isolating freshwater-borne bacteria that can cause outbreak of disease in plants and portrayed QS properties, environmental water sampling was conducted. Here we report the preliminary screening of AHL production using Chromobacterium violaceum CV026 and Escherichia coli [pSB401] as AHL biosensors. The 16S rDNA gene sequence of isolate M009 showed the highest sequence similarity to Pantoea stewartii S9-116, which is a plant pathogen. The isolated Pantoea sp. was confirmed to produce N-3-oxohexanoyl-L-HSL (3-oxo-C6-HSL) through analysis of high resolution mass tandem mass spectrometry.
Quorum sensing is a mechanism for regulating proteobacterial gene expression in response to changes in cell population. In proteobacteria, N-acyl homoserine lactone (AHL) appears to be the most widely used signalling molecules in mediating, among others, the production of extracellular virulence factors for survival. In this work, the genome of B. cepacia strain GG4, a plasmid-free strain capable of AHL synthesis was explored. In silico analysis of the 6.6 Mb complete genome revealed the presence of a LuxI homologue which correspond to Type I quorum sensing. Here, we report the molecular cloning and characterization of this LuxI homologue, designated as BurI. This 609 bp gene was cloned and overexpressed in Escherichia coli BL21(DE3). The purified protein was approximately 25 kDa and is highly similar to several autoinducer proteins of the LuxI family among Burkholderia species. To verify the AHL synthesis activity of this protein, high resolution liquid chromatography-mass spectrometry analysis revealed the production of 3-oxo-hexanoylhomoserine lactone, N-octanoylhomoserine lactone and 3-hydroxy-octanoylhomoserine lactone from induced E. coli BL21 harboring the recombinant BurI. Our data show, for the first time, the cloning and characterization of the LuxI homologue from B. cepacia strain GG4 and confirmation of its AHL synthesis activity.
Cell-cell communication is also known as quorum sensing (QS) that happens in the bacterial cells with the aim to regulate their genes expression in response to increased cell density. In this study, a bacterium (L8A) isolated from dental plaque biofilm was identified as Citrobacter amalonaticus by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). Its N-acylhomoserine-lactone (AHL) production was screened by using two types of AHL biosensors namely Chromobacterium violaceum CV026 and Escherichia coli [pSB401]. Citrobacter amalonaticus strain L8A was identified and confirmed producing numerous types of AHL namely N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL) and N-hexadecanoyl-L-homoserine lactone (C16-HSL). We performed the whole genome sequence analysis of this oral isolate where its genome sequence reveals the presence of QS signal synthase gene and our work will pave the ways to study the function of the related QS genes in this bacterium.
To characterize the production and larvicidal activity of Xenorhabdus stockiae KUT6 Petroleum ether extracts from Luria Broth and induced Quorum sensing medium containing N-3- oxododecanoyl Homoserine Lactone inducer against dengue vector Aedes aegypti. The Galleria mellonella larvae were reared for the isolation of Steinernema saimkayi symbiont Xenorhabdus stockiae KUT6 from Cucumber field soil sample in NBTA. Then for the extraction of compounds the KUT6 strains were cultured in Luria Broth and Quorum Sensing optimized media using N-3-oxododecanoyl homoserine lactone inducer. The larvicidal activity of Xenorhabdus stockiae KUT6 of petroleum ether extracts were bioassayed against 4th instar Aedes aegypti dengue vector. The maximum rate of mortality were recorded of the samples A-24h, B-48h, C-72h, A1-24h, B1-48h, C1-72h at different concentrations 50 µg/ml, 100 µg/ml and 150 µg/ml respectively for 24h to 72h of exposure treatment. The morphological characteristics of Xenorhabdus stockiae KUT6 in NBTA were red core colonies with blue background surrounded by zone of inhibition. After 24h exposure maximum rate of 100% mortality of Aedes aegypti 4th instar larvae was attained when treated with sample C1-72h 50 µg/ml of the petroleum ether extracts of quorum sensed medium whereas the sample C 72h petroleum ether extracts of KUT6 cultured in Luria broth recorded 100% mortality at 150 µg on 24h exposure indicates enhancement in the product yield. The study assures the use of Xenorhabdus stockiae KUT6 petroleum ether extracts as biocontrol agent could be beneficial for the control of dengue vectors.
In the phylum of Proteobacteria, quorum sensing (QS) system is widely driven by synthesis and response of N-acyl homoserine lactone (AHL) signalling molecules. AHL is synthesized by LuxI homologue and sensed by LuxR homologue. Once the AHL concentration achieves a threshold level, it triggers the regulation of target genes. In this study, QS activity of Citrobacter amalonaticus strain YG6 which was isolated from clams was investigated. In order to characterise luxI/R homologues, the genome of C. amalonaticus strain YG6 (4.95 Mbp in size) was sequenced using Illumina MiSeq sequencer. Through in silico analysis, a pair of canonical luxI/R homologues and an orphan luxR homologue were identified and designated as camI, camR, and camR2, respectively. A putative lux box was identified at the upstream of camI. The camI gene was cloned and overexpressed in E. coli BL21 (DE3)pLysS. High-resolution triple quadrupole liquid chromatography mass spectrometry (LC-MS/MS) analysis verified that the CamI is a functional AHL synthase which produced multiple AHL species, namely N‑butyryl‑l‑homoserine lactone (C4-HSL), N‑hexanoyl‑l‑homoserine lactone (C6-HSL), N‑octanoyl‑l‑homoserine lactone (C8-HSL), N‑tetradecanoyl‑l‑homoserine lactone (C14-HSL) and N‑hexadecanoyl‑l‑homoserine lactone (C16-HSL) in C. amalonaticus strain YG6 and camI gene in recombinant E. coli BL21(DE3)pLysS. To our best knowledge, this is the first functional study report of camI as well as the first report describing the production of C14-HSL by C. amalonaticus.
Phylogenetic and taxonomic characterization was performed for bacterium RB-25T, which was isolated from a soil sample collected in a former municipal landfill site in Puchong, Malaysia. Growth occurred at 20-37 °C at pH 5-8 but not in the presence of 9 % (w/v) NaCl or higher. The principal fatty acids were C16:0, C18:1ω7c and summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH). Ubiquinone-8 was the only isoprenoid quinone detected. Polar lipid analysis revealed the presence of phospholipid, phosphoaminolipid, phosphatidylethanolamine, phosphatidylglycerol and one unidentified aminolipid. DNA G+C content was 50.9 mol% phylogenetic analysis based on 16S rRNA gene sequence showed that strain RB-25T formed a distinct lineage within the family Enterobacteriaceae of the class Gammaproteobacteria. It exhibited a low level of 16S rRNA gene sequence similarity with its phylogenetic neighbours Pantoea rwandensis LMG 26275T (96.6 %), Rahnella aquatilis CIP 78.65T (96.5 %), Pectobacterium betavasculorum ATCC 43762T (96.4 %), Pantoea rodasii LMG 26273T (96.3 %), Gibbsiella dentisursi NUM 1720T (96.3 %) and Serratia glossinae C1T (96.2 %). Multilocus sequence analyses based on fusA, pyrG, rplB, rpoB and sucA sequences showed a clear distinction of strain RB-25T from the most closely related genera. Isolate RB-25T could also be distinguished from members of these genera by a combination of the DNA G+C content, respiratory quinone system, fatty acid profile, polar lipid composition and other phenotypic features. Strain RB-25T represents a novel species of a new genus, for which the name Chaniamultitudinisentens gen. nov., sp. nov. is proposed. The type strain is RB-25T (=DSM 28811T=LMG 28304T).