Interspecies Crosstalk via LuxI/LuxR-Type Quorum Sensing Pathways Contributes to Decreased Nematode Survival in Coinfections of and .

Quorum sensing (QS) is a prominent chemical communication mechanism used by common bacteria to regulate group behaviors at high cell density, including many processes important in pathogenesis. There is growing evidence that certain bacteria can use QS to sense not only themselves but also other species and that this crosstalk could alter collective behaviors. In the current study, we report the results of culture-based and coinfection experiments that probe interspecies interactions between the opportunistic pathogens and involving their LuxI/LuxR-type QS circuits.

Combatting melioidosis with chemical synthetic lethality.

has emerged as a nonpathogenic surrogate for , the causative agent of melioidosis, and an important Gram-negative model bacterium for studying the biosynthesis and regulation of secondary metabolism. We recently reported that subinhibitory concentrations of trimethoprim induce vast changes in both the primary and secondary metabolome of . In the current work, we show that the folate biosynthetic enzyme FolE2 is permissive under standard growth conditions but essential for in the presence of subinhibitory doses of trimethoprim.

Regulation of an antibiotic resistance efflux pump by quorum sensing and a TetR-family repressor in .

The soil bacterium uses a single LuxI-R-type quorum-sensing system, CviI-R, to regulate genes in a cell density-dependent manner. CviI synthesizes the signal -hexanoyl-homoserine lactone (C6-HSL) and CviR is a C6-HSL-responsive cytoplasmic transcription regulator. C6-HSL-bound CviR activates dozens of genes, for example the cluster coding for an efflux pump conferring antibiotic resistance.

An Amino Acid Substitution in Elongation Factor EF-G1A Alters the Antibiotic Susceptibility of Pseudomonas aeruginosa LasR-Null Mutants.

The opportunistic bacterium Pseudomonas aeruginosa uses the LasR-I quorum-sensing system to increase resistance to the aminoglycoside antibiotic tobramycin. Paradoxically, -null mutants are commonly isolated from chronic human infections treated with tobramycin, suggesting there may be a mechanism that permits the emergence of -null mutants under tobramycin selection. We hypothesized that some other genetic mutations that emerge in these isolates might modulate the effects of -null mutations on antibiotic resistance.

Cross-species activation of hydrogen cyanide production by a promiscuous quorum-sensing receptor promotes competition in a dual-species model.

Many saprophytic bacteria have LuxR-I-type acyl-homoserine lactone (AHL) quorum-sensing systems that may be important for competing with other bacteria in complex soil communities. LuxR AHL receptors specifically interact with cognate AHLs to cause changes in expression of target genes. Some LuxR-type AHL receptors have relaxed specificity and are responsive to non-cognate AHLs.

Tobramycin adaptation alters the antibiotic susceptibility of Pseudomonas aeruginosa quorum sensing-null mutants.

The opportunistic bacterium Pseudomonas aeruginosa uses the LasR-I quorum sensing system to increase resistance to the aminioglycoside antibiotic tobramycin. Paradoxically, lasR-null mutants are commonly isolated from chronic human infections treated with tobramycin, suggesting there may be a mechanism allowing the lasR-null mutants to persist under tobramycin selection. We hypothesized that the effects of inactivating lasR on tobramycin resistance might be dependent on the presence or absence of other gene mutations in that strain, a phenomenon known as epistasis.

Bacterioferritin Is Assembled from FtnA and BfrB Subunits with the Relative Proportions Dependent on the Environmental Oxygen Availability.

Ferritins are iron storage proteins assembled from 24 subunits into a spherical and hollow structure. The genomes of many bacteria harbor genes encoding two types of ferritin-like proteins, the bacterial ferritins (Ftn) and the bacterioferritins (Bfr), which bind heme. The genome of PAO1 (like the genomes of many bacteria) contains genes coding for two different types of ferritin-like molecules, (PA4235) and (PA3531).

Engineering peptide-polymer hybrids for targeted repair and protection of cervical lesions.

By 2060, nearly 100 million people in the U.S. will be over age 65 years.

Tobramycin Adaptation Enhances Policing of Social Cheaters in Pseudomonas aeruginosa.

The Pseudomonas aeruginosa LasR-LasI (LasR-I) quorum sensing system regulates secreted proteases that can be exploited by cheaters, such as quorum sensing receptor-defective () mutants. mutants emerge in populations growing on casein as a sole source of carbon and energy. These mutants are exploitative cheaters because they avoid the substantial cost of engaging in quorum sensing.

Secondary metabolites from the Burkholderia pseudomallei complex: structure, ecology, and evolution.

Bacterial secondary metabolites play important roles in promoting survival, though few have been carefully studied in their natural context. Numerous gene clusters code for secondary metabolites in the genomes of members of the Bptm group, made up of three closely related species with distinctly different lifestyles: the opportunistic pathogen Burkholderia pseudomallei, the non-pathogenic saprophyte Burkholderia thailandensis, and the host-adapted pathogen Burkholderia mallei. Several biosynthetic gene clusters are conserved across two or all three species, and this provides an opportunity to understand how the corresponding secondary metabolites contribute to survival in different contexts in nature.

Burkholderia thailandensis Methylated Hydroxyalkylquinolines: Biosynthesis and Antimicrobial Activity in Cocultures.

The bacterium produces an arsenal of secondary metabolites that have diverse structures and roles in the ecology of this soil-dwelling bacterium. In coculture experiments, strain E264 secretes an antimicrobial that nearly eliminates another soil bacterium, strain 168. To identify the antimicrobial, we used a transposon mutagenesis approach.

The Chemistry and Biology of Bactobolin: A 10-Year Collaboration with Natural Product Chemist Extraordinaire Jon Clardy.

Bactobolin is a hybrid natural product with potent cytotoxic activity. Its production from was reported as part of a collaboration between the Greenberg and Clardy laboratories in 2010. The collaboration sparked a series of studies leading to the discovery of new analogues and associated structure-activity relationships, the identification of the bactobolin biosynthetic gene cluster and assembly of its unusual amino acid building block, the molecular target of and resistance to the antibiotic, and finally an X-ray crystal structure of the ribosome-bactobolin complex.

The C. elegans CHP1 homolog, pbo-1, functions in innate immunity by regulating the pH of the intestinal lumen.

Caenorhabditis elegans are soil-dwelling nematodes and models for understanding innate immunity and infection. Previously, we developed a novel fluorescent dye (KR35) that accumulates in the intestine of C. elegans and reports a dynamic wave in intestinal pH associated with the defecation motor program.

Inhibiting Iron Mobilization from Bacterioferritin in Impairs Biofilm Formation Irrespective of Environmental Iron Availability.

Although iron is essential for bacteria, the nutrient presents problems of toxicity and solubility. Bacteria circumvent these problems with the aid of iron storage proteins where Fe is deposited and, when necessary, mobilized as Fe for metabolic requirements. In , Fe is compartmentalized in bacterioferritin (BfrB), and its mobilization as Fe requires specific binding of a ferredoxin (Bfd) to reduce the stored Fe.

Potent modulation of the CepR quorum sensing receptor and virulence in a Burkholderia cepacia complex member using non-native lactone ligands.

The Burkholderia cepacia complex (Bcc) is a family of closely related bacterial pathogens that are the causative agent of deadly human infections. Virulence in Bcc species has been shown to be controlled by the CepI/CepR quorum sensing (QS) system, which is mediated by an N-acyl L-homoserine lactone (AHL) signal (C-AHL) and its cognate LuxR-type receptor (CepR). Chemical strategies to block QS in Bcc members would represent an approach to intercept this bacterial communication process and further delineate its role in infection.

Efflux Pumps in Species Increase Antibiotic Resistance and Promote Survival in a Coculture Competition Model.

Members of the genus include opportunistic but often-fatal pathogens and soil saprophytes with highly versatile metabolic capabilities. In previous studies of (formerly ) strain CV017, we identified a resistance nodulation division (RND)-family efflux pump (CdeAB-OprM) that confers resistance to several antibiotics, including the bactobolin antibiotic produced by the soil saprophyte Here, we show the genes increase survival in a laboratory competition model with We also demonstrate that adding sublethal bactobolin concentrations to the coculture increases survival, but this effect is not through CdeAB-OprM. Instead, the increased survival requires a second, previously unreported pump we call CseAB-OprN.

Bacterial Quorum Sensing and Microbial Community Interactions.

Many bacteria use a cell-cell communication system called quorum sensing to coordinate population density-dependent changes in behavior. Quorum sensing involves production of and response to diffusible or secreted signals, which can vary substantially across different types of bacteria. In many species, quorum sensing modulates virulence functions and is important for pathogenesis.

Malleilactone Is a Burkholderia pseudomallei Virulence Factor Regulated by Antibiotics and Quorum Sensing.

, the causative agent of melioidosis, encodes almost a dozen predicted polyketide (PK) biosynthetic gene clusters. Many of these are regulated by LuxR-I-type acyl-homoserine (AHL) quorum-sensing systems. One of the PK gene clusters, the gene cluster, is conserved in the close relative The genes code for the cytotoxin malleilactone and are regulated by a genetically linked LuxR-type transcription factor, MalR.

Quorum-sensing control of antibiotic resistance stabilizes cooperation in Chromobacterium violaceum.

Many Proteobacteria use quorum sensing to regulate production of public goods, such as antimicrobials and proteases, that are shared among members of a community. Public goods are vulnerable to exploitation by cheaters, such as quorum sensing-defective mutants. Quorum sensing- regulated private goods, goods that benefit only producing cells, can prevent the emergence of cheaters under certain growth conditions.

Inhibiting the BfrB:Bfd interaction in Pseudomonas aeruginosa causes irreversible iron accumulation in bacterioferritin and iron deficiency in the bacterial cytosol.

Iron is an essential nutrient for bacteria but the reactivity of Fe and the insolubility of Fe present significant challenges to bacterial cells. Iron storage proteins contribute to ameliorating these challenges by oxidizing Fe using O and HO as electron acceptors, and by compartmentalizing Fe. Two types of iron-storage proteins coexist in bacteria, the ferritins (Ftn) and the heme-containing bacterioferritins (Bfr), but the reasons for their coexistence are largely unknown.

Quorum Sensing Influences Burkholderia thailandensis Biofilm Development and Matrix Production.

Unlabelled: Members of the genus Burkholderia are known to be adept at biofilm formation, which presumably assists in the survival of these organisms in the environment and the host. Biofilm formation has been linked to quorum sensing (QS) in several bacterial species. In this study, we characterized Burkholderia thailandensis biofilm development under flow conditions and sought to determine whether QS contributes to this process.

Draft Genome Sequence of Chromobacterium violaceum Strain CV017.

We announce the draft genome sequence for Chromobacterium violaceum strain CV017, used as a model and tool to understand acyl-homoserine lactone-dependent quorum sensing. The assembly consists of 4,774,638-bp contained in 211 scaffolds.