SciCombinator

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Concept: Pseudomonas aeruginosa

261

There have been an increasing number of reports implicating Gammaproteobacteria often carrying genes of drug resistance from colonized sink traps to vulnerable hospitalized patients. However, the mechanism of transmission from the wastewater of the sink P-trap to patients remains poorly understood. Herein we report the use of a designated hand washing sink lab gallery to model dispersion of green fluorescent protein (GFP)- expressing Escherichia coli from sink wastewater to the surrounding environment. We found no dispersion of GFP-E.coli directly from the P-trap to the sink basin or surrounding countertop with coincident water flow from a faucet. However, when the GFP-E.coli were allowed to mature in the P-trap under conditions similar to a hospital environment a GFP-E.coli containing putative biofilm extended upward over seven days to reach the strainer. This subsequently resulted in droplet dispersion to the surrounding areas (<30 inches) during faucet operation. We also demonstrated that P-trap colonization could occur by retrograde transmission along a common pipe. We postulate that the organisms mobilize up to the strainer from the P-trap resulting in droplet dispersion rather than directly from the P-trap. This work helps to further define the mode of transmission of bacteria from a P-trap reservoir to a vulnerable hospitalized patient.Importance Many recent reports demonstrate that sink drain pipes become colonized with highly consequential multidrug resistant bacteria, which then result in hospital acquired infections. However, the mechanism of dispersal of bacteria from the sink to patients has not been fully elucidated. Through establishment of a unique sink gallery this work found that a staged mode of transmission involving biofilm growth from the lower pipe to the sink strainer and subsequent splatter to the bowl and surrounding area occurs rather than splatter directly from the water in the lower pipe. We have also demonstrated that bacterial transmission can occur via connections in wastewater plumbing to neighboring sinks. This work helps to more clearly define the mechanism and risk of transmission from a wastewater source to hospitalized patients in a world with increasingly antibiotic resistant bacteria which can thrive in wastewater environments and cause infections in vulnerable patients.

Concepts: Protein, Gene, Bacteria, Antibiotic resistance, Escherichia coli, Pseudomonas aeruginosa, Plumbing, Sink

184

Twitching motility-mediated biofilm expansion is a complex, multicellular behavior that enables the active colonization of surfaces by many species of bacteria. In this study we have explored the emergence of intricate network patterns of interconnected trails that form in actively expanding biofilms of Pseudomonas aeruginosa. We have used high-resolution, phase-contrast time-lapse microscopy and developed sophisticated computer vision algorithms to track and analyze individual cell movements during expansion of P. aeruginosa biofilms. We have also used atomic force microscopy to examine the topography of the substrate underneath the expanding biofilm. Our analyses reveal that at the leading edge of the biofilm, highly coherent groups of bacteria migrate across the surface of the semisolid media and in doing so create furrows along which following cells preferentially migrate. This leads to the emergence of a network of trails that guide mass transit toward the leading edges of the biofilm. We have also determined that extracellular DNA (eDNA) facilitates efficient traffic flow throughout the furrow network by maintaining coherent cell alignments, thereby avoiding traffic jams and ensuring an efficient supply of cells to the migrating front. Our analyses reveal that eDNA also coordinates the movements of cells in the leading edge vanguard rafts and is required for the assembly of cells into the “bulldozer” aggregates that forge the interconnecting furrows. Our observations have revealed that large-scale self-organization of cells in actively expanding biofilms of P. aeruginosa occurs through construction of an intricate network of furrows that is facilitated by eDNA.

Concepts: DNA, Archaea, Bacteria, Pseudomonas aeruginosa, Cell wall, Polysaccharide, Biofilm, Quorum sensing

171

Quorum sensing is a process of chemical communication that bacteria use to monitor cell density and coordinate cooperative behaviors. Quorum sensing relies on extracellular signal molecules and cognate receptor pairs. While a single quorum-sensing system is sufficient to probe cell density, bacteria frequently use multiple quorum-sensing systems to regulate the same cooperative behaviors. The potential benefits of these redundant network structures are not clear. Here, we combine modeling and experimental analyses of the Bacillus subtilis and Vibrio harveyi quorum-sensing networks to show that accumulation of multiple quorum-sensing systems may be driven by a facultative cheating mechanism. We demonstrate that a strain that has acquired an additional quorum-sensing system can exploit its ancestor that possesses one fewer system, but nonetheless, resume full cooperation with its kin when it is fixed in the population. We identify the molecular network design criteria required for this advantage. Our results suggest that increased complexity in bacterial social signaling circuits can evolve without providing an adaptive advantage in a clonal population.

Concepts: Bacteria, Microbiology, Pseudomonas aeruginosa, Biofilm, Bacillus, Quorum sensing, Bioluminescence, Vibrio harveyi

171

Quorum sensing (QS) signaling allows bacteria to control gene expression once a critical population density is achieved. The Gram-negative human pathogen Pseudomonas aeruginosa uses N-acylhomoserine lactones (AHL) as QS signals, which coordinate the production of virulence factors and biofilms. These bacterial signals can also modulate human cell behavior. Little is known about the mechanisms of the action of AHL on their eukaryotic targets. Here, we found that N-3-oxo-dodecanoyl-L-homoserine lactone 3O-C(12)-HSL modulates human intestinal epithelial Caco-2 cell migration in a dose- and time-dependent manner. Using new 3O-C(12)-HSL biotin and fluorescently-tagged probes for LC-MS/MS and confocal imaging, respectively, we demonstrated for the first time that 3O-C(12)-HSL interacts and co-localizes with the IQ-motif-containing GTPase-activating protein IQGAP1 in Caco-2 cells. The interaction between IQGAP1 and 3O-C(12)-HSL was further confirmed by pull-down assay using a GST-tagged protein with subsequent Western blot of IQGAP1 and by identifying 3O-C(12)-HSL with a sensor bioassay. Moreover, 3O-C(12)-HSL induced changes in the phosphorylation status of Rac1 and Cdc42 and the localization of IQGAP1 as evidenced by confocal and STED microscopy and Western blots. Our findings suggest that the IQGAP1 is a novel partner for P.aeruginosa 3O-C(12)-HSL and likely the integrator of Rac1 and Cdc42- dependent altered cell migration. We propose that the targeting of IQGAP1 by 3O-C(12)-HSL can trigger essential changes in the cytoskeleton network and be an essential component in bacterial - human cell communication.

Concepts: DNA, Gene, Cell nucleus, Gene expression, Cell, Bacteria, Pseudomonas aeruginosa, Biofilm

167

To isolate and characterize indigenous algicidal bacteria and their algae-lysing compounds active against Microcystis aeruginosa, strains TH1, TH2, and FACHB 905.

Concepts: Immune system, Bacteria, Fungus, T helper cell, Pseudomonas aeruginosa, Bacterial cell structure, Vermilion, Carmine

164

Many Gram-negative plant pathogenic bacteria employ a N-acylhomoserine lactone (AHL)-based quorum sensing (QS) system to regulate their virulence traits. A sustainable biocontrol strategy has been developed using quorum quenching (QQ) bacteria to interfere with QS and protect plants from pathogens. Here, the prevalence and the diversity of QQ strains inhabiting tobacco leaf surfaces were explored. A total of 1177 leaf-associated isolates were screened for their ability to disrupt AHL-mediated QS, using the biosensor Chromobacterium violaceum CV026. One hundred and sixty-eight strains (14%) are capable of interfering with AHL activity. Among these, 106 strains (63%) of the culturable quenchers can enzymatically degrade AHL molecules, while the remaining strains might use other QS inhibitors to interrupt the chemical communication. Moreover, almost 79% of the QQ strains capable of inactivating AHLs enzymatically have lactonase activity. Further phylogenetic analysis based on 16S rDNA revealed that the leaf-associated QQ bacteria can be classified as Bacillus sp., Acinetobacter sp., Lysinibacillus sp., Serratia sp., Pseudomonas sp., and Myroides sp. The naturally occurring diversity of bacterial quenchers might provide opportunities to use them as effective biocontrol reagents for suppressing plant pathogen in situ.

Concepts: Bacteria, Microbiology, Pseudomonas aeruginosa, Pathogen, Cell wall, Biofilm, Quorum sensing, Pathogenic bacteria

156

Pseudomonas aeruginosa biofilm is commonly associated with chronic wound infection. A FDA approved wireless electroceutical dressing (WED), which in the presence of conductive wound exudate gets activated to generate electric field (0.3-0.9V), was investigated for its anti-biofilm properties. Growth of pathogenic P. aeruginosa strain PAO1 in LB media was markedly arrested in the presence of the WED. Scanning electron microscopy demonstrated that WED markedly disrupted biofilm integrity in a setting where silver dressing was ineffective. Biofilm thickness and number of live bacterial cells were decreased in the presence of WED. Quorum sensing genes lasR and rhlR and activity of electric field sensitive enzyme, glycerol-3-phosphate dehydrogenase was also repressed by WED. This work provides first electron paramagnetic resonance spectroscopy evidence demonstrating that WED serves as a spontaneous source of reactive oxygen species. Redox-sensitive multidrug efflux systems mexAB and mexEF were repressed by WED. Taken together, these observations provide first evidence supporting the anti-biofilm properties of WED.

Concepts: Immune system, Oxygen, Bacteria, Infection, Antibiotic resistance, Pseudomonas aeruginosa, Biofilm, Quorum sensing

149

Bacteria have evolved multiple strategies for causing infections that include producing virulence factors, undertaking motility, developing biofilms, and invading host cells. N-acylhomoserine lactone (AHL)-mediated quorum sensing (QS) tightly regulates the expression of multiple virulence factors in the opportunistic pathogenic bacterium Pseudomonas aeruginosa. Thus, inhibiting QS could lead to health benefits. In this study, we demonstrate an anti-virulence activity of a cranberry extract rich in proanthocyanidins (cerPAC) against P. aeruginosa in the model host Drosophila melanogaster and show this is mediated by QS interference. cerPAC reduced the production of QS-regulated virulence determinants and protected D. melanogaster from fatal infection by P. aeruginosa PA14. Quantification of AHL production using liquid chromatography-mass spectrometry confirmed that cerPAC effectively reduced the level of AHLs produced by the bacteria. Furthermore, monitoring QS signaling gene expression revealed that AHL synthases LasI/RhlI and QS transcriptional regulators LasR/RhlR genes were inhibited and antagonized, respectively, by cerPAC. Molecular docking studies suggest that cranberry-derived proanthocyanidin binds to QS transcriptional regulators, mainly interacting with their ligand binding sites. These findings provide insights into the underlying mechanisms of action of a cerPAC to restrict the virulence of P. aeruginosa and can have implications in the development of alternative approaches to control infections.

Concepts: DNA, Gene, Genetics, Gene expression, Bacteria, Microbiology, Pseudomonas aeruginosa, Biofilm

147

Treating hospital patient textiles with ionic silver after each washing results in a significant decrease in microbial contamination. Although further study is needed to better understand the role textiles play in hospital-acquired infections and to quantify the influence of silver textile treatment on health care-associated infection risk and patient outcomes, ionic silver treatment of textiles may prove useful in hospital-acquired infection reduction strategies.

Concepts: Bacteria, Pneumonia, Nosocomial infection, Staphylococcus aureus, Antibiotic resistance, Pseudomonas aeruginosa, Infectious diseases, Clostridium difficile

145

Pseudomonas aeruginosa is a pathogen that is prevalent in serious infections in compromised patients worldwide. A unique virulence factor of this bacterium is the redox-active molecule pyocyanin, which is a potential biomarker for the identification of P. aeruginosa infections. Here we report a direct, selective and rapid detection technique of pyocyanin.

Concepts: Immune system, Bacteria, Opportunistic infection, Microbiology, Antibiotic resistance, Pseudomonas aeruginosa, Pseudomonas, Pseudomonadales