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1.
Genome sizes of Pseudomonas aeruginosa phages phiKZ and EL earlier determined by sequence analysis were shown to correspond to sizes of their DNAs assessed by pulse-electrophoresis (PFGE). Putative "redundant" genes in phiKZ phage genome are supposed to control functions promoting vigorous growth of the phage belonging to this species, compared to phages of EL species.  相似文献   

2.
In recent decades, many researchers have written numerous articles about microbial biofilms. Biofilm is a complex community of microorganisms and an example of bacterial group behavior. Biofilm is usually considered a sessile mode of life derived from the attached growth of microbes to surfaces, and most biofilms are embedded in self-produced extracellular matrix composed of extracellular polymeric substances (EPSs), such as polysaccharides, extracellular DNAs (eDNA), and proteins. Dispersal, a mode of biofilm detachment indicates active mechanisms that cause individual cells to separate from the biofilm and return to planktonic life. Since biofilm cells are cemented and surrounded by EPSs, dispersal is not simple to do and many researchers are now paying more attention to this active detachment process. Unlike other modes of biofilm detachment such as erosion or sloughing, which are generally considered passive processes, dispersal occurs as a result of complex spatial differentiation and molecular events in biofilm cells in response to various environmental cues, and there are many biological reasons that force bacterial cells to disperse from the biofilms. In this review, we mainly focus on the spatial differentiation of biofilm that is a prerequisite for dispersal, as well as environmental cues and molecular events related to the biofilm dispersal. More specifically, we discuss the dispersal-related phenomena and mechanisms observed in Pseudomonas aeruginosa, an important opportunistic human pathogen and representative model organism for biofilm study.  相似文献   

3.
4.
Non-mammalian infection models have been developed over the last two decades, which is a historic milestone to understand the molecular basis of bacterial pathogenesis. They also provide small-scale research platforms for identification of virulence factors, screening for antibacterial hits, and evaluation of antibacterial efficacy. The fruit fly, Drosophila melanogaster is one of the model hosts for a variety of bacterial pathogens, in that the innate immunity pathways and tissue physiology are highly similar to those in mammals. We here present a relatively simple protocol to assess the key aspects of the polymicrobial interaction in vivo between the human opportunistic pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, which is based on the systemic infection by needle pricking at the dorsal thorax of the flies. After infection, fly survival and bacteremia over time for both P. aeruginosa and S. aureus within the infected flies can be monitored as a measure of polymicrobial virulence potential. The infection takes ~24 h including bacterial cultivation. Fly survival and bacteremia are assessed using the infected flies that are monitored up to ~60 h post-infection. These methods can be used to identify presumable as well as unexpected phenotypes during polymicrobial interaction between P. aeruginosa and S. aureus mutants, regarding bacterial pathogenesis and host immunity.  相似文献   

5.
IN 1969, after carbenicillin had been in use for three years in this unit, highly resistant strains of Pseudomonas aeruginosa were isolated for the first time1. Because these resistant strains included, from their first appearance, representatives of two unrelated types, it seemed likely that the resistance was transferable; this hypothesis was supported by experiments showing the transfer of carbenicillin resistance between Ps. aeruginosa and Escherichia coli K12 in vitro and in vivo2–4;. The resistant Ps. aeruginosa produced a penicillinase (β lactamase) similar to that normally produced by some strains of Enterobacteria and different from that normally produced by Ps. aeruginosa2,3, so it seemed likely that the Ps. aeruginosa had initially acquired resistance by the transfer of an R factor from a carbenicillin-resistant member of the Enterobacteriaceae colonizing the same burn. This hypothesis is now supported by a study on strains of Enterobacteria and Ps. aeruginosa isolated in a number of hospitals. We have also found evidence suggesting that Ps. aeruginosa which has acquired this R factor may not show resistance until it has been exposed repeatedly to carbenicillin.  相似文献   

6.

Background  

Pseudomonas aeruginosa is a common pathogen in chronic respiratory tract infections. It typically makes a biofilm, which makes treatment of these infections difficult. In this study, we investigated the inhibitory effects of N-acetylcysteine (NAC) on biofilms produced by P. aeruginosa.  相似文献   

7.
Multi-drug resistant Pseudomonas aeruginosa (MDRPA) are emerging as a major threat in the hospitals as they have become resistant to current antibiotics. There is an immediate requirement of drugs with novel mechanisms as the pipeline of investigational drugs against these organisms is lean. UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) enzyme that catalyzes the first committed step of bacterial cell wall biosynthesis is an ideal target for the discovery of novel antibiotics against Gram negative pathogens as they have only one copy of murA gene in its genome. We have performed biochemical characterization and comparative kinetic analysis of MurA from E. coli and P. aeruginosa. Both enzymes were active at broad range of pH with temperature optima of 37°C. Metal ions did not enhance the activity of both enzymes. These enzymes had an apparent affinity constant (K m ) for its substrate UDP-N-acetylglucosamine 36 ± 5.2 and 17.8 ± 2.5 μM and for phosphoenolpyruvate 0.84 ± 0.13 μM and 0.45 ± 0.07 μM for E. coli and P. aeruginosa enzymes respectively. Both the enzymes showed 5–7 fold shift in IC50 for the known inhibitor fosfomycin upon pre-incubation with the substrate UDP-N-acetylglucosamine. This observation was used to develop a novel rapid sensitive high throughput assay for the screening of MurA inhibitors.  相似文献   

8.
Eight antibiotics (aztreonam, ceftazidim, cefoperazon, cefepim, netilmicin, amikacin, ofloxacin and ciprofloxacin) exhibited antimicrobial activity individually and/or in combinations against 20 wild-type biofilm-forming strains of Pseudomonas aeruginosa. The strains were less susceptible in biofilm; in 10 strains antibiotic synergy was observed for the combination of aztreonam and ciprofloxacin. Synergy was also demonstrated in the case of β-lactams and aminoglycosides, β-lactams and fluoroquinolones, aminoglycosides and fluoroquinolones, and for monobactams and β-lactams although the strains were resistant to the individual antibiotics. Synergism or partial synergism was found with one or more antibiotic combinations against 32.4% of isolates.  相似文献   

9.
Biological control of the cyst forming nematode Heterodera cajani was studied on sesame using plant growth promoting rhizobacteria (PGPR) Pseudomonas aeruginosa LPT3 and LPT5. Based on plant growth promoting attributes, two fluorescent pseudomonads, LPT3 and LPT5 were evaluated for their efficacy against cyst forming nematode Heterodera cajani that parasitize Sesamum indicum. Pseudomonas aeruginosa LPT5 produced IAA, HCN, chitinase, glucanase and siderophore, and also solubilized inorganic phosphate in vitro. Moreover, LPT5 resulted in mortality of second stage juveniles of H. cajani, which was 13% higher as compared to P. aeruginosa LPT3. Interestingly, when both strains were inoculated together for the management of H. cajani on Sesamum indicum the population of H. cajani was reduced significantly, in field trial. Approximately 60% reduction in cyst and juveniles population was recorded with LPT5 coated seeds, while LPT3 resulted in 49% reduction in cyst and juvenile population as compared to control. Plants grown with seeds bacterized with LPT5 and reduced doses of urea, diammonium phosphate (DAP), muriate of potash (K) and gypsum gave maximum increase in yield, in comparison to that of plants raised under the influence of recommended or full doses of the chemical fertilizers. Pseudomonas aeruginosa LPT5 also showed excellent root colonization.  相似文献   

10.
This study deals with production and characterization of biosurfactant from renewable resources by Pseudomonas aeruginosa. Biosurfactant production was carried out in 3L fermentor using waste motor lubricant oil and peanut oil cake. Maximum biomass (11.6 mg/ml) and biosurfactant production (8.6 mg/ml) occurred with peanut oil cake at 120 and 132 h respectively. Characterization of the biosurfactant revealed that, it is a lipopeptide with chemical composition of protein (50.2%) and lipid (49.8%). The biosurfactant (1 mg/ml) was able to emulsify waste motor lubricant oil, crude oil, peanut oil, kerosene, diesel, xylene, naphthalene and anthracene, comparatively the emulsification activity was higher than the activity found with Triton X-100 (1 mg/ml). Results obtained in the present study showed the possibility of biosurfactant production using renewable, relatively inexpensive and easily available resources. Emulsification activity found with the biosurfactant against different hydrocarbons showed its possible application in bioremediation of environments polluted with various hydrocarbons.  相似文献   

11.
Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.  相似文献   

12.
The level of lysozyme in fat body, hemocytes and cell-free hemolymph from Galleria mellonella larvae infected with Pseudomonas aeruginosa was determined and evaluated. In the samples of fat body and hemocytes, an increase in lysozyme content was detected 1 d after infection and then a significant decrease was observed after a prolonged infection time. In the case of cell-free hemolymph, an increase in the lysozyme level was noticeable during the first 30 h post injection and stayed at a similar level for 42 h. The smaller decrease of the lysozyme level after 42 h might be associated with the development of bacteremia of P. aeruginosa in insects. In addition, the gradual increase in the content of lysozyme correlated with the increase of its activity in the hemolymph of the infected larvae as a response to injection with P. aeruginosa. The G. mellonella lysozyme appeared to be insensitive to extracellular proteinases produced in vivo by P. aeruginosa.  相似文献   

13.

Background  

Chinchillas (Chinchilla laniger) are popular as pets and are often used as laboratory animals for various studies. Pseudomonas aeruginosa is a major infectious agent that causes otitis media, pneumonia, septicaemia enteritis, and sudden death in chinchillas. This bacterium is also a leading cause of nosocomial infections in humans. To prevent propagation of P. aeruginosa infection among humans and animals, detailed characteristics of the isolates, including antibiotic susceptibility and genetic features, are needed. In this study, we surveyed P. aeruginosa distribution in chinchillas bred as pets or laboratory animals. We also characterized the isolates from these chinchillas by testing for antibiotic susceptibility and by gene analysis.  相似文献   

14.
Respiratory tract and device associated infections caused by biofilm forming Pseudomonas aeruginosa play a primary role in the pathogenesis and prognosis of cystic fibrosis (CF) diseases. The biofilm formed by these pathogens attributes to the antibiotic resistance and protection from host immune response. Once established, the pathogens respond poorly to therapeutic agents. Recently medicinal plants are largely explored as potential source of bioactive agents. In this context the present study reports the antibiofilm activity of the folkloric medicinal plant Andrographis paniculata against biofilm forming CF causative Pseudomonas aeruginosa isolated from CF sputum. P. aeruginosa was also assessed for their growth and development of the biofilm, phylogenetic relationship and antibiotic susceptibility. Antibiogram of the strains indicated that they were resistant to more than one antibiotic. Six extracts of A. paniculata showed significant antibiofilm activity. P. aeruginosa strains, KMS P03 and KMS P05, were found to be maximally inhibited by the methanol extract to an extent of 88.6 and 87.5% respectively. This is the first report on antibiofilm activity of A. paniculata extracts, and our results indicate scope for development of complementary medicine for biofilm associated infections.  相似文献   

15.
Rhamnolipid biosurfactants are effective antimicrobial agents and provide a promising alternative to synthetic medicine. Rhamnolipid accumulation by Pseudomonas aeruginosa ATCC 9027, and associated antimicrobial activity, was quantified during phosphate limited culture. The onset of rhamnolipid production occurred below 0.35 mg phosphate/l. Thereafter rhamnolipid accumulated during phosphate exhaustion where nitrogen remained above 0.9 g/l. A maximum 4.261 g rhamnolipid/l (measured as 1.333 g rhamnose/l) was attained at a productivity of 0.013 g rhamnose/l/h. Rhamnolipid accumulation under conditions of phosphate exhaustion and nitrogen excess suggests a non-specificity of the limiting nutrient, and that rhamnolipids will be synthesised provided carbon is in excess of the metabolic capacity. Antimicrobial activity was demonstrated against Mycobacterium aurum, a surrogate for M. tuberculosis, the causal agent of most forms of tuberculosis, by a 45 mm zone of M. aurum inhibition around a well of supernatant containing 3.954 g rhamnolipid/l.  相似文献   

16.
Pseudomonas aeruginosa is a Gram-negative bacterium that is responsible for a wide range of infections in humans. Colonies employ quorum sensing (QS) to coordinate gene expression, including for virulence factors, swarming motility and complex social traits. The QS signalling system of P. aeruginosa is known to involve multiple control components, notably the las, rhl and pqs systems. In this paper, we examine the las system and, in particular, the repressive interaction of rsaL, an embedded small regulative protein, employing recent biochemical information to aid model construction. Using analytic methods, we show how this feature can give rise to excitable pulse generation in this subsystem with important downstream consequences for rhamnolipid production. We adopt a symmetric competitive inhibition to capture the binding in the lasI–rsaL intergenic region and show our results are not dependent on the exact choice of this functional form. Furthermore, we examine the coupling of lasR to the rhl system, the impact of the predicted capacity for pulse generation and the biophysical consequences of this behaviour. We hypothesize that the interaction between the las and rhl systems may provide a quorum memory to enable cells to trigger rhamnolipid production only when they are at the edge of an established aggregation.  相似文献   

17.
Planktonic and biofilm cells of a clinical urinary isolate of P. aeruginosa were compared in vitro for their ability to adhere to uroepithelial cells, interaction with macrophages, and for production of virulence factors like extracellular proteinase, elastase, hemolysin, phospholipase C and pyochelin. Biofilm cells showed increased adherence to UECs, which was coupled with reduced uptake and intracellular killing by macrophages. Overall there was a decrease in production of extracellular products by biofilm cells. Comparing the two cell forms for their ability to establish infection in an ascending model of acute pyelonephritis, significant enhancement of renal bacterial load, as well as more pronounced renal pathology developed with biofilm cells.  相似文献   

18.
19.
Keratinase from Pseudomonas aeruginosa KS-1 was expressed constitutively as an extracellular protein in Escherichia coli with high specific activity of 3.7 kU/mg. It was purified fourfold as a 33 kDa monomeric protein by Q-Sepharose ion exchange chromatography with a recovery of 95%. It is a serine protease with optimal activity at pH 9 and 50°C. It was stable from pH 4 to 12 for 1 h with a t1/2 of 12 min at 70°C. It hydrolyzed haemoglobin > fibrin > feather keratin > azo-casein > casein > meat protein > gelatin. Among synthetic substrates, it efficiently hydrolyzed N-Suc-ala-ala-pro-phe-pNA, N-Suc-ala-ala-ala-pNA, N-Suc-ala-ala-pro-leu-pNA and also plasmin substrate, d-Val-Leu-Lys-pNA  相似文献   

20.
An experiment was carried out to evaluate the effects of phosphorus concentration (1, 4 and 10 mg l−1) and temperature (15 and 25°C) on chlorophyll a (chl a) contents and cell size/volume of green alga Scenedesmus obliquus and blue green alga Microcystis aeruginosa. Long-term field data from Lake Taihu, a large, shallow eutrophic lake between Jiangsu and Zhejiang Provinces, China, was also used to evaluate the effect of temperature on the model between chl a and total phosphorus (TP). The chl a content of both algae increased with an increase in phosphorus concentration and temperature. Temperatures showed a significantly different effect on chl a content of S. obliquus at a phosphorus concentration of 10 mg l−1, whereas there was no significant difference at the two lower phosphorus levels. For M. aeruginosa, temperatures presented significantly different effects on the chl a contents at three phosphorus concentrations. Chl a content of neither alga presented an interaction between the nutrient and the temperature. Long-term field data from Lake Taihu also indicated that the addition of temperature to the model increased predictability of chl a by TP. The length/diameter and volume of both algae were greater at the lower temperature and phosphorus concentration. Moderate negative correlations were observed between algal size, volume, and chl a content. Our results suggest that phosphorus concentration and temperature could change chl a contents and size in species-specific algal cells and that temperature should be considered when building the model of TP and chl a concentration.  相似文献   

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