Wagih El-Shouny

The role of extracellular polysaccharides as virulence factors for phytopathogenic pseudomonads and xanthomonads

Bacterial exopolysaccharides (EPS) were investigated for their role as virulence factors of leaf spot diseases caused by pseudomonads and xanthomonads. The capacity of these bacteria to induce persistent water-soaking in leaves plays a crucial role during pathogenesis that seems to be accomplished by a synergistic interaction between bacterial EPS and plant polymers. Under conditions of low EPS production (e.g. in continuously darkened plants) the bacteria were not able to cause typical water-soaked disease symptoms. The main EPS components were alginate and levan (Pseudomonas), xanthan (Xanthomonas), as well as lipopolysaccharides (LPS) and a small amount of proteins. It is suggested that alginate which is very similar to plant pectate is required for establishing bacterial infections in later disease stages. This concept was confirmed by evaluating transposon mutants with EPS deficiencies. LPS may be involved in specific interactions with plant polymers leading to agglutination and precipitation (incompatibility) or gel-formation (compatibility). Bacteria which are embedded in a gel-like matrix inplanta are not easily recognized by the plant and are protected against bacteriostatic compounds and desiccation.

Effect of Gamma Radiation on Growth and Metabolic Activities of Arthrospira platensis

This work aimed to study the influence of gamma radiation on the growth and production of some active substances of Arthrospira platensis. Biomass production was significantly inhibited (p ≤ 0.05) by 21 and 34%, with respect to the control at 2.0 and 2.5 kGy, respectively. Chlorophyll-a content showed 11% reduction at 2.5 kGy compared to the control. As a result of growth and Chl-a inhibition, chlorophyll productivity recorded a continuous significant decrease below the control in the cells exposed to 1, 1.5, 2 and 2.5 kGy by 8, 12, 15 and 25%, respectively after 15 days of incubation. In addition, phycobillins productivity showed significant decrease by 10 and 36% below the control at 2 and 2.5 kGy of gamma radiation, respectively. Protein production decreased significantly by 24% at 1.5 kGy; low doses of gamma irradiation (0.5, 1.0 and 1.5 kGy) induced carbohydrate production by 106, 246 and 146%, respectively. Lipid content increased significantly over the control at 0.5 kGy of gamma irradiation by 22%, which was decreased at higher doses. Interestingly, carotenoid productivity showed significant increase at all used gamma doses up to 155% over the control.

Effect of sewage wastewater treated byNostoc muscorum andAnabaena subcylindrica on the growth ofZea mays andPhaseolus vulgaris

Zea mays (Sakha 321 ) andPhaseolus vulagris (Giza 6) were irrigated with sewage wastewater treated withNostoc muscorum andAnabaena subcylindrica. The results showed that irrigation of plants by untreated or treated wastewater caused stimulation in the measured growth parameters of both plants. In addition pigmentation as well as protein and carbohydrate contents were stimulated. This stimulation was attributed to the presence of high levels of essential nutrients such as nitrogen, phosphorus, and organic matters in wastewater. On the other side, there was a slight inhibitory effect of wastewater on some measured growth parameters of the plants. This effect may be due to the presence of some heavy metals in wastewater.

Drug resistance profile and molecular characterization of extended spectrum beta-lactamase (ESβL)-producing Pseudomonas aeruginosa isolated from burn wound infections. Essential oils and their potential for utilization

OBJECTIVES Pseudomonas aeruginosa producing extended spectrum β-lactamase (ESβL) enzyme had the ability for antimicrobial resistance mechanisms and its multidrug-resistant (MDR) phenotype, has been increasingly reported as a major clinical concern worldwide. The aim of this study was to (i) characterize ESβL-producing MDR P. aeruginosa isolated from burn wound infections phenotypically and molecularly, (ii) evaluate the antibacterial activity of some essential oils (EOs) against selected ESβL-producing drug resistant P. aeruginosa and (iii) characterize a promising EO. METHODS Identification and antibiotic susceptibility tests were performed for all isolates. ESβL production was detected phenotypically by an initial screening test (IST) and a phenotypic confirmatory test (PCT). Additionally, ESβL-producing isolates were also characterized molecularly. The antibacterial activity was detected using a disc diffusion method. Mechanisms of antibacterial action, the fatty acid profile, and functional groups characterization of the promising EO were analyzed using scanning and transmission electron microscopy (SEM & TEM), gas chromatography-mass spectrometry (GC-MS), and Fourier transform infrared (FTIR) spectroscopy, respectively. RESULTS A total of 50 non duplicated P. aeruginosa isolates from the wound samples of burn patients were identified. Of these, MDR and pan-drug resistance (PDR) showed a high prevalence in 38 (76%) isolates obtained from 10 clusters, while 21 (42%) were identified as ESβL-producing MDR or PDR P. aeruginosa isolates. Phenotypic detection of ESβL production showed that 20% were considered positive ESβL-producing P. aeruginosa using the IST, and were increased to 56% by the PCT. The most prevalent ESβL-encoding gene was blaOXA-2 (60.7%), followed by blaIMP-7 (53.6%) and blaOXA-50 (42.8%). Ginger oil is the most efficient antibacterial agent and its antibacterial action mechanism is attributed to the morphological changes in bacterial cells. The oil characterization revealed that 9,12-Octadecadienoic acid methyl ester is the major fatty acid (50.49%) identified. CONCLUSION The high incidence of drug-resistance in ESβL-producing P. aeruginosa isolated from burn wounds is alarming. As proven in vitro, EOs may represent promising natural alternatives against ESβL-producing PDR or MDR P. aeruginosa isolates.

Treatment of sewage and industrial wastewater effluents by the cyanobacteria Nostoc muscorum and Anabaena subcylinderica

The potential of two cyanobacteria, Nostoc muscorum and Anabaena subcylindrica to treat sewage and industrial wastewater effluents was investigated. Two different sites were selected for this study which are located at the drains of sewage plant, a salt and soda production company at Kafr El-Zayat city. All samples were taken from the sewage and/or industrial effluents before treatment. Treatment of the sewage and industrial wastewater effluents by using cyanobacteria (N. muscorum, A. subcylindrica and mixed culture of both) revealed that the pH value of the biologically treated wastewater increased, the electrical conductivity was recovered in a range between (4.7–23.9%) and the total dissolved solids were reduced by (4.4–23.3%). The reduction of turbidity level was in a range between (40–96.4%). The removal efficiency of organic matter (COD, PV) was in a range between (20–57.1%) and (25.7–66.7%), respectively. Phosphorus reduction, nitrate treatment and ammonia elimination efficiencies by cyanobacterial system were (20.8–95%), (19.6–80%) and (20.9–96%), respectively. With respect to the treatment efficiency of wastewater by using single or mixed cultures of cyanobacteria, it was observed that the single cultures in most cases was better than the mixed cultures and this may be due to the competition between mixed cultures for nutrients. However, it could be concluded from the presented data that the treatment of wastewater by cyanobacteria is a fruitful method to produce an effluent of high quality to be used for irrigation.

Exopolysaccharides Produced by Pseudomonas syringae Pathovars

Different pathovars belonging to Pseudomonas syringae were tested for the production of exopolysaccharides (EPS). In shake fiask cultures, maximum yield of EPS (1.8 g/l) and viscosity (4.1 mPas) were achieved by culturing the most promising bacterial strain of P. syringae pv. phaseolicola in gluconate mineral medium at 25°C for 3 days. In batch fermenter culture, yield and viscosity of the EPS increased 3.3-fold compared to shake fiask culture. The partially purified bacterial EPS obtained consisted mainly of alginate and showed better rheologicai characteristics than commercial preparations obtained from aigae. Specimens of EPS from different pathovars were filter sterilized and injected into young leaves of different plant species. In some combinations, persistent water-soaked spots were induced. EPS preparations from different P. syringae pathovars other than P. syringae pv. phaseolicola did not reveal host-specific characters.