Nano-metals forming bacteria in Egypt. II. Efficacy towards biomolecules, ultrastructure, growth parameters, and eco-friendly therapeutic of soft rot/blackleg genera.

The nanoparticles (NPs) formed by Enterococcus thailandicus, Pseudomonas putida, Marinobacter hydrocarbonoclasticus, and P. geniculate were tested against soft rot/blackleg genera. The effects of NPs recorded on bacterial DNA, proteins, and carbohydrates concentration of Pectobacterium carotovorum subsp. carotovorum, Enterobacter cloacae (soft rot), and Dickeya solani (soft rot/blackleg). Treated cells showed degradation in isolated DNA, decreased proteins and carbohydrates concentration compared with untreated cells. Using Scanning Electron Microscope (SEM), the treated cells showed collapsed and small pits in the cell wall. Using Transmission Electron Microscope (TEM), internal changes showed penetration of NPs inside the tested bacterial cells, the appearance of periplasmic space, formation of vacuoles, and condensation of cytoplasm. Disease severity ex vivo of potato tuber infected with tested genera demonstrated that NPs treatment didn't show any rotted tissue compared with untreated. The ability to uptake and accumulate FeNPs from the soil in potato (Solanum tuberosum) seedlings; Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) was used. It recorded an increase in iron content of treated potato (Solanum tuberosum) seedlings with NPs, compared with untreated. FeNPs can be used to control soft rot/blackleg diseases, instead of copper pesticides. It could be a new, approach for disease management and increase the plant's nutritional value.

Nano-metals forming bacteria in Egypt. I. Synthesis, characterization and effect on some phytopathogenic bacteria in vitro.

Bacterial metal reducers were isolated from water samples collected from harsh condition locations in Egypt. Four selected isolates were identified as Enterococcus thailandicus, Pseudomonas putida, Marinobacter hydrocarbonoclasticus, and P. geniculata for Copper (Cu), Iron (Fe), Cobalt (Co) and Zinc (Zn) Nanoparticles (NPs) production sequentially. Nitrate reductase enzyme was assayed for bacterial isolates which demonstrated that P. putida, and M. hydrocarbonoclasticus have the maximum enzyme production. The produced NPs were characterized by using XRD, TEM, UV-VIS spectroscopy. Magnetic properties for all selected metals NPs were measured using Vibrating Sample Magnetometer (VSM) and demonstrated that FeNPs recorded the highest magnetization value. The antibacterial activity of selected metals NPs was tested against some phytopathogenic bacteria causing the following diseases: soft rot (Pectobacterium carotovorum, Enterobacter cloacae), blackleg (Pectobacterium atrosepticum and Dickeya solani), brown rot (Ralstonia solanacearum), fire blight (Erwinia amylovora) and crown gall (Agrobacterium tumefaciens). All metals NPs showed an antagonistic effect against the tested isolates, particularly, FeNPs showed the highest antibacterial activity followed by CuNPs, and ZnNPs. Due to the small size, high reactivity, and large surface area of biologically synthesized NPs, they are used as a good disinfector, and can be considered as a new and alternative approach to traditional disease management methods.

Antibacterial activity of three essential oils and some monoterpenes against Ralstonia solanacearum phylotype II isolated from potato.

The present study describes the possibility of using some essential oils and monoterpens as bioagents against the growth of Ralstonia solanacearum, a causal bacterium of potato brown rot disease. Eight isolates of the bacterium were recovered from infected potato tubers, showing typical symptoms of the disease, Isolates were identified as R.solanacearum phylotype II, based on biochemical and physiological characteristics, as well as, at the molecular level through PCR analysis. Three essential oils extracted from Corymbia citriodora (leaves), Cupressus sempervirens (aerial parts), and Lantana camara (aerial parts) were evaluated for their antibacterial activity against eight isolates of R. solanacearum phylotype II. Results demonstrated that L. camara essential oil (concentration 5000 µg/mL) had the highest effects against the RsMo2, RsSc1 and Rs48, with inhibition zone (IZ) values of 17.33, 16.33, and 17.50 mm, respectively, also against Rs2 (IZ 14.33 mm), and RsIs2 (IZ 16 mm). C. citriodora oil showed the highest activity against RsBe2 (IZ 14 mm), RsFr4 (IZ 13.66 mm) and RsNe1 (IZ 13.66 mm). Gas Chromatography-Mass Spectrometry (GC-MS-FID) analyzed the chemical composition of these essential oils. It was proved that L. camara leaves contains mainly trans-caryophyllene (16.24%) and α-humulene (9.55%), in C. citriodora oil were α-citronellal (56.55%), α-citronellol (14.89%), and citronellol acetate (13.04%), and in Cup. sempervirens aerial parts were cedrol (22.17%), and Δ3-carene (18.59%). Five monoterpenes were evaluated against the most resistance Ralstonia isolate RsFr5 to the three studied essential oils and found that limonene had the highest effect against it compared with the lowest thymol. The results proved the strong bio effects of the essential oil from L. camara leaves as a natural product contained monoterpenes that can inhibit the growth of tested R. solanacearum phylotype II isolates.

Antibacterial activity of the bioactive compounds identified in three woody plants against some pathogenic bacteria.

Three bacterial isolates were identified from infected potato tubers showing soft and blackleg like symptoms as well as one isolate from infected pear tree showing crown gall symptom. Conventional and molecular identification proved that bacterial isolates belonging to Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, Dickeya solani and Agrobacterium tumefaciens. The above plant bacterial isolates and human pathogenic bacteria Escherichia coli, Sarcina lutea, and Staphylococcus aureus were used for the bioassay. The chloroform leaf extracts from Duranta plumieri variegata, Lantana camara, and Citharexylum spinosum were assayed for their antibacterial activity by measuring the inhibition zones and minimum inhibitory concentrations (MICs). The suggested chemical compositions of extracts were analyzed using GC/MS apparatus. The main compounds in leaf extract of L. camara were 5,8-diethyl-dodecane, pyrimidin-2-one, 4-[N-methylureido]-1-[4-methylaminocarbonyloxymethyl, oleic acid,3-(octadecyloxy)propyl ester; in D. plumieri were 4,7-dimethoxy-2-methylindan-1-one and 5-(hexadecyloxy)-2-pentadecyl-,trans-1,3-dioxane; and in C. spinosum were N-[5-(3-hydroxy-2-methylpropenyl)-1,3,4,5-tetrahydrobenzo[cd]indol-3-yl]-N-methylacetamide. Promising activity was found against A. tumefaciens, E. coli, P. carotovorum, Sar. lutea, and Staph. aureus with MIC values of 8, 128, 64, 500 and 500 µg/mL, respectively, as L. camara leaf extract was applied. D. plumieri leaf extract showed good activity against D. solani and P. atrosepticum with MIC values of 16 µg/mL and 128 µg/mL, respectively. On the other hand, weak bioactivity was found with leaf extract from C. spinosum. It could be concluded that leaf extracts from D. plumieri and L. camara have a promising antibacterial agents.

Antibacterial activities of the phytochemicals-characterized extracts of Callistemon viminalis, Eucalyptus camaldulensis and Conyza dioscoridis against the growth of some phytopathogenic bacteria.

Three bacterial isolates were isolated from infected potato tubers showing soft and brown rots like symptoms as well as one isolate from infected peach tree showing crown gall symptom. The morphological, biochemical and molecular assays proved that bacterial isolates belonging to Pectobacterium carotovorum subsp. carotovorum, Ralstonia solanacearum, Dickeya spp. and Agrobacterium tumefaciens. The acetone (AcE) and n-butanol (ButE) extracts of Callistemon viminalis flowers and essential oil from aerial parts of Conyza dioscoridis as well as ButE of Eucalyptus camaldulensis bark are evaluated at different concentrations against the growth of the isolated bacteria. The diameter of inhibition zone (IZ) and the minimum inhibitory concentrations (MICs) are compared. Results indicated that the highest IZ values were 20.0 mm and 18.3 mm for E. camaldulensis bark ButE and C. viminalis flower ButE, respectively, against P. carotovorum; 16.3 mm and 16.0 mm for E. camaldulensis bark ButE and C. viminalis flower ButE, respectively, against R. solanacearum; 18.5 mm for C. viminalis flower AcE and C. dioscoridis aerial parts EO against Dickeya spp.; and 15.0 mm for C. viminalis flower AcE against A. tumefaciens. MICs ranged from <16 µg/mL for D. solani to >4000 µg/mL for A. tumefaciens. It was proved that C. viminalis flowers AcE contains mainly 5-hydroxymethylfurfural (20.6%), palmitic acid (18.5%), and pyrogallol (16.4%); while C. viminalis flower ButE contains palmitic acid (36.3%), 2-hydroxymyristic acid (9.4%), 5-hydroxymethylfurfural (7.2%), and shikimic acid (6.6%); whereas E. camaldulensis bark ButE contains 8-nonynoic acid methyl ester (45.6), camphor (30.9%), menthol (8.8%), and 1,8-cineole (eucalyptol) (8.2%), whilst the EO of C. dioscoridis aerial parts comprises Z-(13,14-epoxy)tetradec-11-en-1-ol acetate (11.6%), γ-elemene (10.2%), tau.-muurolol (7.1%), and cadina-3,9-diene (4.7%). It can be concluded that phytochemical extracts of C. viminalis, E. camaldulensis and C. dioscoridis demonstrated strong to moderate antibacterial effects against the studied plant bacterial pathogens.

In vitro antibacterial, antifungal and antioxidant activities of Eucalyptus spp. leaf extracts related to phenolic composition.

The crude methanolic extracts from leaves of Eucalyptus camaldulensis L., E. camaldulensis var obtusa and E. gomphocephala grown in Egypt were investigated to explore their chemical composition as well as their antibacterial, antifungal and antioxidant activities. Major phenolics found were ellagic acid, quercetin 3-O-rhamnoside, quercetin 3-O-b-D-glucuronide, caffeic acid and chlorogenic acid. The antioxidant activities were examined by the 2,2'-diphenypicrylhydrazyl (DPPH) and ß-Carotene-linoleic acid assays. E. camaldulensis extracts showed the highest phenolic content, antioxidant and antimicrobial activities compared to other cultivars. MIC values reported for antibacterial activity of E. camaldulensis ranged from 0.08 µg/mL (Bacillus cereus) to 0.22 µg/mL (Staphylococcus aureus), while MBC values ranged from 0.16 µg/mL (Dickeya solani and B. cereus) to 0.40 µg/mL (S. aureus). The inhibitory activities against growth of bacteria and fungi used is an indication that E. camaldulensis a might be useful resource for the development and formulation of antibacterial and antifungal drugs.

Chemotyping of diverse Eucalyptus species grown in Egypt and antioxidant and antibacterial activities of its respective essential oils.

The chemical composition of the essential oil from the leaves of Eucalyptus camaldulensis, Eucalyptus camaldulensis var. obtusa and Eucalyptus gomphocephala grown in northern Egypt was analysed by using GC-FID and GC-MS techniques. The antibacterial (agar disc diffusion and minimum inhibitory concentration methods) and antioxidant activities (2,2'-diphenypicrylhydrazyl) were examined. The main oils constituents were 1,8-cineole (21.75%), ß-pinene (20.51%) and methyleugenol (6.10%) in E. camaldulensis; spathulenol (37.46%), p-cymene (17.20%) and crypton (8.88%) in E. gomphocephala; spathulenol (18.37%), p-cymene (19.38%) and crypton (16.91%) in E. camaldulensis var. obtusa. The essential oils from the leaves of Eucalyptus spp. exhibited considerable antibacterial activity against Gram-positive and Gram-negative bacteria. The values of total antioxidant activity were 70 ± 3.13%, 50 ± 3.34% and 84 ± 4.64% for E. camaldulensis, E. camaldulensis var. obtusa and E. gomphocephala, respectively. The highest antioxidant activity value of 84 ± 4.64% could be attributed to the high amount of spathulenol (37.46%).