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Cadmium selenide quantum dots (CdSe QDs) were synthesized by using Providencia vermicola BGRW, which has discriminatory ability to resist many metals such as Selenium, Cadmium, Silver, Zinc, Copper, Lead, Nickel, Cobalt and Bismuth metals. BGRW was able to grow in the presence of 6 mM of CdCl2. The best conditions for extra/intracellular CdSe QDs synthesis were 0.1 mM SeO2: 0.9 mM CdCl2, 37°C, pH 9 within 24 h. The biosynthesis of CdSe QDs was monitored by UV–Visible spectrum that showed surface plasmon resonance (SPR) peaks at 388 nm. Depending on fluorescence property of quantum dots, photoluminescence characteristics of the biogenic CdSe QDs were at 385 nm. Further characterization of synthesized CdSe QDs was carried out using the X-ray Diffraction (XRD), Transmission Electron Microscope (TEM) and Fourier Transform Infrared (FTIR) spectroscopy. TEM and XRD analysis revealed that CdSe QDs was cubic in shape with a size range of ∼2 to 4 nm. EDS analysis confirmed the composition of QDs from cadmium and selenium ions. FTIR spectroscopy confirmed the presence of proteins as the stabilizing agent surrounding the quantum dots. Key words: Quantum dots, cadmium selenide quantum dots, capping agent, transmission electron microscope, fluorescence spectroscopy, X-ray and FTIR analysis.

The present study aims at biosynthesizing, characterizing and evaluating the biogenic silver nanoparticles (AgNPs) as antimicrobial and antibiofilm against Kocuria rosea and Kocuria rhizophila. Cellfree supernatant of Proteus mirabilis culture was used for biosynthesizing AgNPs, which confirmed by visualizing color change and X-ray diffraction. Transmission electron microscopy showed the formation of AgNPs in the range of 5–40 nm. ART-FTIR spectra provided evidence for presence of proteins as possible biomolecules responsible for stability of AgNPs and act as capping agent. AgNPs had ability to inhibit growth of K. rosea and K. rhizophila. The minimum inhibitory concentration (MIC90) of AgNPs against both strains was 25 μg/mL. Antiadhesive effect of AgNPs was verified at sub-MIC90 dose (12.5 μg/mL). The AgNPs concentrations up to 100 μg/mL were not effective for complete removing the already established biofilms with maximum removing percentage of 30.5–34.9%. In conclusion, the present study demonstrated an unprecedented green process for biosynthesizing stable spherical-shaped AgNPs. Early control is suggested by preventing biofilm formation using low AgNPs concentration (12.5 μg/mL) as a potential ingredient for formulating effective chemical sanitizers.

Microbial biofilms, which characterized by their resistance to the traditional antimicrobials, are considered as a renewable source of contamination by pathogens. As alternative antimicrobial and antibiofilm agent selenium nanoparticles (SeNPs) were biosynthesized by treatment of 1 mM SeO 2 with the free-cell supernatant of Bacillus licheniformis isolated from food wastes. The biosynthesized SeNPs were characterized by their spherical shape with diameter range of 10–50 nm and a well-defined absorption peak at 263 nm in UV–vis spectra. The biosynthesized SeNPs were used to control growth and biofilm formation by six foodborne pathogens including Bacillus cereus , Enterococcus faecalis , Staphylococcus aureus , Escherichia coli O157:H7, Salmonella Typhimurium, and Salmonella Enteritidis. The MIC 90 of SeNPs against all tested bacteria was 25 μg/mL, whereas the antibiofilm concentration was 20 μg/mL against all bacteria, except B. cereus . Although the biogenic SeNPs had antimicrobial and antibiofilm effects, they did not show ability to remove the established biofilm up to 50 μg/mL. The concentration of 75 μg/mL showed slight effect on removing the established biofilm. No toxicity on Artemia larvae was demonstrated by SeNPs upto 100 μg/mL. In conclusion, SeNPs produced in the present study can be used as a promising agent for effectively preventing biofilm formation by foodborne pathogens.

Silver nanoparticles (AgNPs) were biosynthesized using the cell-free filtrate of bacterium Proteus mirabilis, reacted with 1 mM of AgNO3 solutions at 37 °C. The synthesis of AgNPs was monitored by UV–Vis spectroscopy and transmission electron microscopy (TEM) equipped with selected area electron diffraction (SAED). The results point to formation of spherical to cubical particles of AgNPs ranging in size from 5 to 35 nm with an average of 25 nm in diameter. The toxicity of Ag on barley (Hordeum vulgare L. cv. Gustoe) that was subjected to Ag+ as AgNO3 and AgNPs was explored. The grain germination and seedling growth of barley decreased in the presence of 0.1 mM Ag+ and was inhibited at 1 mM Ag+. In contrast, our results indicated that the AgNPs at low concentration (0.1 mM) could be useful for barley grain germination and seedling growth. However, the higher concentrations of AgNPs (0.5 and 1 mM) reduced grain germination and exhibited a stronger reduction in the root length. A decline in the photosynthetic pigments and disorganization of chloroplast grana thylakoids in Ag+ and AgNPs-treated plants confirmed the leaf chlorosis. An increase of plastoglobuli within chloroplasts was observed in Ag+ and AgNPs-treated leaves. Ag+ caused dense aggregation of nuclear chromatin materials and degeneration of mitochondria. Ag+ and AgNPs increased contents of malondialdehyde, soluble proteins, total phenolic compounds and activity of guaiacol peroxidase in barley leaves; these results point to activation of plant defence mechanisms against oxidative stress in barley.

The development of a reliable green chemistry process for the biogenic synthesis of nanomaterials is an important aspect of current nanotechnology research. Silver nanoparticles (AgNPs) have been used as antimicrobial and disinfectant agents. However, there is limited information about its toxicity. Therefore, this study focused on the biosynthesis of AgNPs by the bacterium Proteus mirabilis and on determining its preliminary toxic effect on some aspects of animal physiology. A green method for the synthesis of AgNPs using culture supernatant of Proteus mirabilis has been developed in this study and the synthesized AgNPs were characterized by several techniques. The AgNPs showed a maximum absorbance at 445 nm on ultraviolet-visible spectra. The presence of proteins was identified by Fourier transform-infrared spectroscopy. The reduction of Ag+ to elemental silver was characterized by X-ray spectroscopy analysis. The transmission electron micrograph revealed the formation of polydispersed nanoparticles of 5 - 45 nm. The AgNPs were evaluated for their toxic effect on pregnant female albino rat. The result showed that liver enzymes (AST and ALP) were decreased significantly in the group treated with AgNPs. Mean corpuscular hemoglobin concentration also showed significant increase.

Aflatoxins are commonly found in cereals worldwide and bring significant threats to the food industry and animal food production. Among a collection of aflatoxin-degradative endophytic bacteria isolated from grains of corn plant, the strain TUBF1 was selected based on its high-ability to utilize aflatoxin B1 (AFB1) (10 μg/mL) as the sole carbon source. The morphological, physiological, and phylogenetic studies indicated that strain TUBF1 belonged to the Bacillus sp. group. HPLC was used to determine the reduction in AFB1 concentrations. Bacillus sp. TUBF1 had the strongest ability to detoxify toxin, where the degradation percentages of AFB1 was 81.5% and 100% after 48 and 72 h, respectively. The degradation of AFB1 was mainly in the culture supernatant of TUBF1 rather than its cells. About 90% of AFB1 was degraded within the first 12 h and reduced to the undetectable level after 24 h. The supernatant was characterized by considerable activity at wide range of temperatures (10–40°C) with optimal activity a...

Pseudomonas spp. strain Bal1 was isolated from Schistosome vector snails Bulinus Truncates. Strain Bal1 was identified as Pseudomonas putida using partial sequence of 16s rRNA. This strain was able to utilize a Bayluscide as a sole source of carbon and nitrogen. The degradation of Bayluscide by Bal1 strain is mediated by pBal1 (110 Kb) plasmid. The loss of the plasmid resulted irreversibly in a derivative strain that was unable to degrade Bayluscide. The transfer of these plasmids from wild-type strain Bal1 to Bal1M derivative restored completely its capability to degrade the molluscicide. It is proposed that pBal1 is a conjugative plasmid and is involved in the Bayluscide degradation. The effect of bacterial degradation upon toxicity was tested, and it was shown that the molluscicidal action of Bayluscide was significantly reduced by bacterial action.

The diversity and beneficial characteristics of endophytic microorganisms have been studied in Plectranthus tenuiflorus medicinal plant. However, information regarding naturally occurring P. tenuiflorus plant associated endophytes among different organs of host is limited. Endophytic bacteria were isolated from root, stem, and leaves of P. tenuiflorus plant. Among 28 endophytic bacterial isolates from different organs of P. tenuiflorus plant, 8 isolates were identified by partial sequencing of their 16S rRNA gene. The isolated endophytic bacteria were Bacillus sp., Bacillus megaterium, Bacillus pumilus, Bacillus licheniformis, Micrococcus luteus, Paenibacillus sp., Pseudomonas sp., and Acinetobacter calcoaceticus. The most isolates that exhibited extracellular enzymatic activity were belonged to the genus Bacillus. Furthermore, Bacillus sp. (HE613660) exhibited the stronger activities in extracellular enzymes such as amylase, esterase, lipase, protease, pectinase, xylanase, and cellulase than other strains. Considerable antimicrobial activities against a panel of human pathogenic microorganisms (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Streptococcus agalactiae, Proteus mirabilis, and Candida albicans) were recorded using crude extracts of the collected endophytic strains.

Inoculating wheat (cv. Giza 164) with variousFusariumspecies had different effects on the catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) activity in different plant tissues. The CAT activity induced in the shoots of wheat plants by some pathogens (F. merismoides, F. moniliforme, F. poaeandF. sambucinum) was relatively higher than that induced by other pathogens. The results showed an increase in POX activity in infected shoots except those inoculated withF. sambucinum, where the POX activity decreased. Inoculating wheat plants with individualFusariumspecies or with a mixture of pathogens caused an increase in APX in the shoots, except for those treated withF. poae, where the APX activity decreased. The activity of these antioxidant enzymes thus increased in most cases in the shoot system of wheat plants underFusariuminfection. Investigations on the metabolic activity of wheat plants inouculated with individualFusariumspecies or with a mixture of pathogens showed higher contents of all the protein fractions, soluble sugars, total free amino acids and proline. The K+and Ca2+concentrations decreased to various extents in different cases. The Na+content increased in wheat shoots, especially after inoculation withF. merismoides. The results signify that the most serious infection was caused byF. culmorum, F. graminearumandF. oxysporumand by a mixture of all theFusariumspecies.

In this study, among a collection of heavy metals resistant endophytic bacterial strains isolated from aquatic hyperaccumulator plant (Eichhornia crassipes), one plant growth promoting endophytic bacteria (PGPE), SVUB4 was selected for its ability to utilize 1-aminocyclopropane-1-carboxylic acid (ACC) as the sole N source and accumulate different heavy metals. The SVUB4 strain was characterized as Enterobacter sp. on the basis of its 16S rDNA sequences. Assessment of the parameters of plant growth promotion revealed the intrinsic ability of the strain for the production of IAA, siderophore and solubilization of insoluble phosphate. Furthermore, plasmid DNA analysis of Enterobacter sp. strain SVUB4 indicated the presence of a single large plasmid element. The results of plasmid curing experiments demonstrated that the ability of this strain to grow in presence of Cd and Zn was encoded by the 98 kb plasmid, whereas the ability to grow in the presence of Pb appeared to be encoded by the chromosome. The Cd an...

Little is known about the bacterial communities associated with the rose plants inhabiting dry desert ecosystems. The aim of this study was to isolate and characterize endophytic bacteria from different organs of rose plant. Endophytic bacteria were observed in healthy roots, stems, leaves, and flowers of rose plant, with a significantly higher density in roots, followed by stems, leaves, and petals. A total of 38 bacterial endophytes were isolated and are closely related phylogenetically to Acetobacter, Acinetobacter, Methylococcus, Bacillus, Micrococcus, Planococcus by 16S rRNA sequence analysis. Six endophytic bacteria were found to produce IAA, solubilize Ca3(PO4)2 and produce siderophore. The six endophytic bacteria all had the capacity to produce hydrolytic enzyme such as cellulase, xylanase, pectinase, amylase, protease, lipase, and chitinase, but difference existed among these isolates.

Drinking water distribution networks are known to harbor microbial biofilms. The aim of the present work is to (i) identify the culturable bacteria presented in the drinking-water distribution network, (ii) investigate the ability of isolated bacteria to form biofilm under some environmental stress conditions and some eliminating or removing treatments. To achieve it, 57 strains were isolated from biofilm (43 isolates) and water samples (14 isolates) collected from five stations in drinking-water distribution network in Taif city, Kingdom of Saudi Arabia (KSA). Partial sequences of 16S rRNA gene in the 57 isolates ensured the presence of only 22 different strains in biofilm samples. Among these strains, only 14 strains were also detected in water samples. Gram-negative Aeromonas hydrophila was the most occurred bacterium in the microbial biofilm obtained from the purified-water storage tanks followed by Gram-negative Pseudomonas sp. Gram-positive Bacillus subtilis was the most occurred bacterium in the mi...

Thirty soil-isolates of Streptomyces were analyzed to determine their antagonism against plant-pathogenic fungi including Fusarium oxysporum, Pythium aristosporum, Colletotrichum gossypii, and Rhizoctonia solani. Seven isolates showed antifungal activity against one or more strain of the tested fungi. Based on the 16S rDNA sequence analysis, these isolates were identified as Streptomyces tendae (YH3), S. griseus (YH8), S. variabilis (YH21), S. endus (YH24), S. violaceusniger (YH27A), S. endus (YH27B), and S. griseus (YH27C). The identity percentages ranged from 98 to 100%. Although some isolates belonged to the same species, there were many differences in their cultural and morphological characteristics. Six isolates out of seven showed chitinase activity according to a chitinolytic activity test and on colloidal chitin agar plates. Based on the conserved regions among the family 19 chitinase genes of Streptomyces sp. two primers were used for detection of the chitinase (chiC) gene in the six isolates. A DNA fragment of 1.4 kb was observed only for the isolates YH8, YH27A, and YH27C. In conclusion, six Streptomyces strains with potential chitinolytic activity were identified from the local environment in Taif City, Saudi Arabia. Of these isolates, three belong to family 19 chitinases. To our knowledge, this is the first reported presence of a chiC gene in S. violaceusniger YH27A.

Problem statement: Heavy metals are known to be powerful inhibitors of xenobiotics biodegradation activities. Alleviation the inhibitory effect of these metals on the phenol biodegradation activities in presence of heavy metals resistant plasmid was investigated. Approach: Combination of genetic systems of degradation of xenobiotic compound and heavy metal resistance was one of the approaches to the creation of polyfunctional strains for bioremediation of soil after co-contamination with organic pollutants and heavy metals. Results: A bacterial strain Pseudomonas putida PhCN (pPhCN1, pPhCN2) had been obtained. This bacterium contained two plasmids, a 120 Kb catabolic plasmid that encode for breakdown of phenol (pPhCN1) and pPhCN2 plasmid (100 Kb) that code for cadmium and copper resistant. Cyanide assimilation by this bacterium was encoded by chromosomal genes. The inhibitory effect of cadmium (Cd2+) or copper (Cu2+) on the degradation of phenol and cyanide by P. putida strains PhCN and PhCN1 (contained pPhCN1) were investigated. The resistant strain PhCN showed high ability to degrade phenol and cyanide in presence of Cd2+ or Cu2+ comparing with the sensitive strain PhCN1. In addition, Cd2+ or Cu2+ was also found to exert a strong inhibitory effect on the C23O dioxygenase enzyme activity in the presence of cyanide as a nitrogen source. Conclusion: The presence of heavy metal resistance plasmid alleviated the inhibitory effect of metals on the phenol and cyanide assimilation by resistant strain.

Problem statement: The role of plasmid in the heavy metal resistance and accumulation by endophytic bacteria was investigated. Approach: The experimental results showed that high level plasmid mediated Cd2+ and Zn2+ resistance in this strain is due to decreased Cd2+ and/or Zn2+ uptake/accumulation by resistance strain. Results: Based on the fact that subsequent plasmid curing experiments demonstrated that the ability to grow in presence of Cd2+and Zn2+ was encoded by the 98 kb plasmid, whereas the ability to grow in presence of Pb2+ appeared to be encoded by the chromosome. The Cd2+ and Zn2+ removal capacity of the respective metal resistant strain (pBN4) were about 36 and 45 µg g-1 DW respectively, while the removal capacity of the both metal by sensitive variant showed a significant high Cd2+ and Zn2+ removal capacity of 153 and 228 µg g-1 DW respectively. Conclusion: The isolated endophytic Enterobacter was not only tolerant to heavy metals, but also bound considerable amount of heavy metals from the growth medium. The biosorbed order of the metals by parental strain and its cured derivatives strain based on the cell dry weight was found to be in the order of Pb2+> Zn2+>Cd2+.

Combination of genetic systems of degradation of xenobiotic compound and heavy metal resistance is one of the approaches to the creation of polyfunctional strains for bioremediation of soil after co-contamination with organic pollutants and heavy metals. A bacterial strain Pseudomonas putida PhCN (pPhCN1, pPhCN2) has been obtained. This bacterium contains two plasmids, a 120-kb catabolic plasmid that encodes for breakdown of phenol (pPhCN1) and pPhCN2 plasmid that codes for cadmium and copper resistant. Cyanide assimilation by this bacterium is encoded by chromosomal genes. The inhibitory effect of cadmium (Cd2+) or copper (Cu2+) on the degradation of phenol by P. putida strains PhCN and PhCN1 (contained pPhCN1) were investigated in the presence of phenol and cyanide as a sole carbon and nitrogen source, respectively. The resistant strain PhCN showed high ability to degrade phenol and cyanide in presence of Cd2+ or Cu2+ as compared to the sensitive strain PhCN1. In addition, Cd2+ or Cu2+ was also found to exert a strong inhibitory effect on the C23O dioxygenase enzyme activity in the presence of cyanide as a nitrogen source. However, the presence of heavy metal resistance plasmid alleviated the inhibitory effect of metals on the enzyme activity in resistant strain.

Onion bulbs can become contaminated with various molds during the storage period, the most important causal agents being black aspergilli (Aspergillus section Nigri). Taxonomic studies have revealed that this group of Aspergillus contains many species that cannot be reliably identified using standard morphological methods. Therefore, it is necessary to define the fungus causing this problem in the onion exactly, especially since some species assigned to section Nigri are well known as ochratoxin and/or fumonisin producers. Sixty fungal isolates belonging to 10 fungal genera were isolated from 40 onion samples originated from the Taif region in Saudi Arabia. Black aspergilli were detected in 37 onion samples. Using primer pairs (awaspec and Cmd6) designed based on partial calmodulin gene sequence data, 37 isolates were identified as A. welwitschiae. The ochratoxin A and fumonisin B2 contents of the onion samples were examined. No ochratoxins were detected in the collected samples, while fumonisin B2 was detected in 37.5% of the onion samples. Eighteen of 37 isolates of Aspergillus welwitschiae were recognized as potential producers for fumonisin B2. Multiplex polymerase chain reactions designed to detect biosynthetic genes of fumonisins confirmed these results.

This study was carried out to describe the bacterial load and the occurrence of some disease-causing enteric bacteria on raw vegetables sold in Saudi markets. The study further aimed to analyze antibiotic resistance rates, production of extended-spectrum beta lactamase, and plasmid carriage among bacterial population of raw vegetables. Results revealed that none of them contained Bacillus cereus, Salmonella, and Escherichia coli O157:H7. However, Staphylococcus aureus and Shigella were detected in 11.8% and 4.4% of the samples, respectively. The bacterial loads ranged from 3 to 8 log(10) CFUg(-1) for aerobic bacteria and 1 to 4 log(10) CFUg(-1) for coliforms as well as Enterobacteriaceae. The isolates exhibited resistance in decreasing order for ampicillin (76.5%), cephalothin (69.5%), trimethoprime-sulfamethoxazole (36.7%), aminoglycosides (21.9%), tetracycline (17.2%), fluoroquinolones (17.2%), amoxycillin-clavulanic acid (13.3%), and chloramphenicol (7.8%). Maximum resistance to extended-spectrum beta-lactam antibiotics occurred in 14.8% of isolates and the production of extended-spectrum beta-lactamase was achieved by 2.3% of isolates. Multiple resistances to four or more antimicrobial agents along with plasmid with varied sizes were documented. These investigations indicate the occurrence of antibiotic resistance and plasmid carriage among bacterial isolates populating raw vegetables.

The gene(s) encoding enzyme(s) involved in the initial reaction during degradation of zearalenone (ZEA) was characterized from the zearalenone utilizer Pseudomonas putida strain ZEA-1, where ZEA was transformed into product with less or no toxicity. A 5.5 kilobase-pair (kbp) Pst1–Kpn1 fragment containing gene(s) encoding for zearalenone degradation was cloned. The cloned gene(s) was actively expressed in Escherichia coli. ZEA degradation by recombinant E. coli was relatively rapid and effective, leaving no detectable ZEA after 24 h. In further experiments, cell-free extract of E. coli has been used in the same way, both to confirm these observations and the enzymatic nature of the degradation activity.