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In this study, a facile one-pot method has been used for the synthesis of zinc sulfide decorated sulfur-doped reduced graphene-oxide (S-rGO/ZnS) nanocomposite. The photocatalytic applications of ZnS and S-rGO/ZnS) nanocomposite is investigated for the decontamination and disinfection of 2-chlorophenol (2-CP) and real dairy wastewater. The physico-chemical characteristics of ZnS and S-rGO/ZnS were analyzed using photoluminescence spectroscopy, UV visible spectroscopy, scanning electron microscopy and x-ray diffraction. The experimental findings revealed that the S-rGO/ZnS nanocomposite own superior photocatalytic activity with 99.3% degradation of 2-chlorophenol within four hours of solar light exposure. Furthermore, the antimicrobial potential of S-rGO/ZnS was also highlighted with the observed high disinfection potential while treatment of dairy wastewater. Overall, this study may offer useful insights to established visible light S-rGO/ZnS nanocomposite having the potential to be efficiently used for multiple applications in wastewater purification.

BACKGROUND: Aflatoxins (AFs) are fungal secondary metabolites produced by Aspergillus flavus. They contaminate of dietary food with AFs is a worldwide problem that affects both food safety and agricultural economies. AIM: The aim of this study was designed to investigate the AFs contents of human food commodities mostly consumed in Jeddah, Saudi Arabia. METHODS: The study was designed in vitro, contents in six food categories. A total of 288 samples were collected from 78 different markets in Jeddah. AFs were determined by high-performance liquid chromatography with fluorescence detector using immunoaffinity column clean-up. RESULTS: The results indicated that the incidence rate 27.3% of nut samples collected from Jeddah, were contaminated with AFB1, AFB2. The concentrations of AFs (AFB1, AFB2, AFG1, and AFG2) were ranged from 0.19–482.4, 0.09–3.34, 0.19–87.1, to 0.09–579 μg/kg in the nut samples. CONCLUSION: The results demonstrate the importance of routine monitoring of AFs contamination in various dry foods for human consumed should be performed regularly and the nuts contained high levels of AFs. The legal regulations must be unauthorized for human consumption to control the health risks associated with AFs.

This review shall provide support for the suitability of arid environments as preferred location to search for unknown lipid-accumulative bacteria. Bacterial lipids are attracting more and more attention as sustainable replacement for mineral oil in fuel and plastic production. The development of prokaryotic microorganisms in arid desert habitats is affected by its harsh living conditions. Drought, nutrient limitation, strong radiation, and extreme temperatures necessitate effective adaption mechanisms. Accumulation of storage lipids as energy reserve and source of metabolic water represents a common adaption in desert animals and presumably in desert bacteria and archaea as well. Comparison of corresponding literature resulted in several bacterial species from desert habitats, which had already been described as lipid-accumulative elsewhere. Based on the gathered information, literature on microbial communities in hot desert, cold desert, and humid soil were analyzed on its content of lipid-accumulative bacteria. With more than 50% of the total community size in single studies, hot deserts appear to be more favorable for lipid-accumulative species then humid soil (≤20%) and cold deserts (≤17%). Low bacterial lipid accumulation in cold deserts is assumed to result from the influence of low temperatures on fatty acids and the increased necessity of permanent adaption methods.

As oleaginous microorganisms represent an upcoming novel feedstock for the biotechnological production of lipids or lipid-derived biofuels, we searched for novel, lipid-producing strains in desert soil. This was encouraged by the hypothesis that neutral lipids represent an ideal storage compound, especially under arid conditions, as several animals are known to outlast long periods in absence of drinking water by metabolizing their body fat. Ten lipid-accumulating bacterial strains, affiliated to the genera Bacillus, Cupriavidus, Nocardia, Rhodococcus and Streptomyces, were isolated from arid desert soil due to their ability to synthesize poly(β-hydroxybutyrate), triacylglycerols or wax esters. Particularly two Streptomyces sp. strains and one Rhodococcus sp. strain accumulate significant amounts of TAG under storage conditions under optimized cultivation conditions. Rhodococcus sp. A27 and Streptomyces sp. G49 synthesized approx. 30% (w/w) fatty acids from fructose or cellobiose, respectively, while Streptomyces isolate G25 reached a cellular fatty acid content of nearly 50% (w/w) when cultivated with cellobiose. The stored triacylglycerols were composed of 30-40% branched fatty acids, such as anteiso-pentadecanoic or iso-hexadecanoic acid. To date, this represents by far the highest lipid content described for streptomycetes. A biotechnological production of such lipids using (hemi)cellulose-derived raw material could be used to obtain sustainable biodiesel with a high proportion of branched-chain fatty acids to improve its cold-flow properties and oxidative stability.

There is an error in the Original Publication of this paper for “Acknowledgements” section was missing.

A novel Sphingomonas strain was isolated from a sample of desert soil collected near Jeddah in Saudi Arabia. A polyphasic approach was performed to characterize this strain, initially designated as G39T. Cells of strain G39T are motile, Gram-negative, catalase- and oxidase-positive. The strain is able to grow aerobically at 20-35 °C, pH 6.5-8 and tolerates up to 4 % (w/v) NaCl. Based on 16S rRNA gene sequence similarity, the closest relative type strains of G39T are Sphingomonas mucosissima DSM 17494T (98.6 %), S. dokdonensis DSM 21029T (98.4 %) and S. hankookensis DSM 23329T (97.4 %). Furthermore, the average nucleotide identities between the draft genome sequence of strain G39T and the genome sequences of all other available and related Sphingomonas species are significantly below the threshold of 94 %. The G+C content of the draft genome (3.12 Mbp) is 65.84 %. The prevalent (>5 %) cellular fatty acids of G39T were C18 : 1ω7c, C16 : 1ω7c and/or C16 : 1ω6c, C14 : 0 2-OH and C16 : 0. The only detectable respiratory quinone was ubiquinone-10 and the polar lipids profile is composed of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, as well as unidentified lipids, phospholipids and glycolipids. The results of the conducted polyphasic approach confirmed that this isolate represents a novel species of the genus Sphingomonas, for which the name Sphingomonas jeddahensis sp. nov. is proposed. The type strain of this species is G39T (=DSM 103790T=LMG 29955T). peerReviewed

The recovery of polyhydroxyalkanoates (PHAs) from biomass, that is, from bacterial cells, is one of the major obstacles in the industrial production of these polyesters. Since PHAs are naturally synthesized as intracellular storage compounds for carbon and energy and are for this deposited in the cytoplasm of the bacterial cell, PHAs are more or less tightly linked with the entire biomass, and the polyesters must be released from the cells before their isolation and purification can be conducted. This additional step, that is, the release from the cells, is a major difference from most other biotechnological processes where the product occurs outside of the cells because it is secreted into the medium in a bioreactor or because it is synthesized in vitro in an enzyme reactor in a cell free system. This additional step contributes significantly to the overall costs of production. In this review we provide an overview about the different processes that result in the release of PHA from the cells, and we evaluate these processes with regard to the suitability at large scale in the industry.

The present study explored the eco-friendly approach of utilizing plant-growth-promoting rhizobacteria (PGPR) inoculation and foliar application of silicon (Si) to improve the physiology, growth, and yield of mung bean under saline conditions. We isolated 18 promising PGPR from natural saline soil in Saudi Arabia, and screened them for plant-growth-promoting activities. Two effective strains were selected from the screening trial, and were identified as Enterobacter cloacae and Bacillus drentensis using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and 16S rRNA gene sequencing techniques, respectively. Subsequently, in a 2-year mung bean field trial, using a randomized complete block design with a split-split plot arrangement, we evaluated the two PGPR strains and two Si levels (1 and 2 kg ha(-1)), in comparison with control treatments, under three different saline irrigation conditions (3.12, 5.46, and 7.81 dS m(-1)). The results indicated that salt stress substantially reduced stomatal conductance, transpiration rate, relative water content (RWC), total chlorophyll content, chlorophyll a, chlorophyll b, carotenoid content, plant height, leaf area, dry biomass, seed yield, and salt tolerance index. The PGPR strains and Si levels independently improved all the aforementioned parameters. Furthermore, the combined application of the B. drentensis strain with 2 kg Si ha(-1) resulted in the greatest enhancement of mung bean physiology, growth, and yield. Overall, the results of this study provide important information for the benefit of the agricultural industry.

Regulation of expression of the phasin PhaP, which is the major protein at the surface of polyhydroxyalkanoate (PHA) granules in Ralstonia eutropha H16, was studied and analysed at the molecular level. The regulation of PhaP expression is achieved by an autoregulated repressor, which is encoded by phaR in R. eutropha. The occurrence of PhaR homologues and the organization of phaR genes was analysed in detail in 29 different bacteria. Three kinds of molecule to which PhaR binds were identified in cells of R. eutropha, as revealed by gel-mobility-shift assays, DNaseI footprinting, cell fractionation, immunoelectron microscopy studies employing anti-PhaR antibodies raised against purified N-terminal hexahistidine-tagged PhaR and in vitro binding studies employing artificial PHA granules. PhaR binds upstream of phaP at two sites comprising the transcriptional start site plus the -10 region and a region immediately upstream of the -35 region of the sigma(70) promoter of phaP, where two imperfect 12 bp repeat sequences (GCAMMAAWTMMD) were identified on the sense and anti-sense strands. PhaR also binds 86 bp upstream of the phaR translational start codon, where the sigma(54)-dependent promoter was identified. PhaR also binds to the surface of PHA granules. In the cytoplasm of a phaROmegaKm mutant of R. eutropha H16, increased quantities of PhaP were detected and the cells formed by this strain were much smaller and had many more PHA granules present than the wild-type. These data support the following model for the regulation of phaP expression. Under cultivation conditions not permissive for PHA biosynthesis or in mutants defective in PHA biosynthesis, PhaR binds to the phaP promoter region and represses transcription of this gene. After the onset of PHA biosynthesis, under conditions that are permissive for the formation of nascent granules, PhaR binds to PHA granules and phaP is transcribed. At the later stages of PHA accumulation, PhaR no longer binds to the granules and the transcription of phaP is again repressed. In addition to this, phaR expression is subject to autoregulation. Excess PhaR that has not bound to the phaP upstream region or to PHA granules binds to the phaR upstream region, thereby repressing its own transcription.

The control of mosquitoes is an important public health concern around the world. The activity of petroleum ether extracts of Dodonaea viscose, Lantana camara and Ruta chaliphenses have been investigated towards larval development of Aedes aegypti. The plant extracts exhibits variable biological activity against Ae. aegypti. The greatest effect was observed with Dodonaea viscose and Lantana camara. They showed acute LC50 (2days) of 126.2, 136.9 and chronic LC50 (10 days) of 64.6 and 68.5 ppm, respectively. Larvae suffered chronic toxicities leading to 97.8% mortality using Dodonaea viscose and 95.6% using Lantana camara. Egg hatchability was significantly reduced in Dodonaea viscose and Lantana camara concentrations. All extracts concentrations of Dodonaea viscose and Lantana camara as well as higher extract concentration of Ruta chaliphenses caused significant high hindrance of subsequent larval development and consequently reduced both pupation and adult mergence. Drastic retardation of development was shown using Dodonaea viscose extracts (17.3, 7.4%) and Lantana camara extracts (19.3, 9.0%) from larval stage managed to pupal and adult stages, when reared in very low concentration (100 ppm) of the extracts. Ruta chaliphense was only more effective at higher concentrations. Hence, application of these extracts to Ae. aegypti mosquito breeding sites can be used as an innovative valuable alternative to the existing synthetic pesticides for the control of Ae. aegypti.

Electrophoretic analysis of the proteins bound to poly(3-hydroxybutyric acid), PHB-, granules in Methylobacterium extorquens, M. rhodesianum as well as the PHB-leaky mutants Mu 1 and Mu 11, which were isolated from the latter, resulted in two dominant low-molecular weight proteins, which were referred to as GA11 and GA20. After purification of these proteins antibodies against the GA11 and GA20 protein of M. extorquens were obtained. Both proteins bound to the surface of PHB granules as revealed by immunoelectron microscopy of whole cells of M. extorquens and M. rhodesianum. With cells of the PHB-leaky mutants Mu 1 and Mu 11 no specific labeling was observed. The N-terminal amino acid sequences of the GA11 and the GA20 protein were determined. We found significant homologies between the sequences of the investigated strains. The use of oligonucleotide probes based on the N-terminal sequences of the GA20 protein from M. rhodesianum to identify the corresponding structural genes in various genomic libraries failed.

In recent years, glycerol has become an attractive carbon source for microbial processes, as it accumulates massively as a by-product of biodiesel production, also resulting in a decline of its price. A potential use of glycerol in biotechnology is the synthesis of poly(3-hydroxypropionate) [poly(3HP)], a biopolymer with promising properties which is not synthesized by any known wild-type organism. In this study, the genes for 1,3-propanediol dehydrogenase ( dhaT ) and aldehyde dehydrogenase ( aldD ) of Pseudomonas putida KT2442, propionate-coenzyme A (propionate-CoA) transferase ( pct ) of Clostridium propionicum X2, and polyhydroxyalkanoate (PHA) synthase ( phaC1 ) of Ralstonia eutropha H16 were cloned and expressed in the 1,3-propanediol producer Shimwellia blattae . In a two-step cultivation process, recombinant S. blattae cells accumulated up to 9.8% � 0.4% (wt/wt [cell dry weight]) poly(3HP) with glycerol as the sole carbon source. Furthermore, the engineered strain tolerated the application of crude glycerol derived from biodiesel production, yielding a cell density of 4.05 g cell dry weight/liter in a 2-liter fed-batch fermentation process.

Isolation of polyhydroxyalkanoates (PHAs) from bacterial cell matter is a critical step in order to achieve a profitable production of the polymer. Therefore, an extraction method must lead to a high recovery of a pure product at low costs. This study presents a simplified method for large scale poly(3-hydroxybutyrate), poly(3HB), extraction using sodium hypochlorite. Poly(3HB) was extracted from cells of Ralstonia eutropha H16 at almost 96% purity. At different extraction volumes, a maximum recovery rate of 91.32% was obtained. At the largest extraction volume of 50 L, poly(3HB) with an average purity of 93.32% ± 4.62% was extracted with a maximum recovery of 87.03% of the initial poly(3HB) content. This process is easy to handle and requires less efforts than previously described processes.

A recombinant strain of Escherichia coli, which overexpressed phaC and phaE from Chromatium vinosum, was used to isolate poly(3-hydroxyalkanoic acid) synthase. The isolation was performed by a two-step procedure including chromatography on DEAE-Sephacel and Procion Blue H-ERD. The poly(3-hydroxyalkanoic acid) synthase consisted of two different kinds of subunit (PhaC, M(r) 39,500 and PhaE, M(r) 40.500). PhaC was separated from the poly(3-hydroxyalkanoic acid) synthase complex by chromatography on phenyl-Sepharose: PhaE was enriched by solubilization of protein inclusion bodies. The stoichiometry of PhaC and PhaE in the enzyme complex was not determined. The poly(3-hydroxyalkanoic acid) synthase (PhaEC) exhibited a native relative molecular mass of M(r) 400,000 and most probably consists of ten subunits. The Km value of the enzyme for D(-)-3-hydroxybutyryl-CoA was 0.063 mM. The enzyme synthesized poly(3-hydroxybutyric acid) in vitro from D(-)-3-hydroxybutyryl-CoA or, together with propionyl-CoA transferase in a coupled enzyme reaction, synthesized the same product from acetyl-CoA plus D(-)-3-hydroxybutyric acid. Antibodies were raised against both subunits of the poly(3-hydroxyalkanoic acid) synthase. By immunoelectron microscopy, the poly(3-hydroxyalkanoic acid) synthase was localized within the cytoplasm in cells of C. vinosum grown under non-storage conditions. In cells grown under poly(3-hydroxybutyric acid) storage conditions, the enzyme was observed to be located at the surface of the poly(3-hydroxybutyric acid) granules. Immunoblots with anti-PhaC, anti-PhaE IgG and crude extract proteins indicated that poly(3-hydroxyalkanoic acid) synthases with partial sequence similarities are widespread among purple sulphur bacteria.

The N-terminal amino acid sequence of the polyhydroxyalkanoic acid (PHA) granule-associated M(r)-15,500 protein of Rhodococcus ruber (the GA14 protein) was analyzed. The sequence revealed that the corresponding structural gene is represented by open reading frame 3, encoding a protein with a calculated M(r) of 14,175 which was recently localized downstream of the PHA synthase gene (U. Pieper and A. Steinbüchel, FEMS Microbiol. Lett. 96:73-80, 1992). A recombinant strain of Escherichia coli XL1-Blue carrying the hybrid plasmid (pSKXA10*) with open reading frame 3 overexpressed the GA14 protein. The GA14 protein was subsequently purified in a three-step procedure including chromatography on DEAE-Sephacel, phenyl-Sepharose CL-4B, and Superose 12. Determination of the molecular weight by gel filtration as well as electron microscopic studies indicates that a tetrameric structure of the recombinant, native GA14 protein is most likely. Immunoelectron microscopy demonstrated a localization of the GA14 protein at the periphery of PHA granules as well as close to the cell membrane in R. ruber. Investigations of PHA-leaky and PHA-negative mutants of R. ruber indicated that expression of the GA14 protein depended strongly on PHA synthesis.

Frequent spontaneous loss of the magnetic phenotype was observed in stationary-phase cultures of the magnetotactic bacteriumMagnetospirillum gryphiswaldenseMSR-1. A nonmagnetic mutant, designated strain MSR-1B, was isolated and characterized. The mutant lacked any structures resembling magnetosome crystals as well as internal membrane vesicles. The growth of strain MSR-1B was impaired under all growth conditions tested, and the uptake and accumulation of iron were drastically reduced under iron-replete conditions. A large chromosomal deletion of approximately 80 kb was identified in strain MSR-1B, which comprised both the entiremamABandmamDCclusters as well as further putative operons encoding a number of magnetosome-associated proteins. A bacterial artificial chromosome clone partially covering the deleted region was isolated from the genomic library of wild-typeM. gryphiswaldense. Sequence analysis of this fragment revealed that all previously identifiedmamgenes were closely linked with genes encoding other magnetosome-associated proteins within less than 35 kb. In addition, this region was remarkably rich in insertion elements and harbored a considerable number of unknown gene families which appeared to be specific for magnetotactic bacteria. Overall, these findings suggest the existence of a putative large magnetosome island inM. gryphiswaldenseand other magnetotactic bacteria.

The boundary layer of PHA inclusion bodies isolated from Chromatium vinosum, Pseudomonas oleovorans, and Rhodococcus ruber was investigated by negative staining and transmission electron microscopy. A typical boundary layer exhibits a basic lattice composed of regularly arranged phasin molecules and phospholipids, forming a thin, nevertheless mechanically stable cover surrounding the content of the inclusion body. Depending on the bacterial strain under investigation, the lattice parameters of the boundary layer may vary. Usually, values between 3.3 and 9.6nm are observed for the spacing, and the lattice is rectangular. Enzyme particles interpreted as PHA synthase particles are attached to, or inserted into the basic lattice. They cover not more than 20% of the total surface of the inclusion body. These enzyme particles measure between 8 and 12nm in diameter, are made up of subunits and occur as single units or small aggregates. No indications have been obtained which would support the view that the boundary layer is a double-layer of proteins with phospholipids in between. Rather, a visual inspection of detached boundary layers revealed that the boundary layer is a monolayer exhibiting only one kind of basic lattice. In regions where this monolayer had been artificially removed from the inclusion body, the surface of the contents of the inclusion body was exposed.