Biomedical subjects

A Nejidat

Publications and source records attributed to A Nejidat.

17 recordsLinked to original sources

PubMed2005

Environmental impact and health risks associated with greywater irrigation: a case study.

There is an increasing trend to use greywater for irrigation in households. This is partly due to the notion that greywater is of better quality than wastewater and therefore does not need extensive treatment beyond addressing public health issues. The aim of the study was to evaluate the environmental impact and health risks associated with the use of greywater for irrigation on a small private farm. Over a three-year period, each of three plots on a farm was irrigated with either freshwater, fertilized water, or greywater. Irrigation water and soil from the plots were analyzed for a wide range of chemical and microbial variables. Results suggest that greywater may be of similar quality to wastewater in several parameters such as BOD and faecal coliforms. For some other variables such as boron and surfactants, greywater may even be of worse quality than wastewater. Long-term irrigation of arid loess soil with greywater may result in accumulation of salts, surfactants and boron in the soil, causing changes in soil properties and toxicity to plants. Faecal coliforms did not survive in the soil. Treating greywater before using it for irrigation is recommended, even in places where this is not a requirement.

Agriculture↗

PubMed2004

Degradation of 2,4,6-tribromophenol by bacterial cells attached to chalk collected from a contaminated aquifer.

AIM: To investigate the factors governing the adhesion and activity of the 2,4,6-tribromophenol (TBP) degrading bacterium Achromobacter piechaudii TBPZ-N61 on chalk from a contaminated aquifer. METHODS AND RESULTS: Adhesion kinetics of TBPZ-N61 to grey and white chalk from a polluted fractured chalk aquifer was tested in a batch system. Both grey and white chalk contain ca 80% CaCO3, while grey chalk contains more organic matter (2.4%) than the white chalk (0.3%) and also contains Dolmite and Clinoptilolite. Adhesion of the bacterial cells to the chalk particles (<0.2 mm) occurred rapidly (96% of the cells within 15 min). Langmuir-fitted adhesion isotherms suggest that cells in the stationary phase, which are more hydrophobic, adhere to both grey and white chalk more efficiently than cells in the logarithmic growth phase. Increasing the pH (from 6.7 to 8.1) caused a significant reduction in cell adhesion to the chalk. Activity of attached cells was evaluated in both batch and column experiments. Logarithmic cells adhering to white and grey chalk were more active in TBP degradation than cells in suspension. In column experiments, significant TBP degradation was retained up to 30 days after a single injection of TBPZ cells. Thereafter, activity was fully recovered by amendment of yeast extract. Chalk surfaces that were incubated in situ in contaminated groundwater for 20 days still allowed the adhesion and activity of TBPZ cells. CONCLUSIONS: Taken together, our results show that bacteria adhere efficiently to specific sites on the chalk surfaces, and that sustained bacterial activity of the attached cells can be achieved by adding a carbon source such as yeast extract which also overcome toxic constituents that may occur in some chalk types. SIGNIFICANCE AND IMPACT OF THE STUDY: Bioremediation of TBP-contaminated chalk aquifers is made possible by the injection of bacterial cultures.

Achromobacter↗

PubMed2002

The identification and characterization of osmotolerant yeast isolates from chemical wastewater evaporation ponds.

Ramat Hovav is a major chemical industrial park manufacturing pharmaceuticals, pesticides, and various aliphatic and aromatic halogens. All wastewater streams are collected in large evaporation ponds. Salinity in the evaporation ponds fluctuates between 3% (w/v) and saturation and pH values range between 2.0 and 10.0. We looked for microorganisms surviving in these extreme environmental conditions and found that 2 yeast strains dominate this biotope. 18S rDNA sequence analysis identified the isolates as Pichia guilliermondii and Rhodotorula mucilaginosa. Both isolates grew in NaCl concentrations ranging up to 3.5 M and 2.5 M, respectively, and at a pH range of 2-10. There was a distinct difference between the Rhodotorula and Pichia strains and S. cerevisiae RS16 that served as a control strain with respect to accumulation of osmoregulators and internal ion concentrations when exposed to osmotic stress. The Pichia and Rhodotorula strains maintained high glycerol concentration also in media low in NaCl. Utilization of various carbon sources was examined. Using a tetrazolium-based assay we show that the Rhodotorula and Pichia strains are capable of utilizing a wide range of different carbon sources including anthracene, phenanthrene, and other cyclic aromatic hydrocarbons.

Adaptation, Physiological↗

PubMed2001

Transcriptional and posttranscriptional regulation of the glycolate oxidase gene in tobacco seedlings.

The roles of light and of the putative plastid signal in glycolate oxidase (GLO) gene expression were investigated in tobacco (Nicotiana tabacum cv. Samsun NN) seedlings during their shift from skotomorphogenic to photomorphogenic development. GLO transcript and enzyme activities were detected in etiolated seedlings. Their respective levels increased three- and six-fold during 96 h of exposure to light. The GLO transcript was almost undetectable in seedlings in which chloroplast development was impaired by photooxidation with the herbicide norflurazon. In transgenic tobacco seedlings, photooxidation inhibited the light-dependent increase in GUS activity when it was placed under the regulation of the GLO promoter P(GLO). However, even under these photooxidative conditions, a continuous increase in GUS activity was observed as compared to etiolated seedlings. When GUS expression was driven by the CaMV 35S promoter (P35S), no apparent difference was observed between etiolated, deetiolated and photooxidized seedlings. These observations indicate that the effects of the putative plastid development signal and light on GUS expression can be separated. Translational yield analysis indicated that the translation of the GUS transcript in P(GLO)::GUS seedlings was enhanced 30-fold over that of the GUS transcript in P35S::GUS seedlings. The overall picture emerging from these results is that in etiolated seedlings GLO transcript, though present at a substantial level, is translated at a low rate. Increased GLO transcription is enhanced, however, in response to signals originating from the developing plastids. GLO gene expression is further enhanced at the translational level by a yet undefined light-dependent mechanism.

Alcohol Oxidoreductases↗

PubMed1999

Specific detection of p-chlorobenzoic acid by Escherichia coli bearing a plasmid-borne fcbA'::lux fusion.

In this communication we report on a genetically engineered bacterium that reacts by light emission to the presence of 4-chlorobenzoic acid. To construct this strain, DNA fragment (1.7 kb) upstream from the 4-chlorobenzoic acid dehalogenase (fcb) operon of Arthrobacter SU was fused to Vibriofischeri luxCDABE genes. An Escherichia coli strain transformed with a multi-copy plasmid (pASU) bearing this fusion responded to the presence of 4-chlorobenzoic acid and a few closely related compounds by increased luminescence, exhibiting a high specificity but a relatively low sensitivity. While it could be somewhat, improved by manipulating the experimental pH, sensitivity remained too low for real time applicability. Nevertheless, the principle of using dehalogenase promoters as environmental pollution sensor was demonstrated.

Arthrobacter↗

PubMed1998

Promoter activity of the 5' flanking region of a tobacco glycolate oxidase gene in transgenic tobacco plants.

A clone harboring the 5' flanking region of a tobacco glycolate oxidase (GLO) gene was isolated from a lambda EMBL3-tobacco genomic DNA library. Primer extension analysis indicated two major transcripts with 76 and 81 bp 5' UTRs. An RT-PCR assay mapped the major mRNA transcription initiation site to thymine at position 81 upstream of the translation initiation codon. A putative TATA box spanning positions -56 to -50 upstream of the transcription initiation site was found. Promoter activity of the 5' flanking region (-3.0 kb to +82 bp) was demonstrated in tobacco plants transformed with a GLO-beta-glucuronidase (GUS) chimeric gene. Furthermore, in these transgenic plants, GUS expression patterns mimicked the expression patterns of the endogenous GLO.

Alcohol Oxidoreductases↗

PubMed1998

Effect of long-term ammonia starvation on the oxidation of ammonia and hydroxylamine by Nitrosomonas europaea.

Axenic cultures of the ammonia-oxidizing bacterium Nitrosomonas europaea were starved of ammonia (energy source) for up to 342 d. During this time the bacteria retained the ability to respond instantly to ammonia (1 mM) or hydroxylamine (0.1 mM) amendment by oxidizing it to nitrite without initial protein synthesis. In vivo, the ability to oxidize amended ammonia stayed almost constant during the starvation period, but a drop in the hydroxylamine oxidation rate (to 33%) was observed after 4 wk of starvation when exogenous hydroxylamine was supplied as sole energy source. In contrast, it has been shown that the level and in vitro activity of hydroxylamine oxidoreductase were not significantly affected during the starvation period. Only minor changes were detected between the protein patterns on one-dimensional SDS-PAGE of growing and starved cells. Thus, it is concluded that the activities of the energy-generating enzymes in N. europaea were not affected during long-term ammonia starvation.

Ammonia↗

PubMed1997

Variability in the pattern of random amplified polymorphic DNA.

The random amplified polymorphic DNA (RAPD) technique is a simple method to detect DNA polymorphism. It is sensitive to reaction conditions. Small changes in the reactants' concentration cause variations in amplification products. Using DNA from Asparagus officinalis, Dactylis glomerata, Mercurialis annua and Escherichia coli, we examined variability in the amplification pattern associated with reaction constituents. An increase in the ratio of Taq DNA polymerase to DNA in the reaction increased the number of amplified fragments. Increasing the concentration of primer resulted in the amplification of low molecular weight DNA fragments, while lowering the concentration resulted in high molecular weight fragments. Subsets of amplified fragments required different concentrations of magnesium for their highest intensity. Mechanical shearing of DNA obtained by sonication led to reduction in amplification of a subset of products. Enzymatic fragmentation of DNA by restriction enzymes led to loss or gain of specific fragments, depending on the DNA, primer, and restriction enzyme. RAPD markers of pooled DNA of anonymous pedigree should be critically evaluated for frequent 'false positive' markers.

Base Composition↗

PubMed1997

Effect of ammonia starvation on hydroxylamine oxidoreductase activity of Nitrosomonas europaea.

A technique for detection of the activity of hydroxylamine oxidoreductase (HAO) involving denaturing SDS-polyacrylamide gels was developed. The activity of HAO of Nitrosomonas europaea was assayed using this technique, which revealed a single active band of 140 kDa. The HAO activity of other ammonia-oxidizers was also resistant to SDS, the molecular weights being identical to that of N. europaea. N. europaea cells starved of ammonia for up to 72 h retained a considerable amount of HAO, as detected on Western blot analysis, and a significant level of its activity, as found on assaying at the end of the starvation period. Only after 4 h incubation of starved N. europaea cells with 2.0 mM ammonia was some increase in the HAO level observed. The results indicate that HAO remains highly stable during ammonia starvation of N. europaea.

Ammonia↗

PubMed1996

Isolation and characterization of a functional promoter from Nitrosomonas europaea.

A functional promoter from the obligate autotrophic ammonia oxidizing bacterium Nitrosomonas europaea was identified by expression in Escherichia coli, using a promoterless reporter gene. Transcription initiation site of this promoter was determined by primer extension analysis. The sequences at -35 and -10 have low similarity to the -10/-35 consensus sequence of known prokaryotic promoters.

Ammonia↗

PubMed1995

Studies of coat protein-mediated resistance to tobacco mosaic virus (TMV). II. Challenge by a mutant with altered virion surface does not overcome resistance conferred by TMV coat protein.

Transgenic tobacco plants expressing the coat protein (CP) gene of the U1 strain of tobacco mosaic virus (TMV) exhibit CP-mediated resistance (CP-MR) against some, but not all, tobamoviruses. To investigate the role of the amino acid sequences on the surface of the challenge virus in CP-MR, mutant strains of U1 TMV were constructed to contain the amino or carboxy termini of the CP of Sunn hemp mosaic tobamovirus (SHMV). The modified virus was unable to overcome CP-MR in transgenic plants that contained the TMV CP. In contrast, TMV in which the CP was replaced by the SHMV CP overcame CP-MR to the same extent as did SHMV. We conclude that CP-MR conferred by TMV CP involves interactions between amino acid sequences of the challenge viruses and the transgene protein other than those on the surface of the challenge virus.

Amino Acid Sequence↗

PubMed1994

Detection of Nitrosomonas spp. by polymerase chain reaction.

A unique genomic DNA fragment was isolated from Nitrosomonas europaea ATCC 19718. Based on the sequence of this fragment, oligonucleotide primers for polymerase chain reaction amplification were prepared which amplify sequences of 775 and 658 bp. The predicted DNA fragments were both amplified from the genome of N. europaea and a Nitrosomonas spp. isolated from a local oxidation pond. The primers failed to amplify DNA from the genomes of the ammonia oxidiser Nitrosolobous multiformis, the nitrite oxidiser Nitrococcus mobilis as well as from the genomes of other unrelated heterotrophic bacteria. These DNA sequences could be amplified from 0.01 ng of N. europaea genomic DNA or from 100 intact cells, and it was possible to detect Nitrosomonas DNA in a DNA mixture extracted from water samples drawn from a local oxidation pond.

Base Sequence↗

PubMed1991

Transfer of the movement protein gene between two tobamoviruses: influence on local lesion development.

The effects of transfer of the movement gene between the tobamoviruses tobacco mosaic virus (TMV) and tobacco mild green mosaic virus (TMGMV) were studied. The movement protein (MP) gene of TMGMV was cloned into an infectious cDNA of TMV to build the recombinant virus V23. V23, like TMV and TMGMV, caused systemic infection in Nicotiana tabacum Xanthi. In N. sylvestris V23 and TMV spread systemically although TMGMV produces necrotic local lesions on this host. V23 and TMV cause systemic infection on tomato plants while TMGMV does not infect tomato. In Xanthi nc plants, V23 produced necrotic local lesions similar in size to those produced by TMGMV. On the other hand in transgenic Xanthi nc tobacco plants that express a gene encoding the MP of TMV the necrotic lesions produced by V23 and TMGMV were similar in size to those produced by TMV. These results indicate that the size of necrotic lesions produced by TMGMV and TMV on Xanthi nc plants is influenced by the MP gene.

Amino Acid Sequence↗

PubMed1990

Tissue-specific expression of the TMV coat protein in transgenic tobacco plants affects the level of coat protein-mediated virus protection.

Transgenic tobacco plants were produced that express a chimeric gene encoding the coat protein (CP) of tobacco mosaic virus (TMV) under the control of the promoter from a ribulose bisphosphate carboxylase small subunit (rbcS) gene. Plant lines expressing comparable levels of CP from the rbcS and cauliflower mosaic virus 35S promoters were compared for resistance to TMV. In whole plant assays the 35S:CP constructs gave higher resistance than the rbcS:CP constructs. On the other hand, leaf mesophyll protoplasts isolated from both plant lines were equally resistant to infection by TMV. This indicated that the difference in resistance between the lines in the whole plant assay reflects differences at the level of short- and/or long-distance spread of TMV. Therefore, we propose that the difference in tissue-specific expression between the 35S and rbcS promoters accounts for greater resistance in the plant lines that express the 35S:CP chimeric genes.

Blotting, Western↗

PubMed1989

Decreased levels of TMV coat protein in transgenic tobacco plants at elevated temperatures reduce resistance to TMV infection.

Transgenic tobacco plants that accumulate tobacco mosaic virus (TMV) coat protein (CP) are resistant to TMV infection under standard growth conditions. The amount of CP accumulated and the degree of resistance to TMV were found to be temperature dependent. Exposure to continuous high temperatures (30-35 degrees) results in a sharp decrease in the amount of CP within 6 hr with no further change for at least 6 days. Under these conditions the transgenic plants developed typical systemic disease symptoms when inoculated with TMV although disease development was delayed. Transgenic plants which were moved from 35 to 22 degrees accumulated the normal level of CP within several hours. Transgenic tobacco plants inoculated and held at 35/25 degrees day/night cycles retained resistance to TMV infection. The level of CP mRNA was constant at each temperature and was associated with polyribosomes. On the basis of these results we suggest that the low level of CP under elevated temperature is due to instability of the TMV CP. In contrast, TMV CP levels in transgenic tomato plants also dropped under elevated temperatures yet retained high resistance to TMV.

Blotting, Northern↗

PubMedDate not supplied

Biodegradation of alkylpyridines by bacteria isolated from a polluted subsurface.

Ten bacterial strains were isolated from alkylpyridine polluted sediments 7.6 m below the surface. These strains were able to degrade 11 different alkylpyridine isomers. Degradation rates depended on number and position of the alkyl group. Isomers with an alkyl group at position 3 were more resistant to microbial attack. Of the 10 strains, 6 isolates were selected for detailed study. These isolates mineralized the isomers to CO2, NH4+, and biomass. All strains were gram-negative rods with a strict aerobic metabolism. Characterization of physiological and biochemical properties revealed similarity between strains. Eeach strain however, had a limited substrate range which enabled it to degrade no more than 2 to 3 compounds of the 14 alkylpyridine isomers tested. Examination of the genetic variability among cultures with the randomly amplified polymorphic DNA technique revealed high levels of genomic DNA polymorphism. The highest similarity between 2 strains (0.653) was observed between 2-picoline and 3-picoline degrading cultures. The molecular basis of the differences in substrate specificity is under investigation.

Bacteria↗

PubMedDate not supplied

Transgenic tobacco plants expressing a coat protein gene of tobacco mosaic virus are resistant to some other tobamoviruses.

Transgenic tobacco plants expressing the coat protein (CP) gene of tobacco mosaic virus were tested for resistance against infection by five other tobamoviruses sharing 45-82% homology in CP amino acid sequence with the CP of tobacco mosaic virus. The transgenic plants (CP+) showed significant delays in systemic disease development after inoculation with tomato mosaic virus or tobacco mild green mosaic virus compared to the control (CP-) plants, but showed no resistance against infection by ribgrass mosaic virus. On a transgenic local lesion host, the CP+ plants showed greatly reduced numbers of necrotic lesions compared to the CP- plants after inoculation with tomato mosaic virus, pepper mild mottle virus, tobacco mild green mosaic virus, and Odontoglossum ringspot virus but not ribgrass mosaic virus. The implications of these results are discussed in relation to the possible mechanism(s) of CP-mediated protection.

Capsid↗