Nitrite reductase activity of sulphate-reducing bacteria prevents their inhibition by nitrate-reducing,sulphide-oxidizing bacteria

Sulphate-reducing bacteria (SRB) can be inhibited by nitrate-reducing, sulphide-oxidizing bacteria (NR-SOB), despite the fact that these two groups are interdependent in many anaerobic environments. Practical applications of this inhibition include the reduction of sulphide concentrations in oil fields by nitrate injection. The NR-SOB Thiomicrospira sp. strain CVO was found to oxidize up to 15 mM sulphide, considerably more than three other NR-SOB strains that were tested. Sulphide oxidation increased the environmental redox potential (Eh) from -400 to +100 mV and gave 0.6 nitrite per nitrate reduced. Within the genus Desulfovibrio, strains Lac3 and Lac6 were inhibited by strain CVO and nitrate for the duration of the experiment, whereas inhibition of strains Lac15 and D. vulgaris Hildenborough was transient. The latter had very high nitrite reductase (Nrf) activity. Southern blotting with D. vulgaris nrf genes as a probe indicated the absence of homologous nrf genes from strains Lac3 and Lac6 and their presence in strain Lac15. With respect to SRB from other genera, inhibition of the known nitrite reducer Desulfobulbus propionicus by strain CVO and nitrate was transient, whereas inhibition of Desulfobacterium autotrophicum and Desulfobacter postgatei was long-lasting. The results indicate that inhibition of SRB by NR-SOB is caused by nitrite production. Nrf-containing SRB can overcome this inhibition by further reducing nitrite to ammonia, preventing a stalling of the favourable metabolic interactions between these two bacterial groups. Nrf, which is widely distributed in SRB, can thus be regarded as a resistance factor that prevents the inhibition of dissimilatory sulphate reduction by nitrite.     

Inhibition effect of ferric iron on the kinetics of ferrous iron

Ferric iron acted as a non-competitive inhibitor for the biological oxidation of ferrous iron and decreased the inhibitory effects of high concentrations of ferrous iron as well as the auto-inhibitive effect the bacterial cells. A previously developed kinetic model for this reaction was modified to incorporate the inhibition effects of ferric iron. © Rapid Science Ltd. 1998     

Preserving a Comprehensive Vegetation Knowledge Base – An Evaluation of Four Historical Soviet Vegetation Maps of the Western Pamirs (Tajikistan)

We edited, redrew, and evaluated four unpublished historical vegetation maps of the Western Pamirs (Tajikistan) by the Soviet geobotanist Okmir E. Agakhanjanz. These maps cover an area of 5,188 km² and date from 1958 to 1960. The purpose of this article is to make the historic vegetation data available to the scientific community and thus preserve a hitherto non available and up to now neglected or forgotten data source with great potential for studies on vegetation and ecosystem response to global change. The original hand-drawn maps were scanned, georeferenced, and digitized and the corresponding land cover class was assigned to each polygon. The partly differing legends were harmonized and plant names updated. Furthermore, a digital elevation model and generalized additive models were used to calculate response curves of the land cover classes and to explore vegetation-topography relationships quantitatively. In total, 2,216 polygons belonging to 13 major land cover classes were included that are characterized by 252 different plant species. As such, the presented maps provide excellent comparison data for studies on vegetation and ecosystem change in an area that is deemed to be an important water tower in Central Asia.     

Treating Urban Wastewater: Nutrient Removal by Using Immobilized Green Algae in Batch Cultures

Essential roles of microalgae during the tertiary treatment of municipal wastewater have been proven. In order to avoid wash out of the biomass and also modify the quality of the treated wastewater; some techniques such as cell immobilization have been developed. To do so, in this study four samples from two species of microalgae (Chlorella vulgaris and Chlamydomonas sp.) were determined and confirmed by taxonomic identification. The samples were immobilized in calcium alginate beads. Within 10 days the amounts of nitrate (No₃^?-N) and orthophosphate (Po₄^3?-P) were measured to calculate the removal efficacy for each individual sample. Based on the standard methods, the amount of nitrate and orthophosphate were determined every 3 days within 10 days. The results indicate that immobilized microalgae are able to remove the nutrients and reduce the amount of nitrate and orthophosphate, significantly. Furthermore, the C. vulgaris (YG02) was the best species in this experience with 72% and 99% of reduction in the amount of nitrate and orthophosphate, respectively.     

Correlation of circulating omentin-1 with bone mineral density in multiple sclerosis: the crosstalk between bone and adipose tissue

Background

Patients with multiple sclerosis (MS) are at increased risk of osteoporosis and fractures. Adipose tissue-derived adipokines may play important roles in the osteoimmunology of MS. In order to determine whether omentin-1 and vaspin may be related to bone health in MS patients, we compared circulating levels of these recently identified adipokines, between MS patients and healthy controls.

Methods

A total of 35 ambulatory MS patients with relapsing-remitting courses were compared with 38 age- and sex-matched healthy controls. Bone mineral density (BMD) was determined for the lumbar spine (L2–L4) and the proximal femur using dual-energy x-ray absorptiometry. Circulating omentin-1, vaspin, osteocalcin, osteopontin, osteoprotegerin, the receptor activator of nuclear factor-κB ligand, matrix metalloproteinase 9, C-reactive protein and 25-hydroxy vitamin D levels were evaluated by highly specific enzyme-linked immunosorbent assay methods.

Results

There was no significant difference between the two groups regarding bone-related cytokines, adipocytokines, and the BMD measurements of patients with MS and the healthy controls. However, in multiple regression analysis, serum omentin-1 levels were positively correlated with BMD at the femoral neck (β = 0.49, p = 0.016), total hip (β = 0.42, p = 0.035), osteopontin (β = 0.42, p = 0.030) and osteocalcin (β = 0.53, p = 0.004) in MS patients. No correlations were found between vaspin, biochemical, and BMD measures in both groups.

Conclusions

Elevated omentin-1 serum levels are correlated with BMD at the femoral neck and the serum levels of osteocalcin and osteopontin in MS patients. Therefore, there is crosstalk between adipose tissue and bone in MS.     

The First Report and Molecular Analysis of Enterocytozoon bieneusi from Raccoon (Procyon lotor) in North of Iran

Microsporidia are known opportunistic microorganisms and usually transmitted via the fecal–oral route. However, there is no information about human‐infecting microsporidia in wildlife in Iran. This study aimed to investigate and analyze human‐infecting microsporidia isolated from raccoons in north of Iran. Totally, 30 fecal samples were collected; then, DNA extraction was performed and specific fragments of the SSU rRNA gene of Enterocytozoon bieneusi and Encephalitozoon species were amplified. After amplification and sequencing the ITS, the results were compared to the GenBank database. Phylogenetic trees and network analysis were employed to explore probable relationships. E. bieneusi was the only detected microsporidia among samples. Genotyping showed the genotypes D, E, and RA in 15/18 (83.33%), 1/18 (5.55%), and 2/18 (11.11%) of samples, respectively. Novel genotypes RA1 and RA2 grouped together and apart from other genotypes. E. bieneusi genotypes D and E clustered with the genotypes previously reported from animals, humans, and environmental samples. Network analysis revealed six distinct sequence types among raccoon's isolates. This study demonstrated that E. bieneusi genotype D was the most prevalent microsporidia among raccoons. It seems that wildlife may play a role in dispersion of microsporidia spores.     

Design of Localized Surface Plasmon Resonance (LSPR) Biosensor for Immunodiagnostic of E. coli O157:H7 Using Gold Nanoparticles Conjugated to the Chicken Antibody

E. coli O157:H7 is one of the most important pathogens in food-borne diseases and is the main cause of the pseudo pandemic development of hemorrhagic colitis and hemolytic uremic syndrome. Also E. coli O157:H7 is the most common serotype of Shiga-toxin-producing E. coli. Traditional methods for detecting E. coli O157:H7 are expensive, time-consuming, and less sensitive. A method with high sensitivity and high-resolution optical detection is utilizes the LSPR property of spherical gold nanoparticles (GNP). In this work, we constructed a novel nano-bio probe to detect E. coli O157:H7 by synthesizing citrate gold nanoparticle conjugated (non-covalent bond) with specific chicken anti-E. coli O157:H7 antibody (IgY) by changing the pH of the nanoparticles’ environment. UV-visible and DLS methods were used to confirm the bonding between the antibody and nanoparticles and the LSPR sensitivity of the nano-bio probe was evaluated by ELISA method. We could optically detect this bacterium in less than 2 h by measuring the LSPR band λ max shifts of GNPs. The sensitivity of this novel biosensor was determined by about 10 CFU/ml, using the LSPR property of spherical gold nanoparticles. So that, the LSPR λ max red shifted from 530 to 543 nm in presence of 10 CFU bacterium. In conclusion, this nano biosensor can be used to detect this important pathogen among the clinical specimens.

     

The Effect of Cerium Oxide During Pregnancy on the Development of the Testicular Tissue of Newborn NMRI Mice

Biological Trace Element Research - Cerium(IV) oxide is widely used as a catalyst in all aspects of human life and human beings are exposed to these materials. The purpose of this experimental...     

Myricetin loaded in solid lipid nanoparticles induces apoptosis in the HT-29 colorectal cancer cells via mitochondrial dysfunction

Molecular Biology Reports - Among the flavonoids, Myricetin (MCN) has negligible side effects and anti-cancer properties. However, the therapeutic potential of MCN has been limited mainly by its...     

Mechanistic study of microbial control of hydrogen sulfide production in oil reservoirs.

Microbial control of biogenic production of hydrogen sulfide in oil fields was studied in a model system consisting of pure cultures of the nitrate-reducing, sulfide-oxidizing bacterium (NR-SOB) Thiomicrospira sp. strain CVO and the sulfate-reducing bacterium (SRB) Desulfovibrio sp. strain Lac6, as well as in microbial cultures enriched from produced water of a Canadian oil reservoir. The presence of nitrate at concentrations up to 20 mM had little effect on the rate of sulfate reduction by a pure culture of Lac6. Addition of CVO imposed a strong inhibition effect on production of sulfide. In the absence of added nitrate SRB we were able to overcome this effect after an extended lag phase. Simultaneous addition of CVO and nitrate stopped the production of H2S immediately. The concentration of sulfide decreased to a negligible level due to nitrate-dependent sulfide oxidation activity of CVO. This was not prevented by raising the concentration of Na-lactate, the electron donor for sulfate reduction. Similar results were obtained with enrichment cultures. Enrichments of produced water with sulfide and nitrate were dominated by CVO, whereas enrichments with sulfate and Na-lactate were dominated by SRB. Addition of an NR-SOB enrichment to an SRB enrichment inhibited the production of sulfide. Subsequent addition of sufficient nitrate caused the sulfide concentration to drop to zero. A similar response was seen in the presence of nitrate alone, although after a pronounced lag time, it was needed for emergence of a sizable CVO population. The results of the present study show that two mechanisms are involved in microbial control of biogenic sulfide production. First, addition of NR-SOB imposes an inhibition effect, possibly by increasing the environmental redox potential to levels which are inhibitory for SRB. Second, in the presence of sufficient nitrate, NR-SOB oxidize sulfide, leading to its complete removal from the environment. Successful microbial control of H2S in an oil reservoir is crucially dependent on the simultaneous presence of NR-SOB (either indigenous population or injected) and nitrate in the environment.