Shahida Hasnain

Inoculating wheat seedlings with exopolysaccharide-producing bacteria restricts sodium uptake and stimulates plant growth under salt stress

A pot experiment was conducted to elucidate the effects of inoculating five exopolysaccharide- (EPS-) producing bacterial strains on the dry matter yield and the uptake of K+, Na+, and Ca2+ by wheat seedlings grown in a moderately saline soil. The bacteria were isolated from the rhizosphere soil (RS) of wheat grown in a salt-affected soil and included Aeromonas hydrophila/caviae (strain MAS-765), Bacillus insolitus (strain MAS17), and Bacillus sp. (strains MAS617, MAS620 and MAS820). The inoculation substantially increased the dry matter yield of roots (149–527% increase) and shoots (85–281% increase), and the mass of RS (176–790% increase). All the strains, except MAS617, also increased the RS mass/root mass ratio as well as the population density of EPS bacteria on the rhizoplane, and both these parameters were significantly correlated with the content of water-insoluble saccharides in the RS. Inoculation restricted Na+ uptake by roots, which was not attributable to the binding of Na+ by the RS, or to the ameliorative effects of Ca2+ under salinity. The decreased Na+ uptake by roots of inoculated than uninoculated plants was probably caused by a reduced passive (apoplasmic) flow of Na+ into the stele due to the higher proportion of the root zones covered with soil sheaths in inoculated treatments. Among the strains tested, MAS820 was the most efficient in all respects, whereas MAS617 was the least effective. Results suggested that inoculating selected EPS-producing bacteria could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.

De novo lipogenesis in health and disease

BACKGROUND De novo lipogenesis (DNL) is a complex and highly regulated metabolic pathway. In normal conditions DNL converts excess carbohydrate into fatty acids that are then esterified to storage triacylglycerols (TGs). These TGs could later provide energy via β-oxidation. In human body this pathway is primarily active in liver and adipose tissue. However, it is considered to be a minor contributor to the serum lipid homeostasis. Deregulations in the lipogenic pathway are associated with diverse pathological conditions. SCOPE OF REVIEW The present review focuses on our current understanding of the lipogenic pathway with special reference to the causes and consequences of aberrant DNL. MAJOR CONCLUSIONS The deregulation of DNL in the major lipogenic tissues of the human body is often observed in various metabolic anomalies - including obesity, non-alcoholic fatty liver disease and metabolic syndrome. In addition to that de novo lipogenesis is reported to be exacerbated in cancer tissues, virus infected cells etc. These observations suggest that inhibitors of the DNL pathway might serve as therapeutically significant compounds. The effectiveness of these inhibitors in treatment of cancer and obesity has been suggested by previous works. GENERAL SIGNIFICANCE De novo lipogenesis - which is an intricate and highly regulated pathway - can lead to adverse metabolic consequences when deregulated. Therapeutic targeting of this pathway may open a new window of opportunity for combating various lipogenesis-driven pathological conditions - including obesity, cancer and certain viral infections.

Auxin production by plant associated bacteria: impact on endogenous IAA content and growth of Triticum aestivum L.

Aims:  The aim of this study was to investigate the potential of bacterial strains of Bacillus, Pseudomonas, Escherichia, Micrococcus and Staphylococcus genera associated with wild herbaceous flora to enhance endogenous indole‐3‐acetic acid (IAA) content and growth of Triticum aestivum var. Inqalab‐91.

Exposure of Soil Microbial Communities to Chromium and Arsenic Alters Their Diversity and Structure

Extensive use of chromium (Cr) and arsenic (As) based preservatives from the leather tanning industry in Pakistan has had a deleterious effect on the soils surrounding production facilities. Bacteria have been shown to be an active component in the geochemical cycling of both Cr and As, but it is unknown how these compounds affect microbial community composition or the prevalence and form of metal resistance. Therefore, we sought to understand the effects that long-term exposure to As and Cr had on the diversity and structure of soil microbial communities. Soils from three spatially isolated tanning facilities in the Punjab province of Pakistan were analyzed. The structure, diversity and abundance of microbial 16S rRNA genes were highly influenced by the concentration and presence of hexavalent chromium (Cr (VI)) and arsenic. When compared to control soils, contaminated soils were dominated by Proteobacteria while Actinobacteria and Acidobacteria (which are generally abundant in pristine soils) were minor components of the bacterial community. Shifts in community composition were significant and revealed that Cr (VI)-containing soils were more similar to each other than to As contaminated soils lacking Cr (VI). Diversity of the arsenic resistance genes, arsB and ACR3 were also determined. Results showed that ACR3 becomes less diverse as arsenic concentrations increase with a single OTU dominating at the highest concentration. Chronic exposure to either Cr or As not only alters the composition of the soil bacterial community in general, but affects the arsenic resistant individuals in different ways.

Production of surfactin from Bacillus subtilis MZ-7 grown on pharmamedia commercial medium

BackgroundCommercial medium (Pharmamedia) was investigated for the production of surfactin by Bacillus subtilis MZ-7. Different media (defined, semi-defined, and complex media) were compared for the production of surfactin after fixing the least influential variables in standardized fermentation conditions. Carbohydrate and nitrogen supplements were also tried to improve production in Pharmamedia.ResultsSurfactin production was confirmed using PCR along with other analytical techniques and monitored by RP-HPLC and MALDI-TOF-MS. We found that optimized and brain heart infusion media were best for production of surfactin (280 mg/L) and a relatively comparable production with Pharmamedia (220 mg/L), however, supplementing Pharmamedia with Fe+ (4.0 mM) and sucrose (2 g/L) leads to a maximum production of about (300 mg/L).ConclusionCottonseed-derived medium proved to be a suitable substrate for the production of bioactive substances including surfactin, a useful compound in both medical and biotechnological fields. The medium provided not only higher product accumulations but at considerably lower cost with potential for large scale industrial applications.

Growth stimulation of Triticum aestivum seedlings under Cr-stresses by non-rhizospheric pseudomonad strains

Four chromium-resistant non-rhizospheric strains SPCr-1, SPCr-2, SPCr-3 and SPCr-4 (Pseudomonads), which were isolated from the effluents of an ICI paint factory and could tolerate 2-3 mg ml(-1) chromium in a minimal medium and 40 mg ml(-1) in a rich medium, were used to inoculate seeds of Triticum aestivum. Both inoculated and non-inoculated seeds were germinated and grown under different concentrations of chromium salts (K2CrO4, 0, 100, 250, 500; CrCl3, 0, 250, 500, 1000 microg ml(-1)). Germination and growth parameters were severely affected by chromium-salts. K2CrO4 had more drastic effects than CrCl3 treatments. Seedlings had a hard and brittle texture and showed symptoms of hypertrophy. Brown spots on leaves and stems were visible and the tips of leaves were bifurcated and curled. The root system was also impaired, ranging from a browning of the tip to complete destruction of cortical tissues. Under chromium-stress conditions, inoculated plants had significantly better germination and growth as compared to non-inoculated treatments. Bacterial growth enhancement of seedlings was associated with reduced chromium-uptake, increased auxin content and the formation of stress specific proteins. With bacterial inoculations, symptoms of chromium toxicity were reversed, especially at lower concentrations of chromium salts.

Effect of Peganum harmala or its β-Carboline Alkaloids on Certain Antibiotic Resistant Strains of Bacteria and Protozoa from Poultry

In the present study the antimicrobial potential of various extracts from 12 medicinal plants has been investigated in vitro on multiple antibiotic resistant pathogens and some selected protozoa isolated from poultry. The initial examination was performed on E. coli (n = 10) using disc and agar well diffusion assays. Only two plants, Peganum harmala (seeds) and Eucalyptus globulus (leaves) showed positive responses. The active extracts were also investigated against an additional 19 bacteria and the clonal cultures of three protozoa (Histomonas meleagridis, Tetratrichomonas gallinarum and Blastocystis sp.). Only Peganum harmala was found to inhibit the growth of all bacteria and protozoa at 0.38–1.55 mg/mL and 0.63–1.65 mg/mL, respectively. To investigate the potential role of alkaloids in crude extracts of Peganum harmala, four known β‐carbolin alkaloids were quantified and their antimicrobial activity was compared using a microdilution assay. Harmaline was found to be in the highest concentration followed by harmine and harmalol, whereas harmane could not be detected. The activity of the pure alkaloids was in the order harmane > harmaline > harmalol ≥ harmine for all bacteria, while for protozoa, it was different depending on the microorganism. It is concluded that Peganum harmala or its alkaloids could probably be used for the control of antibiotic resistant isolates of bacteria as well as protozoa. Copyright

Growth stimulatory effect of Ochrobactrum intermedium and Bacillus cereus on Vigna radiata plants

Aims:  This study assessed the plant growth‐promoting ability of the bacterial strains Ochrobactrum intermedium (isolate CrT‐1) and Bacillus cereus (isolate S‐6).

Comparative study of Cr(VI) uptake and reduction in industrial effluent by Ochrobactrum intermedium and Brevibacterium sp.

Two chromium-resistant bacterial strains, CrT-1 and CrT-13, tolerant up to 40mg K2CrO4 ml−1 on nutrient agar, 25mgml−1 in nutrient broth, and up to 10mgml−1 in acetate-minimal media, were identified as Ochrobactrum intermedium and Brevibacterium sp., respectively, on the basis of 16S rRNA gene sequencing. Uptake of chromate was greater in living cells than in heat-killed on dried cells. CrT-1 reduced 82%, 28% and 16% of Cr(VI) at 100, 500, and 1000μgml−1 after 24h while CrT-13 reduced 41%, 14% and 9%. Other heavy metals at low concentrations did not affect these reductions. At 150 and 300μgml−1 in an industrial effluent sample Cr(VI) was reduced by 87% and 71%, respectively, with CrT-1 and by 68% and 47% with CrT-13.

Leptin deficiency and leptin gene mutations in obese children from Pakistan

BACKGROUND Congenital leptin deficiency is a rare human genetic condition clinically characterized by hyperphagia and acute weight gain usually during the first postnatal year. The worldwide data on this disorder includes only 14 cases and four pathogenic mutations have been reported in the leptin gene. STUDY OBJECTIVE The objectives of this study were to measure serum leptin levels in obese children and to detect leptin gene mutations in those found to be leptin deficient. PATIENTS AND RESULTS A total of 25 obese children were recruited for the study. Leptin deficiency was detected in nine of them. Leptin gene sequencing identified mutations in homozygous state in all the leptin deficient children. Two cases carried novel mutations (c.481_482delCT and c.104_106delTCA) and each of the remaining seven the previously reported frameshift mutation (c.398delG). CONCLUSION The results suggest that leptin deficiency caused by mutations in the leptin gene may frequently be seen in obese Pakistani children from Central Punjab.