Sikander Sultan

Plants as Useful Vectors to Reduce Environmental Toxic Arsenic Content

Arsenic (As) toxicity in soil and water is an increasing menace around the globe. Its concentration both in soil and environment is due to natural and anthropogenic activities. Rising arsenic concentrations in groundwater is alarming due to the health risks to plants, animals, and human beings. Anthropogenic As contamination of soil may result from mining, milling, and smelting of copper, lead, zinc sulfide ores, hide tanning waste, dyes, chemical weapons, electroplating, gas exhaust, application of municipal sludge on land, combustion of fossil fuels, As additives to livestock feed, coal fly ash, and use of arsenical pesticides in agricultural sector. Phytoremediation can be viewed as biological, solar-driven, pump-and-treat system with an extensive, self-extending uptake network (the root system) that enhances the natural ecosystems for subsequent productive use. The present review presents recent scientific developments regarding phytoremediation of arsenic contaminated environments and its possible detoxification mechanisms in plants.

Bioaerosols in residential micro-environments in low income countries: a case study from Pakistan.

Our knowledge of the concentrations of bioaerosols in residential micro-environments in low income countries is scanty. The present investigation was conducted to assess the culturable concentration and size distribution of bacteria, gram negative bacteria and fungi in two rural and an urban site in Pakistan. The highest indoor culturable bacteria concentration was found at Rural Site II (14,650 CFU/m3) while the outdoor maximum occurred at the urban site (16,416 CFU/m3). With reference to fungi, both indoor and outdoor concentrations were considerably higher at Rural Site I than the other sites. The size distribution of culturable bacteria at all sites showed greater variability than that of culturable fungi. At all sites more than the half (55-93%) of the culturable bacterial and fungal counts were observed in the respirable fraction (<4.7 μm) and so had the potential to penetrate into lower respiratory system.

Soil bacteria showing a potential of chlorpyrifos degradation and plant growth enhancement

Background Since 1960s, the organophosphate pesticide chlorpyrifos has been widely used for the purpose of pest control. However, given its persistence and toxicity towards life forms, the elimination of chlorpyrifos from contaminated sites has become an urgent issue. For this process bioremediation is the method of choice. Results Two bacterial strains, JCp4 and FCp1, exhibiting chlorpyrifos-degradation potential were isolated from pesticide contaminated agricultural fields. These isolates were able to degrade 84.4% and 78.6% of the initial concentration of chlorpyrifos (100 mg L−1) within a period of only 10 days. Based on 16S rRNA sequence analysis, these strains were identified as Achromobacter xylosoxidans (JCp4) and Ochrobactrum sp. (FCp1). These strains exhibited the ability to degrade chlorpyrifos in sterilized as well as non-sterilized soils, and were able to degrade 93–100% of the input concentration (200 mg kg−1) within 42 days. The rate of degradation in inoculated soils ranged from 4.40 to 4.76 mg−1 kg−1 d−1 with rate constants varying between 0.047 and 0.069 d−1. These strains also displayed substantial plant growth promoting traits such as phosphate solubilization, indole acetic acid production and ammonia production both in absence as well as in the presence of chlorpyrifos. However, presence of chlorpyrifos (100 and 200 mg L−1) was found to have a negative effect on indole acetic acid production and phosphate solubilization with percentage reduction values ranging between 2.65–10.6% and 4.5–17.6%, respectively. Plant growth experiment demonstrated that chlorpyrifos has a negative effect on plant growth and causes a decrease in parameters such as percentage germination, plant height and biomass. Inoculation of soil with chlorpyrifos-degrading strains was found to enhance plant growth significantly in terms of plant length and weight. Moreover, it was noted that these strains degraded chlorpyrifos at an increased rate (5.69 mg−1 kg−1 d−1) in planted soil. Conclusion The results of this study clearly demonstrate that the chlorpyrifos-degrading strains have the potential to develop into promising candidates for raising the productivity of crops in pesticide contaminated soils.

Bacterial community analysis of cypermethrin enrichment cultures and bioremediation of cypermethrin contaminated soils.

Cypermethrin is widely used for insect control; however, its toxicity toward aquatic life requires its complete removal from contaminated areas where the natural degradation ability of microbes can be utilized. Agricultural soil with extensive history of CM application was used to prepare enrichment cultures using cypermethrin as sole carbon source for isolation of cypermethrin degrading bacteria and bacterial community analysis using PCR‐DGGE of 16 S rRNA gene. DGGE analysis revealed that dominant members of CM enrichment culture were associated with α‐proteobacteria followed by γ‐proteobacteria, Firmicutes, and Actinobacteria. Three potential CM‐degrading isolates identified as Ochrobactrum anthropi JCm1, Bacillus megaterium JCm2, and Rhodococcus sp. JCm5 degraded 86–100% of CM (100 mg L−1) within 10 days. These isolates were also able to degrade other pyrethroids, carbofuran, and cypermethrin degradation products. Enzyme activity assays revealed that enzymes involved in CM‐degradation were inducible and showed activity when strains were grown on cypermethrin. Degradation kinetics of cypermethrin (200 mg kg−1) in soils inoculated with isolates JCm1, JCm2, and JCm5 suggested time‐dependent disappearance of cypermethrin with rate constants of 0.0516, 0.0425, and 0.0807 d−1, respectively, following first order rate kinetics. The isolated bacterial strains were among dominant genera selected under CM enriched conditions and represent valuable candidates for in situ bioremediation of contaminated soils and waters.

Plant growth promotion traits and Cr (VI) reduction potentials of Cr (VI) resistant Streptomyces strains

The most toxic form of chromium [Cr (VI)] can be converted to less toxic Cr (III) by reduction with the help of microbes. A total of 6 Streptomyces strains (S. matansis BG5, Streptomyces sp. RSF17, S. vinaceus CRF2, Streptomyces sp. CRF14, S. pulcher CRF17, S. griseoincarnatus SCF18) which were previously isolated from saline farmlands of Punjab, Pakistan, were used in this work. These strains showed varying levels of resistance to Cr (VI) from 800 μg ml−1 to 1000 mg l−1. Their plant growth promoting and Cr (VI) reduction potentials were assessed. Two strains showed positive phosphate solubilization activity. All the strains had ability to produce indole acetic acid (IAA) except one strain (CRF17). The maximum production of IAA was observed by strain BG5 that was 16 mg l−1 in the presence of 50 mg l−1 of Cr (VI). All the strains were able to produce ammonia both in the absence and presence of Cr (VI). The highest Cr (VI) reduction in majority of the strains was observed at 28 °C and pH 9. The complete reduction of 150 mg l−1 of Cr (VI) occurred after 168 hrs. The chromium (VI) concentration of 200 mg l−1 could be reduced above 90% by most of these strains. The presence of other metals also enhanced Cr (VI) reduction by most of the strains. The results indicate the potential capacity of Streptomyces strains as tool for plant growth promotion and Cr (VI) bioremediation and also is the first report about plant growth promoting traits of Cr (VI) resistant Streptomyces strains.

Corrigendum to “Plants as Useful Vectors to Reduce Environmental Toxic Arsenic Content”

[This corrects the article DOI: 10.1155/2014/921581.].