Effect of plant extract on the degradation of nitroaromatic compounds by soil microorganisms

Assessment of herbal drugs for promising anti-Candida activity

BACKGROUND

Microbial infections are diverse and cause serious human diseases. Candida albicans infections are serious healthcare-related infections that are complicated by its morphological switching from yeast to hyphae, resistant biofilm formation and mixed infections with bacteria. Due to the increase in drug resistance to currently used antimicrobial agents and the presence of undesirable side effects, the need for safe and effective novel therapies is important. Compounds derived from plants are known for their medicinal properties including antimicrobial activities. The purpose of the study was to compare and evaluate the anti-Candida activities of several medicinal plants in order for the selection of a herbal drug for human use as effective antimicrobial. The selection was taking into considerations two important parameters; parameters related to the selected drug including activity, stability, solubility and toxicity and parameters related to the pathogen including its different dynamic growth and its accompanied secondary bacterial infections.

METHODS

Seven different plants including Avicennia marina (Qurm), Fagonia indica (Shoka'a), Lawsania inermis (Henna), Portulaca oleracea (Baq'lah), Salvadora persica (Souwak), Ziziphus spina- Christi (Sidr) and Asphodelus tenuifolius (Kufer) were ground and extracted with ethanol. The ethanol extracts were evaporated and the residual extract dissolved in water prior to testing against Candida albicans in its different morphologies. The antibacterial and cytotoxic effects of the plants extracts were also tested.

RESULTS

Out of the seven tested plants, L. inermis and P. oleracea showed significant anti-Candida activity with MIC ~10 μg/mL. Furthermore, both plant extracts were able to inhibit C. albicans growth at its dynamic growth phases including biofilm formation and age resistance. Accompanied secondary bacterial infections can complicate Candida pathogenesis. L. inermis and P. oleracea extracts showed effective antibacterial activities against S. aureus, P. aeruginosa, E. coli, and the multidrug resistant (MDR) A. baumannii and Klebsiella pneumoniae. Both extracts showed no toxicity when measured at their MIC on human erythrocytes.

CONCLUSION

The results from this study suggested that L. inermis and P. oleracea extracts and/or their chemicals are likely to be promising drugs for human use against C. albicans and MDR bacteria.

Removal of pharmaceuticals from municipal wastewaters at laboratory scale by treatment with activated sludge and biostimulation

Municipal wastewater containing 21 pharmaceutical compounds, as well as activated sludge obtained from the aeration tank of the same wastewater treatment plant were used in lab-scale biodegradation experiments. The concentrations of pharmaceutical compounds were determined by high-performance liquid chromatography coupled to Orbitrap high-resolution mass spectrometry and ranged from 13.2ng/L to 51.8μg/L. Activated sludge was characterized in the terms of phylogenetic and catabolic diversity of microbial community, as well as its morphology. Proteobacteria (24.0%) represented the most abundant phylum, followed by Bacteroidetes (19.8%) and Firmicutes (13.2%). Bioaugmentation of wastewater with activated sludge stimulated the biodegradation process for 14 compounds. The concentration of carbamazepine in non-amended and bioaugmented WW decreased during the first 17h up to 30% and 70%, respectively. Diclofenac and ibuprofen demonstrated comparatively slow removal. The stimulating effect of the added nutrients was observed for the degradation of almost all pharmaceuticals detected in WW. The most pronounced effect of nutrients was found for erythromycin. The results were compared with those obtained for the full-scale WW treatment process.

Brassica napus hairy roots and rhizobacteria for phenolic compounds removal

Phenolic compounds are contaminants frequently found in water and soils. In the last years, some technologies such as phytoremediation have emerged to remediate contaminated sites. Plants alone are unable to completely degrade some pollutants; therefore, their association with rhizospheric bacteria has been proposed to increase phytoremediation potential, an approach called rhizoremediation. In this work, the ability of two rhizobacteria, Burkholderia kururiensis KP 23 and Agrobacterium rhizogenes LBA 9402, to tolerate and degrade phenolic compounds was evaluated. Both microorganisms were capable of tolerating high concentrations of phenol, 2,4-dichlorophenol (2,4-DCP), guaiacol, or pentachlorophenol (PCP), and degrading different concentrations of phenol and 2,4-DCP. Association of these bacterial strains with B. napus hairy roots, as model plant system, showed that the presence of both rhizospheric microorganisms, along with B. napus hairy roots, enhanced phenol degradation compared to B. napus hairy roots alone. These findings are interesting for future applications of these strains in phenol rhizoremediation processes, with whole plants, providing an efficient, economic, and sustainable remediation technology.

The role of nutrients in the biodegradation of 2,4,6-trinitrotoluene in liquid and soil

The widely used explosive 2,4,6-trinitrotoluene (TNT) has residues that are potentially explosive, toxic, and mutagenic. TNT and other explosives can be degraded by microorganisms; however, biostimulation is needed for process efficiency. To investigate the effectiveness of using biostimulation to degrade TNT, we added varying concentrations of a nutrient amendment consisting of inorganic salts, plant extracts, and molasses to soil and liquid media. For the inoculum we used a consortium of bacteria AM 06 that had exhibited the ability to degrade TNT and which had been previously isolated from explosives-contaminated soils. Phylogenetically, the clones clustered into seven different genera: Klebsiella, Raoultella, Serratia, Stenotrophomonas, Pseudoxanthomonas, Achromobacter and Pseudomonas. The addition of AM 06 consortium to a liquid environment along with 100% nutrient amendment decreased the amount of TNT (and its degradation products) by up to 90% after 14 days incubation. At the total amount of TNT was less than 100 mg/l, the concentration of TNT did not influence the amount of sugar consumed by the bacteria consortium. In soil media, the TNT degradation process was dependent on the concentration of nutrient amendment added. At higher initial concentrations of TNT (500 mg/kg), bioaugmentation (i.e., addition of bacteria inoculum) had a demonstrated effect, especially when nutrient concentrations of 50% and 100% were added to the soil. Findings of this study could further the understanding of the TNT biodegradation processes in water and soil and provide for optimization of the technological conditions for bioremediation.