Changes in Lolium perenne L. rhizosphere microbiome during phytoremediation of Cd- and Hg-contaminated soils

The contamination of soil and water by metals such as mercury (Hg) and cadmium (Cd) has been increasing in recent years, because of anthropogenic activities such as mining and agriculture, respectively. In this work, the changes in the rhizosphere microbiome of Lolium perenne L. during the phytoremediation of soils contaminated with Hg and Cd were evaluated. For this, two soil types were sampled, one inoculated with mycorrhizae and one without. The soils were contaminated with Hg and Cd, and L. perenne seeds were sown and harvested after 30 days. To assess changes in the microbiome, DNA isolation tests were performed, for which samples were subjected to two-step PCR amplification with specific 16S rDNA V3-V4 primers (337F and 805R). With mycorrhizae, changes had been found in the absorption processes of metals and a new distribution. While with respect to microorganisms, families such as the Enterobacteriaceae have been shown to have biosorption and efflux effects on metals such as Hg and Cd. Mycorrhizae then improve the efficiency of removal and allow the plant to better distribute the absorbed concentrations. Overall, L. perenne is a species with a high potential for phytoremediation of Cd- and Hg-contaminated soils in the tropics. Inoculation with mycorrhizae modifies the phytoremediation mechanisms of the plant and the composition of microorganisms in the rhizosphere. Mycorrhizal inoculation and changes in the microbiome were associated with increased plant tolerance to Cd and Hg. Microorganism-assisted phytoremediation is an appropriate alternative for L. perenne

The impact of iron on the function and composition of the human gut microbiota

Iron-supplements are widely consumed; however, most of the iron is not absorbed and enters the colon where potentially pathogenic bacteria can utilise it for growth. Assessing iron bioavailability and the effects on bacterial groups is an evolving subject area and forms the basis of the research presented in this thesis. The growth of Escherichia coli and Salmonella Typhimurium was significantly impaired when cultured independently in iron-deficient media (p<0.0001). These observations positively correlated with a decrease in water-soluble iron concentrations present in the culture. However, depletion of iron did not affect the growth of the beneficial species, Lactobacillus rhamnosus. Culturing human faecal microbiotas in an in vitro colon model identified changes in the growth of different bacterial taxa. 16S rDNA-based metataxonomics indicated that under conditions of iron depletion through BPDS, a chemical iron chelator, the relative abundance of several taxa decreased, including a 10% and 15% decrease in Escherichia and Bifidobacterium, respectively. This was supported by observations of lower viable counts of Enterobacteriaceae and bifidobacteria. Analysis using 1H NMR indicated that the production of acetate, butyrate and propionate in vitro was reduced under iron-restricted conditions. Iron chelation through phytin, a dietary compound, illustrated similar results with the exception of a 33% increase in the relative abundance of Bifidobacterium and 225% increase in Collinsella. Furthermore, increases in propionate and formate concentrations were also observed when cultured with phytin. A 6-week, crossover double-blinded randomised human dietary intervention trial was performed (n=14), where participants were asked to consume encapsulated phytin or placebo. Capsules were coated with a specialised formulation, Phloral®, designed to release phytin directly in the colon. No conclusions could be made regarding the iron chelating properties of phytin as analysis of stool samples collected revealed clumps of phytin and therefore, unsuccessful dispersal of phytin within the colonic lumen. This pilot human intervention study indicates that the form of phytin is an important factor and this should be considered for follow-up studies

Assessment and Remediation of Soils Contaminated by Potentially Toxic Elements (PTE)

Many soils worldwide are contaminated with potentially toxic elements (PTEs). These elements can be taken up by plant roots and accumulate in plants’ organs, thus becoming a danger for the health of humans and animals. Therefore, it is still essential and urgent to understand the behavior of such contaminants in soil and find sustainable approaches to reduce the risk posed by their presence in soil systems. This volume contains ten original research articles. Four articles deal with the assessment of bioavailability of PTEs in contaminated soils, three articles report results on the application of phytoremediation to PTEs contaminated soils, one paper is related to the source–sink relationships of PTEs at basin scale, and two manuscripts address the issue of PTE contamination in urban soils

Synthesis of new pyrazolium based tunable aryl alkyl ionic liquids and their use in removal of methylene blue from aqueous solution

In this study, two new pyrazolium based tunable aryl alkyl ionic liquids, 2-ethyl-1-(4-methylphenyl)-3,5- dimethylpyrazolium tetrafluoroborate (3a) and 1-(4-methylphenyl)-2-pentyl-3,5-dimethylpyrazolium tetrafluoroborate (3b), were synthesized via three-step reaction and characterized. The removal of methylene blue (MB) from aqueous solution has been investigated using the synthesized salts as an extractant and methylene chloride as a solvent. The obtained results show that MB was extracted from aqueous solution with high extraction efficiency up to 87 % at room temperature at the natural pH of MB solution. The influence of the alkyl chain length on the properties of the salts and their extraction efficiency of MB was investigated