Cadmium-affected synthesis of exopolysaccharides by rhizosphere bacteria.

AIM: Study is focused on the influence of cadmium addition to growth media on production yield, their size and molecular mass of exopolysaccharides (EPS) synthesized by three rhizosphere bacteria strains. Inhibition of bacterial growth by increasing concentrations of Cd2+ was also analysed. METHODS AND RESULTS: The highest impact of Cd2+ was noticed on the growth of Arthrobacter sp. and Rhizobium metallidurans. Chryseobacterium sp. and Arthrobacter sp. produced significantly lower when compared to R. metallidurans amounts of EPS under the influence of Cd2+ . In all bacterial strains both size and molecular mass decreased after addition of Cd2+ to growth media. It causes a change in EPS conformation to more planar, which minimizes the volume of liquid in the interglobular space next to the bacterial wall. Results confirmed strong effect of Cd2+ on the structure and synthesis of bacterial EPS what can be a key factor in the interactions between rhizosphere bacteria and host plants in heavy metal polluted soils. CONCLUSION: This work proves that due to the presence of cadmium ions, the size and conformation of EPS produced by selected bacterial strains is changed to minimize their impact on cell. We suggest that shifting in EPS conformation from bigger globular particles to the smaller planar ones could be one of the probable mechanisms of Cd resistance in metallotolerant bacteria, and finally explain increased efficiency of heavy metal phytoextraction by EPS-producing plant growth-promoting micro-organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: One of the most promising remediation technique for Cd-contaminated areas is the phytoremediation in which rhizosphere bacteria play an important role by protecting plants' roots from toxic condition thus enhancing efficiency of intake. EPS secretion by bacteria is one of the most common mechanisms to protect the cell from impact of unpleasant environmental conditions, for example, toxicity of heavy metals like Cd.

Determination of the effect of selected diseases on the level of zinc and magnesium in teeth extracted from patients for clinical reasons.

As in other human tissues, determination of the content of elements in dentition may be of significance in disease diagnostics. Zinc and magnesium are bioelements that play an important role in humans. The tissue and serum concentrations of these elements may be linked to numerous diseases; thus, they may be useful biomarkers in the early detection of diseases. The objective of this study was to compare the content of zinc and magnesium in teeth extracted for clinical reasons from patients of both genders in different age groups, who were diagnosed with the following medical conditions: cardiovascular diseases, digestive diseases, infectious disorders, other chronic diseases, and hereditary diseases. Furthermore, the study attempted to determine the effect of the drugs used by the patients on the content of zinc and magnesium in their teeth. After cleaning and fragmenting, the extracted teeth were mineralized, and subsequently the content of the investigated elements was determined by flame atomic absorption spectrometry. In patients with chronic diseases, who continuously received drugs, a statistically significantly higher level of zinc (p < 0.001) and magnesium (p < 0.001) was observed as compared with the patients who did not take those medicines. People without chronic diseases but having cardiovascular diseases also exhibited a higher level of zinc. The highest zinc level in teeth was determined in people aged above 50 (p = 0.11). Furthermore, the levels of zinc and magnesium in the teeth of the study group were related and an increase in zinc concentration was observed with an increase in the concentration of magnesium (p < 0.001). Moreover, a statistically significant correlation was observed between the age of the examined people and the level of zinc (p > 0.04). The older patient had the higher the level of zinc in teeth. The level of magnesium was statistically significantly higher in the teeth of persons with other chronic diseases (p = 0.01) and those who were on medication (p < 0.001). The accumulation of zinc and magnesium in the teeth of patients is partially a result of the physiological and pathological processes occurring in aged humans. For this reason, determination of the content of these elements in teeth, which are intended for disposal according to standards, could offer diagnostic information and enable restricting the effect of pathological environmental factors on the patient's health status.

Chronic but not acute antidepresant treatment alters serum zinc/copper ratio under pathological/zinc-deficient conditions in mice.

Depression is the leading psychiatric disorder with a high risk of morbidity and mortality. Clinical studies report lower serum zinc in depressed patients, suggesting a strong link between zinc and mood disorders. Also copper as an antagonistic element to zinc seems to play a role in depression, where elevated concentration is observed. In the present study we investigated serum copper and zinc concentration after acute or chronic antidepressant (AD) treatment under pathological/zinc-deficient conditions. Zinc deficiency in mice was induced by a special diet administered for 6 weeks (zinc adequate diet - ZnA, contains 33.5 mgZn/kg; zinc deficient diet - ZnD, contains 0.2 mgZn/kg). Animals received acute or chronically saline (control), imipramine, escitalopram, reboxetine or bupropion. To evaluate changes in serum copper and zinc concentrations the total reflection X-ray fluorescence (TXRF) and flame atomic absorption spectrometry (FAAS) was performed. In ZnD animals serum zinc level was reduced after acute ADs treatment (similarly to vehicle treatment), however, as demonstrated in the previous study after chronic ADs administration no differences between both ZnA and ZnD groups were observed. Acute ADs in ZnD animals caused different changes in serum copper concentration with no changes after chronic ADs treatment. The calculated serum Zn/Cu ratio is reduced in ZnD animals (compared to ZnA subjects) treated with saline (acutely or chronically) and in animals treated acutely with ADs. However, chronic treatment with ADs normalized (by escitalopram, reboxetine or bupropion) or increased (by imipramine) this Zn/Cu ratio. Observed in this study normalization of serum Zn/Cu ratio in depression-like conditions by chronic (but not acute) antidepressants suggest that this ratio may be consider as a marker of depression or treatment efficacy.