Chromium tolerance and accumulation in Aspergillus flavus isolated from tannery effluent.

Cr(VI) tolerance in Aspergillus flavus, strain SFL, isolated from tannery effluent was measured and compared with a reference strain of A. flavus, A1120. On solid medium, SFL had a high level of Cr(VI) tolerance (1,600 mg/L), which was 16 times that of A1120 and greater than most previously analyzed fungal strains. When in 100 mg/L of Cr(VI), SFL completely depleted Cr(VI) within 72 h while A1120 depleted 85% of Cr(VI). SFL was more effective in reducing extracellular Cr(VI) than A1120. While A1120 showed greater biosorption of Cr(VI) than SFL, intracellular accumulation was approximately 50% greater in SFL and was more energy-dependent than A1120. Cr(VI) modified the external surface of the hyphae. Cr speciation detected the presence of only Cr(III), corresponding to Cr(OH)3 , which precipitated on the hyphal surface. Cr(VI) bound to the functional groups carboxyl, amine, and hydroxyl in both SFL and A1120. Transmission electron microscopy energy-dispersive X-ray detected Cr on the fungal wall and within membrane-bound organelles of the cytoplasm. In conclusion, the greater tolerance of SFL to Cr(VI) relative to A1120 is due to more effective energy-dependant uptake of Cr(VI) into the cell and increased capacity of SFL to store Cr in intracellular vacuoles compared with A1120.

Critical effects of polar fluorescent probes on the interaction of DHA with POPC supported lipid bilayers.

The understanding of lipid bilayer structure and function has been advanced by the application of molecular fluorophores. However, the effects of these probe molecules on the physicochemical properties of membranes being studied are poorly understood. A quartz crystal microbalance with dissipation monitoring instrument was used in this work to investigate the impact of two commonly used fluorescent probes, 1­palmitoyl­2­{12­[(7­nitro­2­1,3­benzoxadiazol­4­yl)amino]dodecanoyl}­sn­glycero­3­phosphocholine (NBD-PC) and 1,2­dipalmitoyl­sn­glycero­3­phosphoethanolamine­n­(lissamine rhodamine­B­sulfonyl) (Lis-Rhod PE), on the formation and physicochemical properties of a 1­palmitoyl­2­oleoyl­sn­glycero­3­phosphocholine supported lipid bilayer (POPC-SLB). The interaction of the POPC-SLB and fluorophore-modified POPC-SLB with docosahexaenoic acid, DHA, was evaluated. The incorporation of DHA into the POPC-SLB was observed to significantly decrease in the presence of the Lis-Rhod PE probe compared with the POPC-SLB. In addition, it was observed that the small concentration of DHA incorporated into the POPC:NBD-PC SLB can produce rearrangement processes followed by the lost not only of DHA but also of POPC or NBD-PC molecules or both during the washing step. This work has significant implications for the interpretation of data employing fluorescent reporter molecules within SLBs.

Ceruloplasmin is regulated by copper and lactational hormones in PMC42-LA mammary epithelial cell culture models.

Ceruloplasmin (Cp) is a multicopper ferroxidase that is considered to be an important source of copper in milk for normal neonatal development. We investigated the expression, subcellular localization and secretion of Cp in PMC42-LA cell culture models representative of resting, lactating and suckled human mammary epithelia. Both secreted Cp (sCp) and plasma membrane associated glycosylphosphatidylinositol-linked Cp (GPI-Cp) were expressed in PMC42-LA cells. In all three epithelial models (resting, lactating and suckled), the expression and secretion of copper-bound, ferroxidase active, Cp (holo-Cp) was dependent on media copper concentration. In low copper (bathocuproinedisulphonic acid/d-penicillamine treated models) there was greater than a 2-fold decrease in holo-Cp expression and secretion, which was mirrored by a 2-fold increase in the expression and secretion of copper-free Cp protein (apo-Cp). Cell surface biotinylation studies revealed that the state of PMC42-LA cell differentiation (functionality), and the level of extracellular copper, had no significant effect on the level of plasma membrane bound GPI-Cp. Quantitative real time PCR analyses determined that there was no significant (P > 0.05) difference in Cp mRNA levels across all copper conditions investigated (0, 5, 50 µM). However, there was a significant (P < 0.05) increase (∼2-fold) in Cp mRNA in both the lactating and suckled models in comparison to the resting model. Furthermore, the Cp mRNA increase in response to PMC42-LA differentiation corresponded with more secreted Cp protein, both apo and holo forms, indicating a link between function and Cp requirement. Our results provide significant insight on the regulation of Cp expression and secretion in lactation and copper incorporation into milk.