Two strategies of stubborn biofouling strains surviving from NaClO membrane cleaning: EPS shielding and/or quorum sensing.

The declined performance of repeated chemically-enhanced-backwashing (CEB) seriously hampered the sustainable operation of membrane bioreactor (MBR) in long-term, and could be partially attributed to the strengthened anti-cleaning properties of residual stubborn microbes. Although plenty of research has been done towards either the model strains or the whole post-CEB microbial community, little was known about the resisting behavior of practical stubborn strains when confronting oxidative stresses induced by NaClO. Hence, this study isolated 21 strains from samples in a large-scale MBR plant with routine CEB treatment. To unravel how they survive and affect membrane fouling, their anti-oxidation ability, fouling potential and quorum sensing (QS) effect before and after NaClO stimuli were evaluated. The composition and molecular weight distribution of extracellular polymeric substance (EPS) were also investigated to understand their roles during the anti-CEB process. It was found that typical stubborn strains tended to secrete more EPS as protective shields, where polysaccharides (especially the ones >1 kDa) made major contribution. However, sometimes EPS could not well resist the stimuli, with consequent low survival rate and high intracellular ROS level. Under such circumstances, stubborn strains would rather choose to be sensitive with surged QS level and quick population regrowth to maintain vitality under the oxidative stresses. Both strategies aggravated biofouling and eventually enhanced the anti-cleaning properties of biofilm.

Cycle arrest and apoptosis in MDA-MB-231/Her2 cells induced by curcumin.

Breast cancers with an overexpression of Her-2 or Skp2 overlap with those affected by reduced p27 expression. In breast cancer, the loss of p27 is associated with a poor prognosis. Curcumin, the main constituent of turmeric, has been found to stabilize p27 levels in breast cancer, but whether this effect is mediated through changes in Skp2 or Her2 expression remains unclear. This study investigates whether curcumin inhibits Skp2-mediated p27 ubiquitination in Her2/Skp2-overexpressing cancer cell lines (MDA-MB-231/Her2 cells). The results show that curcumin represses cell proliferation, induces G1 arrest at a lower dosage (30µM), triggers apoptosis at a higher dosage (50µM) and blocks cell migration in MDA-MB-231/Her2 cells. A low dose of curcumin increases p27 and decreases Skp2, Her2, Cyclin E, CDK kinases in a time- and dose-dependent manner, suggesting that p27, Skp2 and Her2 may be involved in the growth inhibition in MDA-MB-231/Her2 cells induced by curcumin. However, higher doses of curcumin produce a dose-dependent apoptotic death in MDA-MB-231/Her2 cells, which is related to cleaved forms of PARP and caspase 3. The findings indicate that curcumin is of potential value for the chemoprevention of breast cancer, especially in breast cancer with Skp2/Her2 overexpression.