Hypochlorite Stress Assay for Phenotypic Analysis of the Halophilic Archaeon Haloferax volcanii Using an Improved Incubation Method and Growth Monitoring

The study of haloarchaea provides an opportunity to expand understanding of the mechanisms used by extremophiles to thrive in and respond to harsh environments, including hypersaline and oxidative stress conditions. A common strategy used to investigate molecular mechanisms of stress response involves the deletion and/or site-directed mutagenesis of genes identified through omics studies followed by a comparison of the mutant and wild-type strains for phenotypic differences. The experimental methods used to monitor these differences must be controlled and reproducible. Current methods to examine recovery of halophilic archaea from extreme stress are complicated by extended incubation times, nutrients not typically encountered in the environment, and other related limitations. Here we describe a method for assessing the function of genes during hypochlorite stress in the halophilic archaeon Haloferax volcanii that overcomes these types of limitations. The method was found reproducible and informative in identifying genes needed for H. volcanii to recover from hypochlorite stress.

Expression and tandem affinity purification of 20S proteasomes and other multisubunit complexes in Haloferax volcanii

Tandem affinity purification is a useful strategy to isolate multisubunit complexes of high yield and purity but can be limited when working with halophilic proteins that are not properly expressed in Escherichia coli. Halophilic proteins are desirable for bioindustrial applications as they are often stable and active in organic solvents; however, these proteins can be difficult to express, fold, and purify by traditional technologies. Haloarchaea provide a useful alternative for expression of halophilic proteins. These microorganisms use a salt-in strategy to maintain homeostasis and express most of their proteins with halophilic properties and low pI. Here, we provide detailed protocols for the genetic modification, expression and tandem affinity purification of "salt-loving" multisubunit complexes from the haloarchaeon Haloferax volcanii. The strategy for isolation of affinity tagged 20S proteasomes that form cylindrical proteolytic nanomachines of α1, α2 and β subunits is described.

High-level synthesis and secretion of laccase, a metalloenzyme biocatalyst, by the halophilic archaeon Haloferax volcanii

Haloarchaea and their enzymes have extremophilic properties desirable for use as platform organisms and biocatalysts in the bioindustry. These GRAS (generally regarded as safe) designated microbes thrive in hypersaline environments and use a salt-in strategy to maintain osmotic homeostasis. This unusual strategy has resulted in the evolution of most of the intracellular and extracellular enzymes of haloarchaea to be active and stable not only in high salt (2-5M) but also in low salt (0.2M). This salt tolerance is correlated with a resilience to low water activity, thus, rendering the haloarchaeal enzymes active and stable in organic solvent and temperatures of 50-60°C used in the enzymatic biodelignification and saccharification of lignocellulosic materials. High-level secretion of haloarchaeal enzymes to the extracellular milieu is useful for many applications, including enzymes that deconstruct biomass to allow for lignin depolymerization and simultaneous fermentation of sugars released from hemicellulose and cellulose fractions of lignocellulosics. Here we detail strategies and methods useful for high-level secretion of a laccase, HvLccA, that mediates oxidation of various phenolics by engineering a recombinant strain of the haloarchaeon Haloferax volcanii.

Abstract P6-14-15: Impaired Nuclear Translocation of Estrogen Receptor Alfa Could Be Associated with the Antineoplastic Effect of Iodine in Premenopausal Breast Cancer

Several laboratories including ours have shown that iodine (I2) intake exhibits potent antiproliferative and apoptotic effects in vivo and in vitro models of mammary cancer. Molecular analysis of these effects indicates that antioxidant; cellular arrest and apoptotic pathways are involved. As the cellular mechanism that triggers these antineoplastic effects we have proposed that I2 could act in 2 possible ways, directly as antioxidant or indirectly by generating an iodinated arachidonic acid (6-iodoloctone) which exhibits apoptotic effects and is a specific ligand of proliferative peroxisome activated receptor gamma (PPARg). In previous preliminary reports, we corroborated an antiproliferative I2 effect (decreased PCNA) in premenopausal (pre-M) and an apoptotic action (triggering the Bax-Caspase pathway) in both pre-M and post menopausal (post-M) women with early stage breast cancer. In the present report we raise the casuistic and deeply in the analysis of mechanisms involved in this antineoplastic effect of I2. This study includes 22 women (average age 52.9 ± 12.6) diagnosed with early stage breast cancer (IIa and IIb). Patients were divided according to hormonal status into pre-M and post-M groups and were supplemented with I2 (5 mg daily) or placebo (vegetable dye) for2-5 weeks before surgery. Thyroid status (T3 and TSH; RIA) and iodine intake (urine, HPLC) were analyzed. In biopsies (beginning) and/or tumors (final), the level and location (cytosol or nuclear) of estrogen receptor alfa (ERα) and beta (ERb) were analyzed by immunohistochemistry. In tumors, we measured PPARg expression, invasive potential [hypoxia-inducible factor (HIF) and vascular endothelial growth factor (VEGF) by real time PCR] and fibrosis content (Masson's trichromic method). The results show that I2 supplementation in pre-M women is accompanied by a significant increase in the concentration of total ERα and PPARg and no change in total ERb; however, the fraction of ERα in the nucleus was significant lower, and the fibrosis content was higher (70%) than in the placebo group (40%).

In contrast, I2 supplements significantly decreased HIF and VEGF expression in both pre-and post-M women. In conclusion, our data show that, in addition to the apoptotic and anti-invasive effects on mammary cancer exhibited by I2 that are independent of hormonal status, in pre-M women, I2 also acts to diminish the effects of estrogen (decreases nuclear translocation of ERα). Experiments that analyze the possible role of PPARg in these actions are in progress.

We thank Dr. Jorge Alvarez-Aguirre2,3, Dr. Alonso Gallegos-Corona2, Lic. Concepción Correa-Tinajero3, Alejandro Nuñez-Nolasco2,3, Dra. Norma Uribe Uribe4, Jaime Ayala García4 and Dr. Dorothy Pless1. This work was supported by in part by PAPIIT-UNAM IN201210 and CONACyT 78955 and 85952.