Microbial Activity Response to Solar Radiation across Contrasting Environmental Conditions in Salar de Huasco, Northern Chilean Altiplano

Indexación: Web of Science; Scopus.In high altitude environments, extreme levels of solar radiation and important differences of ionic concentrations over narrow spatial scales may modulate microbial activity. In Salar de Huasco, a high-altitude wetland in the Andean mountains, the high diversity of microbial communities has been characterized and associated with strong environmental variability. Communities that differed in light history and environmental conditions, such as nutrient concentrations and salinity from different spatial locations, were assessed for bacterial secondary production (BSP, H-3-leucine incorporation) response from short-term exposures to solar radiation. We sampled during austral spring seven stations categorized as: (a) source stations, with recently emerged groundwater (no-previous solar exposure); (b) stream running water stations; (c) stations connected to source waters but far downstream from source points; and (d) isolated ponds disconnected from ground sources or streams with a longer isolation and solar exposure history. Very high values of 0.25 mu E m(-2) s(-1), 72 W m(-2) and 12 W m(-2) were measured for PAR, UVA, and UVB incident solar radiation, respectively. The environmental factors measured formed two groups of stations reflected by principal component analyses (near to groundwater sources and isolated systems) where isolated ponds had the highest BSP and microbial abundance (35 microalgae taxa, picoeukaryotes, nanoflagellates, and bacteria) plus higher salinities and PO43- concentrations. BSP short-term response (4 h) to solar radiation was measured by H-3-leucine incorporation under four different solar conditions: full sun, no UVB, PAR, and dark. Microbial communities established in waters with the longest surface exposure (e.g., isolated ponds) had the lowest BSP response to solar radiation treatments, and thus were likely best adapted to solar radiation exposure contrary to ground source waters. These results support our light history (solar exposure) hypothesis where the more isolated the community is from ground water sources, the better adapted it is to solar radiation. We suggest that factors other than solar radiation (e.g., salinity, PO43-, NO3-) are also important in determining microbial productivity in heterogeneous environments such as the Salar de Huasco.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01857/ful

Mycobacterium tuberculosis WhiB3 Maintains Redox Homeostasis by Regulating Virulence Lipid Anabolism to Modulate Macrophage Response

The metabolic events associated with maintaining redox homeostasis in Mycobacterium tuberculosis (Mtb) during infection are poorly understood. Here, we discovered a novel redox switching mechanism by which Mtb WhiB3 under defined oxidizing and reducing conditions differentially modulates the assimilation of propionate into the complex virulence polyketides polyacyltrehaloses (PAT), sulfolipids (SL-1), phthiocerol dimycocerosates (PDIM), and the storage lipid triacylglycerol (TAG) that is under control of the DosR/S/T dormancy system. We developed an in vivo radio-labeling technique and demonstrated for the first time the lipid profile changes of Mtb residing in macrophages, and identified WhiB3 as a physiological regulator of virulence lipid anabolism. Importantly, MtbΔwhiB3 shows enhanced growth on medium containing toxic levels of propionate, thereby implicating WhiB3 in detoxifying excess propionate. Strikingly, the accumulation of reducing equivalents in MtbΔwhiB3 isolated from macrophages suggests that WhiB3 maintains intracellular redox homeostasis upon infection, and that intrabacterial lipid anabolism functions as a reductant sink. MtbΔwhiB3 infected macrophages produce higher levels of pro- and anti-inflammatory cytokines, indicating that WhiB3-mediated regulation of lipids is required for controlling the innate immune response. Lastly, WhiB3 binds to pks2 and pks3 promoter DNA independent of the presence or redox state of its [4Fe-4S] cluster. Interestingly, reduction of the apo-WhiB3 Cys thiols abolished DNA binding, whereas oxidation stimulated DNA binding. These results confirmed that WhiB3 DNA binding is reversibly regulated by a thiol-disulfide redox switch. These results introduce a new paradigmatic mechanism that describes how WhiB3 facilitates metabolic switching to fatty acids by regulating Mtb lipid anabolism in response to oxido-reductive stress associated with infection, for maintaining redox balance. The link between the WhiB3 virulence pathway and DosR/S/T signaling pathway conceptually advances our understanding of the metabolic adaptation and redox-based signaling events exploited by Mtb to maintain long-term persistence

Low levels of p27 in association with deregulated p53-pRb protein status enhance tumor proliferation and chromosomal instability in non-small cell lung carcinomas.

BACKGROUND: Down-regulation or overexpression of the cyclin-dependent kinase inhibitor p27 have been observed in a range of malignancies, including lung cancer. To further elucidate the role of the molecule in tumor growth regulation, we evaluated p27 expression in a series of non-small cell lung carcinomas (NSCLCs), and examined its relation with histology, kinetic parameters, ploidy, and overall survival. We extended our investigation into the association of p27 levels with the presence of Ki-ras mutations, as well as with the expression status of p53 and pRb in tumor cells. MATERIAL AND METHODS: p27, p53, and pRb status were immunohistochemically evaluated in a total of 69 NSCLCs. In situ assays were employed to assess the kinetic parameters (Ki-67 immunohistochemistry for proliferation index, Tdt-mediated dUTP nick end labeling assay for apoptotic index). The ploidy status of the tumors was assessed after staining nuclei with the Feulgen procedure, and the presence of Ki-ras mutations was examined by restriction fragment length polymorphisms. All possible associations were assessed with a series of statistical methods. RESULTS: Immunoreactivity for p27 was observed in the entire series of specimens, with the mean percentage of positive cells being 33%. Adenocarcinomas (AdCs) exhibited higher p27 levels compared to squamous cell carcinomas (SqCCs) (p < 0.01). An inverse correlation was established between p27 expression and proliferation index (PI) (r = -0.834, p < 0.01) but not with apoptotic index (AI), whereas aneuploid tumors were characterized by lower p27 levels than diploid ones (p < 0.01). No difference in p27 immunostaining was observed with regard to the presence of Ki-ras mutations, whereas aberrant p53 and/or pRb expression patterns were associated with p27 underexpression (p < 0.01 for p53 status, p < 0.05 regarding pRb levels, and p < 0.01 for a combined deregulation of both proteins). Two or more alterations in the p27/p53/pRb protein network (i.e., p27 levels lower than the estimated mean value, overexpressed p53, and/or aberrant pRb) were associated with increased PI and aneuploidy (p < 0.001 and p < 0.01, respectively). A powerful trend was found between p27 expression and overall survival (p = 0.066). CONCLUSIONS: Our findings confirm the heterogeneity between AdCs and SqCCs, and are suggestive of an increased proliferative activity in NSCLCs underexpressing p27. Furthermore, our analysis supports the concept of p27 forming a functionally compact network with p53 and pRb, which is actively involved in the regulation of cellular proliferation and chromosomal stability