Heavy Metal Pollution as a Biodiversity Threat

Heavy metals exert their toxic effects through different mechanisms. Lately, increasing attention has been focused on understanding the long-term ecological effects of chronically exposed populations and communities and their consequences to the ecosystem. The long-term exposure to heavy metals in the environment represents a threat to wild populations, affecting communities and putting ecosystem integrity at risk. Therefore, this type of exposure represents a threat to biodiversity. In the field, metal exposure is generally characterized by low doses and chronic exposures. This type of exposure exerts alterations across levels of biological organization. Distribution and abundance of populations, the community structure and the ecosystem dynamics may be altered. This chapter will focus on how chronically metal exposures in the field affect negatively populations and communities becoming a threat to biodiversity. Also, attention is put on the tools that enable to characterize and analyze the detrimental effects of heavy metal exposure on wild populations. Hence, the use and development of biomarkers in ecotoxicology will be discussed

The Use of Biosensors for Biomonitoring Environmental Metal Pollution

The use of biosensors for biomonitoring environmental health has gained much attention in the last decades. The environment is continuously loaded with xenobiotics released by anthropogenic activities that pollute ecosystems, putting their integrity at risk. Therefore, there is an urgent need to study the negative effects of xenobiotics, specifically chemical agents. Biosensors or organisms that integrate exposure to pollutants in their environment and which respond in some measurable and predictable way are useful tools to study the extent of chemical pollution and its consequences across levels of biological organization. Among chemical pollutants, heavy metals are among the most toxic elements to nearly all living organisms. Wildlife is chronically exposed to complex metal mixtures in which effects on ecosystem health are difficult to assess. Therefore, different organisms may serve as biosensors to estimate detrimental effects of metal pollution. In this chapter, we will analyze bacteria, small mammals, some plant species, and lichens as biosensors for environmental metal pollution. Also, we will assess the importance of using different biomarkers on biosensors

Transcriptional analysis reveals the metabolic state of Burkholderia zhejiangensis CEIB S4-3 during methyl parathion degradation

Burkholderia zhejiangensis CEIB S4-3 has the ability to degrade methyl parathion (MP) and its main hydrolysis byproduct p-nitrophenol (PNP). According to genomic data, several genes related with metabolism of MP and PNP were identified in this strain. However, the metabolic state of the strain during the MP degradation has not been evaluated. In the present study, we analyzed gene expression changes during MP hydrolysis and PNP degradation through a transcriptomic approach. The transcriptional analysis revealed differential changes in the expression of genes involved in important cellular processes, such as energy production and conversion, transcription, amino acid transport and metabolism, translation, ribosomal structure and biogenesis, among others. Transcriptomic data also exhibited the overexpression of both PNP-catabolic gene clusters (pnpABA′E1E2FDC and pnpE1E2FDC) present in the strain. We found and validated by quantitative reverse transcription polymerase chain reaction the expression of the methyl parathion degrading gene, as well as the genes responsible for PNP degradation contained in two clusters. This proves the MP degradation pathway by the strain tested in this work. The exposure to PNP activates, in the first instance, the expression of the transcriptional regulators multiple antibiotic resistance regulator and Isocitrate Lyase Regulator (IclR), which are important in the regulation of genes from aromatic compound catabolism, as well as the expression of genes that encode transporters, permeases, efflux pumps, and porins related to the resistance to multidrugs and other xenobiotics. In the presence of the pesticide, 997 differentially expressed genes grouped in 104 metabolic pathways were observed. This report is the first to describe the transcriptomic analysis of a strain of B. zhejiangensis during the biodegradation of PNP

Population genomics applications for conservation: the case of the tropical dry forest dweller Peromyscus melanophrys

Recent advances in genomic sequencing have opened new horizons in the study of population genetics and evolution in non-model organisms. However, very few population genomic studies have been performed on wild mammals to understand how the landscape affects the genetic structure of populations, useful information for the conservation of biodiversity. Here, we applied a genomic approach to evaluate the relationship between habitat features and genetic patterns at spatial and temporal scales in an endangered ecosystem, the Tropical Dry Forest (TDF). We studied populations of the Plateau deer mouse Peromyscus melanophrys to analyse its genomic diversity and structure in a TDF protected area in the Huautla Mountain Range (HMR), Mexico based on 8,209 SNPs obtained through Genotyping-by-Sequencing. At a spatial scale, we found a significant signature of isolation-by-distance, few significant differences in genetic diversity indices among study sites, and no significant differences between habitats with different levels of human perturbation. At a temporal scale, while genetic diversity levels fluctuated significantly over time, neither seasonality nor disturbance levels had a significant effect. Also, outlier analysis revealed loci potentially under selection. Our results suggest that the population genetics of P. melanophrys may be little impacted by anthropogenic disturbances, or by natural spatial and temporal habitat heterogeneity in our study area. The genome-wide approach adopted here provides data of value for conservation planning, and a baseline to be used as a reference for future studies on the effects of habitat fragmentation and seasonality in the HMR and in TDF

Theodore J. Lowi, El presidente personal: facultad otorgada, promesa no cumplida, México, Fondo de Cultura Económica, 1993.

El libro de Theodore J. Lowi se inscribe en la polémica contemporánea en torno a uno de los mayores acontecimientos políticos del siglo XX; el desplazamiento del parlamentarismo por el gobierno ejecutivo, en el cual la autoridad suprema reside en el presidente personal y no en la asamblea deliberativa. Desde este punto de vista, la Segunda República o la presidencia plebiscitaria de Estados Unidos podría ser considerada como un producto irreversible de la historia

Theodore J. Lowi, El presidente personal: facultad otorgada, promesa no cumplida, México, Fondo de Cultura Económica, 1993.

El libro de Theodore J. Lowi se inscribe en la polémica contemporánea en torno a uno de los mayores acontecimientos políticos del siglo XX; el desplazamiento del parlamentarismo por el gobierno ejecutivo, en el cual la autoridad suprema reside en el presidente personal y no en la asamblea deliberativa. Desde este punto de vista, la Segunda República o la presidencia plebiscitaria de Estados Unidos podría ser considerada como un producto irreversible de la historia