Health Effects of Toxin-Producing Cyanobacteria: “The CyanoHABs”

Increasingly, harmful algal blooms (HABs) are being reported worldwide due to several factors, primarily eutrophication, climate change and more scientific monitoring. All but cyanobacteria toxin poisonings (CTPs) are mainly a marine occurrence. CTPs occur in fresh (lakes, ponds, rivers and reservoirs) and brackish (seas, estuaries, and lakes) waters throughout the world. Organisms responsible include an estimated 40 genera but the main ones are Anabaena, Aphanizomenon, Cylindrospermopsis, Lyngbya, Microcystis, Nostoc, and Oscillatoria (Planktothrix). Cyanobacteria toxins (cyanotoxins) include cytotoxins and biotoxins with biotoxins being responsible for acute lethal, acute, chronic and sub-chronic poisonings of wild/domestic animals and humans. The biotoxins include the neurotoxins; ana-toxin-a, anatoxin-a(s) and saxitoxins plus the hepatotoxins; microcystins, nodularins and cylindrospermopsins. Confirmations of human deaths from cyanotoxins are limited to exposure through renal dialysis at a haemodialysis center in Caruaru, Brazil, in 1996. A major effort to compile all available information on toxic cyanobacteria including issues of human health, safe water practices, management, prevention and remediation have been published by the World Health Organization. This paper will review our current understanding of CTP's including their risk to human health.     

The Semiosis of “Side Effects” in Genetic Interventions

Genetic interventions, which include transgenic engineering, gene editing, and other forms of genome modification aimed at altering the information “in” the genetic code, are rapidly increasing in power and scale. Biosemiotics offers unique tools for understanding the nature, risks, scope, and prospects of such technologies, though few in the community have turned their attention specifically in this direction. Bruni (2003, 2008) is an important exception. In this paper, I examine how we frame the concept of “side effects” that result from genetic interventions and how the concept stands up to current perspectives of the role of organism activity in development. I propose that once the role of living systems in constructing and modifying the informational value of their various developmental resources is taken into account, the concept of a “side effect” will need to be significantly revised. Far from merely a disturbance brought about in a senseless albeit complex system, a biosemiotic view would take “side effects” as at least sometimes the organism’s active re-organization in order to accommodate or make use of novelty. This insight is nascent in the work of developmental plasticity and niche construction theory (West-Eberhard 2003; Odling-Smee et al. 2003), but it is brought into sharper focus by the explicitly interpretive perspective offered by biosemiotics. Understanding the “side effects” of genetic interventions depends in part on being able to articulate when and where unexpected consequences are a result of semiotic activity at various levels within the system. While a semiotic interpretation of “side effects” puts into question the naive attitude that would see all unintended side effects as indications of disturbance in system functionality, it certainly does not imply that such side effects are of no concern for the viability of the organisms in the system. As we shall see, the fact that such interventions do not respect the translation of information that occurs in multi-level biological systems ensures that disruption is still likely. But it does unprivilege the human agent as the sole generator of meaning and information in the products of biotechnology, with important consequences on how we understand our relationship with other species.     

Effects of Experimental Choices and Analysis Noise on Surveys of the “Rare Biosphere”

When planning a survey of 16S rRNA genes from a complex environment, investigators face many choices including which primers to use and how to taxonomically classify sequences. In this study, we explored how these choices affected a survey of microbial diversity in a sample taken from the aerobic basin of the activated sludge of a North Carolina wastewater treatment plant. We performed pyrosequencing reactions on PCR products generated from primers targeting the V1-V2, V6, and V6-V7 variable regions of the 16S rRNA gene. We compared these sequences to 16S rRNA gene sequences found in a whole-genome shotgun pyrosequencing run performed on the same sample. We found that sequences generated from primers targeting the V1-V2 variable region had the best match to the whole-genome shotgun reaction across a range of taxonomic classifications from phylum to family. Pronounced differences between primer sets, however, occurred in the “rare biosphere” involving taxa that we observed in fewer than 11 sequences. We also examined the results of analysis strategies comparing a classification scheme using a nearest-neighbor approach to directly classifying sequences with a naïve Bayesian algorithm. Again, we observed pronounced differences between these analysis schemes in infrequently observed taxa. We conclude that if a study is meant to probe the rare biosphere, both the experimental conditions and analysis choices will have a profound impact on the observed results.For nearly 3 decades, investigations of the distribution of microbes in complex environments have focused on the use of rRNA genes (1, 2, 4, 11, 16, 18, 19, 22, 24). Because the full-length 16S rRNA sequence can be obtained with paired-end reads via traditional Sanger sequencing, until recently most studies of the 16S rRNA gene captured most or nearly most of the 16S sequence length. New pyrosequencing technologies, however, have recently been introduced that greatly reduce the per base cost of sequencing but with shorter read lengths than traditional Sanger sequencing (17). This new approach has proven powerful, yielding a previously unobtainable view of rare taxa (7, 12-14, 25).The shorter reads produced by pyrosequencing require the choice of a particular region of the 16S rRNA gene to target for pyrosequencing as well as the choice of an algorithm to classify the taxonomy of the shorter reads. In their initial surveys of microbial diversity with pyrosequencing (12, 14, 25), Sogin and colleagues targeted the V6 variable region, in part because it is was small enough to be captured with the 100-bp reads of the pyrosequencing technology available at the time. Recently, the read length of 454 pyrosequencing machines has been increased to an average of ∼250 bp. This allows for more flexibility in primer design and opens up the possibility of targeting regions of the 16S rRNA gene other than V6. In recent work, Huse et al. took advantage of this new capability to compare the classifications made for the human gut microbiome with the V6 and longer V3 regions (13). Plotting the taxonomic abundance of these two sequence sets against each other yielded an excellent correlation (r² = 0.99), suggesting that the choice of which variable region to target makes little difference. In this report, we introduce a data set examining the performance of sets of primers targeting the V1-V2, V6, and V6-V7 regions. By using a sample for which we have also generated a whole-genome shotgun sequencing run with 250 bp reads, we were able to compare the observed 16S rRNA genes in samples with and without an initial PCR step targeting the 16S rRNA gene. Our results demonstrate that experimental choices such as which region of the 16S rRNA gene to sequence and which algorithm to use to classify taxa are much more likely to affect observations of the “rare biosphere” than more commonly observed taxa.     

“Direct” and “Indirect” Effects of Histone Modifications: Modulation of Sterical Bulk as a Novel Source of Functionality

The chromatin-regulatory principles of histone post-translational modifications (PTMs) are discussed with a focus on the potential alterations in chromatin functional state due to steric and mechanical constraints imposed by bulky histone modifications such as ubiquitin and SUMO. In the classical view, PTMs operate as recruitment platforms for histone “readers,” and as determinants of chromatin array compaction. Alterations of histone charges by “small” chemical modifications (e.g., acetylation, phosphorylation) could regulate nucleosome spontaneous dynamics without globally affecting nucleosome structure. These fluctuations in nucleosome wrapping can be exploited by chromatin-processing machinery. In contrast, ubiquitin and SUMO are comparable in size to histones, and it seems logical that these PTMs could conflict with canonical nucleosome organization. An experimentally testable hypothesis that by adding sterical bulk these PTMs can robustly alter nucleosome primary structure is proposed. The model presented here stresses the diversity of mechanisms by which histone PTMs regulate chromatin dynamics, primary structure and, hence, functionality.     

Erratum to: “Effects of Different Conservation Methods on the Genetic Stability of Potato Germplasm”

Russian Journal of Plant Physiology -     

Effects of AM colonization on “wild tobacco” plants grown in zinc-contaminated soil

This greenhouse study aimed to determine the effect of colonization by the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) on the “wild” tobacco (Nicotiana rustica L. var. Azteca), under soil–zinc (Zn) conditions. Plants of N. rustica were grown in AM or non-AM inoculated substrate and subjected to four soil–[Zn] concentrations (0, 50, 100, and 250 mg Zn kg⁻¹ dry soil). The AM root colonization increased markedly from 14 to 81% with the increasing soil–[Zn] and the mycorrhizal structures were significantly more abundant at the highest soil–[Zn], suggesting that Zn may be involved directly or indirectly in AM root colonization. In addition, total Zn content or Zn concentrations in shoots and roots were shown to increase as soil–[Zn] increased in both AM and non-AM plants. As for the growth parameters studied, there were no significant differences between treatments despite the increase in Zn content or concentration. The AM roots subjected to the highest soil–[Zn] had a significant reduction by about 50% of total Zn content and Zn concentration compared to non-AM roots. Still, the relative extracted Zn percentage decreased dramatically as soil–[Zn] increased. Soil pH was significantly lower in non-AM than AM treatments at the highest soil–[Zn]. In summary, AM plants (particularly roots) showed lower Zn content and concentration than non-AM plants. In this regard, the AM fungi have a protective role for the host plant, thus playing an important role in soil-contaminant immobilization processes; and, therefore, are of value in phytoremediation, especially when heavy metals approach toxic levels in the soil.     

Effects of long-term isolation and anticipation of significant event on sleep: Results of the project “Mars-520”

The purpose of the research was to study the effects of long-term isolation on night sleep of the healthy human. The data were collected during international ground simulation of the interplanetary manned flight “Mars-500.” Polysomnography recordings of six healthy men were performed before, four times during and after 520-days confinement. During the isolation sleep efficiency and delta-latency decreased, while sleep latency increased mainly one month and half before the end of the isolation. Post-hoc analysis demonstrated significant differences between background and the last measure during isolation. Frequency of the nights with low sleep efficiency significantly increased before important events for the subjects, those like simulation of Mars landing and the end of the confinement. Two weeks after landing simulation the amount of the nights with low sleep efficiency significantly decreased. Therefore, anticipation of the significant event during long-term isolation might be an additional factor for sleep worsening and result in difficulties to fall asleep in previously healthy men.     

Cryoenzymology of β-galactosidase: Effects of cryosolvents

Experimental support for the use of fluid aqueous organic solvent systems and subzero temperatures in mechanistic studies of β-galactosidase is presented. The enzyme was stable and retained catalytic activity and structural integrity in 50% aqueous dimethyl sulfoxide and 60% aqueous methanol at 0°C; at lower temperatures higher concentrations of cosolvent may be successfully used. The effects of dimethyl sulfoxide on the catalytic and structural properties of the enzyme were investigated in detail. For the β-galactoside-catalyzed h ydrolysis ofo-nitrophenyl-β-D-galactoside the value ofk _cat decreased in a linear manner with increasing cosolvent concentration, whereasK _m increased exponentially. The decrease ink _cat paralleled the decrease in water concentration, consistent with rate-limiting hydrolysis of a galactosylenzyme intermediate. The increase inK _m is attributed to less favorable partitioning of the substrate to the active site in the cryosolvent compared to aqueous solution. ThepH*-rate profile for this reaction at 0°C in 50% dimethyl sulfoxide was similar to that in aqueous solution, withpK*₁=5.8 andpK*₂=8.0. Linear Arrhenius plots, with energies of activation of 13.9 and 16.0 kcal mol^?1, respectively, were obtained for the β-galactosidase-catalyzed hydrolysis ofo-nitrophenyl- andp-nitrophenyl-β-D-galactosides in 50% dimethyl sulfoxide at temperatures to ?57°C. Examination of the intrinsic fluorescence and ultraviolet spectra of the enzyme as a function of increasing cosolvent concentration showed no evidence for structural perturbation up to and including 50% dimethyl sulfoxide at 0°C. We conclude that these cryosolvent systems are suitable for mechanistic investigations of β-galactosidase, in particular for trapping intermediates at subzero temperatures.