Changes in the Gut Microbiome of the Sea Lamprey during Metamorphosis

Vertebrate metamorphosis is often marked by dramatic morphological and physiological changes of the alimentary tract, along with major shifts in diet following development from larva to adult. Little is known about how these developmental changes impact the gut microbiome of the host organism. The metamorphosis of the sea lamprey (Petromyzon marinus) from a sedentary filter-feeding larva to a free-swimming sanguivorous parasite is characterized by major physiological and morphological changes to all organ systems. The transformation of the alimentary canal includes closure of the larval esophagus and the physical isolation of the pharynx from the remainder of the gut, which results in a nonfeeding period that can last up to 8 months. To determine how the gut microbiome is affected by metamorphosis, the microbial communities of feeding and nonfeeding larval and parasitic sea lamprey were surveyed using both culture-dependent and -independent methods. Our results show that the gut of the filter-feeding larva contains a greater diversity of bacteria than that of the blood-feeding parasite, with the parasite gut being dominated by Aeromonas and, to a lesser extent, Citrobacter and Shewanella. Phylogenetic analysis of the culturable Aeromonas from both the larval and parasitic gut revealed that at least five distinct species were represented. Phenotypic characterization of these isolates revealed that over half were capable of sheep red blood cell hemolysis, but all were capable of trout red blood cell hemolysis. This suggests that the enrichment of Aeromonas that accompanies metamorphosis is likely related to the sanguivorous lifestyle of the parasitic sea lamprey.     

Defoliation-induced enhancement of total aboveground nitrogen yield of grasses

We conducted an experiment in a northern mixed-grass prairie at Wind Cave National Park, South Dakota, USA to evaluate the effect of defoliation frequency on aboveground net primary production (ANPP), shoot nitrogen concentration, and aboveground N yield of graminoids. ANPP was significantly reduced at weekly and biweekly defoliation frequencies, but unaffected relative to unclipped controls at monthly and bimonthly frequencies. By contrast, clipping at all frequencies increased shoot N concentration above that of controls, and this increase was greatest at monthly or more frequent defoliations. Total aboveground N yield and potential N yield to grazers were greatest at intermediate (bimonthly to biweekly) frequencies. We suggest that grazers may maximize their nutritional status in this system by periodically regrazing areas at frequencies near the approximately monthly optimum that we observed.     

Selected Contribution: Pulmonary hypertension in mice following intermittent hypoxia.

Sleep apnea (intermittent periods of hypoxia with or without hypercapnia) is associated with systemic hypertension and increased mortality from cardiovascular disease, but the relationship to pulmonary hypertension is uncertain. Previous studies on intermittent hypoxia (IH) in rats that demonstrated pulmonary hypertension utilized relatively long periods of hypoxia. Recent studies that utilized brief periods of hypoxia have conflicting reports of right ventricular (RV) hypertrophy. In addition, many studies have not measured pulmonary hemodynamics to asses the severity of pulmonary hypertension in vivo. Given the increasing availability of genetically engineered mice and the need to establish a rodent model of IH-induced pulmonary hypertension, we studied the effect of IH (2-min cycles of 10% and 21% O2, 8 h/day, 4 wk) on wild-type mice, correlating in vivo measurements of pulmonary hypertension with RV mass and pulmonary vascular remodeling. RV systolic pressure was increased after IH (36 +/- 0.9 mmHg) compared with normoxia (29.5 +/- 0.6) but was lower than continuous hypoxia (44.2 +/- 3.4). RV mass [RV-to-(left ventricle plus septum) ratio] correlated with pressure measurements (IH = 0.27 +/- 0.02, normoxia = 0.22 +/- 0.01, and continuous hypoxia = 0.34 +/- 0.01). Hematocrits were also elevated after IH and continuous hypoxia (56 +/- 1.6 and 54 +/- 1.1 vs. 44.3 +/- 0.5%). Evidence of neomuscularization of the distal pulmonary circulation was found after IH and continuous hypoxia. We conclude that mice develop pulmonary hypertension following IH, representing a possible animal model of pulmonary hypertension in response to the repetitive hypoxia-reoxygenation of sleep apnea.     

What paths do advantageous alleles take during short‐term evolutionary change?

Combining experimental evolution with whole‐genome resequencing is a promising new strategy for investigating the dynamics of evolutionary change. Published studies that have resequenced laboratory‐selected populations of sexual organisms have typically focused on populations sampled at the end of an evolution experiment. These studies have attempted to associate particular alleles with phenotypic change and attempted to distinguish between different theoretical models of adaptation. However, neither the population used to initiate the experiment nor multiple time points sampled during the evolutionary trajectory are generally available for examination. In this issue of Molecular Ecology, Orozco‐terWengel et al. (2012) take a significant step forward by estimating genome‐wide allele frequencies at the start, 15 generations into and at the end of a 37‐generation Drosophila experimental evolution study. The authors identify regions of the genome that have responded to laboratory selection and describe the temporal dynamics of allele frequency change. They identify two common trajectories for putatively adaptive alleles: alleles either gradually increase in frequency throughout the entire 37 generations or alleles plateau at a new frequency by generation 15. The identification of complex trajectories of alleles under selection contributes to a growing body of literature suggesting that simple models of adaptation, whereby beneficial alleles arise and increase in frequency unimpeded until they become fixed, may not adequately describe short‐term response to selection.     

Clinical mass spectrometry in neuroscience. Proteomics and peptidomics.

In this review we discuss the merits and drawbacks with the use of proteomic and peptidomic strategies for identification of proteins and peptides in their multidimensional interactions in complex biological processes. The progress in proteomics and peptidomics during the last years offer us new challenges to study changes in the protein and peptide synthesis. These strategies also offer new tools to follow post-translational modifications and other disturbed chemical processes that may be indicative of pathophysiological alteration(s). Furthermore these techniques can contribute to improvements in the diagnosis and therapy of neurodegenerative diseases, such as Alzheimer's disease, and psychiatric diseases, as depression and post traumatic stress disorders. We also consider different practical aspects of the applications of mass spectrometry in clinical neuroscience, illustrated by example from our laboratories. The new proteomic and peptidomic strategies will further enable the progress for clinical neuroscience research.     

Plasmodesmata signaling: many roles, sophisticated statutes.

Recent advances have increased our understanding of plasmodesmata function, their architecture as it relates to signaling capacity, the temporal and spatial regulation of their permeability, and their roles in systemic transport of macromolecules, non-cell autonomous development, and, potentially, plant defense.     

Preface

Molecular and Cellular Biochemistry -     

Biodegradation of BTEX by bacteria on powdered activated carbon

Aerobic degradation of a mixture of benzene, toluene, ethylbenzene and the mixed xylenes (BTEX) by a mixed bacterial population was studied in a continuously fed, completely mixed bioreactor in the presence of powdered activated carbon (PAC). Adsorption was characterized in the presence and in the absence of bacteria on PAC, and the affinity of virgin PAC to individual BTEX components was shown to be inversely correlated to their solubility in water. Bacteria colonizing the PAC particles are essential for simultaneous adsorption–biodegradation processes. In order to restrict biofilm formation and thereby mass transfer resistance of pollutants from the bulk to the PAC, the slurry was recirculated in the reactor system using a high shear pump. The bacteria on the PAC surface were constantly in a flux between the adsorbed and free phase, a phenomenon that prevented the formation of a biofilm on the PAC surface and thereby extended the life of the PAC.