Mystery pufferfish create elaborate circular nests at mesophotic depths in Australia

In 2011, the enigma of “mystery circles,” small but complex underwater structures first observed by divers from southern Japan in 1995, was solved when a new species of pufferfish, white-spotted pufferfish (Torquigener albomaculosus Matsuura 2014), was identified as the responsible agent. To date these circles have been described only from Japan, where they are formed on a sandy seafloor in water depths less than 30 m. A survey of oil field infrastructure on the North West Shelf of Western Australia in 2018 using a remotely operated vehicle and hybrid autonomous underwater vehicle (HAUV) recorded a high-resolution video and bathymetric data of 21 circular formations with similar features to those described in Japan. The circles display dimensions and morphology like those described from Japan, but were observed in water depths between 129 and 137 m. The HAUV also recorded high-resolution photographs which captured a Torquigener sp. fish in the immediate vicinity of the circles. An additional circle and Torquigener sp. were observed in images collected by baited remote underwater stereo-video in a nearby location in 129 m depth. These circles are the first to be found in Australia. The pufferfish species responsible cannot be identified from images collected. Such a discovery not only generates intrigue and wonder among scientists and the general public but also provides an insight into the reproductive behaviour and evolution of pufferfish globally.     

Intergenerational effects of CO2‐induced stream acidification in the Trinidadian guppy (Poecilia reticulata)

Rising atmospheric carbon dioxide levels are driving decreases in aquatic pH. As a result, there has been a surge in the number of studies examining the impact of acidification on aquatic fauna over the past decade. Thus far, both positive and negative impacts on the growth of fish have been reported, creating a disparity in results. Food availability and single‐generation exposure have been proposed as some of the reasons for these variable results, where unrealistically high food treatments lead to fish overcoming the energetic costs associated with acclimating to decreased pH. Likewise, exposure of fish to lower pH for only one generation may not capture the likely ecological response to acidification that wild populations might experience over two or more generations. Here we compare somatic growth rates of laboratory populations of the Trinidadian guppy (Poecilia reticulata) exposed to pH levels that represent the average and lowest levels observed in streams in its native range. Specifically, we test the role of maternal acclimation and resource availability on the response of freshwater fishes to acidification. Acidification had a negative impact on growth at more natural, low food treatments. With high food availability, fish whose mothers were acclimated to the acidified treatment showed no reduction in growth, compared to controls. Compensatory growth was observed in both control–acidified (maternal–natal environment) and acidified–control groups, where fish that did not experience intergenerational effects achieved the same size in response to acidification as those that did, after an initial period of stunted growth. These results suggest that future studies on the effects of shifting mean of aquatic pH on fishes should take account of intergenerational effects and compensatory growth, as otherwise effects of acidification may be overestimated.     

Genomic data reveal Toxoplasma gondii differentiation mutants are also impaired with respect to switching into a novel extracellular tachyzoite state

Toxoplasma gondii pathogenesis includes the invasion of host cells by extracellular parasites, replication of intracellular tachyzoites, and differentiation to a latent bradyzoite stage. We present the analysis of seven novel T. gondii insertional mutants that do not undergo normal differentiation to bradyzoites. Microarray quantification of the variation in genome-wide RNA levels for each parasite line and times after induction allowed us to describe states in the normal differentiation process, to analyze mutant lines in the context of these states, and to identify genes that may have roles in initiating the transition from tachyzoite to bradyzoite. Gene expression patterns in wild-type parasites undergoing differentiation suggest a novel extracellular state within the tachyzoite stage. All mutant lines exhibit aberrant regulation of bradyzoite gene expression and notably some of the mutant lines appear to exhibit high proportions of the intracellular tachyzoite state regardless of whether they are intracellular or extracellular. In addition to the genes identified by the insertional mutagenesis screen, mixture model analysis allowed us to identify a small number of genes, in mutants, for which expression patterns could not be accounted for using the three parasite states--genes that may play a mechanistic role in switching from the tachyzoite to bradyzoite stage.     

Becoming physically active after bariatric surgery is associated with improved weight loss and health-related quality of life

The purpose of this study was to determine whether pre- to postoperative increases in physical activity (PA) are associated with weight loss and health-related quality of life (HRQoL) following bariatric surgery. Participants were 199 Roux-en-Y gastric bypass (RYGB) surgery patients. The International Physical Activity Questionnaire (IPAQ) was used to categorize participants into three groups according to their preoperative and /1-year postoperative PA level: (i) Inactive/Active (<200-min/week/>or=200-min/week), (ii) Active/Active (>or=200-min/week/>or=200-min/week) and (iii) Inactive/Inactive (<200-min/week/<200-min/week). The Medical Outcomes Study Short Form-36 (SF-36) was used to assess HRQoL. Analyses of covariance were conducted to examine the effects of PA group on weight and HRQoL changes. Inactive/Active participants, compared with Inactive/Inactive individuals, had greater reductions in weight (52.5 +/- 15.4 vs. 46.4 +/- 12.8 kg) and BMI (18.9 +/- 4.6 vs. 16.9 +/- 4.2 kg/m(2)). Weight loss outcomes in the Inactive/Active and Active/Active groups were similar to each other. Inactive/Active and Active/Active participants reported greater improvements than Inactive/Inactive participants on the mental component summary (MCS) score and the general health, vitality and mental health domains (P < 0.01). Although the direction of causation is not clear, these findings suggest that RYGB patients who become active postoperatively achieve weight losses and HRQoL improvements that are greater than those experienced by patients who remain inactive and comparable to those attained by patients who stay active. Future randomized controlled trials should examine whether assisting patients who are inactive preoperatively to increase their PA postoperatively contributes to optimization of weight loss and HRQoL outcomes.     

Hypoxia: A novel function for VIN3

VERNALIZATION INSENSITIVE 3 (VIN3) encodes a PHD domain chromatin remodelling protein that is induced in response to cold and is required for the establishment of the vernalization response in Arabidopsis thaliana.¹ Vernalization is the acquisition of the competence to flower after exposure to prolonged low temperatures, which in Arabidopsis is associated with the epigenetic repression of the floral repressor FLOWERING LOCUS C (FLC).^2,3 During vernalization VIN3 binds to the chromatin of the FLC locus,¹ and interacts with conserved components of Polycomb-group Repressive Complex 2 (PRC2).^4,5 This complex catalyses the tri-methylation of histone H3 lysine 27 (H3K27me3),^4,6,7 a repressive chromatin mark that increases at the FLC locus as a result of vernalization.^4,7–10 In our recent paper¹¹ we found that VIN3 is also induced by hypoxic conditions, and as is the case with low temperatures, induction occurs in a quantitative manner. Our experiments indicated that VIN3 is required for the survival of Arabidopsis seedlings exposed to low oxygen conditions. We suggested that the function of VIN3 during low oxygen conditions is likely to involve the mediation of chromatin modifications at certain loci that help the survival of Arabidopsis in response to prolonged hypoxia. Here we discuss the implications of our observations and hypotheses in terms of epigenetic mechanisms controlling gene regulation in response to hypoxia.Key words: arabidopsis, VIN3, FLC, hypoxia, vernalization, chromatin remodelling, survival     

Characterization of Metabolism in the Fe(III)-Reducing Organism Geobacter sulfurreducens by Constraint-Based Modeling

Geobacter sulfurreducens is a well-studied representative of the Geobacteraceae, which play a critical role in organic matter oxidation coupled to Fe(III) reduction, bioremediation of groundwater contaminated with organics or metals, and electricity production from waste organic matter. In order to investigate G. sulfurreducens central metabolism and electron transport, a metabolic model which integrated genome-based predictions with available genetic and physiological data was developed via the constraint-based modeling approach. Evaluation of the rates of proton production and consumption in the extracellular and cytoplasmic compartments revealed that energy conservation with extracellular electron acceptors, such as Fe(III), was limited relative to that associated with intracellular acceptors. This limitation was attributed to lack of cytoplasmic proton consumption during reduction of extracellular electron acceptors. Model-based analysis of the metabolic cost of producing an extracellular electron shuttle to promote electron transfer to insoluble Fe(III) oxides demonstrated why Geobacter species, which do not produce shuttles, have an energetic advantage over shuttle-producing Fe(III) reducers in subsurface environments. In silico analysis also revealed that the metabolic network of G. sulfurreducens could synthesize amino acids more efficiently than that of Escherichia coli due to the presence of a pyruvate-ferredoxin oxidoreductase, which catalyzes synthesis of pyruvate from acetate and carbon dioxide in a single step. In silico phenotypic analysis of deletion mutants demonstrated the capability of the model to explore the flexibility of G. sulfurreducens central metabolism and correctly predict mutant phenotypes. These results demonstrate that iterative modeling coupled with experimentation can accelerate the understanding of the physiology of poorly studied but environmentally relevant organisms and may help optimize their practical applications.