The effects of simulated transportation conditions on the core body and extremity temperature, blood physiology, and behavior of white-strain layer pullets.

Transportation of poultry is stressful. The transportation of broilers has been well studied, while the transportation of layer pullets from rearing to laying facilities has not been thoroughly evaluated. This experiment aimed to establish the effects of temperature (T)/RH combinations and duration (D) of transport, via a 5 × 2 factorial arrangement of simulated transport conditions using 5 T/RH combinations (21°C with 30% RH [21/30], 21°C with 80% RH [21/80], 30°C with 30% RH [30/30], 30°C with 80% RH [30/80], and -15°C with uncontrolled RH [-15]), and 2 exposure D (4 or 8 h). Pullets (18-19 wk; n = 240) were obtained from 3 commercial farms (N = 3 farms). Pretreatment, birds were orally administered a miniature data logger to record core body temperature (CBT), an initial blood sample was taken (5 birds/replicate), and initial foot T was recorded. Behavior during exposure was video recorded. Following exposure, a final blood sample was taken (analyzed for heterophil to lymphocyte ratio, partial pressure of CO2, total CO2, bicarbonate, and glucose), birds were slaughtered, and data loggers were retrieved. Data were analyzed as a randomized complete block design via Proc Mixed (SAS 9.4) and significance was declared at P ≤ 0.05. There were no interactions observed for the T/RH and D combinations throughout the study. The CBT and foot T were lowest in pullets exposed to -15 compared with all other treatments. Foot T was also highest in pullets exposed to 30/80 compared with -15, 21/30, and 21/80. There was no impact of T/RH on pullet blood physiology. Activity and thermoregulatory behaviors were impacted by the T/RH combinations. Pullets exposed to 30/30 and 30/80 spent the most time panting. Pullets exposed to 30/80 also spent the least amount of time motionless. Duration had minor impacts on pullet CBT, blood physiology, and behavior. These data indicate that as a response to thermal stress, layer pullets were successful at implementing mechanisms to maintain homeostasis.

The effects of simulated transport conditions on the muscle tissue characteristics of white-strain layer pullets.

The objective of this study was to evaluate the effects of temperature (T)/relative humidity (RH) combinations and exposure duration (D) on the muscle tissue characteristics of layer pullets during simulated transport. While layer pullets are not processed for meat, muscle physiology can be used as an indicator to assess welfare. Pullets (n = 240) were randomly assigned to 1 of 5 T/RH combinations (-15°C uncontrolled RH [-15], 21°C 30%RH [21/30], 21°C 80%RH [21/80], 30°C 30%RH [30/30], and 30°C 80%RH [30/80]) and 2 D (4 or 8 h) in a 5 x 2 factorial arrangement (3 replications). Birds were weighed before exposure, crated (density 45.5 kg/m2) and exposed to the conditions above. After exposure, birds were weighed (live shrink calculated) and slaughtered using a small-scale facility. Postslaughter, carcasses were eviscerated, and an initial pH was obtained from the right breast and thigh. Final breast and thigh pH and color values (lightness [L∗], yellowness [b∗], and redness [a∗]) were obtained 30 h postslaughter. Left breast muscles were frozen and analyzed for thaw and cook loss 4 wk postslaughter. Data were analyzed as a randomized complete block design via ANOVA (Proc Mixed; SAS 9.4), with farm of origin as block. Differences were considered significant when P ≤ 0.05. Live shrink (kg) was higher for pullets exposed to 30/30 and 30/80 compared with those exposed to 21/80 (P = 0.04) and for pullets exposed for 8 h compared with 4 h (P < 0.01). Breast muscle thaw loss (%) was higher in pullets exposed for 4 h compared with 8 h (P = 0.01). Breast and thigh muscle a∗ were higher for pullets exposed to 30/30 compared with 21/30 (P = 0.02). Thigh muscle b∗ was lower for pullets exposed to -15 compared with 21/80 (P = 0.05). Breast b∗ was higher for pullets exposed for 8 h compared with 4 h (P = 0.04). The results from this study demonstrates that increasing exposure D had minor effects on pullet muscle characteristics. In addition, layer pullets coped well with thermal stressors associated with simulated transport.

Author Correction: Constraining the rise of oxygen with oxygen isotopes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Constraining the rise of oxygen with oxygen isotopes.

After permanent atmospheric oxygenation, anomalous sulfur isotope compositions were lost from sedimentary rocks, demonstrating that atmospheric chemistry ceded its control of Earth's surficial sulfur cycle to weathering. However, mixed signals of anoxia and oxygenation in the sulfur isotope record between 2.5 to 2.3 billion years (Ga) ago require independent clarification, for example via oxygen isotopes in sulfate. Here we show <2.31 Ga sedimentary barium sulfates (barites) from the Turee Creek Basin, W. Australia with positive sulfur isotope anomalies of ∆33S up to + 1.55‰ and low δ18O down to -19.5‰. The unequivocal origin of this combination of signals is sulfide oxidation in meteoric water. Geochemical and sedimentary evidence suggests that these S-isotope anomalies were transferred from the paleo-continent under an oxygenated atmosphere. Our findings indicate that incipient oxidative continental weathering, ca. 2.8-2.5 Ga or earlier, may be diagnosed with such a combination of low δ18O and high ∆33S in sulfates.

Mesophilic microorganisms build terrestrial mats analogous to Precambrian microbial jungles.

Development of Archean paleosols and patterns of Precambrian rock weathering suggest colonization of continents by subaerial microbial mats long before evolution of land plants in the Phanerozoic Eon. Modern analogues for such mats, however, have not been reported, and possible biogeochemical roles of these mats in the past remain largely conceptual. We show that photosynthetic, subaerial microbial mats from Indonesia grow on mafic bedrocks at ambient temperatures and form distinct layers with features similar to Precambrian mats and paleosols. Such subaerial mats could have supported a substantial aerobic biosphere, including nitrification and methanotrophy, and promoted methane emissions and oxidative weathering under ostensibly anoxic Precambrian atmospheres. High C-turnover rates and cell abundances would have made these mats prime locations for early microbial diversification. Growth of landmass in the late Archean to early Proterozoic Eons could have reorganized biogeochemical cycles between land and sea impacting atmospheric chemistry and climate.

Authigenic iron oxide proxies for marine zinc over geological time and implications for eukaryotic metallome evolution.

Here, we explore enrichments in paleomarine Zn as recorded by authigenic iron oxides including Precambrian iron formations, ironstones, and Phanerozoic hydrothermal exhalites. This compilation of new and literature-based iron formation analyses track dissolved Zn abundances and constrain the magnitude of the marine reservoir over geological time. Overall, the iron formation record is characterized by a fairly static range in Zn/Fe ratios throughout the Precambrian, consistent with the shale record (Scott et al., 2013, Nature Geoscience, 6, 125-128). When hypothetical partitioning scenarios are applied to this record, paleomarine Zn concentrations within about an order of magnitude of modern are indicated. We couple this examination with new chemical speciation models to interpret the iron formation record. We present two scenarios: first, under all but the most sulfidic conditions and with Zn-binding organic ligand concentrations similar to modern oceans, the amount of bioavailable Zn remained relatively unchanged through time. Late proliferation of Zn in eukaryotic metallomes has previously been linked to marine Zn biolimitation, but under this scenario the expansion in eukaryotic Zn metallomes may be better linked to biologically intrinsic evolutionary factors. In this case, zinc's geochemical and biological evolution may be decoupled and viewed as a function of increasing need for genome regulation and diversification of Zn-binding transcription factors. In the second scenario, we consider Archean organic ligand complexation in such excess that it may render Zn bioavailability low. However, this is dependent on Zn-organic ligand complexes not being bioavailable, which remains unclear. In this case, although bioavailability may be low, sphalerite precipitation is prevented, thereby maintaining a constant Zn inventory throughout both ferruginous and euxinic conditions. These results provide new perspectives and constraints on potential couplings between the trajectory of biological and marine geochemical coevolution.

Role of extracellular polymeric substances in the surface chemical reactivity of Hymenobacter aerophilus, a psychrotolerant bacterium.

Bacterial surface layers, such as extracellular polymeric substances (EPS), are known to play an important role in metal sorption and biomineralization; however, there have been very few studies investigating how environmentally induced changes in EPS production affect the cell's surface chemistry and reactivity. Acid-base titrations, cadmium adsorption assays, and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the surface reactivities of Hymenobacter aerophilus cells with intact EPS (WC) or stripped of EPS (SC) and purified EPS alone. Linear programming modeling of titration data showed SC to possess functional groups corresponding to phosphoryl (pKa approximately 6.5), phosphoryl/amine (pKa approximately 7.9), and amine/hydroxyl (pKa approximately 9.9). EPS and WC both possess carboxyl groups (pKa approximately 5.1 to 5.8) in addition to phosphoryl and amine groups. FT-IR confirmed the presence of polysaccharides and protein in purified EPS that can account for the additional carboxyl groups. An increased ligand density was observed for WC relative to that for SC, leading to an increase in the amount of Cd adsorbed (0.53 to 1.73 mmol/liter per g [dry weight] and 0.53 to 0.59 mmol/liter per g [dry weight], respectively). Overall, the presence of EPS corresponds to an increase in the number and type of functional groups on the surface of H. aerophilus that is reflected by increased metal adsorption relative to that for EPS-free cells.

A cytosolic trans-activation domain essential for ammonium uptake.

Polytopic membrane proteins are essential for cellular uptake and release of nutrients. To prevent toxic accumulation, rapid shut-off mechanisms are required. Here we show that the soluble cytosolic carboxy terminus of an oligomeric ammonium transporter from Arabidopsis thaliana serves as an allosteric regulator essential for function; mutations in the C-terminal domain, conserved between bacteria, fungi and plants, led to loss of transport activity. When co-expressed with intact transporters, mutants inactivated functional subunits, but left their stability unaffected. Co-expression of two inactive transporters, one with a defective pore, the other with an ablated C terminus, reconstituted activity. The crystal structure of an Archaeoglobus fulgidus ammonium transporter (AMT) suggests that the C terminus interacts physically with cytosolic loops of the neighbouring subunit. Phosphorylation of conserved sites in the C terminus are proposed as the cognate control mechanism. Conformational coupling between monomers provides a mechanism for tight regulation, for increasing the dynamic range of sensing and memorizing prior events, and may be a general mechanism for transporter regulation.