Comparative transcriptomics reveals the molecular toolkit used by an algivorous protist for cell wall perforation

Microbial eukaryotes display a stunning diversity of feeding strategies, ranging from generalist predators to highly specialised parasites. The unicellular protoplast feeders represent a fascinating mechanistic intermediate, as they penetrate other eukaryotic cells (algae, fungi) like some parasites, but then devour their cell contents by phagocytosis. Besides prey recognition and attachment, this complex behaviour involves the local, pre-phagocytotic dissolution of the prey cell wall, which results in well-defined perforations of species-specific size and structure. Yet, the molecular processes that enable protoplast feeders to overcome cell walls of diverse biochemical composition remain unknown. We used the flagellate Orciraptor agilis (Viridiraptoridae, Rhizaria) as a model protoplast feeder, and applied differential gene expression analysis to examine its penetration of green algal cell walls. Besides distinct expression changes that reflect major cellular processes (e.g. locomotion, cell division), we found lytic carbohydrate-active enzymes that are highly expressed and upregulated during the attack on the alga. A putative endocellulase (family GH5_5) with a secretion signal is most prominent, and a potential key factor for cell wall dissolution. Other candidate enzymes (e.g. lytic polysaccharide monooxygenases) belong to families that are largely uncharacterised, emphasising the potential of non-fungal micro-eukaryotes for enzyme exploration. Unexpectedly, we discovered various chitin-related factors that point to an unknown chitin metabolism in Orciraptor, potentially also involved in the feeding process. Our findings provide first molecular insights into an important microbial feeding behaviour, and new directions for cell biology research on non-model eukaryotes.

Nutritional and Physiological Constraints Contributing to Limitations in Small Intestinal Starch Digestion and Glucose Absorption in Ruminants

Increased efficiency of nutrient utilization can potentially be gained with increased starch digestion in the small intestine in ruminants. However, ruminants have quantitative limits in the extent of starch disappearance in the small intestine. The objective is to explore the nutritional and physiological constraints that contribute to limitations of carbohydrate assimilation in the ruminant small intestine. Altered digesta composition and passage rate in the small intestine, insufficient pancreatic α-amylase and/or small intestinal carbohydrase activity, and reduced glucose absorption could all be potentially limiting factors of intestinal starch assimilation. The absence of intestinal sucrase activity in ruminants may be related to quantitative limits in small intestinal starch hydrolysis. Multiple sequence alignment of the sucrase-isomaltase complex gives insight into potential molecular mechanisms that may be associated with the absence of intestinal sucrase activity, reduced capacity for intestinal starch digestion, and limitations in the efficiency of feed utilization in cattle and sheep. Future research efforts in these areas will aid in our understanding of small intestinal starch digestion and glucose absorption to optimize feeding strategies for increased meat and milk production efficiency.

The oscillating Mucin-type protein DPY-6 has a conserved role in nematode mouth and cuticle formation

Nematodes show an extraordinary diversity of mouth structures and strikingly different feeding strategies, which has enabled an invasion of all ecosystems. However, nearly nothing is known about the structural and molecular architecture of the nematode mouth (stoma). Pristionchus pacificus is an intensively studied nematode that exhibits unique life history traits, including predation, teeth-like denticle formation, and mouth-form plasticity. Here, we used a large-scale genetic screen to identify genes involved in mouth formation. We identified Ppa-dpy-6 to encode a Mucin-type hydrogel-forming protein that is macroscopically involved in the specification of the cheilostom, the anterior part of the mouth. We used a recently developed protocol for geometric morphometrics of miniature animals to characterize these defects further and found additional defects that affect mouth form, shape, and size resulting in an overall malformation of the mouth. Additionally, Ppa-dpy-6 is shorter than wild-type with a typical Dumpy phenotype, indicating a role in the formation of the external cuticle. This concomitant phenotype of the cheilostom and cuticle provides the first molecular support for the continuity of these structures and for the separation of the cheilostom from the rest of the stoma. In C. elegans, dpy-6 was an early mapping mutant but its molecular identity was only determined during genome-wide RNAi screens and not further investigated. Strikingly, geometric morphometric analysis revealed previously unrecognized cheilostom and gymnostom defects in Cel-dpy-6 mutants. Thus, the Mucin-type protein DPY-6 represents to the best of our knowledge, the first protein involved in nematode mouth formation with a conserved role in cuticle deposition. This study opens new research avenues to characterize the molecular composition of the nematode mouth, which is associated with extreme ecological diversification.

Bolus Versus Continuous Nasogastric Feeds for Infants With Bronchiolitis: A Randomized Trial

BACKGROUND AND OBJECTIVES: Infants hospitalized with bronchiolitis are commenced on nasogastric feeding to maintain hydration. Feeding strategies vary according to physician or institution preference. The current study hypothesized that continuous nasogastric feeding would prolong length of stay (LOS) when compared to bolus feeding. METHODS: A randomized, parallel-group, superiority clinical trial was performed within an Australian children’s hospital throughout 2 bronchiolitis seasons from May 2018 to October 2019. Infants <12 months hospitalized with bronchiolitis and requiring supplemental nasogastric feeding were randomly assigned to continuous or bolus nasogastric regimens. LOS was the primary outcome. Secondary outcome measures included pulmonary aspirations and admissions to intensive care. RESULTS: The intention-to-treat analysis included 189 patients: 98 in the bolus nasogastric feeding group and 91 in the continuous group. There was no significant difference in LOS (median LOS of the bolus group was 54.25 hours [interquartile range 40.25–82] and 56 hours [interquartile range 38–78.75] in the continuous group). A higher proportion of admissions to intensive care was detected in the continuous group (28.57% [26 of 91] of the continuous group vs 11.22% [11 of 98] of the bolus group [P value 0.004]). There were no clinically significant pulmonary aspirations or statistically significant differences in vital signs between the groups within 6 hours of feed initiation. CONCLUSIONS: No significant difference in LOS was found between bolus and continuous nasogastric feeding strategies for infants hospitalized with bronchiolitis. The continuous feeding group had a higher proportion of intensive care admissions, and there were no aspiration events.

Effect of Changes in Dietary Net Energy Concentration on Growth Performance, Fat Deposition, Skatole Production, and Intestinal Morphology in Immunocastrated Male Pigs

Nutritional requirements of heavy immunocastrated (IM) pigs and therefore appropriate feeding strategies have not yet been determined. Thus, the effects of changes in dietary net energy (NE) content were studied in 41 IM pigs, fed ad libitum diets with low, medium, and high NE content (LNE, MNE, and HNE diets, with 8.5, 9.3, and 10.0 MJ NE/kg, respectively), from 84 days of age until slaughter at an average age of 172 days and an average body weight of 122.5 kg. In the period from 143 to 170 days of age, there was a tendency for a greater NE intake (p = 0.08) in pigs fed the HNE diet along with greater (p < 0.01) backfat gain. Dietary treatment affected carcass composition, as lower backfat thickness (p = 0.01) and lower area of fat over the longissimus muscle (p = 0.05) were observed in the LNE and MNE pigs. In addition, greater lean meat content (p = 0.04) was observed in the LNE pigs. Reducing the NE of the diet by replacement of cereals and soybean meal with high-fiber ingredients resulted in lower indole production in the ascending colon (p < 0.01) and greater skatole production (p < 0.01) in the cecum. Greater villus area, width, height and perimeter, crypt depth, and thickness of the intestinal mucosa in the jejunum, ileum, ascending colon, and descending colon were found in the LNE group (p < 0.01) than in the HNE group, while those in the MNE group was intermediate. Cell proliferation was not affected by dietary treatment (p > 0.05). The present results show that a reduction in dietary NE concentration lowers lipid deposition, without affecting performance or energy efficiency in IM pigs. This technique provides an advantage in terms of improved leanness, without affecting growth rate in IM pigs after immunization, which is particularly important when the backfat thickness is a determinant of carcass value and IM pigs are fattened to higher weights (e.g., in heavy pig production) or when a longer delay between immunization and slaughter is practiced.

Gut Microbiome and Degradation Product Formation during Biodegradation of Expanded Polystyrene by Mealworm Larvae under Different Feeding Strategies

Polystyrene (PS) is a plastic polymer extensively used for food packaging. PS is difficult to decompose and has low recycling rates, resulting in its accumulation in the environment, in the form of microplastic particles causing pollution and harming oceans and wildlife. Degradation of PS by mealworms (Tenebrio molitor) has been suggested as a possible biological strategy for plastic contamination; however, the biodegradation mechanism of PS by mealworms is poorly understood. It is hypothesized that the gut microbiome plays an important role in the degradation of PS by mealworms. This study carried out a comparative analysis of the gut microbiome of Tenebrio molitor larvae under different feeding strategies, and of the formation of degradation compounds (monomers, oligomers). A diet of bran:PS at 4:1 and 20:1 ratios was tested. The diet with the low ratio of bran:PS led to the presence of higher amounts of these compounds, compared to that with the high ratio. In addition, it was demonstrated that the addition of H2O significantly improved the biodegradation of PS monomer and oligomer residues, which could be identified only in the frass. The protein and nitrogen contents in insects’ biomass and frass varied amongst treatments. The diets resulted in differences in the gut microbiota, and three potential bacterial strains were identified as candidates involved in the biodegradation of PS.

Comparative analysis of the digestive system’s anatomical parts in two zoophagous bird species: White Stork (Ciconia ciconia) and Common Buzzard (Buteo buteo)

Aristotle in his anatomical observations is marking the beginning of functional anatomy followed by Georges Cuvier that formulate the low of the correlation of parts. According with this we can expect that the digestive system structures tend to be similar between species that consume approximately the same type of food. In this study we chose to evaluate macroscopic the digestive system of two different zoophytophagous species, with similar body size but different life behavior and feeding strategies: White Stork (Ciconia ciconia) and Common Buzzard (Buteo buteo). Data were collected after the dissection of 10 carcass (5 White Stork and 5 Common Buzzard). The digestive tract and its structures were measured and weighed. In common buzzard the beak is strong and short adapted for the laceration of the prey. In white stork the beak is long, strong, straight adapted to capture prey like a harpoon. In both species, the esophagus is located on the right side of the neck, the length is different, proportional to the neck. In common buzzard the crop is present and absent in white storks. The cuticle or koilin layer is highlighted in white stork compared to common buzzard. In common buzzard, the small intestine is reduced in size, without marked transition between the duodenum and the ileum. The white storks have a long small intestine with many loops, with no transition between the segments. In both species, the cecum is reduced in size and has a vestigial appearance; the colon is reduced in size, and extends from the level of the ileo-colic junction to the cloaca. The digestive system is adapted to a strictly carnivorous diet and the differences identified between the anatomical structures of the digestive tract of the two species are correlated with the differences of their feeding behavior.

Trace metal accumulation in decapods and its use in monitoring the marine environment

<p>Coastal habitats are susceptible to severe contamination due to their exposure to both marine and terrestrial inputs, many of which contain toxic heavy metals. Trace metals in the marine environment can have severe impacts on the health of coastal ecosystems, as even those with essential functions can be toxic at high concentrations, and non-essential elements can cause impairment of biological functions even at low levels. It is important to understand the chemistry of New Zealand’s marine environment, in order to successfully monitor any changes to the chemical profile of the environment from anthropogenic pollutants. Biological indicators are a useful tool for monitoring ecosystem health, and the impact of human activity on the environment. Crustaceans fulfil all the criteria of being good environmental indicators, as well as having a range of feeding strategies, and being present at multiple trophic levels. The aim of this research was to 1) investigate spatial variation and the effect of urbanisation in trace metal concentration in two native decapod species, Heterozius rotundifrons and Petrolisthes elongatus, which co-occur but feed at different trophic levels; and 2) examine how essential and non-essential trace metals are accumulated into different body tissues of the decapod Jasus edwardsii, a significant cultural and fishery species. To assess spatial variation and trophic level differences between decapods, baseline data of the concentrations of thirty trace metals was collected and analysed from both species at three sites in the Wellington region. Little variation was found between the sites, despite their differences in proximity to urban development, but significant differences were found between species, with the consumer H. rotundifrons having higher concentrations of most trace metals than the filter feeder P. elongatus. To assess trace metal accumulation into tissues of J. edwardsii, an experiment was run exposing juveniles to water doped with an elevated copper and neodymium treatment. Copper was preferentially accumulated into the organ tissue, as was expected for an essential element. Neodymium was accumulated differentially into organ and exoskeleton tissue depending on the treatment, with specimens in the elevated treatment taking it up into the shell rather than the organs. A second experiment was also run to investigate whether moulted exoskeletons would passively absorb copper from their environment, which was shown to be the case. This research aids in understanding the importance of multiple species monitoring, as trace element accumulation was shown to be highly variable depending on species and metals, and contributes valuable geochemical data on native New Zealand species, which have been little studied in this context.</p>