Revisiting the coupling of fatty acid to phospholipid synthesis in bacteria with FapR regulation

A key aspect in membrane biogenesis is the coordination of fatty acid to phospholipid synthesis rates. In most bacteria, PlsX is the first enzyme of the phosphatidic acid synthesis pathway, the common precursor of all phospholipids. Previously, we proposed that PlsX is a key regulatory point that synchronizes the fatty acid synthase II with phospholipid synthesis in Bacillus subtilis. However, understanding the basis of such coordination mechanism remained a challenge in Gram-positive bacteria. Here, we show that the inhibition of fatty acid and phospholipid synthesis caused by PlsX depletion leads to the accumulation of long-chain acyl-ACPs, the end products of the fatty acid synthase II. Hydrolysis of the acyl-ACP pool by heterologous expression of a cytosolic thioesterase relieves the inhibition of fatty acid synthesis, indicating that acyl-ACPs are feedback inhibitors of this metabolic route. Unexpectedly, inactivation of PlsX triggers a large increase of malonyl-CoA leading to induction of the fap regulon. This finding discards the hypothesis, proposed for B. subtilis and extended to other Gram-positive bacteria, that acyl-ACPs are feedback inhibitors of the acetyl-CoA carboxylase. Finally, we propose that the continuous production of malonyl-CoA during phospholipid synthesis inhibition provides an additional mechanism for fine-tuning the coupling between phospholipid and fatty acid production in bacteria with FapR regulation.     

Differentially expressed proteins during an incompatible interaction between common bean and the fungus Pseudocercospora griseola

The common bean (Phaseolus vulgaris L.) is the main source of protein and an important source of minerals in several countries around the world. Angular leaf spot, caused by the fungus Pseudocercospora griseola, is one of the major diseases of the common bean. In this work, we used two-dimensional gel electrophoresis and mass spectrometry to analyze alterations in the proteome of common bean leaves challenged with an incompatible race of P. griseola. Twenty-three differentially expressed proteins were detected in leaves of cultivar AND 277 collected at 12, 24 and 48 h after inoculation. The proteins were digested with trypsin and submitted to MALDI-TOF/TOF and MicrOTOF-Q electrospray mass spectrometry. Nineteen of them were identified upon MS/MS fragmentation. Most of these proteins are involved with amino acid metabolism, terpenoid metabolism, phenylpropanoid biosynthesis, antioxidant systems, vitamin and cofactor metabolism, plant–pathogen interaction, carbohydrate metabolism, photosynthesis, or genetic information processing, showing that the interaction in this pathosystem affects different genes from various metabolic pathways and processes.     

Electron tomography of Plasmodium falciparum merozoites reveals core cellular events that underpin erythrocyte invasion

Erythrocyte invasion by merozoites forms of the malaria parasite is a key step in the establishment of human malaria disease. To date, efforts to understand cellular events underpinning entry have been limited to insights from non‐human parasites, with no studies at sub‐micrometer resolution undertaken using the most virulent human malaria parasite, Plasmodium falciparum. This leaves our understanding of the dynamics of merozoite sub‐cellular compartments during infectionincomplete, in particular that of the secretory organelles. Using advances in P. falciparum merozoite isolation and new imaging techniques we present a three‐dimensional study of invasion using electron microscopy, cryo‐electron tomography and cryo‐X‐ray tomography. We describe the core architectural features of invasion and identify fusion between rhoptries at the commencement of invasion as a hitherto overlooked event that likely provides a critical step that initiates entry. Given the centrality of merozoite organelle proteins to vaccine development, these insights provide a mechanistic framework to understand therapeutic strategies targeted towards the cellular events of invasion.     

The Schistosome Oesophageal Gland: Initiator of Blood Processing

Background

Although the ultrastructure of the schistosome esophageal gland was described >35 years ago, its role in the processing of ingested blood has never been established. The current study was prompted by our identification of MEG-4.1 expression in the gland and the observation of erythrocyte uncoating in the posterior esophagus.

Methodology/Principal Findings

The salient feature of the posterior esophagus, characterized by confocal and electron microscopy, is the enormous increase in membrane surface area provided by the plate-like extensions and basal invaginations of the lining syncytium, with unique crystalloid vesicles releasing their contents between the plates. The feeding process was shown by video microscopy to be divided into two phases, blood first accumulating in the anterior lumen before passing as a bolus to the posterior. There it streamed around a plug of material revealed by confocal microscopy as tethered leucocytes. These were present in far larger numbers than predicted from the volume of the lumen, and in varying states of damage and destruction. Intact erythrocytes were detected in the anterior esophagus but not observed thereafter, implying that their lysis occurred rapidly as they enter the posterior. Two further genes, MEGs 4.2 and 14, were shown to be expressed exclusively in the esophageal gland. Bioinformatics predicted that MEGs 4.1 and 4.2 possessed a common hydrophobic region with a shared motif, while antibodies to SjMEG-4.1 showed it was bound to leucocytes in the esophageal lumen. It was also predicted that MEGs 4.1 and 14 were heavily O-glycosylated and this was confirmed for the former by 2D-electrophoresis and Western blotting.

Conclusions/Significance

The esophageal gland and its products play a central role in the processing of ingested blood. The binding of host antibodies in the esophageal lumen shows that some constituents are antibody targets and could provide a new source of vaccine candidates.     

Note on the diet of the jaguar in central Brazil

Diet of the jaguar Panthera onca in the Cerrado, central Brazil, was investigated based on a sample of genetically identified jaguar scats. At least nine prey species were observed in 35 scat samples. Giant anteaters Myrmecophaga tridactyla contributed more than 75 % of biomass to the observed diet. Tapirs Tapirus terrestris and peccaries Tayassu pecari and Pecari tajacu contributed approximately 6 % to jaguar diet each, and small mammals contributed least to the jaguar diet. At 0.121, dietary niche breadth was narrower than reported in most other studies. Due to their physical characteristics and abundance, giant anteaters are likely the most profitable prey for jaguars in Emas National Park, and as an important prey, they should be included in jaguar conservation efforts.     

Length-weight relationship of twelve mesopelagic fishes from the western Tropical Atlantic

Length-weight relationship parameters were calculated for twelve mesopelagic fish species from the western Tropical Atlantic: Diretmus argenteus, Melamphaes polylepis, Bolinichthys distofax, Diaphus lucidus, Diaphus splendidus, Electrona risso, Hygophum taaningi, Taaningichthys bathyphilus, Melanolagus bericoides, Winteria telescopa, Diplophos taenia, Astronesthes similus. Data was collected off northeastern Brazil from April 9th to May 6th, 2017. Hauls were conducted during day and night at 47 stations by using a micronekton trawl (body mesh: 40 mm, cod-end mesh: 10 mm) from 10 to 1,113 m depth. The material was fixed in a 4% formalin solution for 1 month and then preserved in a 70% alcohol solution for proximally 6 months before processing for length (nearest 0.1 cm of standard length) and weight (nearest 0.01 g of total weight). A new maximum standard length for Winteria telescopa is also provided.     

Characterisation of the effects of leaf galls of Clusiamyia nitida (Cecidomyiidae) on Clusia lanceolata Cambess. (Clusiaceae): Anatomical aspects and chemical analysis of essential oil

Galls develop in different plant organs and are induced by the activity of various organisms. Some studies have investigated the ecological interactions between species of Clusia and gall-inducing insects. The goal of our study is to characterise changes in leaf anatomy caused by the activity of gall insects in Clusia lanceolata. Additionally, we also investigated the chemical composition of volatile compounds of normal leaves and those with galls to detect possible effects on the host plants. For anatomical studies, we used botanical material fixed in FAA₅₀. Transversal sections of the leaf blade were obtained from samples of leaves located on the third and fourth nodes from both male and female individuals. Material was studied from both sexes both with unaffected leaves and leaves containing galls. Fresh leaves of C. lanceolata were used for the extraction of volatile compounds, which were submitted to stem distillation using a modified Clevenger apparatus determining the oil yields subsequently (w/w). The unaffected leaves of female and male individuals of C. lanceolata exhibit similar anatomical structures. However, galls on leaves of both sexes show anatomical differences. The activity of the gall insect Clusiamyia nitida induces several changes in the foliar anatomy and the distribution of metabolic compounds in new tissues during gall development. However, the larvae are not able to induce significant changes in the volatile compounds of inflected leaves from male and female individuals.     

Mercury Concentration in Breast Milk and Infant Exposure Assessment During the First 90 Days of Lactation in a Midwestern Region of Brazil

Breast milk samples collected from 18 nursing mothers between the 15th and 90th day of lactation were digested in nitric acid in a microwave, and total mercury (THg) levels were quantified by atomic fluorescence spectrometry. Participants responded to a 24-h dietary recall questionnaire on the 74th and 76th day of lactation and to a Food Frequency Questionnaire querying the frequency of fish intake over the last 90 days. Usual intake was estimated using the PC-SIDE software package. A meal of fish was offered on the 75th day of lactation. Mothers’ individual mean THg levels ranged from <0.76 to 22.7 ng/mL during the period, and the mean level for all samples (n?=?142) was 6.47?±6.04 ng/mL. The multilevel mixed linear model used showed high heterogeneity of the mercury levels among the mothers, and THg levels did not change significantly over the period under study. However, a significant increase in THg levels was observed after the intervention with the fish meal. Exposure increased for most infants on the 90th day of lactation, with intakes exceeding the THg provisional tolerable weekly intake (PTWI) at least once during the period for 77.8 % of samples. Mothers consumed mostly food from the fat and grain groups, and a significant correlation was detected between consumption of food of these groups and breast milk THg levels (p?=?0.006 and 0.007). A significant correlation was also found between vegetable consumption and carbohydrate intake and THg levels in the samples (p?=?0.015 and 0.045, respectively). No correlation was found between mothers’ daily fish consumption frequency and THg levels. Although this study showed that mercury intake by infants during lactation may exceed the toxicologically safe exposure level (PTWI), we nevertheless believe that the benefits of lactation for both the mother and the infant outweigh the eventual risks that this exposure may represent.