Nutrient-poor Conditions Research Articles

Neisseria meningitidis Sibling Small Regulatory RNAs Connect Metabolism with Colonization by Controlling Propionate Use.

Neisseria meningitidis (meningococcus) colonizes the human nasopharynx, primarily as a commensal, but sporadically causing septicemia and meningitis. During colonization and invasion, it encounters different niches with specific nutrient compositions. Small noncoding RNAs (sRNAs) are used to fine-tune expression of genes, allowing adaptation to their physiological differences. We have previously characterized sRNAs (Neisseria metabolic switch regulators [NmsRs]) controlling switches between cataplerotic and anaplerotic metabolism. Here, we extend the NmsR regulon by studying methylcitrate lyase (PrpF) and propionate kinase (AckA-1) involved in the methylcitrate cycle and serine hydroxymethyltransferase (GlyA) and 3-hydroxyacid dehydrogenase (MmsB) involved in protein degradation. These proteins were previously shown to be dysregulated in a ΔnmsRs strain. Levels of transcription of target genes and NmsRs were assessed by reverse transcriptase quantitative PCR (RT-qPCR). We also used a novel gene reporter system in which the 5' untranslated region (5' UTR) of the target gene is fused to mcherry to study NmsRs-target gene interaction in the meningococcus. Under nutrient-rich conditions, NmsRs downregulate expression of PrpF and AckA-1 by direct interaction with the 5' UTR of their mRNA. Overexpression of NmsRs impaired growth under nutrient-limiting growth conditions with pyruvate and propionic acid as the only carbon sources. Our data strongly suggest that NmsRs downregulate propionate metabolism by lowering methylcitrate enzyme activity under nutrient-rich conditions. Under nutrient-poor conditions, NmsRs are downregulated, increasing propionate metabolism, resulting in higher tricarboxylic acid (TCA) activities. IMPORTANCE Neisseria meningitidis colonizes the human nasopharynx, forming a reservoir for the sporadic occurrence of epidemic invasive meningococcal disease like septicemia and meningitis. Propionic acid generated by other bacteria that coinhabit the human nasopharynx can be utilized by meningococci for replication in this environment. Here, we showed that sibling small RNAs, designated NmsRs, riboregulate propionic acid utilization by meningococci and, thus, colonization. Under conditions mimicking the nasopharyngeal environment, NmsRs are downregulated. This leads to the conversion of propionic acid to pyruvate and succinate, resulting in higher tricarboxylic acid cycle activity, allowing colonization of the nasopharynx. NmsRs link metabolic state with colonization, which is a crucial step on the trajectory to invasive meningococcal disease.

FoxO directly regulates the expression of odorant receptor genes to govern olfactory plasticity upon starvation in Bactrocera dorsalis

Under nutrient-poor conditions, animals must save energy by adjusting their behavior and physiology in order to survive. Although the impact of feeding state on olfactory sensory neuron activity has been well studied, the regulatory mechanisms underlying the transcriptional changes in odorant receptors (Ors) induced by feeding signals are seldom mentioned. Here, we showed that starvation could attenuate antennal responses of Bactrocera dorsalis toward multiple odorants, which could be reverted by sugar re-feeding, but not by a protein-rich diet. Using methyl eugenol (ME) as a paradigm, our study provided molecular evidence that Forkhead Box protein O (FoxO) can be expressed in antennal tissues to govern starvation-induced olfactory modifications by binding to the upstream regulatory regions of ME-responsive Ors and regulating their expressions. Since the consensus FoxO binding motif was also identified in other 17 Ors whose expression levels were also significantly altered upon FoxO knockdown and starvation, our data suggest that FoxO-dependent binding is likely a universal regulatory mechanism for Or genes during starvation and re-feeding cycles. Taken together, the FoxO-Ors axis elucidated in this study provides an improved understanding of how the insulin signaling pathway senses the feeding state and certain macronutrient composition to shape olfactory plasticity, allowing flies to dynamically alter chemosensory sensitivities toward different odors. Our study also highlights sugar as a satiety signal, which could increase ME-mediated trap efficiency in the field.

EFFECT OF SEVERAL TYPES AND DOSES OF COMPOST FROM CELLULOLYTIC MICROBIAL DEGRADATION ON AGGREGATE STABILITY OF ULTISOLS SOIL

Ultisolss are one of the marginal soil types that dominate drylands in Indonesia. The main problem of Ultisolss is poor nutrient conditions and low physical properties. The productivity of this soil is low because it has low soil aggregate stability and also has poor biological and physical properties. Research on superior cellulotic microbes in termite nests used as a starter for the decomposition of agricultural waste and changes in the physical properties of Ultisols soil needs to be carried out to determine the effect of applying the type and dose of compost resulting from the degradation of cellulotic microbes to improve the physical properties of Ultisols soil. This experiment was conducted from July 2019 to September 2021 at Ciparanje Experimental Farm, Faculty of Agriculture, Univesitas Padjadjaran. The method used was experiment with Randomized Block Design consisting of 9 treatments and repeated 3 times, namely straw compost 5 tons/ha, 10 tons/ha, 15 tons/ha; sugarcane bagasse compost 5 tons/ha, 10 tons/ha, 15 tons/ha; oil palm empty fruit bunch compost 5 tons/ha, 10 tons/ha, 15 tons/ha. Based on the research of compost degradation results by cellulotic microbes, rice straw compost 15 tons/ha can provide the best aggregate stability results.

Flight-reproduction trade-offs are weak in a field cage experiment across multiple Drosophila species

Flight-reproduction trade-offs, such that more mobile individuals sacrifice reproductive output (e.g., fecundity) or incur fitness costs, are well-studied in a handful of wing-dimorphic model systems. However, these trade-offs have not been systematically assessed across reproduction-related traits and taxa in wing monomorphic species despite having broad implications for the ecology and evolution of pterygote insect species. Here we therefore determined the prevalence, magnitude and direction of flight-reproduction trade-offs on several fitness-related traits in a semi-field setting by comparing disperser and resident flies from repeated releases of five wild-caught, laboratory-reared Drosophila species, and explicitly controlling for a suite of potential confounding effects (maternal effects, recent thermal history) and potential morphological covariates (wing-loading, body mass). We found almost no systematic differences in reproductive output (egg production), reproductive fitness (offspring survival), or longevity between flying (disperser) and resident flies in our replicated releases, even if adjusting for potential morphological variation. After correction for false discovery rates, none of the five species showed evidence of a significant fitness trade-off associated with increased flight (sustained, simulated voluntary field dispersal). Our results therefore suggest that flight-reproduction trade-offs are not as common as might have been expected when assessed systematically across species and under the relatively standardized conditions and field setting employed here, at least not in the genus Drosophila. The magnitude and direction of potential dispersal- or flight-induced trade-offs, and the conditions that promote them, clearly require closer scrutiny. We argue that flight or dispersal is either genuinely cheaper than expected, or the costs manifest differently than those assessed here. Lost opportunities (i.e., time spent on mate-finding, mating or foraging) or nutrient-poor conditions could promote fitness costs to dispersal in our study system and that could be explored in future.

Cancer Cells Rely on Pain-Sensing Nerves in Nutrient-Scarce Conditions.

Cross-talk between cancer cells and nociceptive nerves aids tumor growth in nutrient-poor conditions.

Ericoid mycorrhizal fungi mediate the response of ombrotrophic peatlands to fertilization: a modeling study.

Ericaceous shrubs adapt to the nutrient-poor conditions in ombrotrophic peatlands by forming symbiotic associations with ericoid mycorrhizal (ERM) fungi. Increased nutrient availability may diminish the role of ERM pathways in shrub nutrient uptake, consequently altering the biogeochemical cycling within bogs. To explore the significance of ERM fungi in ombrotrophic peatlands, we developed the model MWMmic (a peat cohort-based biogeochemical model) into MWMmic-NP by explicitly incorporating plant-soil nitrogen (N) and phosphorus (P) cycling and ERM fungi processes. The new model was applied to simulate the biogeochemical cycles in the Mer Bleue (MB) bog in Ontario, Canada, and their responses to fertilization. MWMmic_NP reproduced the carbon(C)-N-P cycles and vegetation dynamics observed in the MB bog, and their responses to fertilization. Our simulations showed that fertilization increased shrub biomass by reducing the C allocation to ERM fungi, subsequently suppressing the growth of underlying Sphagnum mosses, and decreasing the peatland C sequestration. Our species removal simulation further demonstrated that ERM fungi were key to maintaining the shrub-moss coexistence and C sink function of bogs. Our results suggest that ERM fungi play a significant role in the biogeochemical cycles in ombrotrophic peatlands and should be considered in future modeling efforts.

ATM inhibition drives metabolic adaptation via induction of macropinocytosis.

Macropinocytosis is a nonspecific endocytic process that may enhance cancer cell survival under nutrient-poor conditions. Ataxia-Telangiectasia mutated (ATM) is a tumor suppressor that has been previously shown to play a role in cellular metabolic reprogramming. We report that the suppression of ATM increases macropinocytosis to promote cancer cell survival in nutrient-poor conditions. Combined inhibition of ATM and macropinocytosis suppressed proliferation and induced cell death both in vitro and in vivo. Supplementation of ATM-inhibited cells with amino acids, branched-chain amino acids (BCAAs) in particular, abrogated macropinocytosis. Analysis of ATM-inhibited cells in vitro demonstrated increased BCAA uptake, and metabolomics of ascites and interstitial fluid from tumors indicated decreased BCAAs in the microenvironment of ATM-inhibited tumors. These data reveal a novel basis of ATM-mediated tumor suppression whereby loss of ATM stimulates protumorigenic uptake of nutrients in part via macropinocytosis to promote cancer cell survival and reveal a potential metabolic vulnerability of ATM-inhibited cells.

S6.3d Candida albicans commensalism in the oral mucosa is favored by limited virulence and metabolic adaptation

S6.3 Fungal adaptation and evolution, September 22, 2022, 4:45 PM - 6:15 PM ObjectivesAs part of the human microbiota, the fungus Candida albicans colonizes the oral cavity and other mucosal surfaces. Commensalism is tightly controlled by complex fungus-host interactions that preclude fungal elimination but also fungal overgrowth and invasion that would result in disease. As such, defects in antifungal T cell immunity render individuals susceptible to oral thrush due to interrupted immunosurveillance. The factors that promote commensalism and ensure persistence of C. albicans in a fully immunocompetent host remain less clear. In this study, we aimed at identifying determinants of C. albicans commensalism in the oral cavity.MethodsWe used an experimental model of C. albicans oral colonization in mice, profiled the transcriptome of the fungus in the mucosal tissue, and conducted functional studies with the prototypical commensal isolate 101 in host-free and host-involving conditions.Results C. albicans commensalism is associated with a characteristic metabolic profile tailored to the nutrient-poor conditions in the stratum corneum of the epithelium where the fungus resides. Metabolic adaptation of the commensal isolate 101 was also reflected in enhanced nutrient acquisition when grown on oral mucosa substrates. Persistent colonization of the oral mucosa by C. albicans also correlated inversely with the capacity of the fungus to induce epithelial cell damage and to elicit an inflammatory response. These immune evasive properties of isolate 101 are explained by a strong attenuation of numerous virulence genes, including those linked to filamentation. De-repression of the hyphal program by deletion or conditional repression of the transcriptional repressor NRG1 abolished the commensal behavior of isolate 101.ConclusionsThis study establishes a central role of NRG1 in the commensal lifestyle of C. albicans in the oral niche of the host.

Genotypes exhibit no variation in precision foraging in mycorrhizal Norway spruce seedlings

AimsFine roots, that comprise the adjustable part of the root system, are important in spatially heterogeneous boreal forest soils. We investigated the soil exploring patterns of Norway spruce (Picea abies) seedlings of equal height belonging to families representing two contrasting growth phenotypes that have shown fast and slow growth rates in long-term experiments. We hypothesised that seedlings of the fast-growing phenotype would show a more explorative root growth strategy, intense branching, and root proliferation in response to the nutrient patch, and that slow-growing phenotypes would be more tolerant to drought stress.MethodsSeedlings were grown in flat Perspex microcosms with a clod of humus placed in the mid-bottom part of each microcosm for eight months. The order-based and functional classification, branching topology, and size of seedling root systems were studied with WinRHIZO™ image-analysis software and root exploration patterns with LIGNUM-model simulations. In addition, transpiration, stomatal conductance, net assimilation rate responses were measured.ResultsNo differences were found in the early foraging of roots for the humus clod nor net assimilation rate and transpiration between the phenotype groups. Seedlings were favouring exploitation over exploration in the early phases of development regardless of growth phenotype group. However, in fast-growing phenotypes, the main roots were longer, and the lateral root pool favoured long and bifurcated laterals that formed larger absorptive root area.ConclusionsOur results indicate that in nutrient-poor conditions, better growth of lateral roots precedes future differences in the aboveground growth rate of Norway spruce.

Coordination of gene expression with cell size enables Escherichia coli to efficiently maintain motility across conditions

To swim and navigate, motile bacteria synthesize a complex motility machinery involving flagella, motors, and a sensory system. A myriad of studies has elucidated the molecular processes involved, but less is known about the coordination of motility expression with cellular physiology: In Escherichia coli, motility genes are strongly up-regulated in nutrient-poor conditions compared to nutrient-replete conditions; yet a quantitative link to cellular motility has not been developed. Here, we systematically investigated gene expression, swimming behavior, cell growth, and available proteomics data across a broad spectrum of exponential growth conditions. Our results suggest that cells up-regulate the expression of motility genes at slow growth to compensate for reduction in cell size, such that the number of flagella per cell is maintained across conditions. The observed four or five flagella per cell is the minimum number needed to keep the majority of cells motile. This simple regulatory objective allows E. coli cells to remain motile across a broad range of growth conditions, while keeping the biosynthetic and energetic demands to establish and drive the motility machinery at the minimum needed. Given the strong reduction in flagella synthesis resulting from cell size increases at fast growth, our findings also provide a different physiological perspective on bacterial cell size control: A larger cell size at fast growth is an efficient strategy to increase the allocation of cellular resources to the synthesis of those proteins required for biomass synthesis and growth, while maintaining processes such as motility that are only needed on a per-cell basis.

Growth conditions inducing G1 cell cycle arrest enhance lipid production in the oleaginous yeast Lipomyces starkeyi.

Lipid droplets are cytoplasmic organelles that store lipids for energy and membrane synthesis. The oleaginous yeast Lipomyces starkeyi is one of the most promising lipid producers and has attracted attention as a biofuel source. It is known that the expansion of lipid droplets is enhanced under nutrient-poor conditions. Therefore, we prepared a novel nitrogen-depleted medium (N medium) in which to culture L. starkeyi cells. Lipid accumulation was rapidly induced, and this was reversed by the addition of ammonium. In this condition, cell proliferation stopped, and cells with giant lipid droplets were arrested in G1 phase. We investigated whether cell cycle arrest at a specific phase is required for lipid accumulation. Lipid accumulation was repressed in hydroxyurea-synchronized S phase cells and was increased in nocodazole-arrested G2/M phase cells. Moreover, the enrichment of G1 phase cells seen upon rapamycin treatment induced massive lipid accumulation. From these results, we conclude that L. starkeyi cells store lipids from G2/M phase and then arrest cell proliferation in the subsequent G1 phase, where lipid accumulation is enhanced. Cell cycle control is an attractive approach for biofuel production.

Can Sphagnum removal reverse the undesired succession of rich fens under different alkalinity and fertility levels?

An undesired succession of rich fens leads to the formation of dense Sphagnum carpets that outcompete brown mosses and some vascular plants, resulting in biodiversity loss in fen habitats of high conservation importance. Small-scale Sphagnum removal is a rarely implemented conservational measure, whose success may depend on soil alkalinity and fertility (i.e., nutrient availability). Therefore, characterizing the effects of pH and fertility levels would potentially allow for the development of better Sphagnum removal strategies. Two experiments were conducted across 24 rich fens of different alkalinity and fertility located in an area of ~32,000 km2 spanning from the Bohemian Massif to the Western Carpathians (Europe). We hypothesized that high alkalinity and low fertility support the restoration of rich fen vegetation after Sphagnum removal. Our study focused on four different Sphagnum groups. In Experiment 1, the treatment plots remained unfenced. In Experiment 2, the treatment plots were fenced off and target brown mosses were transplanted from the surroundings to overcome dispersal limitations. A repeated-measures design was used, with vegetation composition recorded over a 5-year period. High alkalinity rather than fertility facilitated species richness and the appearance of target brown mosses. High alkalinity generally hindered Sphagnum recovery, whereas high fertility supported the recurrence of S. teres and S. recurvum agg. Under high pH conditions, enhanced fertility further correlated with the spread of nonsphagnaceous generalist bryophytes of low conservation value. Despite sustaining a significant overall reduction, all Sphagnum taxa began to recover throughout the experiment, albeit less obviously in fens with S. warnstorfii. Sphagnum removal may reverse biodiversity loss and allow for the restoration of brown mosses in rich fens where Sphagnum cover had increased due to slight eutrophication, acidification, or a decrease in the water table. In alkaline and nutrient-poor conditions (e.g., S. warnstorfii fens), the effect is evident and long lasting and the intervention may not be extensive. In fens dominated by S. teres or S. recurvum agg., repeated or large-scale removal may be needed if high nutrient availability (potassium, phosphorus) or low alkalinity supports Sphagnum recolonization. Treatment plots with S. subgenus Sphagnum exhibited the least promising brown-moss restoration prospects.

Activating mTOR Mutations Are Detrimental in Nutrient-Poor Conditions.

This study suggests that cells need to inactivate mTOR to survive nutrient stress, which could explain the rarity of mTOR mutations and the limited clinical activity of mTOR inhibitors in cancer.

Tailored Additives for Incorporation of Antibacterial Functionality Into Laser Sintered Parts

Infectious disease is a major cause of death worldwide, and novel methods capable of controlling the spread of disease are in high demand. This research presents a method of producing antimicrobial microcomposites by exploiting the powder-based nature of the Laser Sintering Additive Manufacturing process, via the incorporation of silver-containing additives. Silver phosphate glass additives in different formulations were designed to determine the effect of dissolution rate on the antimicrobial efficacy. These were characterised and successfully incorporated into polyamide 12 parts, without affecting the mechanical properties. The printed microcomposite parts displayed both bactericidal and antibiofouling effects against Gram-positive and Gram-negative bacteria in nutrient-poor conditions, with the efficacy found to be more sensitive to silver content than degradation rate.

Landscape of Global Gene Expression Reveals Distinctive Tissue Characteristics in Bactrian Camels (Camelus bactrianus)

Bactrian camels (Camelus bactrianus) are highly adapted to the desert and semi-desert environments of Asia and developed unique physiological adaptations to cold, heat, drought, and nutrient-poor conditions. These animals are an ideal model for studying desert adaptation. However, the transcriptome of different Bactrian camel tissues has not been profiled. This study performed a comprehensive transcriptome analysis of nine fetal and adult tissues. A total of 20,417 coding genes were identified, and 2.4 billion reads were generated. Gene expression and functional analyses revealed that approximately 50% of the identified genes were ubiquitously expressed, and one-third were tissue-elevated genes, which were enriched in pathways related to the biological functions of the corresponding tissue. Weighted gene co-expressed network analysis (WGCNA) identified four modules—fat metabolism, water balance, immunity, and digestion—and several hub genes, including APOA1, TMEM174, CXCL12, and MYL9. The analysis of differentially expressed genes (DEGs) between fetal and adult tissues revealed that downregulated genes were enriched in tissue development, whereas upregulated genes were enriched in biological function in adult camels. DEGs in the hump were enriched in immune-related pathways, suggesting that this tissue is involved in immunity. This study is the first to generate a transcriptome atlas of major tissues in Bactrian camels and explores the genes potentially involved in the adaptation to desert environments.

Heterogeneity of metabolic adaptive capacity affects the prognosis among pancreatic ductal adenocarcinomas

BackgroundEvolutionary cancer has a supply mechanism to satisfy higher energy demands even in poor-nutrient conditions. Metabolic reprogramming is essential to supply sufficient energy. The relationship between metabolic reprogramming and the clinical course of pancreatic ductal adenocarcinoma (PDAC) remains unclear. We aimed to clarify the differences in metabolic status among PDAC patients.MethodsWe collected clinical data from 128 cases of resectable PDAC patients undergoing surgery. Sixty-three resected tissues, 15 tissues from the low carbohydrate antigen 19-9 (CA19-9), 38–100 U/mL, and high CA19-9, > 500 U/mL groups, and 33 non-tumor control parts, were subjected to tandem mass spectrometry workflow to systematically explore metabolic status. Clinical and proteomic data were compared on the most used PDAC biomarker, preoperative CA19-9 value.ResultsHigher CA19-9 levels were clearly associated with higher early recurrence (p < 0.001), decreased RFS (p < 0.001), and decreased DSS (p = 0.025). From proteomic analysis, we discovered that cancer evolution-related as well as various metabolism-related pathways were more notable in the high group. Using resected tissue immunohistochemical staining, we learned that high CA19-9 PDAC demonstrated aerobic glycolysis enhancement, yet no decrease in protein synthesis. We found a heterogeneity of various metabolic processes, including carbohydrates, proteins, amino acids, lipids, and nucleic acids, between the low and the high groups, suggesting differences in metabolic adaptive capacity.ConclusionsOur study found metabolic adaptation differences among PDAC cases, pertaining to both cancer evolution and the prognosis. CA19-9 can help estimate the metabolic adaptive capacity of energy supply for PDAC evolution.

Root-specific activation of plasma membrane H+-ATPase 1 enhances plant growth and shoot accumulation of nutrient elements under nutrient-poor conditions in Arabidopsis thaliana

Plasma membrane (PM) H+-ATPase contributes to nutrient uptake and stomatal opening by creating proton gradient across the membrane. Previous studies report that a dominant mutation in the OPEN STOMATA2 locus (OST2-2D) constitutively activates Arabidopsis PM H+-ATPase 1 (AHA1), which enlarges proton motive force for root nutrient uptake. However, the stomatal opening is also constitutively enhanced in the ost2-2D, causing drought hypersensitivity. To develop plants with improved nutrient acquisition and normal stomatal movement, we generated grafted plants (scion/rootstock: Col-0 (WT)/ost2-2D), and compared their growth, nutrient element content, and transcriptomes with those of control plants (WT/WT) under nutrient-rich or nutrient-poor conditions. WT/ost2-2D shoots had larger weights, rosette diameter, leaf blade area, and content of C, N, K, Ca, S, P, Mg, Na, Mn, B, Co, and Mo under nutrient-poor conditions compared with WT/WT shoots. The root weights and primary root length were greater in WT/ost2-2D plants than in WT/WT plants under both nutrient conditions. Root expression of the high-affinity nitrate transporter NRT2.1, potassium transporter HAK5, and divalent cation transporter IRT1 was higher in WT/ost2-2D plants than in WT/WT plants under nutrient-poor conditions. These results suggest that root-specific activation of PM H+-ATPase enhances plant growth by increasing root uptake of nutrient elements under nutrient-poor conditions. Our study presents a novel approach to improving nutrient uptake efficiency in crops for low-input sustainable agriculture.

A Perilipin Affects Lipid Droplet Homeostasis and Aerial Hyphal Growth, but Has Only Small Effects on Virulence in the Insect Pathogenic Fungus Beauveria bassiana.

Lipid assimilation, storage, and turnover impact growth, development, and virulence in many microbial pathogens including fungi. Perilipins are proteins associated with lipid droplets (LDs) that mediate their assembly and turnover. Here, we characterized the Beauveria bassiana (BbPlin1) perilipin. BbPlin1 expression was higher in minimal media than in rich media, and, using a BbPlin1::eGFP fusion protein, the protein was shown to be co–localized to LDs, with the high expression seen during infection and proliferation within the insect (Galleria mellonella) host that dramatically decreased to almost no expression during fungal outgrowth on cadavers including in conidia, but that BbPlin1 production resumed in the conidia once placed in nutrient–containing media allowing for germination and growth. Characterization of a targeted gene deletion strain (ΔBbPlin1) revealed a dramatic (>30%) reduction in cellular LD content, promotion of aerial hyphal growth, and a small decrease in virulence, with little to no effects on vegetative growth and stress responses. However, in the ΔBbPlin1 strain, expression of the complementary LD–associated caleosin gene, BbCal1, was enhanced under nutrient–poor conditions, although no changes in BbPlin1 expression were seen in a ΔBbCal1 strain and the expression of BbPlin1 in the ΔBbCal1 strain did not change LD patterns in cells. Transcriptome and RT–PCR analyses indicated increased expression of lipid metabolism–related genes, including triacylglyercol lipase 3, enoyl–CoA isomerase, and diacylglycerol–O–acetyl transferase in the BbPlin1 deletion mutant. Lipid profile analyses confirmed that the loss of BbPlin1 significantly reduced the cellular levels of contents of triacylglycerol, diacylglycerol, and phosphatidylethanolamine as compared to the wild–type strain. These results demonstrate the involvement of the B. bassiana perilipin in mediating lipid homeostasis, fungal aerial hyphal growth, and virulence, revealing critical cycling from high expression during nutrient utilization within host cadavers to low expression during growth on the surface of the cadaver during the infection process.

Drivers of periphyton biomass in south-western Cape rivers, South Africa, and the implications for management

In open-canopied temperate rivers, periphyton plays a pivotal role by converting dissolved nutrients into food for biota. International research suggests that periphyton is particularly responsive to flow and nutrient alterations and therefore ideally suited to aiding the prediction and monitoring of the effects of altered flow regimes. Given that one of South Africa’s key focus areas for river management has been the provision of flows to sustain aquatic ecosystems, this study aimed to quantify the relative importance of potential environmental drivers of periphyton, particularly flow, under different nutrient conditions in rivers of the south-western Cape. The study focused on two perennial rivers, the Berg and Molenaars Rivers. Quantitative monthly samples of periphyton biomass were collected from four sites, representative of different flow and nutrient regimes, over a 21-month sampling period between September 2007 and May 2009. The frequency of flood disturbance over the wet season was found to be the single most important driver of periphyton communities. It accounted for almost 75% of the total variation in periphyton biomass under natural flow and nutrient-poor conditions and it was therefore identified as the primary driver of periphyton communities. Its role was smaller under moderately enriched conditions and accounted for 45% of the total variation. These findings suggest that periphyton in south-western Cape rivers has great potential as a tool for predicting and monitoring the effects of altered flow regimes under different nutrient enrichment regimes. Together with some insight into community structure, the next step is to develop periphyton indicators that reflect different aspects of ecosystem integrity, for use in scenario modelling and other management aspects.

Fungal polysaccharides are altered by lyophilization resulting in decreased antibody binding

The capsule of Cryptococcus neoformans is unique in the fungal kingdom. Its hydrophilic nature and relative neutrality have complicated characterization (1). Even the synthesis of the polysaccharide capsule, being nutrient costly yet induced by nutrient poor conditions, seems counter intuitive. While the encapsulation of cryptococcal species is unique, the secretion of its signature polysaccharide – glucuronoxylomannan (GXM) – is not. Histoplasma capsulatum (2), Paracoccidioides brasiliensis (3), and many of the Trichosporonaceae family including Trichosporon asahii, Trichosporon inkin, Apiotrichum montevideense, Trichosporon japonicum, Trichosporon faecale, Trichosporon ovoides, Cutaneotrichosporon debeurmannianum, and Cutaneotrichosporon arboriformis all produce GXM‐like polymers (4, 5). Even basidiomycete fungal symbionts of many lichens Tremella and Cyphobasidium are predicted to produce a GXM‐like polysaccharide (6). As we investigate the role these glycans play in other fungal species it is important that physicochemical properties be conserved. Recent work by our group has shown that the lyophilization of polysaccharide preparations alters them such that antibody binding is reducing, suggesting that these changes have a functional effect. The difference between the polysaccharides before and after lyophilization is stark. Natively isolated polysaccharide preparations have ordered polymers that form small, loosely packed aggregates and contain extracellular vesicles. However, after lyophilization polymers are disordered and form dense rosette‐like aggregates and are absent extracellular vesicles. In addition, lyophilized and re‐solubilized samples allowed to incubate for 28 days did not return to the pre‐lyophilized, native state. This suggests that the changes induced by lyophilization many not be reversible. As we explore the role of these glycans in host‐microbe interactions, we need to consider the effects of lyophilization on the biological and immunological attributes of polysaccharides.