Functional consequences of nutrient translocation in mycelial fungi

Fungi are of fundamental importance for plant and microbial nutrition with primary roles in decomposition and nutrient recycling. They also have great potential for use in areas of biotechnology such as bioremediation of organic and inorganic pollutants and biocontrol of plant pathogens. In all these contexts, environmental heterogeneity has a strong influence on growth and function. A large class of fungi overcome the difficulties encountered in such environments by the mechanism of translocation which results in the internal redistribution of nutrients within the fungal mycelium. In this paper, we use a combination of experimental techniques and mathematical modelling to examine fungal growth in general, and in particular, translocation in the common soil saprophytic fungus Rhizoctonia solani. A detailed mathematical model is presented where translocation is considered to have both diffusive and metabolically-driven components. A calibration experiment provided the necessary parameter values. Growth experiments were compared with model solutions and thus we provide strong evidence that diffusion is the dominant mechanism for translocation in homogeneous environments. In heterogeneous environments, we conclude that diffusion is still vital for exploration, i.e. the expansion of the fungal network into the surrounding area. However, we also conclude that localized resources may be utilized faster if energy is invested, i.e. when exploitation of the fungal microenvironment is enhanced by metabolically driven translocation.     

Growth and function of fungal mycelia in heterogeneous environments

As decomposer organisms, pathogens, plant symbionts and nutrient cyclers, fungi are of fundamental importance in the terrestrial environment. Moreover, in addition to their well-known applications in industry, many species also have great potential in environmental biotechnology. The study of this important class of organisms is difficult through experimental means alone due to the heterogeneity of their natural growth habitat and the microscopic scale of growth. In this work we present a mathematical model for colony expansion that is derived through consideration of the growth characteristics on the microscale. The model equations are of mixed hyperbolic-parabolic type and are treated with a numerical scheme that preserves positivity and conserves mass. The numerical solutions are compared against experimental results in a variety of environments. Thus the effect of different translocation mechanisms on fungal growth and function are identified. The derivation and analysis of an approximation to the full model yields further results concerning basic properties of mycelial growth. Finally, the acidification of the growth habitat is considered and the model thus provides important predictions on the functional consequences of the redistribution of internally-located material.     

Characterization of the interaction of phospholipase A(2) with phosphatidylcholine-phosphatidylglycerol mixed lipids

The first requirement in the hydrolysis of phospholipid bilayers by phospholipase A(2) is the interaction of the enzyme with the bilayer surface. The catalytic ability of phospholipase A(2) has been shown to be extremely sensitive to the topology of the bilayer to which it binds and hydrolyzes. Phospholipid bilayer properties and composition such as unsaturation, charge, and the presence of reaction products are known regulators of the catalytic activity of phospholipase A(2) toward the phospholipids and influences the binding of enzyme to the membrane. We show in this paper that the effect of increased anionic lipid results in enhanced binding that can be described quantitatively in terms of a simple phenomenological model. However, the interaction with anionic lipid does not singularly dominate the thermodynamics of binding, nor can the lag phase observed in the time course of hydrolysis of large unilamellar vesicles simply be the result of limited interaction between the enzyme and the bilayer. Furthermore, we show that phospholipase A(2) from Akgistrodon piscivorus piscivorus can exist in at least two bilayer-bound states and that the absence of a fluorescence change upon mixing the enzyme with lipid bilayers does not necessarily indicate the absence of an interaction.     

Capture and commercialization of blue land crabs ("guaiamum") Cardisoma guanhumi (Lattreille, 1825) along the coast of Bahia State, Brazil: an ethnoecological approach

Background

Blue Land Crab (Cardisoma guanhumi) is one of the most important crustacean species captured and commercialized in Brazil. Although this species is not considered to be threatened with extinction, populations of C. guanhumi are known to be rapidly diminishing due to heavy harvesting pressures and degradation of their natural habitats, highlighting the necessity of developing and implanting management and protection strategies for their populations. There have been no ethnozoological publications that have focused specifically on C. guanhumi, in spite of importance of this type of information for developing efficient management plans of resource utilization. So, the present work describes the ethnoecological aspects of the capture and commercialization of C. guanhumi by a fishing community in northeastern Brazil.

Methods

Field work was carried out in the municipality of Mucuri, Bahia in Brazil, between the months of January and March/2011 through the use of open semi-structured interviews with all of the crustacean harvesters in city who acknowledged their work in capturing this species, totaling 12 interviewees. The informants were identified through the use of the "snowball" sampling technique. In addition to the interviews themselves, the "guided tour" technique and direct observations was employed.

Results

According all the interviewees, the C. guanhumi is popularly called "guaiamum" and is collected in "apicum" zones. They recognize sexual dimorphism in the species based on three morphological characteristics and the harvesters also pointed two stages in the reproductive cycle during the year and another phase mentioned by the interviewees was ecdysis. All of the interviewed affirmed that the size and the quantities C. guanhumi stocks in Mucuri have been diminishing. All of the interviewees agreed that the species and other mangrove resources constituted their principal source of income. The harvesters dedicated three to five days a week to collect Blue Land Crabs and the principal technique utilized for capturing is a trap called a "ratoeira" (rat-trap).

Conclusions

The results of the present work demonstrated that the community retains a vast and important volume of knowledge about C. guanhumi that could subsidize both scientific studies and the elaboration of viable management and conservation strategies for this species.     

Antenatal breast expression in women with diabetes: outcomes from a retrospective cohort study

Background

Women with diabetes are sometimes advised to express breast milk antenatally to prepare for breastfeeding and to store colostrum for infant feeding in preventing or treating hypoglycaemia after the birth. The acceptability, risks and benefits of this practice have not been evaluated. This was aimed to investigate the pattern of antenatal breast expression uptake and its relationship with birth outcomes in women with diabetes.

Methods

This was part of a two year retrospective cohort study of pregnant women with diabetes (type 1, 2 and gestational diabetes) who gave birth during 2001–2003 in Derby Hospitals NHS Foundation Trust (n = 94). The information on the practice of antenatal breastfeeding expression and birth outcomes was collected via self-administered questionnaires and by examining maternity records.

Results

Thirty-seven percent of women (35/94) recalled that they were advised to express antenatally and 17% did (16/94). The mean gestational age at birth for women who hand-expressed was lower than that for those who did not (mean difference (MD) (95% confidence intervals (CI)): -1.2 (?2.4 to 0.04), p = 0.06). A higher proportion of babies from the antenatal expression group were admitted to special care baby units (SCBU) (MD (95% CI): 21% (?3.9 to 46.3).

Conclusions

Less than half the women who stated that they were advised to express, did so. There seems to be an indication that antenatal breast milk expression and lower gestational age at birth are associated. The trend of a higher rate of SCBU admission for babies from the breast milk expression group compared to those who did not express antenatally is of concern. An appropriately-powered randomised controlled trial is needed to determine the safety of this practice and its acceptability to women and health professionals before it can be recommended for implementation in practice.

     

Measuring the quality of observational study data in an international HIV research network

Observational studies of health conditions and outcomes often combine clinical care data from many sites without explicitly assessing the accuracy and completeness of these data. In order to improve the quality of data in an international multi-site observational cohort of HIV-infected patients, the authors conducted on-site, Good Clinical Practice-based audits of the clinical care datasets submitted by participating HIV clinics. Discrepancies between data submitted for research and data in the clinical records were categorized using the audit codes published by the European Organization for the Research and Treatment of Cancer. Five of seven sites had error rates >10% in key study variables, notably laboratory data, weight measurements, and antiretroviral medications. All sites had significant discrepancies in medication start and stop dates. Clinical care data, particularly antiretroviral regimens and associated dates, are prone to substantial error. Verifying data against source documents through audits will improve the quality of databases and research and can be a technique for retraining staff responsible for clinical data collection. The authors recommend that all participants in observational cohorts use data audits to assess and improve the quality of data and to guide future data collection and abstraction efforts at the point of care.     

Lead transformation to pyromorphite by fungi

Lead (Pb) is a serious environmental pollutant in all its chemical forms [1]. Attempts have been made to immobilize lead in soil as the mineral pyromorphite using phosphate amendments (e.g., rock phosphate, phosphoric acid, and apatite [2-5]), although our work has demonstrated that soil fungi are able to transform pyromorphite into lead oxalate [6, 7]. Lead metal, an important structural and industrial material, is subject to weathering, and soil contamination also occurs through hunting and shooting [8, 9]. Although fungi are increasingly appreciated as geologic agents [10-12], there is a distinct lack of knowledge about their involvement in lead geochemistry. We examined the influence of fungal activity on lead metal and discovered that metallic lead can be transformed into chloropyromorphite, the most stable lead mineral that exists. This is of geochemical significance, not only regarding lead fate and cycling in the environment but also in relation to the phosphate cycle and linked with microbial transformations of inorganic and organic phosphorus. This paper provides the first report of mycogenic chloropyromorphite formation from metallic lead and highlights the significance of this phenomenon as a biotic component of lead biogeochemistry, with additional consequences for microbial survival in lead-contaminated environments and bioremedial treatments for Pb-contaminated land.     

Evaluation of apoptosis markers in different cell lines infected with equine arteritis virus

Equine arteritis virus (EAV) induces apoptosis in infected cells. Cell death caused by EAV has been studied mainly using three cell lines, BHK-21, RK-13 and Vero cells. The mechanism of apoptosis varies among cell lines and results cannot be correlated owing to differences in EAV strains used. We evaluated different markers for apoptosis in BHK-21, RK-13 and Vero cell lines using the Bucyrus EAV reference strain. Acridine orange/ethidium bromide staining revealed morphological changes in infected cells, while flow cytometry indicated the extent of apoptosis. We also observed DNA fragmentation, but the DNA ladder was detected at different times post-infection depending on the cell line, i.e., 48, 72 and 96 h post-infection in RK-13, Vero and BHK-21 cells, respectively. Measurement of viral titers obtained with each cell line indicated that apoptosis causes interference with viral replication and therefore decreased viral titers. As an unequivocal marker of apoptosis, we measured the expression of caspase-3 and caspases-8 and -9 as extrinsic and intrinsic markers of apoptosis pathways, respectively. Caspase-8 in BHK-21 cells was the only protease that was not detected at any of the times assayed. We found that Bucyrus EAV strain exhibited a distinctive apoptosis pathway depending on the cell line.     

Potential role of viruses in white plague coral disease

White plague (WP)-like diseases of tropical corals are implicated in reef decline worldwide, although their etiological cause is generally unknown. Studies thus far have focused on bacterial or eukaryotic pathogens as the source of these diseases; no studies have examined the role of viruses. Using a combination of transmission electron microscopy (TEM) and 454 pyrosequencing, we compared 24 viral metagenomes generated from Montastraea annularis corals showing signs of WP-like disease and/or bleaching, control conspecific corals, and adjacent seawater. TEM was used for visual inspection of diseased coral tissue. No bacteria were visually identified within diseased coral tissues, but viral particles and sequence similarities to eukaryotic circular Rep-encoding single-stranded DNA viruses and their associated satellites (SCSDVs) were abundant in WP diseased tissues. In contrast, sequence similarities to SCSDVs were not found in any healthy coral tissues, suggesting SCSDVs might have a role in WP disease. Furthermore, Herpesviridae gene signatures dominated healthy tissues, corroborating reports that herpes-like viruses infect all corals. Nucleocytoplasmic large DNA virus (NCLDV) sequences, similar to those recently identified in cultures of Symbiodinium (the algal symbionts of corals), were most common in bleached corals. This finding further implicates that these NCLDV viruses may have a role in bleaching, as suggested in previous studies. This study determined that a specific group of viruses is associated with diseased Caribbean corals and highlights the potential for viral disease in regional coral reef decline.     

Regulation of vectorial supply of vesicles to the hyphal tip determines thigmotropism in Neurospora crassa

Thigmotropism is the ability of an organism to respond to a topographical stimulus by altering its axis of growth. The thigmotropic response of the model fungus Neurospora crassa was quantified using microfabricated glass slides with ridges of defined height. We show that the polarity machinery at the hyphal tip plays a role in the thigmotropic response of N. crassa. Deletion of N. crassa genes encoding the formin, BNI-1, and the Rho-GTPase, CDC-42, an activator of BNI-1 in yeast, CDC-24, its guanine nucleotide exchange factor (GEF), and BEM-1, a scaffold protein in the same pathway, were all shown to significantly decrease the thigmotropic response. In contrast, deletion of genes encoding the cell end-marker protein, TEA-1, and KIP-1, the kinesin responsible for the localisation of TEA-1, significantly increased the thigmotropic response. These results suggest a mechanism of thigmotropism involving vesicle delivery to the hyphal tip via the actin cytoskeleton and microtubules. Neurospora crassa thigmotropic response differed subtly from that of Candida albicans where the stretch-activated calcium channel, Mid1, has been linked with thigmotropic behaviour. The MID-1 deficient mutant of N. crassa (Δmid-1) and the effects of calcium depletion were examined here but no change in the thigmotropic response was observed. However, SPRAY, a putative calcium channel protein, was shown to be required for N. crassa thigmotropism. We propose that the thigmotropic response is a result of changes in the polarity machinery at the hyphal tip which are thought to be downstream effects of calcium signalling pathways triggered by mechanical stress at the tip.