A key challenge in the production of second generation biofuels is the conversion of lignocellulosic substrates into fermentable sugars. Enzymes, particularly those from fungi, are a central part of ...this process, and many have been isolated and characterised. However, relatively little is known of how fungi respond to lignocellulose and produce the enzymes necessary for dis-assembly of plant biomass. We studied the physiological response of the fungus Aspergillus niger when exposed to wheat straw as a model lignocellulosic substrate. Using RNA sequencing we showed that, 24 hours after exposure to straw, gene expression of known and presumptive plant cell wall-degrading enzymes represents a huge investment for the cells (about 20% of the total mRNA). Our results also uncovered new esterases and surface interacting proteins that might form part of the fungal arsenal of enzymes for the degradation of plant biomass. Using transcription factor deletion mutants (xlnR and creA) to study the response to both lignocellulosic substrates and low carbon source concentrations, we showed that a subset of genes coding for degradative enzymes is induced by starvation. Our data support a model whereby this subset of enzymes plays a scouting role under starvation conditions, testing for available complex polysaccharides and liberating inducing sugars, that triggers the subsequent induction of the majority of hydrolases. We also showed that antisense transcripts are abundant and that their expression can be regulated by growth conditions.
The manufacture of flaked stone artifacts represents a major milestone in the technology of the human lineage. Although the earliest production of primitive stone tools, predating the genus Homo and ...emphasizing percussive activities, has been reported at 3.3 million years ago (Ma) from Lomekwi, Kenya, the systematic production of sharp-edged stone tools is unknown before the 2.58–2.55 Ma Oldowan assemblages from Gona, Ethiopia. The organized production of Oldowan stone artifacts is part of a suite of characteristics that is often associated with the adaptive grade shift linked to the genus Homo. Recent discoveries from Ledi-Geraru (LG), Ethiopia, place the first occurrence of Homo ∼250 thousand years earlier than the Oldowan at Gona. Here, we describe a substantial assemblage of systematically flaked stone tools excavated in situ from a stratigraphically constrained context Bokol Dora 1, (BD 1) hereafter at LG bracketed between 2.61 and 2.58 Ma. Although perhaps more primitive in some respects, quantitative analysis suggests the BD 1 assemblage fits more closely with the variability previously described for the Oldowan than with the earlier Lomekwian or with stone tools produced by modern nonhuman primates. These differences suggest that hominin technology is distinctly different from generalized tool use that may be a shared feature of much of the primate lineage. The BD 1 assemblage, near the origin of our genus, provides a link between behavioral adaptations—in the form of flaked stone artifacts—and the biological evolution of our ancestors.
Conidial germination is fundamentally important to the growth and dissemination of most fungi. It has been previously shown (K. Hayer, M. Stratford, and D. B. Archer, Appl. Environ. Microbiol. ...79:6924-6931, 2013, http://dx.doi.org/10.1128/AEM.02061-13), using sugar analogs, that germination is a 2-stage process involving triggering of germination and then nutrient uptake for hyphal outgrowth. In the present study, we tested this 2-stage germination process using a series of nitrogen-containing compounds for the ability to trigger the breaking of dormancy of Aspergillus niger conidia and then to support the formation of hyphae by acting as nitrogen sources. Triggering and germination were also compared between A. niger and Aspergillus nidulans using 2-deoxy-D-glucose (trigger), D-galactose (nontrigger in A. niger but trigger in A. nidulans), and an N source (required in A. niger but not in A. nidulans). Although most of the nitrogen compounds studied served as nitrogen sources for growth, only some nitrogen compounds could trigger germination of A. niger conidia, and all were related to L-amino acids. Using L-amino acid analogs without either the amine or the carboxylic acid group revealed that both the amine and carboxylic acid groups were essential for an L-amino acid to serve as a trigger molecule. Generally, conidia were able to sense and recognize nitrogen compounds that fitted into a specific size range. There was no evidence of uptake of either triggering or nontriggering compounds over the first 90 min of A. niger conidial germination, suggesting that the germination trigger sensors are not located within the spore.
•A solid state fungal fermentation strategy converting wheat straw to hydrolysate.•A biological pre-treatment of wheat straw by culturing A. niger on wheat straw.•24.0±1.76U/g cellulase was produced ...using wheat straw as the main substrate.•The fungal extract was used to hydrolyze the fermented wheat straw.•19% higher hydrolysis efficiency using freshly-prepared fungal extract than Ctec2.
This paper reports a solid-state fungal fermentation-based pre-treatment strategy to convert wheat straw into a fermentable hydrolysate. Aspergillus niger was firstly cultured on wheat straw for production of cellulolytic enzymes and then the wheat straw was hydrolyzed by the enzyme solution into a fermentable hydrolysate. The optimum moisture content and three wheat straw modification methods were explored to improve cellulase production. At a moisture content of 89.5%, 10.2±0.13U/g cellulase activity was obtained using dilute acid modified wheat straw. The addition of yeast extract (0.5% w/v) and minerals significantly improved the cellulase production, to 24.0±1.76U/g. The hydrolysis of the fermented wheat straw using the fungal culture filtrate or commercial cellulase Ctec2 was performed, resulting in 4.34 and 3.13g/L glucose respectively. It indicated that the fungal filtrate harvested from the fungal fermentation of wheat straw contained a more suitable enzyme mixture than the commercial cellulase.
Weak-acid preservatives, such as sorbic acid and acetic acid, are used in many low pH foods to prevent spoilage by fungi. The spoilage yeast Zygosaccharomyces bailii is notorious for its extreme ...resistance to preservatives and ability to grow in excess of legally-permitted concentrations of preservatives. Extreme resistance was confirmed in 38 strains of Z. bailii to several weak-acid preservatives. Using the brewing yeast Saccharomyces cerevisiae as a control, tests showed that Z. bailii was ~3-fold more resistant to a variety of weak-acids but was not more resistant to alcohols, aldehydes, esters, ethers, ketones, or hydrophilic chelating acids. The weak acids were chemically very diverse in structure, making it improbable that the universal resistance was caused by degradation or metabolism. Examination of Z. bailii cell populations showed that extreme resistance to sorbic acid, benzoic acid and acetic acid was limited to a few cells within the population, numbers decreasing with concentration of weak acid to <1 in 1000. Re-inoculation of resistant sub-populations into weak-acid-containing media showed that all cells now possessed extreme resistance. Resistant sub-populations grown in any weak-acid preservative also showed ~100% cross-resistance to other weak-acid preservatives. Tests using 14C-acetic acid showed that weak-acid accumulation was much lower in the resistant sub-populations. Acid accumulation is caused by acid dissociation in the higher pH of the cytoplasm. Tests on intracellular pH (pHi) in the resistant sub-population showed that the pH was much lower, ~ pH5.6, than in the sensitive bulk population. The hypothesis is proposed that extreme resistance to weak-acid preservatives in Z. bailii is due to population heterogeneity, with a small proportion of cells having a lower intracellular pH. This reduces the level of accumulation of any weak acid in the cytoplasm, thus conferring resistance to all weak acids, but not to other inhibitors.
•Z. bailii resistance to weak acids was due to population heterogeneity.•Resistant Z. bailii sub-populations were cross resistant to all other weak acids.•Weak acid accumulation is determined by cell internal pH.•Resistant Z. bailii sub-populations had a lower internal pH, ~0.6 pH units.•Resistant Z. bailii sub-populations absorbed 3-fold less 14C acetic acid.
Genes encoding the key transcription factors (TF) XlnR, ClrA and ClrB were deleted from
Aspergillus niger
and the resulting strains were assessed for growth on glucose and wheat straw, transcription ...of genes encoding glycosyl hydrolases and saccharification activity. Growth of all mutant strains, based in straw on measurement of pH and assay of glucosamine, was impaired in relation to the wild-type (WT) strain although deletion of
clrA
had less effect than deletion of
xlnR
or
clrB
. Release of sugars from wheat straw was also lowered when culture filtrates from TF deletion strains were compared with WT culture filtrates. Transcript levels of
cbhA
,
eglC
and
xynA
were measured in all strains in glucose and wheat straw media in batch culture with and without pH control. Transcript levels from
cbhA
and
eglC
were lowered in all mutant strains compared to WT although the impact of deleting
clrA
was not pronounced with expression of
eglC
and had no effect on
xynA
. The impact on transcription was not related to changes in pH. In addition to impaired growth on wheat straw, the
ΔxlnR
strain was sensitive to oxidative stress and displayed cell wall defects in the glucose condition suggesting additional roles for XlnR. The characterisation of TFs, such as ClrB, provides new areas of improvement for industrial processes for production of second generation biofuels.
A Report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents and the American Heart Association Developed in Collaboration With the American College of Chest ...Physicians; American Thoracic Society, Inc.; and the Pulmonary Hypertension Association Often the topic is the subject of ongoing investigation. ...the reader should view the ECD as the best attempt of the ACCF and the cosponsors to inform and guide clinical practice in areas where rigorous evidence may not be available or the evidence to date is not widely accepted. Some topics covered by ECDs will be addressed subsequently by the ACCF/AHA Practice Guidelines Committee. Because the development of expert consensus documents depends on the knowledge and experience of experts and investigators in the field, many of whom have relationships with industry (RWI), the policy addressing writing committee members' RWI must be realistic, workable, and implemented in a way that protects the integrity of the process while allowing an open and honest exchange of the most up-to-date information. Dr. Javed Butler Content Reviewer--ACCF Heart Failure & Transplant Committee None Boehringer Ingelheim* GlaxoSmithKline* Novartis* None None None No Dr. David E. Lanfear Content Reviewer--ACCF Heart Failure & Transplant Committee * Thoratec None None None None No Dr. Donna F. Petruccelli Content Reviewer--ACCF Heart Failure & Transplant Committee None None None None None No Dr. Louis Bezold Content Reviewer--ACCF Adult Congenital & Pediatric Cardiology Council None None None None None No Dr. Meryl Cohen Content Reviewer--ACCF Adult Congenital & Pediatric Cardiology Council None None None None None No Dr. Jeffrey A. Feinstein Content Reviewer--ACCF Adult Congenital & Pediatric Cardiology Council Eli Lilly United Therapeutics None None iNO Therapeutics Pfizer None No Dr. Charles R. Bridges Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None No Dr. Alice Jacobs Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None No Dr. David J. Moliterno Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents Boston Scientific Schering-Plough None None None * Boston Scientific No Dr. Debabrata Mukherjee Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None No Dr. Richard S. Schofield Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents * Medtronic AtCor Medical Novartis Scios None None None No Dr. James H. Stein Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents Amgen LipoScience Merck Pfizer KOS Pfizer* Takeda* * Wisconsin Alumni Research Foundation AstraZeneca* Bristol-Myers Squibb* LipoScience PreMD Sanofi-Aventis Sonosite * KOS No Ms. Deborah Wesley-Farrington Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None No Appendix 2 Peer Reviewer Relationships With Industry and Other Entities--ACCF/AHA 2009 Expert Consensus Document on Pulmonary Hypertension This table represents the relevant relationships with industry and other entities that were disclosed at the time of peer review.
Osmotolerance or halotolerance are used to describe resistance to sugars and salt, or only salt, respectively. Here, a comprehensive screen of more than 600 different yeast isolates revealed that ...osmosensitive species were equally affected by NaCl and glucose. However, the relative toxicity of salt became increasingly prominent in more osmoresistant species. We confirmed that growth inhibition by glucose in a laboratory strain of
occurred at a lower water activity (A
) than by salt (NaCl), and pre-growth in high levels of glucose or salt gave enhanced cross-resistance to either. Salt toxicity was largely due to osmotic stress but with an additive enhancement due to effects of the relevant cation. Almost all of the yeast isolates from the screen were also noted to exhibit hetero-resistance to both salt and sugar, whereby high concentrations restricted growth to a small minority of cells within the clonal populations. Rare resistant colonies required growth for up to 28 days to become visible. This cell individuality was more marked with salt than sugar, a possible further reflection of the ion toxicity effect. In both cases, heteroresistance in
was strikingly dependent on the
gene product, important for glycerol synthesis. In contrast, a
deletant impaired for trehalose showed altered MIC but no change in heteroresistance. Effects on heteroresistance were evident in chronic (but not acute) salt or glucose stress, particularly relevant to growth on low A
foods. The study reports diverse osmotolerance and halotolerance phenotypes and heteroresistance across an extensive panel of yeast isolates, and indicates that Gpd1-dependent glycerol synthesis is a key determinant enabling growth of rare yeast subpopulations at low A
, brought about by glucose and in particular salt.
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