Effects of white phosphorus on the cellular morphology and protein profile of <i>Aspergillus niger</i>

Microorganisms are known for their ability to adapt easily to any environment, forming specific ecosystems capable of surviving in harsh media. White phosphorus is one of the most dangerous and toxic pollutants, whose widespread use for various industrial and military purposes creates conditions for environmental pollution. It has previously been shown that some microbial cultures can adapt to the presence of white phosphorus in the environment, oxidizing it to a phosphate and then using it as a source of biogenic macronutrients. In prior studies, we have demonstrated the possibility of white phosphorus biodegradation by the fungal strains of Aspergillus niger. However, it is important to study the resistance of this species to such a toxic substance as white phosphorus. There may be several probable mechanisms, including the following: the cell wall of the fungus is a barrier to the penetration of white phosphorus into the cell, in which case an increase in the thickness of the cell wall should be observed in response to the impact of the toxicant; a mechanism associated with the expression of stress genes and the production of proteins involved in the disposal of toxins, including white phosphorus. In addition, white phosphorus causes an overall activation of metabolism, accompanied by an increase in the number and size of mitochondria in the cells. It is likely that the active forms of oxygen produced by mitochondria are involved in the detoxification of both white phosphorus and its transformation products. Microscopic and proteomic studies have confirmed the presence of the above-mentioned resistance mechanisms.

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The Cell Envelope Stress Response of Bacillus subtilis towards Laspartomycin C

Antibiotics ◽

10.3390/antibiotics9110729 ◽

2020 ◽

Vol 9 (11) ◽

pp. 729

Author(s):

Angelika Diehl ◽

Thomas M. Wood ◽

Susanne Gebhard ◽

Nathaniel I. Martin ◽

Georg Fritz

Keyword(s):

Cell Wall ◽

Bacillus Subtilis ◽

Stress Response ◽

Cell Envelope ◽

Resistance Mechanisms ◽

Detailed Knowledge ◽

Knock Out ◽

Lipid Ii ◽

Envelope Stress ◽

The Impact

Cell wall antibiotics are important tools in our fight against Gram-positive pathogens, but many strains become increasingly resistant against existing drugs. Laspartomycin C is a novel antibiotic that targets undecaprenyl phosphate (UP), a key intermediate in the lipid II cycle of cell wall biosynthesis. While laspartomycin C has been thoroughly examined biochemically, detailed knowledge about potential resistance mechanisms in bacteria is lacking. Here, we use reporter strains to monitor the activity of central resistance modules in the Bacillus subtilis cell envelope stress response network during laspartomycin C attack and determine the impact on the resistance of these modules using knock-out strains. In contrast to the closely related UP-binding antibiotic friulimicin B, which only activates ECF σ factor-controlled stress response modules, we find that laspartomycin C additionally triggers activation of stress response systems reacting to membrane perturbation and blockage of other lipid II cycle intermediates. Interestingly, none of the studied resistance genes conferred any kind of protection against laspartomycin C. While this appears promising for therapeutic use of laspartomycin C, it raises concerns that existing cell envelope stress response networks may already be poised for spontaneous development of resistance during prolonged or repeated exposure to this new antibiotic.

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Impact of AmpC Derepression on Fitness and Virulence: the Mechanism or the Pathway?

mBio ◽

10.1128/mbio.01783-16 ◽

2016 ◽

Vol 7 (5) ◽

Cited By ~ 22

Author(s):

Marcelo Pérez-Gallego ◽

Gabriel Torrens ◽

Jane Castillo-Vera ◽

Bartolomé Moya ◽

Laura Zamorano ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Cell Wall ◽

Antibiotic Resistance ◽

Resistance Mechanism ◽

Resistance Mechanisms ◽

Major Effect ◽

Major Step ◽

Alternative Pathways ◽

The Impact ◽

Cell Wall Recycling

ABSTRACTUnderstanding the interplay between antibiotic resistance and bacterial fitness and virulence is essential to guide individual treatments and improve global antibiotic policies. A paradigmatic example of a resistance mechanism is the intrinsic inducible chromosomal β-lactamase AmpC from multiple Gram-negative bacteria, includingPseudomonas aeruginosa, a major nosocomial pathogen. The regulation ofampCexpression is intimately linked to peptidoglycan recycling, and AmpC-mediated β-lactam resistance is frequently mediated by inactivating mutations inampD, encoding anN-acetyl-anhydromuramyl-l-alanine amidase, affecting the levels ofampC-activating muropeptides. Here we dissect the impact of the multiple pathways causing AmpC hyperproduction onP. aeruginosafitness and virulence. Through a detailed analysis, we demonstrate that the lack of all threeP. aeruginosaAmpD amidases causes a dramatic effect in fitness and pathogenicity, severely compromising growth rates, motility, and cytotoxicity; the latter effect is likely achieved by repressing key virulence factors, such as protease LasA, phospholipase C, or type III secretion system components. We also show thatampCoverexpression is required but not sufficient to confer the growth-motility-cytotoxicity impaired phenotype and that alternative pathways leading to similar levels ofampChyperexpression and resistance, such as those involving PBP4, had no fitness-virulence cost. Further analysis indicated that fitness-virulence impairment is caused by overexpressingampCin the absence of cell wall recycling, as reproduced by expressingampCfrom a plasmid in an AmpG (muropeptide permease)-deficient background. Thus, our findings represent a major step in the understanding of β-lactam resistance biology and its interplay with fitness and pathogenesis.IMPORTANCEUnderstanding the impact of antibiotic resistance mechanisms on bacterial pathogenesis is critical to curb the spread of antibiotic resistance. A particularly noteworthy antibiotic resistance mechanism is the β-lactamase AmpC, produced byPseudomonas aeruginosa, a major pathogen causing hospital-acquired infections. The regulation of AmpC is linked to the cell wall recycling pathways, and frequently, resistance to β-lactams is caused by mutation of several of the components of the cell wall recycling pathways such as AmpD. Here we dissect the impact of the pathways for AmpC hyperproduction on virulence, showing that the lack of all threeP. aeruginosaAmpD amidases causes a major effect in fitness and pathogenicity, compromising growth, motility, and cytotoxicity. Further analysis indicated that fitness-virulence impairment is specifically caused by the hyperproduction of AmpC in the absence of cell wall recycling. Our work provides valuable information for delineating future strategies for combatingP. aeruginosainfections by simultaneously targeting virulence and antibiotic resistance.

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Potent Chitin Synthase Inhibitors from Plants

Current Bioactive Compounds ◽

10.2174/1573407213666180719145831 ◽

2020 ◽

Vol 16 (1) ◽

pp. 58-63

Author(s):

Amrutha Vijayakumar ◽

Ajith Madhavan ◽

Chinchu Bose ◽

Pandurangan Nanjan ◽

Sindhu S. Kokkal ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Caenorhabditis Elegans ◽

Aspergillus Niger ◽

Small Molecules ◽

Tip Growth ◽

Chitin Synthase ◽

Chitin Synthesis ◽

Hyphal Tip Growth ◽

Hyphal Tip

Background: Chitin is the main component of fungal, protozoan and helminth cell wall. They help to maintain the structural and functional characteristics of these organisms. The chitin wall is dynamic and is repaired, rearranged and synthesized as the cells develop. Active synthesis can be noticed during cytokinesis, laying of primary septum, maintenance of lateral cell wall integrity and hyphal tip growth. Chitin synthesis involves coordinated action of two enzymes namely, chitin synthase (that lays new cell wall) and chitinase (that removes the older ones). Since chitin synthase is conserved in different eukaryotic microorganisms that can be a ‘soft target’ for inhibition with small molecules. When chitin synthase is inhibited, it leads to the loss of viability of cells owing to the self- disruption of the cell wall by existing chitinase. Methods: In the described study, small molecules from plant sources were screened for their ability to interfere with hyphal tip growth, by employing Hyphal Tip Burst assay (HTB). Aspergillus niger was used as the model organism. The specific role of these small molecules in interfering with chitin synthesis was established with an in-vitro method. The enzyme required was isolated from Aspergillus niger and its activity was deduced through a novel method involving non-radioactively labelled substrate. The activity of the potential lead molecules were also checked against Candida albicans and Caenorhabditis elegans. The latter was adopted as a surrogate for the pathogenic helminths as it shares similarity with regard to cell wall structure and biochemistry. Moreover, it is widely studied and the methodologies are well established. Results: Out of the 11 compounds and extracts screened, 8 were found to be prospective. They were also found to be effective against Candida albicans and Caenorhabditis elegans. Conclusion: Purified Methyl Ethyl Ketone (MEK) Fraction1 (F1) of Coconut (Cocos nucifera) Shell Extract (COSE) was found to be more effective against Candida albicans with an IC50 value of 3.04 μg/mL and on L4 stage of Caenorhabditis elegans with an IC50 of 77.8 μg/mL.

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Association of Genetic Polymorphisms in Oxidative Stress and Inflammation Pathways with Glaucoma Risk and Phenotype

Journal of Clinical Medicine ◽

10.3390/jcm10051148 ◽

2021 ◽

Vol 10 (5) ◽

pp. 1148

Author(s):

Makedonka Atanasovska Velkovska ◽

Katja Goričar ◽

Tanja Blagus ◽

Vita Dolžan ◽

Barbara Cvenkel

Keyword(s):

Oxidative Stress ◽

Ocular Hypertension ◽

Gene Deletion ◽

Open Angle Glaucoma ◽

Protective Role ◽

Control Group ◽

Nucleotide Polymorphisms ◽

Gstm1 Gene ◽

Stress Genes ◽

The Impact

Oxidative stress and neuroinflammation are involved in the pathogenesis and progression of glaucoma. Our aim was to evaluate the impact of selected single-nucleotide polymorphisms in inflammation and oxidative stress genes on the risk of glaucoma, the patients’ clinical characteristics and the glaucoma phenotype. In total, 307 patients with primary open-angle glaucoma or ocular hypertension were enrolled. The control group included 339 healthy Slovenian blood donors. DNA was isolated from peripheral blood. Genotyping was performed for SOD2 rs4880, CAT rs1001179, GPX1 rs1050450, GSTP1 rs1695, GSTM1 gene deletion, GSTT1 gene deletion, IL1B rs1143623, IL1B rs16944, IL6 rs1800795 and TNF rs1800629. We found a nominally significant association of GSTM1 gene deletion with decreased risk of ocular hypertension and a protective role of IL1B rs16944 and IL6 rs1800629 in the risk of glaucoma. The CT and TT genotypes of GPX1 rs1050450 were significantly associated with advanced disease, lower intraocular pressure and a larger vertical cup–disc ratio. In conclusion, genetic variability in IL1B and IL6 may be associated with glaucoma risk, while GPX and TNF may be associated with the glaucoma phenotype. In the future, improved knowledge of these pathways has the potential for new strategies and personalised treatment of glaucoma.

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Evaluating polymer interplay after hot water pretreatment to investigate maize stem internode recalcitrance

Biotechnology for Biofuels ◽

10.1186/s13068-021-02015-8 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Amandine Leroy ◽

Xavier Falourd ◽

Loïc Foucat ◽

Valérie Méchin ◽

Fabienne Guillon ◽

...

Keyword(s):

Cell Wall ◽

Negative Impact ◽

Lignin Content ◽

Structural Features ◽

Hot Water ◽

Condensed State ◽

Structural Factors ◽

Water Pretreatment ◽

Hot Water Pretreatment ◽

The Impact

Abstract Background Biomass recalcitrance is governed by various molecular and structural factors but the interplay between these multiscale factors remains unclear. In this study, hot water pretreatment (HWP) was applied to maize stem internodes to highlight the impact of the ultrastructure of the polymers and their interactions on the accessibility and recalcitrance of the lignocellulosic biomass. The impact of HWP was analysed at different scales, from the polymer ultrastructure or water mobility to the cell wall organisation by combining complementary compositional, spectral and NMR analyses. Results HWP increased the kinetics and yield of saccharification. Chemical characterisation showed that HWP altered cell wall composition with a loss of hemicelluloses (up to 45% in the 40-min HWP) and of ferulic acid cross-linking associated with lignin enrichment. The lignin structure was also altered (up to 35% reduction in β–O–4 bonds), associated with slight depolymerisation/repolymerisation depending on the length of treatment. The increase in $${T}_{1\rho }^{H}$$ T 1 ρ H , $${T}_{HH}$$ T HH and specific surface area (SSA) showed that the cellulose environment was looser after pretreatment. These changes were linked to the increased accessibility of more constrained water to the cellulose in the 5–15 nm pore size range. Conclusion The loss of hemicelluloses and changes in polymer structural features caused by HWP led to reorganisation of the lignocellulose matrix. These modifications increased the SSA and redistributed the water thereby increasing the accessibility of cellulases and enhancing hydrolysis. Interestingly, lignin content did not have a negative impact on enzymatic hydrolysis but a higher lignin condensed state appeared to promote saccharification. The environment and organisation of lignin is thus more important than its concentration in explaining cellulose accessibility. Elucidating the interactions between polymers is the key to understanding LB recalcitrance and to identifying the best severity conditions to optimise HWP in sustainable biorefineries.

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Sorting out the Superbugs: Potential of Sortase A Inhibitors among Other Antimicrobial Strategies to Tackle the Problem of Antibiotic Resistance

Antibiotics ◽

10.3390/antibiotics10020164 ◽

2021 ◽

Vol 10 (2) ◽

pp. 164 ◽

Cited By ~ 1

Author(s):

Nikita Zrelovs ◽

Viktorija Kurbatska ◽

Zhanna Rudevica ◽

Ainars Leonchiks ◽

Davids Fridmanis

Keyword(s):

Cell Wall ◽

Antibiotic Resistance ◽

Pathogenic Bacteria ◽

Resistance Mechanisms ◽

Surface Proteins ◽

Sortase A ◽

Inhibitory Compounds ◽

Alternative Means ◽

Alternative Approaches ◽

Conventional Antibiotics

Rapid spread of antibiotic resistance throughout the kingdom bacteria is inevitably bringing humanity towards the “post-antibiotic” era. The emergence of so-called “superbugs”—pathogen strains that develop resistance to multiple conventional antibiotics—is urging researchers around the globe to work on the development or perfecting of alternative means of tackling the pathogenic bacteria infections. Although various conceptually different approaches are being considered, each comes with its advantages and drawbacks. While drug-resistant pathogens are undoubtedly represented by both Gram(+) and Gram(−) bacteria, possible target spectrum across the proposed alternative approaches of tackling them is variable. Numerous anti-virulence strategies aimed at reducing the pathogenicity of target bacteria rather than eliminating them are being considered among such alternative approaches. Sortase A (SrtA) is a membrane-associated cysteine protease that catalyzes a cell wall sorting reaction by which surface proteins, including virulence factors, are anchored to the bacterial cell wall of Gram(+) bacteria. Although SrtA inhibition seems perspective among the Gram-positive pathogen-targeted antivirulence strategies, it still remains less popular than other alternatives. A decrease in virulence due to inactivation of SrtA activity has been extensively studied in Staphylococcus aureus, but it has also been demonstrated in other Gram(+) species. In this manuscript, results of past studies on the discovery of novel SrtA inhibitory compounds and evaluation of their potency were summarized and commented on. Here, we discussed the rationale behind the inhibition of SrtA, raised some concerns on the comparability of the results from different studies, and touched upon the possible resistance mechanisms as a response to implementation of such therapy in practice. The goal of this article is to encourage further studies of SrtA inhibitory compounds.

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The Arabidopsis Root Tip (Phospho)Proteomes at Growth-Promoting versus Growth-Repressing Conditions Reveal Novel Root Growth Regulators

Cells ◽

10.3390/cells10071665 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1665

Author(s):

Natalia Nikonorova ◽

Evan Murphy ◽

Cassio Flavio Fonseca de Lima ◽

Shanshuo Zhu ◽

Brigitte van de Cotte ◽

...

Keyword(s):

Cell Wall ◽

Root Growth ◽

Growth Regulators ◽

Growth Regulation ◽

Phosphorylation Site ◽

Primary Root ◽

Root Tip ◽

Arabidopsis Root ◽

Growth Promoting ◽

The Impact

Auxin plays a dual role in growth regulation and, depending on the tissue and concentration of the hormone, it can either promote or inhibit division and expansion processes in plants. Recent studies have revealed that, beyond transcriptional reprogramming, alternative auxin-controlled mechanisms regulate root growth. Here, we explored the impact of different concentrations of the synthetic auxin NAA that establish growth-promoting and -repressing conditions on the root tip proteome and phosphoproteome, generating a unique resource. From the phosphoproteome data, we pinpointed (novel) growth regulators, such as the RALF34-THE1 module. Our results, together with previously published studies, suggest that auxin, H+-ATPases, cell wall modifications and cell wall sensing receptor-like kinases are tightly embedded in a pathway regulating cell elongation. Furthermore, our study assigned a novel role to MKK2 as a regulator of primary root growth and a (potential) regulator of auxin biosynthesis and signalling, and suggests the importance of the MKK2 Thr31 phosphorylation site for growth regulation in the Arabidopsis root tip.

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The Aspergillus niger MADS-box transcription factor RlmA is required for cell wall reinforcement in response to cell wall stress

Molecular Microbiology ◽

10.1111/j.1365-2958.2005.04827.x ◽

2005 ◽

Vol 58 (1) ◽

pp. 305-319 ◽

Cited By ~ 59

Author(s):

Robbert A. Damveld ◽

Mark Arentshorst ◽

Angelique Franken ◽

Patricia A. VanKuyk ◽

Frans M. Klis ◽

...

Keyword(s):

Cell Wall ◽

Transcription Factor ◽

Aspergillus Niger ◽

Wall Stress ◽

Mads Box ◽

Cell Wall Stress ◽

Cell Wall Reinforcement

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MicroRNA-Regulated Signaling Pathways: Potential Biomarkers for Pancreatic Ductal Adenocarcinoma

Stresses ◽

10.3390/stresses1010004 ◽

2021 ◽

Vol 1 (1) ◽

pp. 30-47

Author(s):

Maria Mortoglou ◽

David Wallace ◽

Aleksandra Buha Buha Djordjevic ◽

Vladimir Djordjevic ◽

E. Damla Arisan ◽

...

Keyword(s):

Pancreatic Ductal Adenocarcinoma ◽

Metabolic Stress ◽

Resistance Mechanisms ◽

Current Data ◽

Cellular Damage ◽

Ductal Adenocarcinoma ◽

Aberrant Expression ◽

Metabolic Alterations ◽

Limited Effectiveness ◽

The Impact

Pancreatic ductal adenocarcinoma (PDAC) is the most aggressive and invasive type of pancreatic cancer (PCa) and is expected to be the second most common cause of cancer-associated deaths. The high mortality rate is due to the asymptomatic progression of the clinical features until the advanced stages of the disease and the limited effectiveness of the current therapeutics. Aberrant expression of several microRNAs (miRs/miRNAs) has been related to PDAC progression and thus they could be potential early diagnostic, prognostic, and/or therapeutic predictors for PDAC. miRs are small (18 to 24 nucleotides long) non-coding RNAs, which regulate the expression of key genes by targeting their 3′-untranslated mRNA region. Increased evidence has also suggested that the chemoresistance of PDAC cells is associated with metabolic alterations. Metabolic stress and the dysfunctionality of systems to compensate for the altered metabolic status of PDAC cells is the foundation for cellular damage. Current data have implicated multiple systems as hallmarks of PDAC development, such as glutamine redox imbalance, oxidative stress, and mitochondrial dysfunction. Hence, both the aberrant expression of miRs and dysregulation in metabolism can have unfavorable effects in several biological processes, such as apoptosis, cell proliferation, growth, survival, stress response, angiogenesis, chemoresistance, invasion, and migration. Therefore, due to these dismal statistics, it is crucial to develop beneficial therapeutic strategies based on an improved understanding of the biology of both miRs and metabolic mediators. This review focuses on miR-mediated pathways and therapeutic resistance mechanisms in PDAC and evaluates the impact of metabolic alterations in the progression of PDAC.

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