scholarly journals Coral-associated micro-organisms and their roles in promoting coral health and thwarting diseases

2013 ◽  
Vol 280 (1755) ◽  
pp. 20122328 ◽  
Author(s):  
Cory J. Krediet ◽  
Kim B. Ritchie ◽  
Valerie J. Paul ◽  
Max Teplitski
Keyword(s):  
Cell Signalling ◽  
Taxonomic Diversity ◽  
Microbial Interactions ◽  
Opportunistic Pathogens ◽  
Functional Capabilities ◽  
Evolutionarily Conserved ◽  
Coral Health ◽  
Micro Organisms

Over the last decade, significant advances have been made in characterization of the coral microbiota. Shifts in its composition often correlate with the appearance of signs of diseases and/or bleaching, thus suggesting a link between microbes, coral health and stability of reef ecosystems. The understanding of interactions in coral-associated microbiota is informed by the on-going characterization of other microbiomes, which suggest that metabolic pathways and functional capabilities define the ‘core’ microbiota more accurately than the taxonomic diversity of its members. Consistent with this hypothesis, there does not appear to be a consensus on the specificity in the interactions of corals with microbial commensals, even though recent studies report potentially beneficial functions of the coral-associated bacteria. They cycle sulphur, fix nitrogen, produce antimicrobial compounds, inhibit cell-to-cell signalling and disrupt virulence in opportunistic pathogens. While their beneficial functions have been documented, it is not certain whether or how these microbes are selected by the hosts. Therefore, understanding the role of innate immunity, signal and nutrient exchange in the establishment of coral microbiota and in controlling its functions will probably reveal ancient, evolutionarily conserved mechanisms that dictate the outcomes of host–microbial interactions, and impact the resilience of the host.

scholarly journals Novel Rhamnosyltransferase Involved in Biosynthesis of Serovar 4-Specific Glycopeptidolipid from Mycobacterium avium Complex

2010 ◽  
Vol 192 (21) ◽  
pp. 5700-5708 ◽  
Author(s):  
Yuji Miyamoto ◽  
Tetsu Mukai ◽  
Takashi Naka ◽  
Nagatoshi Fujiwara ◽  
Yumi Maeda ◽  
...  
Keyword(s):  
Mycobacterium Avium ◽  
Protein Gene ◽  
Functional Characterization ◽  
Epidemiological Studies ◽  
Biosynthetic Gene Cluster ◽  
Biosynthetic Gene ◽  
Opportunistic Pathogens ◽  
Fucose Residue

ABSTRACT Glycopeptidolipids (GPLs) are one of the major glycolipid components present on the surface of Mycobacterium avium complex (MAC) that belong to opportunistic pathogens distributed in the natural environment. The serovars of MAC, up to around 30 types, are defined by the variable oligosaccharide portions of the GPLs. Epidemiological studies show that serovar 4 is the most prevalent type, and the prognosis of pulmonary disease caused by serovar 4 is significantly worse than that caused by other serovars. However, little is known about the biosynthesis of serovar 4-specific GPL, particularly the formation of the oligosaccharide portion that determines the properties of serovar 4. To investigate the biosynthesis of serovar 4-specific GPL, we focused on one segment that included functionally unknown genes in the GPL biosynthetic gene cluster of a serovar 4 strain. In this segment, a putative hemolytic protein gene, hlpA, and its downstream gene were found to be responsible for the formation of the 4-O-methyl-rhamnose residue, which is unique to serovar 4-specific GPL. Moreover, functional characterization of the hlpA gene revealed that it encodes a rhamnosyltransferase that transfers a rhamnose residue via 1→4 linkage to a fucose residue of serovar 2-specific GPL, which is a key pathway leading to the synthesis of oligosaccharide of serovar 4-specific GPL. These findings may provide clues to understanding the biological role of serovar 4-specific GPL in MAC pathogenicity and may also provide new insights into glycosyltransferase, which generates structural and functional diversity of GPLs.

Myotubularins, PtdIns5P, and ROS in ABA-mediated stomatal movements in dehydrated Arabidopsis seedlings

2018 ◽  
Vol 45 (2) ◽  
pp. 259 ◽  
Author(s):  
Akanksha Nagpal ◽  
Ammar Hassan ◽  
Ivan Ndamukong ◽  
Zoya Avramova ◽  
František Baluška
Keyword(s):  
Cell Signalling ◽  
Membrane Dynamics ◽  
Dehydration Stress ◽  
Oxygen Species ◽  
Secondary Messenger ◽  
Signalling Molecule ◽  
Ros Accumulation ◽  
Evolutionarily Conserved ◽  
Stomatal Movements

Myotubularins (MTMs) are lipid phosphoinositide 3-phosphate phosphatases and the product of their enzyme activity – phosphoinositide 5-phosphate (PtdIns5P) – functions as a signalling molecule in pathways involved in membrane dynamics and cell signalling. Two Arabidopsis genes, AtMTM1 and AtMTM2, encode enzymatically active phosphatases but although AtMTM1 deficiency results in increased tolerance to dehydration stress and a decrease in cellular PtdIns5P, the role of AtMTM2 is less clear, as it does not contribute to the PtdIns5P pool upon dehydration stress. Here we analysed the involvement of AtMTM1, AtMTM2 and PtdIns5P in the response of Arabidopsis seedlings to dehydration stress/ABA, and found that both AtMTM1 and AtMTM2 were involved but affected oppositely stomata movement and the accumulation of reactive oxygen species (ROS, e.g. H2O2). Acting as a secondary messenger in the ABA-induced ROS production in guard cells, PtdIns5P emerges as an evolutionarily conserved signalling molecule that calibrates cellular ROS under stress. We propose the biological relevance of the counteracting AtMTM1 and AtMTM2 activities is to balance the ABA-induced ROS accumulation and cellular homeostasis under dehydration stress.

scholarly journals Antagonism and synergism in Gardnerella vaginalis strains isolated from women with bacterial vaginosis

2010 ◽  
Vol 59 (8) ◽  
pp. 891-897 ◽  
Author(s):  
G. S. Teixeira ◽  
K. L. K. Soares-Brandão ◽  
K. M. G. R. Branco ◽  
J. L. M. Sampaio ◽  
R. M. D. Nardi ◽  
...  
Keyword(s):  
Bacterial Vaginosis ◽  
Chemical Nature ◽  
Growth Conditions ◽  
Antagonistic Activity ◽  
Gardnerella Vaginalis ◽  
Ecological Role ◽  
Micro Organisms

Antagonistic and synergistic substances are important for interactions between micro-organisms associated with human body surfaces, either in healthy or in diseased conditions. In the present study, such compounds produced by Gardnerella vaginalis strains isolated from women with bacterial vaginosis (BV) were detected in vitro and the antagonistic ones were partially characterized. Among 11 G. vaginalis strains tested, all showed antagonistic activity against at least one of the 22 indicator bacteria assayed. Interestingly, for some of these strains, antagonism reverted to synergism, favouring one of the indicator strains (Peptostreptococcus anaerobius) when the growth medium was changed. Partial characterization of antagonistic substances suggested a bacteriocin-like chemical nature. Depending on growth conditions, G. vaginalis isolated from women with BV produced antagonistic or synergistic compounds for other bacterial components of the vaginal ecosystem. This is the first report to our knowledge of the production of antagonistic and/or synergistic substances by G. vaginalis. This ability may be a pivotal factor in understanding BV and the ecological role of this bacterium in the vaginal environment.

scholarly journals High-Throughput Fluorescence Assay for Small-Molecule Inhibitors of Autophagins/Atg4

2011 ◽  
Vol 16 (2) ◽  
pp. 174-182 ◽  
Author(s):  
Chih-Wen Shu ◽  
Charitha Madiraju ◽  
Dayong Zhai ◽  
Kate Welsh ◽  
Paul Diaz ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Caspase 3 ◽  
Bioactive Molecules ◽  
Dependent Manner ◽  
Chemical Libraries ◽  
Evolutionarily Conserved ◽  
Identification And Characterization

Autophagy is an evolutionarily conserved process for catabolizing damaged proteins and organelles in a lysosome-dependent manner. Dysregulation of autophagy may cause various diseases, such as cancer and neurodegeneration. However, the relevance of autophagy to diseases remains controversial because of the limited availability of chemical modulators. Herein, the authors developed a fluorescence-based assay for measuring activity of the autophagy protease, autophagin-1(Atg4B). The assay employs a novel reporter substrate of Atg4B composed of a natural substrate (LC3B) fused to an assayable enzyme (PLA2) that becomes active upon cleavage by this cysteine protease. A high-throughput screening (HTS) assay was validated with excellent Z′ factor (>0.7), remaining robust for more than 5 h and suitable for screening of large chemical libraries. The HTS assay was validated by performing pilot screens with 2 small collections of compounds enriched in bioactive molecules ( n = 1280 for Lopac™ and 2000 for Spectrum™ library), yielding confirmed hit rates of 0.23% and 0.70%, respectively. As counterscreens, PLA2 and caspase-3 assays were employed to eliminate nonspecific inhibitors. In conclusion, the LC3B-PLA2 reporter assay provides a platform for compound library screening for identification and characterization of Atg4B-specific inhibitors that may be useful as tools for interrogating the role of autophagy in disease models.

scholarly journals Biosynthesis of mycobacterial methylmannose polysaccharides requires a unique 1-O-methyltransferase specific for 3-O-methylated mannosides

2019 ◽  
Vol 116 (3) ◽  
pp. 835-844 ◽  
Author(s):  
Jorge Ripoll-Rozada ◽  
Mafalda Costa ◽  
José A. Manso ◽  
Ana Maranha ◽  
Vanessa Miranda ◽  
...  
Keyword(s):  
Cell Envelope ◽  
3D Structure ◽  
Host Immune System ◽  
Opportunistic Pathogens ◽  
Docking Simulations ◽  
Optimal Function ◽  
Wide Group ◽  
Identification And Characterization

Mycobacteria are a wide group of organisms that includes strict pathogens, such as Mycobacterium tuberculosis, as well as environmental species known as nontuberculous mycobacteria (NTM), some of which—namely Mycobacterium avium—are important opportunistic pathogens. In addition to a distinctive cell envelope mediating critical interactions with the host immune system and largely responsible for their formidable resistance to antimicrobials, mycobacteria synthesize rare intracellular polymethylated polysaccharides implicated in the modulation of fatty acid metabolism, thus critical players in cell envelope assembly. These are the 6-O-methylglucose lipopolysaccharides (MGLP) ubiquitously detected across the Mycobacterium genus, and the 3-O-methylmannose polysaccharides (MMP) identified only in NTM. The polymethylated nature of these polysaccharides renders the intervening methyltransferases essential for their optimal function. Although the knowledge of MGLP biogenesis is greater than that of MMP biosynthesis, the methyltransferases of both pathways remain uncharacterized. Here, we report the identification and characterization of a unique S-adenosyl-l-methionine–dependent sugar 1-O-methyltransferase (MeT1) from Mycobacterium hassiacum that specifically blocks the 1-OH position of 3,3′-di-O-methyl-4α-mannobiose, a probable early precursor of MMP, which we chemically synthesized. The high-resolution 3D structure of MeT1 in complex with its exhausted cofactor, S-adenosyl-l-homocysteine, together with mutagenesis studies and molecular docking simulations, unveiled the enzyme’s reaction mechanism. The functional and structural properties of this unique sugar methyltransferase further our knowledge of MMP biosynthesis and provide important tools to dissect the role of MMP in NTM physiology and resilience.

scholarly journals Redox-active secondary metabolites act as interspecies modulators of antibiotic resilience

2021 ◽  
Author(s):  
Lucas A. Meirelles ◽  
Dianne K. Newman
Keyword(s):  
Secondary Metabolites ◽  
Burkholderia Cepacia ◽  
Defense Responses ◽  
Microbial Interactions ◽  
Opportunistic Pathogens ◽  
Burkholderia Gladioli ◽  
Redox Active ◽  
Wide Range ◽  
Genes Encoding

ABSTRACTBacterial opportunistic pathogens make a wide range of secondary metabolites both in the natural environment and when causing infections, yet how these molecules mediate microbial interactions and their consequences for antibiotic treatment are still poorly understood. Here, we explore the role of two redox-active secondary metabolites, pyocyanin and toxoflavin, as interspecies modulators of antibiotic resilience. We find that these molecules dramatically change susceptibility levels of diverse bacteria to clinical antibiotics. Pyocyanin is made by Pseudomonas aeruginosa, while toxoflavin is made by Burkholderia gladioli, organisms that infect cystic fibrosis and other immunocompromised patients. Both molecules alter the susceptibility profile of pathogenic species within the “Burkholderia cepacia complex” to different antibiotics, either antagonizing or potentiating their effects, depending on the drug’s class. Defense responses regulated by the redox-sensitive transcription factor SoxR potentiate the antagonistic effects these metabolites have against fluoroquinolones, and the presence of genes encoding SoxR and the efflux systems it regulates can be used to predict how these metabolites will affect antibiotic susceptibility of different bacteria. Finally, we demonstrate that inclusion of secondary metabolites in standard protocols used to assess antibiotic resistance can dramatically alter the results, motivating the development of new tests for more accurate clinical assessment.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

The role of intracanal medicaments in inhibition of bacteria isolated from root canals of infected primary molars

2019 ◽  
Vol 14 (1) ◽  
pp. 92
Author(s):  
Dr. Maha Abdul- Kareem Mahmood ◽  
Dr. Huda Elias Ali ◽  
Dr. Haraa Khairi Abdul-Kadher
Keyword(s):  
Antimicrobial Activity ◽  
Streptococcus Mutans ◽  
Normal Saline ◽  
Root Canal ◽  
Primary Teeth ◽  
Primary Molars ◽  
Root Canals ◽  
Etiologic Agents ◽  
Micro Organisms

Microbes are considered as the primary etiologic agents in endodontic diseases.Disinfection of the root canal is obtained by the combined effect of biomechanicalpreparation, irrigation and intra canal medicament. The aim of the present study wasto assess the antimicrobial activity of intracanal medicaments (formocresol andEndosepton) against two micro organisms (Streptococcus mutans and staphylococcusaureus) isolated from 15 necrotic pulps of primary molars indicated for pulpectomyprocedure. The samples were cultured, and purified using microbiological evaluation.Broth dilution test was performed in our study by preparing test tubes containing10 ml of BHI broth (pH. 7) which then inoculated with strains of the tested bacteriaand incubated at 37 C° for 24 h. After over night incubaction, ten fold dilution weremade in test tubes containing 9 ml of normal saline by adding 1 ml of the inoculum tothe first tube . Then from dilution 10-1 , 0.1 ml of cell suspension was added to 9.9 mlof formocresol and endosepton, then 0.1 ml was taken and spread on duplicates ofBHI agar plates at different intervals and incubated aerobically for 24 h. at 37 C°.Colonies on the plates were counted after incubation and CFU/mL (colony formingunit) was calculated. Our results indicating that there were no significant differencesbetween the intracanal medicaments, but there were high significant differencesbetween the intervals time of the study. We concluded that both materials had greatantibacterial effect against the pathogens commonly isolated from necrotic pulpaltissue of primary teeth.

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