scholarly journals NUCLEAR MUTATION INCREASES STREPTOMYCIN AND SPECTINOMYCIN SENSITIVITY IN CHLAMYDOMONAS

Genetics ◽  
1978 ◽  
Vol 88 (4) ◽  
pp. 643-650
Author(s):  
Robert W Lee ◽  
Jan A Sapp
Keyword(s):  
Large Subunit ◽  
Small Subunit ◽  
Wild Type ◽  
Resistance Mutations ◽  
Erythromycin Resistance ◽  
Spectinomycin Resistance ◽  
Nuclear Mutation ◽  
Resistant Strains ◽  
Nuclear Locus ◽  
Type Strains

ABSTRACT A spontaneously arising nuclear mutation, ss-1, has been identified in Chlamydomonas reinhardtii that decreases both streptomycin and spectinomycin resistance levels about 10-fold after its introduction into all wild-type, streptomycin-resistant and spectinomycin-resistant strains examined. The mutations for resistance map to nuclear and uniparentally inherited (chloroplast) loci. In contrast, no modification of erythromycin resistance was detected after introducing ss-1 into wild-type strains or into strains carrying nuclear or uniparentally inherited erythromycin-resistance mutations. We suggest that ss-1 affects the small subunit of the chloroplast ribosome because others have shown that streptomycin and spectinomycin resistance in C. reinhardtii are associated with this subunit, whereas erythromycin resistance is associated with the large subunit. ss-1 shows no linkage with the nuclear locus for streptomycin resistance.

scholarly journals Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

2012 ◽  
Vol 56 (8) ◽  
pp. 4146-4153 ◽  
Author(s):  
Zaid Al-Nakeeb ◽  
Ajay Sudan ◽  
Adam R. Jeans ◽  
Lea Gregson ◽  
Joanne Goodwin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Therapeutic Strategies ◽  
Wild Type ◽  
Content Type ◽  
Exposure Response ◽  
Prevention And Treatment ◽  
Resistant Infection ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

scholarly journals Mutations Conferring Aminoglycoside and Spectinomycin Resistance in Borrelia burgdorferi

2006 ◽  
Vol 50 (2) ◽  
pp. 445-452 ◽  
Author(s):  
Daniel Criswell ◽  
Virginia L. Tobiason ◽  
J. Stephen Lodmell ◽  
D. Scott Samuels
Keyword(s):  
16S Rrna ◽  
Borrelia Burgdorferi ◽  
Type Strain ◽  
Wild Type Strain ◽  
Small Subunit ◽  
Wild Type ◽  
Spectinomycin Resistance ◽  
E Coli ◽  
Resistant Mutants

ABSTRACT We have isolated and characterized in vitro mutants of the Lyme disease agent Borrelia burgdorferi that are resistant to spectinomycin, kanamycin, gentamicin, or streptomycin, antibiotics that target the small subunit of the ribosome. 16S rRNA mutations A1185G and C1186U, homologous to Escherichia coli nucleotides A1191 and C1192, conferred >2,200-fold and 1,300-fold resistance to spectinomycin, respectively. A 16S rRNA A1402G mutation, homologous to E. coli A1408, conferred >90-fold resistance to kanamycin and >240-fold resistance to gentamicin. Two mutations were identified in the gene for ribosomal protein S12, at a site homologous to E. coli residue Lys-87, in mutants selected in streptomycin. Substitutions at codon 88, K88R and K88E, conferred 7-fold resistance and 10-fold resistance, respectively, to streptomycin on B. burgdorferi. The 16S rRNA A1185G and C1186U mutations, associated with spectinomycin resistance, appeared in a population of B. burgdorferi parental strain B31 at a high frequency of 6 × 10−6. These spectinomycin-resistant mutants successfully competed with the wild-type strain during 100 generations of coculture in vitro. The aminoglycoside-resistant mutants appeared at a frequency of 3 × 10−9 to 1 ×10−7 in a population and were unable to compete with wild-type strain B31 after 100 generations. This is the first description of mutations in the B. burgdorferi ribosome that confer resistance to antibiotics. These results have implications for the evolution of antibiotic resistance, because the 16S rRNA mutations conferring spectinomycin resistance have no significant fitness cost in vitro, and for the development of new selectable markers.

Modulation of procaspase-7 self-activation by PEST amino acid residues of the N-terminal prodomain and intersubunit linker

2017 ◽  
Vol 95 (6) ◽  
pp. 634-643
Author(s):  
Juliano Alves ◽  
Miguel Garay-Malpartida ◽  
João M. Occhiucci ◽  
José E. Belizário
Keyword(s):  
Amino Acid ◽  
Large Subunit ◽  
Small Subunit ◽  
Cleavage Sites ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Caspase 7 ◽  
Caspase Family ◽  
The Impact

Procaspase-7 zymogen polypeptide is composed of a short prodomain, a large subunit (p20), and a small subunit (p10) connected to an intersubunit linker. Caspase-7 is activated by an initiator caspase-8 and -9, or by autocatalysis after specific cleavage at IQAD198↓S located at the intersubunit linker. Previously, we identified that PEST regions made of amino acid residues Pro (P), Glu (E), Asp (D), Ser (S), Thr (T), Asn (N), and Gln (Q) are conserved flanking amino acid residues in the cleavage sites within a prodomain and intersubunit linker of all caspase family members. Here we tested the impact of alanine substitution of PEST amino acid residues on procaspase-7 proteolytic self-activation directly in Escherichia coli. The p20 and p10 subunit cleavage were significantly delayed in double caspase-7 mutants in the prodomain (N18A/P26A) and intersubunit linker (S199A/P201A), compared with the wild-type caspase-7. The S199A/P201A mutants effectively inhibited the p10 small subunit cleavage. However, the mutations did not change the kinetic parameters (kcat/KM) and optimal tetrapeptide specificity (DEVD) of the purified mutant enzymes. The results suggest a role of PEST-amino acid residues in the molecular mechanism for prodomain and intersubunit cleavage and caspase-7 self-activation.

scholarly journals Infection Components of Wild-Type and Mutant Strains of Colletotrichum gloeosporioides f. sp. aeschynomene on Northern Jointvetch

Plant Disease ◽  
1997 ◽  
Vol 81 (4) ◽  
pp. 404-409 ◽  
Author(s):  
Y. Luo ◽  
D. O. TeBeest
Keyword(s):  
Fungal Pathogens ◽  
Wild Type Strain ◽  
Colletotrichum Gloeosporioides ◽  
Wild Type ◽  
Biological Control Of Weeds ◽  
Lesion Number ◽  
Mutant Strains ◽  
Controlled Environments ◽  
Resistant Strains ◽  
Type Strains

Colletotrichum gloeosporioides f. sp. aeschynomene causes an anthracnose of northern jointvetch, Aeschynomene virginica. Infection components, including lesion number, latent period, lesion expansion rate, and sporulation, were measured in experiments conducted in controlled environments. Two wild-type strains (3-1-3 and CLA 5A), four benomyl-resistant strains (B13, B15, B18 and B21), and four nitrate nonutilizing mutant strains (Nit A, Nit R, Nit L, and Nit T) of the pathogen were tested. Nitrate nonutilizing strains caused significantly fewer lesions on northern jointvetch than did wild-type and benomyl-resistant strains. Latent periods were significantly shorter for the wild-type strain CLA 5A than for most other strains. Lesion expansion rates of all benomyl-resistant strains were significantly slower than those of the wild- type strains. Large variations in sporulation were observed for most strains, and no differences in sporulation were found between wild-type and mutant strains. The usefulness of infection component analysis for the identification of competitiveness of strains of fungal pathogens for biological control of weeds is discussed.

scholarly journals SEARCH FOR NEW ANTILEISHMANIAL CHEMOTHERAPEUTICS

2018 ◽  
Vol 10 (1) ◽  
pp. 46
Author(s):  
Nabanita Kar ◽  
Santanu Ghosh ◽  
Leena Kumari ◽  
Shreyasi Chakraborty ◽  
Tanmoy Bera
Keyword(s):  
Betulinic Acid ◽  
Leishmania Donovani ◽  
Antileishmanial Activity ◽  
Gas Chromatography Mass Spectrometry ◽  
Drug Resistant ◽  
Wild Type ◽  
Leaf Oil ◽  
Resistant Strains ◽  
Type Strains

Objective: The objective of this work was to screen a number of compounds for their antileishmanial efficacy and cytotoxicity profiling.Methods: Curry leaf oil, cypress oil and spikenard oil were identified by gas chromatography-mass spectrometry (GC/MS) analysis. Betulinic acid, spikenard oil, cypress oil and curry leaf oil were evaluated for their in vitro antileishmanial activity against Leishmania donovani AG83 wild-type, sodium stibogluconate resistant (SSG-resistant), paromomycin (PMM-resistant) and GE1 field type strains on axenic and cellular amastigote model and compared the results with standard drugs used to treat leishmaniasis.Results: Betulinic acid showed strong antileishmanial activity against wild-type (SI= 192.8), SSG-resistant (SI= 19.3) and GE1 strains (SI= 100), whereas cypress oil has produced highest antileishmanial activity against PMM-resistant strains (SI= 15.09) among all the tested drugs. The data obtained also revealed that cypress oil had the maximum CC50 value of 452.9 μl among all standard and tested drugs.Conclusion: All tested drugs had antileishmanial property but among them, betulinic acid possess strong antileishmanial activity in case of both wild-type and drug-resistant leishmaniasis.

scholarly journals Activity of a Novel 1,3-Beta-D-Glucan Synthase Inhibitor, Ibrexafungerp (Formerly SCY-078), against Candida glabrata

2019 ◽  
Vol 63 (12) ◽  
Author(s):  
M. Ghannoum ◽  
L. Long ◽  
N. Isham ◽  
C. Hager ◽  
R. Wilson ◽  
...  
Keyword(s):  
Candida Glabrata ◽  
Wild Type ◽  
Glucan Synthase ◽  
Content Type ◽  
Clinical Strains ◽  
Resistant Strains ◽  
Oral Availability ◽  
Synthase Inhibitor ◽  
Time Kill ◽  
Type Strains

ABSTRACT Ibrexafungerp (formerly SCY-078), a novel glucan synthase inhibitor with oral availability, was evaluated for activity against Candida glabrata. The susceptibility of clinical strains to ibrexafungerp was determined by microdilution and time-kill assays. The MIC range against wild-type strains was 1 to 2 μg/ml. Ibrexafungerp was also active against the majority of echinocandin-resistant strains. Time-kill studies showed 4- to 6-log-unit reductions in growth at 24 and 48 h with concentrations of 0.25 to 4 μg/ml.

A mutant of rice lacking the leaf large subunit of ADP-glucose pyrophosphorylase has drastically reduced leaf starch content but grows normally

2007 ◽  
Vol 34 (6) ◽  
pp. 480 ◽  
Author(s):  
Sandrine Rösti ◽  
Brendan Fahy ◽  
Kay Denyer
Keyword(s):  
Environmental Conditions ◽  
No Reduction ◽  
Starch Content ◽  
Large Subunit ◽  
Starch Synthesis ◽  
Small Subunit ◽  
Wild Type ◽  
Gene Encoding ◽  
Subunit Protein ◽  
Adp Glucose Pyrophosphorylase

A mutant of rice was identified with a Tos17 insertion in OsAPL1, a gene encoding a large subunit (LSU) of ADP-glucose pyrophosphorylase (AGPase). The insertion prevents production of a normal transcript from OsAPL1. Characterisation of the mutant (apl1) showed that the LSU encoded by OsAPL1 is required for AGPase activity in rice leaf blades. In mutant leaf blades, the AGPase small subunit protein is not detectable and the AGPase activity and starch content are reduced to <1 and <5% of that in wild type blades, respectively. The mutation also leads to a reduction in starch content in the leaf sheaths but does not significantly affect AGPase activity or starch synthesis in other parts of the plant. The sucrose, glucose and fructose contents of the leaves are not affected by the mutation. Despite the near absence of starch in the leaf blades, apl1 mutant rice plants grow and develop normally under controlled environmental conditions and show no reduction in productivity.

scholarly journals A Novel Spirooxindole Derivative Inhibits the Growth of Leishmania donovani Parasites bothIn VitroandIn Vivoby Targeting Type IB Topoisomerase

2016 ◽  
Vol 60 (10) ◽  
pp. 6281-6293 ◽  
Author(s):  
Sourav Saha ◽  
Chiranjit Acharya ◽  
Uttam Pal ◽  
Somenath Roy Chowdhury ◽  
Kahini Sarkar ◽  
...  
Keyword(s):  
Leishmania Donovani ◽  
Nuclear Dna ◽  
Large Subunit ◽  
Peritoneal Macrophages ◽  
Small Subunit ◽  
Drug Resistant ◽  
Wild Type ◽  
Content Type ◽  
Fluorescence Studies ◽  
Topoisomerase Ib

ABSTRACTVisceral leishmaniasis is a fatal parasitic disease, and there is an emergent need for development of effective drugs against this neglected tropical disease. We report here the development of a novel spirooxindole derivative,N-benzyl-2,2′α-3,3′,5′,6′,7′,7α,α′-octahydro-2methoxycarbonyl-spiro[indole-3,3′-pyrrolizidine]-2-one (compound 4c), which inhibitsLeishmania donovanitopoisomerase IB (LdTopIB) and kills the wild type as well as drug-resistant parasite strains. This compound inhibits catalytic activity of LdTopIB in a competitive manner. Unlike camptothecin (CPT), the compound does not stabilize the DNA-topoisomerase IB cleavage complex; rather, it hinders drug-DNA-enzyme covalent complex formation. Fluorescence studies show that the stoichiometry of this compound binding to LdTopIB is 2:1 (mole/mole), with a dissociation constant of 6.65 μM. Molecular docking with LdTopIB using the stereoisomers of compound 4c produced two probable hits for the binding site, one in the small subunit and the other in the hinge region of the large subunit of LdTopIB. This spirooxindole is highly cytotoxic to promastigotes ofL. donovaniand also induces apoptosis-like cell death in the parasite. Treatment with compound 4c causes depolarization of mitochondrial membrane potential, formation of reactive oxygen species inside parasites, and ultimately fragmentation of nuclear DNA. Compound 4c also effectively clears amastigote forms of wild-type and drug-resistant parasites from infected mouse peritoneal macrophages but has less of an effect on host macrophages. Moreover, compound 4c showed strong antileishmanial efficacies in the BALB/c mouse model of leishmaniasis. This compound potentially can be used as a lead for developing excellent antileishmanial agents against emerging drug-resistant strains of the parasite.

scholarly journals In VitroActivity of Ceftazidime-Avibactam Combination inIn VitroCheckerboard Assays

2014 ◽  
Vol 59 (2) ◽  
pp. 1138-1144 ◽  
Author(s):  
Johanna Berkhout ◽  
Maria J. Melchers ◽  
Anita C. van Mil ◽  
Wright W. Nichols ◽  
Johan W. Mouton
Keyword(s):  
Antibacterial Activity ◽  
Enterobacter Cloacae ◽  
Resistance Mechanisms ◽  
Maximum Effect ◽  
Wild Type ◽  
Dependent Effect ◽  
Content Type ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTTo evaluate thein vitroeffects of the combination of ceftazidime and avibactam on the MICs of both compounds, checkerboard assays were performed for 81 clinical strains, including 55Enterobacteriaceaestrains (32Klebsiella pneumoniae, 19Escherichia coli, 1Citrobacter freundii, and 3Enterobacter cloacae) and 26 strains ofPseudomonas aeruginosa, all with known resistance mechanisms such as extended-spectrum β-lactamases (ESBLs) and carbapenemases, phenotypically or molecularly determined. Phenotypically ceftazidime-resistant strains (n= 69) were analyzed in more detail. For theEnterobacteriaceaestrains, a concentration-dependent effect of avibactam was found for most strains with a maximum effect of avibactam at a concentration of 4 mg/liter, which decreased all ceftazidime MICs to ≤4 mg/liter. Avibactam alone also showed antibacterial activity (the MIC50and MIC90being 8 and 16 mg/liter, respectively). For the ceftazidime-resistantP. aeruginosastrains, considerable inhibition of β-lactamases by avibactam was acquired at a concentration of 4 mg/liter, which decreased all ceftazidime MICs except one to ≤8 mg/liter (the CLSI and EUCAST susceptible breakpoint). Increasing the concentration of avibactam further decreased the MICs, resulting in a maximum effect for most strains at 8 to 16 mg/liter. In summary, for most strains, the tested addition of avibactam of 4 mg/liter restored the antibacterial activity of ceftazidime to a level comparable to that of wild-type strains, indicating full inhibition, and strains became susceptible according to the EUCAST and CLSI criteria. Based on thesein vitrodata, avibactam is a promising inhibitor of different β-lactamases, including ESBLs and carbapenemases.

scholarly journals MeaA, a Putative Coenzyme B12-Dependent Mutase, Provides Methylmalonyl Coenzyme A for Monensin Biosynthesis in Streptomyces cinnamonensis

2001 ◽  
Vol 183 (6) ◽  
pp. 2071-2080 ◽  
Author(s):  
Weiwen Zhang ◽  
Kevin A. Reynolds
Keyword(s):  
Coenzyme A ◽  
Large Subunit ◽  
Significant Degree ◽  
Structural Features ◽  
Small Subunit ◽  
Erythromycin Resistance ◽  
Partial Restoration ◽  
Streptomyces Cinnamonensis ◽  
Insertional Inactivation ◽  
Monensin A

ABSTRACT The ratio of the major monensin analogs produced byStreptomyces cinnamonensis is dependent upon the relative levels of the biosynthetic precursors methylmalonyl-coenzyme A (CoA) (monensin A and monensin B) and ethylmalonyl-CoA (monensin A). ThemeaA gene of this organism was cloned and sequenced and was shown to encode a putative 74-kDa protein with significant amino acid sequence identity to methylmalonyl-CoA mutase (MCM) (40%) and isobutyryl-CoA mutase (ICM) large subunit (36%) and small subunit (52%) from the same organism. The predicted C terminus of MeaA contains structural features highly conserved in all coenzyme B12-dependent mutases. Plasmid-based expression of meaA from the ermE∗ promoter in the S. cinnamonensis C730.1 strain resulted in a decreased ratio of monensin A to monensin B, from 1:1 to 1:3. Conversely, this ratio increased to 4:1 in a meaA mutant, S. cinnamonensis WM2 (generated from the C730.1 strain by insertional inactivation of meaA by using the erythromycin resistance gene). In both of these experiments, the overall monensin titers were not significantly affected. Monensin titers, however, did decrease over 90% in an S. cinnamonensis WD2 strain (anicm meaA mutant). Monensin titers in the WD2 strain were restored to at least wild-type levels by plasmid-based expression of the meaA gene or the Amycolatopsis mediterranei mutAB genes (encoding MCM). In contrast, growth of the WD2 strain in the presence of 0.8 M valine led only to a partial restoration (<25%) of monensin titers. These results demonstrate that themeaA gene product is significantly involved in methylmalonyl-CoA production in S. cinnamonensis and that under the tested conditions the presence of both MeaA and ICM is crucial for monensin production in the WD2 strain. These results also indicate that valine degradation, implicated in providing methylmalonyl-CoA precursors for many polyketide biosynthetic processes, does not do so to a significant degree for monensin biosynthesis in the WD2 mutant.

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