Optimization on the selection of auxotrophic mutants in Candida utilis by snail enzyme treatment

1979 ◽  
Vol 25 (4) ◽  
pp. 486-490 ◽  
Author(s):  
J. M. Delgado ◽  
L. S. Herrera ◽  
C. Pérez ◽  
R. López
Keyword(s):  
Candida Utilis ◽  
Wild Type Strain ◽  
Selection Procedure ◽  
Enzyme Treatment ◽  
Wild Type ◽  
Digestion Method ◽  
Auxotrophic Mutants ◽  
Snail Enzyme ◽  
Selection Of

The determination of the best conditions for the application of the snail enzyme digestion method in the enrichment of auxotrophic mutants in Candida utilis was carried out following Box and Wilson's mathematical method. The selection procedure proposed was tested in the enrichment of auxotrophic mutants from a mutagenized culture of a wild-type strain. Mutant frequency was increased 46-fold by treatment with snail enzyme. The method also proved useful in the selection of additional auxotrophic mutations from single auxotrophs.

Selection of auxotrophic mutants inSaccharomyces cerevisiae by a snail enzyme digestion method

1976 ◽  
Vol 21 (5) ◽  
pp. 337-341 ◽  
Author(s):  
D. Piedra ◽  
L. Herrera
Keyword(s):  
Enzyme Digestion ◽  
Digestion Method ◽  
Auxotrophic Mutants ◽  
Snail Enzyme ◽  
Selection Of

scholarly journals A New Test of Filterability for Unprocessed Wines Evaluation of the Enzyme Efficiency

2021 ◽  
Vol 10 (2) ◽  
pp. 55-66
Author(s):  
Amélie Vallet-Courbin ◽  
Soizic Lacampagne ◽  
Rose Marie Canal-Llauberes ◽  
Sigolène Mattalana Malzieu ◽  
Tihomir Kanev ◽  
...  
Keyword(s):  
Suspended Matter ◽  
Measurement Method ◽  
Membrane Filtration ◽  
Enzyme Treatment ◽  
Filtration Process ◽  
Enzyme Efficiency ◽  
Different Types ◽  
Definition Of ◽  
Selection Of

A new Test of Filterability has been developed. Measurements carried out with different types of wines indicate that the new filterability index is a useful tool for understanding and predicting the propensity to fouling of treated or untreated wines, e.g. with or without enzyme addition. The measurement method used in the Test of Filterability, requires only one type of membrane for all types of wine, and uses the same equipment as the traditional Fouling Index. Numerous trials have demonstrated that the filtration of wines is governed by standard blocking law. The definition of the new Test of Filterability, based on this filtration law, is proposed. The choice of membrane and the selection of the optimal pore size were based on the results of the experiments. Current methods used for the determination of fouling properties in wine filtration have been developed for the membrane filtration of small quantities of suspended matter. Enzyme treatment is a process often used in wine clarification. The new Test of Filterability indicates the best conditions for the filtration of all types of wines. The test is easy to implement and has been validated with various wines. This new Test of Filterability is an important tool for winemakers as it constitutes a simplified test of a wine's filterability. The new test may also be used to determine the filtration process that is best adapted to each wine while reducing the number of operations. The same approach may be adopted for the filtration of other liquids. 

scholarly journals Structural determination of a 5-O-methyl-deaminated neuraminic acid (Kdn)-containing polysaccharide isolated from Sinorhizobium fredii

1998 ◽  
Vol 334 (3) ◽  
pp. 585-594 ◽  
Author(s):  
Antonio M. GIL-SERRANO ◽  
Miguel A. ÍGUEZ-CARVAJAL RODR ◽  
Pilar TEJERO-MATEO ◽  
José L. ESPARTERO ◽  
Jane THOMAS-OATES ◽  
...  
Keyword(s):  
Fast Atom Bombardment ◽  
Wild Type Strain ◽  
Auxotrophic Mutant ◽  
Neuraminic Acid ◽  
Wild Type ◽  
1H And 13C Nmr ◽  
One Dimensional ◽  
In The Wild ◽  
Fast Atom Bombardment Ms

The structure of a polysaccharide from Sinorhizobium frediiSVQ293, a thiamine auxotrophic mutant of S. fredii HH103, has been determined. This polysaccharide was isolated following the protocol for lipopolysaccharide extraction. On the basis of monosaccharide analysis, methylation analysis, fast atom bombardment MS, collision-induced dissociation tandem MS, one-dimensional 1H and 13C NMR and two-dimensional NMR experiments, the structure was shown to consist of the following trisaccharide repeating unit → 2)-α-d-Galp-(1 → 2)-β-d-Ribf-(1 → 9)-α-5-O-Me-Kdnp-(2 →, in which Kdn stands for deaminated neuraminic acid; 25% of the Kdn residues are not methylated. The structure of this polysaccharide is novel and this is the first report of the presence of Kdn in a rhizobial polysaccharide, as well as being the first structure described containing 5-O-Me-Kdn. This Kdn-containing polysaccharide is not present in the wild-type strain HH103, which produces a 3-deoxy-d-manno-2-octulosonic acid (Kdo)-rich polysaccharide. We conclude that it is likely that the appearance of this new Kdn-containing polysaccharide is a consequence of the mutation.

Biosynthesis of lysine in Saccharomyces cerevisiae: properties and spectrophotometric determination of homocitrate synthase activity

1976 ◽  
Vol 22 (11) ◽  
pp. 1664-1667 ◽  
Author(s):  
Gary S. Gray ◽  
J. K. Bhattacharjee
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Biosynthetic Pathway ◽  
Wild Type Strain ◽  
Wild Type ◽  
Temperature Optimum ◽  
Acetyl Coa ◽  
Metal Chelating ◽  
Binding Agents ◽  
Homocitrate Synthase

A rapid assay is described for homocitrate synthase (EC 4.1.3.21) of the lysine biosynthetic pathway of Saccharomyces cerevisiae. The α-ketoglutarate-dependent cleavage of acetyl-coA was measured spectrophotometrically as decrease in absorbance at 600 nm in the presence of 2, 6-dichlorophenol-indophenol and enzyme from the wild-type strain X2180. This activity was also present in a citrate synthaseless glutamate auxotroph glu3, and the activity was inhibited by 5 mML-lysine. Radioactive homocitric acid was obtained from a reaction mixture containing [1-14C]acetyl-coA. Homocitrate synthase activity was dependent upon time, both substrates, and enzyme. The activity exhibited a pH and temperature optimum of 7.5–8.0 and 32 °C, respectively, and was inhibited by metal-chelating and sulfhydryl-binding agents.

scholarly journals Determination of the dependence of competitive results on the procedure of sports selection among Greco-Roman wrestlers

2019 ◽  
Vol 23 (4) ◽  
pp. 182-188 ◽  
Author(s):  
R.S. Nagovitsyn ◽  
A.Yu. Osipov ◽  
A.G. Kapustin ◽  
O.V. Anfilatova ◽  
S.Yu. Senator
Keyword(s):  
Martial Arts ◽  
Objective Assessment ◽  
Selection Procedure ◽  
Test Results ◽  
Greco Roman ◽  
Motor Tests ◽  
Student’S T ◽  
Selection Of ◽  
Sports Selection

Introduction : the problems of sports selection and selection of prospective children in martial arts schools are quite relevant in the sports practice. It was revealed the use of various selection techniques in the practice of martial arts. There is no unified methodological system for selection in martial arts schools. The purpose of the study : to determine the dependence of the dynamics of sports results of elite athletes on the procedure of sports selection (for example, the Greco-Roman wrestling). Material and methods : elite Greco-Roman wrestlers (n = 114) took part in the research. Age of athletes: 25-45 years. Qualification: International masters of sport (n = 8), masters of sport (n = 49), candidates in masters of sport (n = 57). Athletes filled out a diagnostic card with data on the procedure of sports selection. It was indicated the dynamics of competitive results during the sports career. Indicators of performance and stability of athletes were calculated applying the mathematical statistics methods ( ). The reliability of the results was determined by Student's t-test. Results : Data analysis showed that a significant part of athletes did not pass the selection procedure (n = 23). Many athletes passed only a partial selection procedure (n = 39). Some athletes did not pass the selection procedure. These athletes are not inferior in terms of stability to athletes who passed the selection at the 1st and 2nd levels of competitive results. In subsequent competitions, these athletes demonstrated the reliable (P <0.05) decrease in indicators of stability in comparison with other athletes. It was revealed a significant (P <0.05) advantage in indicators of stability among athletes who passed a partial selection procedure at the 4th level of competitive results. Conclusions : It was found the dependence of stability indicators at high levels of competitive results on the selection procedure of athletes. The athletes who passed the selection procedure demonstrate higher stability at high levels of competitive results. It was revealed a formal attitude to the selection procedure in some coaches and specialists. The trainers do not pay due attention to the indicators of maintaining body balance and coordination abilities during the selection of candidates. It has been revealed that the motor tests applied in the selection procedure do not allow an objective assessment of the potential of athletes' competitive achievements.

scholarly journals Estimating the strength of selection for new SARS-CoV-2 variants

2021 ◽  
Author(s):  
Christiaan H van Dorp ◽  
Emma E Goldberg ◽  
Nicolas Hengartner ◽  
Ruian Ke ◽  
Ethan Obie Romero-Severson
Keyword(s):  
Molecular Epidemiology ◽  
Type Strain ◽  
Wild Type Strain ◽  
Sequence Data ◽  
Relative Magnitude ◽  
Global Perspective ◽  
Wild Type ◽  
Country Level ◽  
Selection For ◽  
Selection Of

A challenge to controlling the SARS-CoV-2 pandemic is the ability of the virus to adapt to its new human hosts, with novel and more transmissible strains of the virus being continually identified. Yet there are no generally accepted methods to consistently estimate the relative magnitude of the change in transmissiblity of newly emerging variants. In this paper we consider three methods for examining and quantifying positive selection of new and emerging strains of SARS-CoV-2 over an existing wild-type strain. We consider replication at the level of countries and allow for the action of other processes that can change variants' frequencies, specifically migration and drift. We apply these methods to the D614G spike mutation and the variant designated B.1.1.7, in every country where there is sufficient sequence data. For each of D614G and B.1.1.7, we find evidence for strong selection (greater than 25% increased contagiousness) in more than half of countries analyzed. Our results also shows that the selective advantages of these strains are highly heterogeneous at the country level, suggesting the need for a truly global perspective on the molecular epidemiology of SARS-CoV-2.

Improvement of olfactometric measurement accuracy and repeatability by optimization of panel selection procedures

2010 ◽  
Vol 61 (5) ◽  
pp. 1267-1278 ◽  
Author(s):  
L. Capelli ◽  
S. Sironi ◽  
R. Del Rosso ◽  
P. Céntola ◽  
S. Bonati
Keyword(s):  
Degrees Of Freedom ◽  
Selection Procedure ◽  
Selection Procedures ◽  
Accuracy And Precision ◽  
Repeated Analysis ◽  
The Right ◽  
Accuracy And Repeatability ◽  
Selection Of ◽  
Dynamic Olfactometry

The EN 13725:2003, which standardizes the determination of odour concentration by dynamic olfactometry, fixes the limits for panel selection in terms of individual threshold towards a reference gas (n-butanol in nitrogen) and of standard deviation of the responses. Nonetheless, laboratories have some degrees of freedom in developing their own procedures for panel selection and evaluation. Most Italian olfactometric laboratories use a similar procedure for panel selection, based on the repeated analysis of samples of n-butanol at a concentration of 60 ppm. The first part of this study demonstrates that this procedure may originate a sort of “smartening” of the assessors, which means that they become able to guess the right answers in order to maintain their qualification as panel members, independently from their real olfactory perception. For this reason, the panel selection procedure has been revised with the aim of making it less repetitive, therefore preventing the possibility for panel members to be able to guess the best answers in order to comply with the selection criteria. The selection of new panel members and the screening of the active ones according to this revised procedure proved this new procedure to be more selective than the “standard” one. Finally, the results of the tests with n-butanol conducted after the introduction of the revised procedure for panel selection and regular verification showed an effective improvement of the laboratory measurement performances in terms of accuracy and precision.

In vivo selection of a population of Trypanosoma cruzi and clones resistant to benznidazole

Parasitology ◽  
1998 ◽  
Vol 116 (2) ◽  
pp. 165-171 ◽  
Author(s):  
S. M. F. MURTA ◽  
A. J. ROMANHA
Keyword(s):  
Mortality Rate ◽  
Trypanosoma Cruzi ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Long Term Treatment ◽  
Resistant Population ◽  
Parasitaemia Level ◽  
Selection Of

A benznidazole-resistant population of Trypanosoma cruzi, Y strain, was selected after 25 successive passages (8 months) in mice treated with a single high drug dose. Initially, the resistant parasites produced a low parasitaemia level and low mortality rate in infected mice. Thereafter, the parasitaemia level and mortality rate increased to the same value obtained for mice infected with the wild-type strain. Long-term treatment with benznidazole (100 mg/kg/day) cured 71–80% of mice infected with the wild-type strain. No cure was observed in mice infected with the selected resistant parasite population. Treatment with 500 mg/kg of benznidazole at peak parasitaemia cleared all blood parasites from mice infected with wild-type parasites. No effect on parasitaemia level was observed in mice infected with the selected parasites. Benznidazole-resistant parasites showed cross-resistance to different drugs. Contrary to wild type, all clones analysed from the resistant T. cruzi population were resistant to benznidazole. Without drug pressure the resistance phenotype of clones was far more stable than that presented by the resistant population. This work demonstrates, for the first time, the in vivo selection of a population and clones of T. cruzi resistant to benznidazole, and makes available an experimental model for the study of mechanisms of drug resistance in T. cruzi.

scholarly journals Role of Respiratory Nitrate Reductase in Ability ofPseudomonas fluorescens YT101 To Colonize the Rhizosphere of Maize

2000 ◽  
Vol 66 (9) ◽  
pp. 4012-4016 ◽  
Author(s):  
Jean-Fran�ois Ghiglione ◽  
Fran�ois Gourbiere ◽  
Patrick Potier ◽  
Laurent Philippot ◽  
Robert Lensi
Keyword(s):  
Nitrate Reductase ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Replacement Series ◽  
Gene Encoding ◽  
Direct Demonstration ◽  
Respiratory Nitrate Reductase ◽  
Selection Of

ABSTRACT Selection of the denitrifying community by plant roots (i.e., increase in the denitrifier/total heterotroph ratio in the rhizosphere) has been reported by several authors. However, very few studies to evaluate the role of the denitrifying function itself in the selection of microorganisms in the rhizosphere have been performed. In the present study, we compared the rhizosphere survival of the denitrifyingPseudomonas fluorescens YT101 strain with that of its isogenic mutant deficient in the ability to synthesize the respiratory nitrate reductase, coinoculated in nonplanted or planted soil. We demonstrated that under nonlimiting nitrate conditions, the denitrifying wild-type strain had an advantage in the ability to colonize the rhizosphere of maize. Investigations of the effect of the inoculum characteristics (density of the total inoculum and relative proportions of mutant and wild-type strains) on the outcome of the selection demonstrated that the selective effect of the plant was expressed only during the phase of bacterial multiplication and that the intensity of selection was dependent on the magnitude of this phase. Moreover, application of the de Wit replacement series technique to our results suggests that the advantage of the wild-type strain was maximal when the ratio between the two strains in the inoculum was close to 1:1. This work constitutes the first direct demonstration that the presence of a functional structural gene encoding the respiratory nitrate reductase confers higher rhizosphere competence to a microorganism.

scholarly journals Threshold and adaptation in Phycomyces. Their interrelation and regulation by light.

1984 ◽  
Vol 84 (1) ◽  
pp. 119-132 ◽  
Author(s):  
P Galland ◽  
V E Russo
Keyword(s):  
Growth Rate ◽  
Dark Adaptation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Light Sensitivity ◽  
Growth Conditions ◽  
Continuous Illumination ◽  
Growth Responses ◽  
Wild Type

The absolute light sensitivity of Phycomyces sporangiophores was determined by analyzing the intensity dependence of the phototropic bending rate and of the light growth and dark growth responses to step changes of the intensity. We found that the different methods give approximately the same results for the wild-type strain, as well as for several behavioral mutants with defects in the genes madA, madB, and madC. A crucial factor in the determination of thresholds is the light intensity at which the strains grow during the 4 d after inoculation and prior to the experiment. When the wild-type strain grows in the dark, its threshold for the bending rate is 10(-9) W X m-2, compared with 2 X 10(-7) W X m-2 when it is grown under continuous illumination. Further, the maximal bending rate is twice as high in dark-grown strains. This phenomenon is further complicated by the fact that the diameter and growth rate of the sporangiophores also depend on the illumination conditions prior to the experiment: light-grown sporangiophores have an increased diameter and an increased growth rate compared with dark-grown ones. Some of the behavioral mutants, however, are indifferent to this form of light control. Another factor that is controlled by the growth conditions is adaptation: the kinetics of dark adaptation are slower in light-grown sporangiophores than in dark-grown ones. We found empirically a positive correlation between the slower dark adaptation constant and the threshold of the bending rate, which shows that the two underlying phenomena are functionally related.

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