scholarly journals Specific point mutations in Lactobacillus casei ATCC 27139 cause a phenotype switch from Lac− to Lac+

Microbiology ◽  
2009 ◽  
Vol 155 (3) ◽  
pp. 751-760 ◽  
Author(s):  
Yu-Kuo Tsai ◽  
Hung-Wen Chen ◽  
Ta-Chun Lo ◽  
Thy-Hou Lin
Keyword(s):  
Gene Cluster ◽  
Point Mutation ◽  
Lactobacillus Casei ◽  
Stop Codon ◽  
Single Point ◽  
Point Mutations ◽  
Premature Stop Codon ◽  
Gene Clusters ◽  
Single Point Mutation ◽  
Phenotype Switch

Lactose metabolism is a changeable phenotype in strains of Lactobacillus casei. In this study, we found that L. casei ATCC 27139 was unable to utilize lactose. However, when exposed to lactose as the sole carbon source, spontaneous Lac+ clones could be obtained. A gene cluster (lacTEGF–galKETRM) involved in the metabolism of lactose and galactose in L. casei ATCC 27139 (Lac−) and its Lac+ revertant (designated strain R1) was sequenced and characterized. We found that only one nucleotide, located in the lacTEGF promoter (lacTp), of the two lac–gal gene clusters was different. The protein sequence identity between the lac–gal gene cluster and those reported previously for some L. casei (Lac+) strains was high; namely, 96–100 % identity was found and no premature stop codon was identified. A single point mutation located within the lacTp promoter region was also detected for each of the 41 other independently isolated Lac+ revertants of L. casei ATCC 27139. The revertants could be divided into six classes based on the positions of the point mutations detected. Primer extension experiments conducted on transcription from lacTp revealed that the lacTp promoter of these six classes of Lac+ revertants was functional, while that of L. casei ATCC 27139 was not. Northern blotting experiments further confirmed that the lacTEGF operon of strain R1 was induced by lactose but suppressed by glucose, whereas no blotting signal was ever detected for L. casei ATCC 27139. These results suggest that a single point mutation in the lacTp promoter was able to restore the transcription of a fully functional lacTEGF operon and cause a phenotype switch from Lac− to Lac+ for L. casei ATCC 27139.

scholarly journals Within-population variability in a moth sex pheromone blend, part 2: selection towards fixation

2019 ◽  
Vol 6 (3) ◽  
pp. 182050 ◽  
Author(s):  
Astrid T. Groot ◽  
Michiel van Wijk ◽  
Ernesto Villacis-Perez ◽  
Peter Kuperus ◽  
Gerhard Schöfl ◽  
...  
Keyword(s):  
Communication Systems ◽  
Sexual Communication ◽  
Stop Codon ◽  
Single Point ◽  
Premature Stop Codon ◽  
Behavioural Response ◽  
Population Variation ◽  
Single Point Mutation ◽  
Knock Out ◽  
Female Pheromone

To understand how variation in sexual communication systems evolves, the genetic architecture underlying sexual signals and responses needs to be identified. Especially in animals where mating signals are important for mate recognition, and signals and responses are governed by independently assorting genes, it is difficult to envision how signals and preferences can (co)evolve. Moths are a prime example of such animals. In the noctuid moth Heliothis virescens , we found within-population variation in the female pheromone. In previous selection experiments followed by quantitative trait locus (QTL) analysis and expression analysis of candidate desaturase genes, we developed a model involving a trans -acting repressor of the delta-11-desaturase. In our current study with new selection lines, we fixed the most extreme phenotype and found a single underlying mutation: a premature stop codon in the first coding exon of delta-11-desaturase, which we could trace back to its origin in the laboratory. Interestingly, we found no pleiotropic effects of this knock-out mutation on the male physiological or behavioural response, or on growth or fertility. This finding is in contrast to Drosophila melanogaster , where a single desaturase gene affects both female pheromone production and male behavioural response, but similar to other Lepidoptera where these traits are under independent genetic control. To our knowledge, this is the first time that a single point mutation has been identified that underlies the phenotypic variation in the pheromone signal of a moth.

scholarly journals Single-point mutation detection in RNA extracts using gold nanoparticles modified with hydrophobic molecular beacon-like structures

2014 ◽  
Vol 50 (23) ◽  
pp. 3018-3020 ◽  
Author(s):  
Alfonso Latorre ◽  
Christian Posch ◽  
Yolanda Garcimartín ◽  
Susana Ortiz-Urda ◽  
Álvaro Somoza
Keyword(s):  
Gold Nanoparticles ◽  
Point Mutation ◽  
Mutation Detection ◽  
Molecular Beacon ◽  
Single Point ◽  
Point Mutations ◽  
Single Point Mutation ◽  
Target Sequence ◽  
Cholesterol Derivative ◽  
Single Point Mutations

The functionalization of gold nanoparticles with a cholesterol derivative affords a sensor that is able to detect single-point mutations. The solubility of the nanoparticles is modulated by the presence of the target sequence inducing its aggregation.

scholarly journals Increasing Prevalence of Quinolone Resistance in Human Nontyphoid Salmonella enterica Isolates Obtained in Spain from 1981 to 2003

2004 ◽  
Vol 48 (10) ◽  
pp. 3789-3793 ◽  
Author(s):  
José M. Marimón ◽  
María Gomáriz ◽  
Carmen Zigorraga ◽  
Gustavo Cilla ◽  
Emilio Pérez-Trallero
Keyword(s):  
Nalidixic Acid ◽  
Point Mutation ◽  
Salmonella Enterica ◽  
Single Point ◽  
Point Mutations ◽  
Fluoroquinolone Resistance ◽  
Human Consumption ◽  
Single Point Mutation ◽  
Gene Coding ◽  
Serovar Typhimurium

ABSTRACT From January 1981 to December 2003, susceptibility to nalidixic acid was tested in 10,504 nontyphoid Salmonella enterica isolates from patients with acute enteric disease in Gipuzkoa, Spain. The prevalence of nalidixic acid resistance steadily increased from less than 0.5% before 1991 to 38.5% in 2003, mainly due to the increase in resistance among isolates of the most prevalent serovar, S. enterica serovar Enteritidis. For nalidixic acid-resistant isolates, the ciprofloxacin MIC was eightfold higher than that for susceptible isolates, and the nalidixic acid-resistant isolates contained a single point mutation in the gyrA gene (at codons for Ser83 or Asp87). The same mutations were found in a sample of nalidixic acid-resistant nontyphoid Salmonella strains isolated between 1999 and 2003 from retail food for human consumption. In 2003, we identified five S. enterica serovar Typhimurium clinical isolates with high-level fluoroquinolone resistance (ciprofloxacin MIC, 16 μg/ml) with two point mutations in the gyrA gene (coding for Ser83→Phe and Asp87→Asn) and one point mutation in the parC gene (coding for Ser80→Arg). Strict sanitary controls are needed to avoid the spread of ciprofloxacin-resistant serovar Typhimurium isolates, and a more efficient veterinary policy must be adopted to decrease the large burden of Salmonella serovar Enteritidis infections in humans in our region.

scholarly journals A single point mutation converts a proton-pumping rhodopsin into a red-shifted, turn-on fluorescent sensor for chloride

2021 ◽  
Author(s):  
Jasmine N. Tutol ◽  
Jessica Lee ◽  
Hsichuan Chi ◽  
Farah N. Faizuddin ◽  
Sameera S. Abeyrathna ◽  
...  
Keyword(s):  
Point Mutation ◽  
Fluorescent Sensor ◽  
Single Point ◽  
Proton Pumping ◽  
Single Point Mutation ◽  
Turn On ◽  
Gloeobacter Violaceus

By utilizing laboratory-guided evolution, we have converted the fluorescent proton-pumping rhodopsin GR from Gloeobacter violaceus into GR1, a red-shifted, turn-on fluorescent sensor for chloride.

scholarly journals Structural basis for a complex I mutation that blocks pathological ROS production

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhan Yin ◽  
Nils Burger ◽  
Duvaraka Kula-Alwar ◽  
Dunja Aksentijević ◽  
Hannah R. Bridges ◽  
...  
Keyword(s):  
Point Mutation ◽  
Complex I ◽  
Structural Changes ◽  
Ischemia Reperfusion ◽  
Single Point ◽  
Structural Basis ◽  
Single Point Mutation ◽  
Ros Production

AbstractMitochondrial complex I is central to the pathological reactive oxygen species (ROS) production that underlies cardiac ischemia–reperfusion (IR) injury. ND6-P25L mice are homoplasmic for a disease-causing mtDNA point mutation encoding the P25L substitution in the ND6 subunit of complex I. The cryo-EM structure of ND6-P25L complex I revealed subtle structural changes that facilitate rapid conversion to the “deactive” state, usually formed only after prolonged inactivity. Despite its tendency to adopt the “deactive” state, the mutant complex is fully active for NADH oxidation, but cannot generate ROS by reverse electron transfer (RET). ND6-P25L mitochondria function normally, except for their lack of RET ROS production, and ND6-P25L mice are protected against cardiac IR injury in vivo. Thus, this single point mutation in complex I, which does not affect oxidative phosphorylation but renders the complex unable to catalyse RET, demonstrates the pathological role of ROS production by RET during IR injury.

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