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Genetic properties of amber uvrA and uvrB mutants of Escherichia coli K-12 are described. The isolation of three amber uvrA and two amber uvrB mutants indicates that the products of these genes are proteins.
A dominant mutation at a new locus affecting resistance to cycloheximide has been isolated by exploiting a synergistic relationship with a previously known mutation for cycloheximide resistance in Tetrahymena. The new mutation (ChxB) was induced in a line homozygous for ChxA and was recovered from that background by a new technique termed interrupted genomic exclusion. Segregation data from the interrupted genomic exclusion suggest that ChxA and ChxB are separate, linked loci showing 30% recombination. Minimal lethal doses of cycloheximide for the four possible combinations of the wild-type and mutant alleles of these two genes are: wild type 6 microgram/ml, ChxA 125 microgram/ml, ChxB 10 microgram/ml, ChxA-ChxB 175 microgram/ml.
Historical demographic data extending back approximately 300 years were analysed to determine the demographic and genetic impact of in-migrants to an endogamous Swiss Alpine village. In-migrants were involved in only 14% of the marriages recorded in the village. In addition, only slightly more than 50% of the in-migrants were represented in the 1970 gene pool of the village. However, in-migrants accounted for nearly 38% of this gene pool. This seemingly anomalous situation can be explained by the fact that while the fertility of in-migrants and the marriage rate among their children are reduced (accounting for the near 50% "drop-our rate" of in-migrants from the gene pool), the fertility of the children of in-migrants and the marriage rate among the grandchildren of in-migrants are increased relative to village natives (accounting for the high proportion of genes in the gene pool ultimately attributable to in-migrants). Our results clearly demonstrate that although this community forms an endogamous population, it is definitely not a genetic isolate. Other investigators are cautioned against automatic invocation of the simplifying (and, thus, extremely tempting) assumption that endogamy is equivalent to genetic isolation.
A mutant derivative of Escherichia coli K-12 has been isolated which is permissive for bacteriophage T5 infection even when harboring a wild-type ColIb plasmid. The fully permissive phenotype was the result of two mutations that are located near the rpsL-rpsE region on the E. coli chromosome and are recessive to the wild-type alleles. These mutations had little or no effect on induction of colicin synthesis and did not affect the expression of antibiotic resistance by the resistance plasmids R64drd11 or R1drd19. Cells harboring the mutant alleles grew more slowly than isogenic wild-type derivatives in either minimal or complete media.
Spontaneous chloramphenicol (capr)- and erythromycin (eryr)-resistant mutants were isolated from strain ade7-50 h- and the antimycin-resistant mutant anar-8 ade 7-50 h- of Schizosaccharomyces pombe (Sch. p.). By mitotic segregation analysis all 154 capr- and 120 eryr-mutants derived from ade 7-50 h- proved to be recessive chromosomal, whereas all 108 capr- and 200 eryr-mutants originating from anar-8 were extrachromosomally inherited. The rate of spontaneous capr- and eryr-mutants was about hundredfold in anar-8 compared to ade 7-50 h-. Growth of capr- and eryr-mutants was not inhibited by chloramphenicol or erythromycin, respectively, in glucose-medium and only slightly in glycerol-medium at concentrations which completely inhibited anar-8. By mitotic segregation-, tetrad-, and mitotic haploidization-analysis the extrachromosomal inheritance of mutants derived from anar-8 was established. Segregational patterns of capr- and eryr-determinants during mitosis, meiosis, and mitotic haploidization of diploids are discussed.
Deletions of colicin E1 (colE1) plasmid deoxyribonucleic acid (DNA) carrying the TnA transposon have been isolated. All except two were generated by nuclease digestion of plasmid DNA from its EcoRI-sensitive site. A plasmid containing about 16% of the ColE1 DNA (6.5 X 10(5) daltons) was generated that also contained the part of the TnA transposon conferring ampicillin resistance. The extents of different deletions were determined by analysis of restriction endonuclease fragments generated by the restriction endonucleases HaeII, BamHI, and HincII.
In order to find new genetic loci and functions on the yeast mitochondrial DNA, especially mutations affecting the mitochondrial protein synthesis apparatus, temperature sensitive mutants have been isolated after MnCl2 mutagenesis and mitochondrial and nuclear mutants classified according to their pattern of recombination with three rho- tester strains. Eighteen cold- and heat-sensitive respiratory deficient mitochondrial mutants have been isolated and localized on the mitochondrial genome by deletion mapping using 113 rho- strains. Eight of them appear to represent new loci, among which some are probably mutations of the tRNA and rRNA genes.
Taking advantage of the Spi (sensitivity to P2 interference) phenomenon, bacterial mutants seemingly resistant to phage lambdasusNnin5, but sensitive to phage lambdaspi, were isolated from a strain of E. coli K12 carrying no nonsense suppressor and lysogenic for P2. A class of these mutants, designated nitA (N-independent transcription), is described here. Upon infection of the nitA mutants with a trp transducing phage lambdasusN7N53ptrp46 which carries the E. coli trpE and D genes in the CIII-att region of the lambda genome, formation of anthranilate synthetase (ASase, a complex protein of trp E and D gene products) was clearly demonstrated. In contrast, no ASase formation was observed in the parent nitA+ strain under the same conditions. The synthesis is subject to "turn off" control, and is completely repressed by the CI repressor of phage lambda. The nitA cells lysogenic for lambdaCI857susN7N53 are killed by thermal induction much more efficiently than the parent cells lysogenic for the same phage. The nitA mutants support the growth of lambdasusN7N53byp much better than the parent. These results suggest that the nitA mutation permits the early leftward and rightward transcription of the lambda genome in the absence of the N gene product. On the E. coli genetic map, nitA is located between ilv and metE, nearer to ilv. The mutant allele is recessive to the wild-type allele. The present evidence, together with results of biochemical investigations to be reported, suggests that nitA is a gene specifying the transcription termination factor rho.
A girl from a Spanish Gypsy family developed idiopathic torsion dystonia when 12 years old. Parents were first cousins and both the pattern of clinical involvement and the rate of progression corresponded to that usually found in the autosomal recessive form of the disorder. Serum dopamin-beta-hydroxylase activity in the patient and close family members were also in keeping with this hereditary form. A nationwide inquiry failed to detect further cases of torsion dystonia among Gypsies, but revealed a relatively large number of recessively inherited disorders of the nervous system in this inbred, genetically isolated population. Thirty-six additional cases of torsion dystonia were collected from the general Spanish population, including four with a family history for this condition. The gene responsible for the recessive illness appears to be rare in many countries, explaining the sporadic nature of the disorder and its eventual appearance only in genetic isolates or after consanguineous matings.
Lambda transducing phages carrying the excision repair genes uvrA+ and uvrC+ were selected from a pool of lambda phages carrying EcoR1 fragments of E. coli DNA. These phages and also lambdauvrB+ (obtained from Gottesman) were used to make lysogens of excision-defective strains carrying uvrA-, uvrB- or uvrC-. Lambda uvrA+ was found to transduce strains carrying uvrA- but not those carrying uvrB- or uvrC-, to normal ultraviolet resistance. Similarly, lambdauvrB+ and lambdauvrC+ were found to complement only the corresponding uvr- allele. The lambda transducing phages were co-transduced with gal+ by P1 phage into lysogenic gal- recipients, and presumably were integrated at the normal prophage site.
Drosophila melanogaster collected from natural populations were examined fo thermostability variants within electrophoretic mobility classes of two enzymes. In alcohol dehydrogenases, two discrete forms of the "slow" allozyme and three discrete forms of the "fast" allozyme were revealed by postelectrophoretic treatments ranging from 15 sec at 40 C to 40 sec at 43 C. All variants have been mapped to within 0.7 unit of the Adh locus. Results of a geographic survey indicate that two alleles giving rise to fast-moderate and slow-moderate allozymes are common everywhere; other variants have a collective frequency ranging from 0% to 7%. In a test of the possibility that the rare Adh alleles could be generated by intragenic recombination between the two common alleles, electrophoresis and heat treatment of progeny recombinant for flanking markers of Adh revealed no new allozymes. Among 27 stocks containing slow alpha-glycerophosphate dehydrogenase allozymes and 109 fast stocks, heat treatments revealed no additional variation.
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BACKGROUND: Multidrug-Resistant Organism (MDRO) refers to bacteria that are Resistant to three or more types of antibiotics in clinical use. The global health threat posed by multidrug-resistant (MDR) bacterial pathogens and their cross-species transmission necessitates rigorous Surveillance. This urgency is amplified in China where antibiotic growth promoters were widely used in animal husbandry until the 2020 implementation of Announcement No. 194 launched by Ministry of Agriculture and Rural Affairs (Announcement 194), banning non-therapeutic antibiotics in feed. This study conducted a decade long investigation on the correlation between antimicrobial resistance (AMR) phenotypes and genetic determinants in 314 Salmonella isolates collected from waterfowl across Guangdong Province, China, utilizing disk diffusion (Kirby-Bauer method) and PCR-based detection of antibiotic resistance genes (ARGs). The study period covered the antibiotic policy transition in China, specifically encompassing the pre-ban (2013-2019) and post-ban (2020-2023) phases of the nationwide prohibition on growth-promoting antimicrobials in animal feed. METHODS: Antimicrobial Susceptibility profiles against 16 agents were determined via Kirby-Bauer testing, while PCR amplification targeted 20 ARGs. Statistical analyses evaluated phenotype-genotype correlations using Pearson`s chi-square test. RESULTS: Surveillance revealed escalating resistance rates annually. Highest resistance prevalence was observed against β-lactams and amphenicols (92.25%), whereas amikacin exhibited the lowest resistance rate (9.55%). MDR prevalence reached 87.23%, with the AMP-CAZ-GEN-FFC-TET resistance profile predominating (51.6% of isolates). Genetic analysis identified 3 to 16 ARGs per isolate was harboring, with blaTEM demonstrating the highest detection frequency (90.76%). Significant phenotype-genotype correlations (p < 0.05) were observed for 13 genes: blaCTX-M, blaTEM, blaOXA, aacC2, aph(3')-I, aac(3)-IV, aadA1, qnrS, qnrA, clmA, floR, sulII, tetA. Notably, significant declines in resistance to aminoglycosides (e.g., gentamicin from 71.7 to 3.5%) and florfenicol (from 81.1 to 9.6%) were observed after China's 2019 antibiotic ban policy (p < 0.001), underscoring the impact of targeted antimicrobial stewardship in avian husbandry. CONCLUSIONS: Analysis of 314 waterfowl Salmonella strains revealed severe multidrug resistance (MDR) and diverse resistance genes (DRGs), with 13 DRGs linked to resistance. China's antibiotic ban reduced targeted resistance, but MDR persists alarmingly via acquired DRGs and adaptation. Continued enforcement may lower aminoglycoside/phenicol resistance, but β-lactam resistance will likely endure, worsened by transcontinental blaCTX-M spread. Critically, plasmid co-selection threatens to amplify MDR, demanding genomic surveillance. Mitigation requires boosting policy compliance, developing non-antibiotic therapies, mapping mutations, establishing cross-species barriers, and prioritizing One Health interventions to block resistance spread.
Pathogens rarely mix freely throughout host populations, and the presence of barriers to transmission can be detected as patterns of increased genetic isolation among pathogen isolates. Despite the importance of transmission patterns in host societies, and the risk of epizootics from wildlife disease systems, barriers to open pathogen transmission are poorly understood in wild hosts. We tested the influence of host kinship and social structure on genetic divergence among strains of Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB), in a wild badger population. We measured genetic distances between M. bovis isolates from badger hosts that varied in their own genetic similarity (a proxy for kinship) and in their social group affiliations. Using jack-knifing analyses to control for pseudoreplication, we found that genetic distances between pathogen isolates decreased with increasing kinship of host dyads, but only when hosts shared the same social group. Our findings suggest that the open transmission of bTB in wild hosts is constrained by a combination of social and kin structure, in particular the sharing of similar pathogen strains among kin within social groups. We discuss the implications of these transmission structures for the understanding and management of wildlife diseases.
Two families affected with Wilson's disease living in submontane villages of Lower Beskid are presented. The previous observations are confirmed that most of the subjects affected with the disease in Poland origin from geographic isolates. This phenomen is due to increased number of homozygotes in genetically isolated groups.
Laeonereis acuta is a polychaete species typically found at high abundance in estuarine and coastal lagoon environments. Due to its association with polluted habitats, it is commonly used in ecotoxicological studies. Moreover, its occurrence in spatially discontinuous environments with high environmental variability makes it a suitable model for evolutionary studies of local adaptation, genetic landscape, and early stages of speciation. This study aimed to develop primers and characterize microsatellite markers for L. acuta sampled from three coastal lagoons in southwestern Brazil. A total of 10 loci were characterized based on the genotyping of 40 individuals. The number of alleles per locus ranged from 2 to 19. Evidence of null alleles was detected at five loci, although their frequency decreased when coastal lagoons were analyzed separately. When considering all individuals as a single population, five loci showed positive and significant FIS values, and seven loci deviated from Hardy-Weinberg equilibrium. Maricá and Guarapina exhibited heterozygote excess at several loci, whereas Jaconé showed evidence of population genetic isolation. The 10 microsatellite loci were polymorphic and suitable for population genetic analysis in L. acuta, although these patterns may not necessarily be representative of other geographic regions. These markers may contribute to ecotoxicological studies by clarifying whether physiological responses to pollutants are associated with genetic differentiation among populations. Furthermore, they provide valuable tools for investigating genetic structure and connectivity in discontinuous environments.
Mutants of the yeast Saccaromyces cerevisiae which can grow on glycerol medium in the presence of 0.05% D (+) glucosamine have been isolated. Genetic analysis of 13 of these glucosamine resistant (GR) mutants demonstrated two modes of inheritance. One group of mutants (GR 5, 6, 7, 8, 9 and 10) gave results characteristic of non-Mendelian inheritance and it is suggested that these mutants represent one or more new mitochondial loci. Four of the remaining mutants showed clear-cut Mendelian inheritance. These mutants fell into two complementation groups and subsequent mapping experiments demonstrated that two independent loci, gay 1 and gay 2, unlinked to each other or to the centromeres of chromosomes I, II, IV, VIII or IX, were responsible for conferring glucosamine resistance in these mutants.
Two reproductively isolated demes of brown trout coexist in a small Swedish mountain lake, Lake Bunnersjörna. We electrophoretically examined 102 specimens from that lake for 27 enzymes encoded by 54 loci. The two demes are fixed for different alleles at a lactate dehydrogenase locus (LDH-1); statistically significant allele frequency differences at five other loci further support the complete lack of gene flow between these demes. There are significant differences in growth rates between fish in the two demes, but no further morphological differentiation h-s been detected.--In light of these findings, the genetic distance between these populations is surprisingly small (Nei's I = 0.975). These demes represent one of the least genetically divergent, reproductively isolated sympatric pair of vertebrate populations that have been identified. The results are discussed from both an evolutionary and ecological perspective.