scholarly journals Dislodgement and thymineless elimination of N-group plasmids

1977 ◽  
Vol 30 (1) ◽  
pp. 21-30 ◽  
Author(s):  
R. J. Pinney ◽  
A. E. Jacob ◽  
R. W. Hedges ◽  
J. T. Smith
Keyword(s):  
Plasmid Dna ◽  
Elimination Rate ◽  
Nuclease Activity ◽  
Incompatibility Group ◽  
R Factor ◽  
Thymine Starvation ◽  
Normal Frequency ◽  
Compatible Plasmid ◽  
No Elimination ◽  
R Factors

SUMMARYThymineless strains ofEscherichia coliC600 were constructred harbouring both an R factor of the N incompatibility group (R46 or R447b) and a compatible plasmid (Plac-of the A-C group or the Iα plasmid R62), which contained a segment of N group DNA. Selection was made for the transferred plasmid and dislodgement phenomena were manifest either as loss of an entire plasmid or as deletions of a region of plasmid DNA. Even after the two R factors had become established as separate replicons, the N group R factor but not the other plasmid exhibited instability.Thymine starvation of strain C600thy(R447b/R62) increased the elimination rate of the N group plasmid R447b but no elimination of R62 was observed. However, thymine starvation of strain C600thy(R46/Plac-) not only increased the rate of elimination of R46 but also increased the rate of loss of Plac-. There was no detectable increase in nuclease activity in unstarved R46/Plac-strains and it is concluded that dislodgement of R46 from these strains is not due to induction of the nuclease that has been proposed to be responsible for the elimination of N group plasmids during thymine starvation.Two variants of Plac-were isolated. These did not dislodge R46 from unstarved R46/Plac-strains and were not lost during thymine starvation even though thymineless elimination of R46 occurred at normal frequency.

Further properties of P-2 R-factors of Pseudomonas aeruginosa and their relationship to other plasmid groups

1975 ◽  
Vol 21 (5) ◽  
pp. 592-605 ◽  
Author(s):  
M. S. Shahrabadi ◽  
L. E. Bryan ◽  
H. M. Van Den Elzen
Keyword(s):  
Electron Microscopy ◽  
Pseudomonas Aeruginosa ◽  
Host Range ◽  
Dna Hybridization ◽  
Classification Scheme ◽  
Incompatibility Group ◽  
R Factor ◽  
Significant Homology ◽  
Pseudomonas Species ◽  
R Factors

R-factors of the P-2 (prototype R-factor R931) incompatibility group pf plasmids detected in Pseudomonas are compatible with group P, C, W, and N R-factors which are plasmids that can be transferred to Pseudomonas aeruginosa recipients. Members of the P-2 group (R130, R931) have significant homology by DNA–DNA hybridization. R-factors of the P-group (RP1, RP9) and F-group (R1) exhibited homology with P-2 R-factors but to a lesser extent than R130 with R931. Members of the 1, C, and W groups showed no significant homology with P-2 R-factors. Minicircular DNA of strain 931(R931) was not homologous with R931 DNA. The host range of R931 and R130 is limited mainly to certain Pseudomonas species including P. aeruginosa, P. fluorescens, P. putida, and P. stutzeri. These R-factors could not be transferred at detectable frequencies to any member of the Enterobacteriaceae examined. R-factor-specified pili were strongly suggested by the detection of pili by electron microscopy in R+ but not R− non-piliated mutants of P. aeruginosa strain PA01. The combined properties of R-factors 931 and similar R-factors reported before and in this study strongly support our previous contention that this group of R-factors form a significant new group of plasmids. A classification scheme previously proposed for plasmids occurring in Pseudomonas has been modified and four groups have been specified.

scholarly journals Analysis of the resistance mediated by several R-factors to Tetracycline and Minocycline

1972 ◽  
Vol 20 (2) ◽  
pp. 239-252 ◽  
Author(s):  
J. M. Robertson ◽  
E. C. R. Reeve
Keyword(s):  
Tetracycline Resistance ◽  
Klebsiella Aerogenes ◽  
R Factor ◽  
Before And After ◽  
Challenge Tests ◽  
Simple Growth ◽  
High Level ◽  
K 12 ◽  
R Factors ◽  
Level Group

SUMMARYThe resistance levels conferred by the T-determinants in four R-factors to Tetracycline and Minocycline in cells ofEscherichia coliK 12, before and after induction of maximum resistance by treatment with sub-inhibitory concentrations of the drugs, are measured by simple growth-and-challenge tests. The effect of a plasmid TKwhich confers tetracycline resistance on its hostKlebsiella aerogenesis tested in the same way. The five T-determinants fall into a high-level and a low-level group for resistance, the former giving 3- to 4-fold higher resistance in both induced and uninduced cells than the latter. The T-determinants all confer much lower resistance to Minocycline (a tetracycline molecule modified at the C-6 and C-7 positions) than to Tetracycline. The main cause of this difference is that cells carrying a T-determinant exclude Minocycline much less efficiently than Tetracycline, but in addition Minocycline is less effective than Tetracycline in inducing increased resistance. These results are discussed in the light of a model put forward to explain the inducible nature of R-factor resistance to the tetracyclines.

scholarly journals Values of rainfall erosivity factor for the Czech Republic

2013 ◽  
Vol 61 (2) ◽  
pp. 97-102 ◽  
Author(s):  
Miloslav Janeček ◽  
Vít Květoň ◽  
Eliška Kubátová ◽  
Dominika Kobzová ◽  
Michaela Vošmerová ◽  
...  
Keyword(s):  
Czech Republic ◽  
Water Erosion ◽  
Rainfall Erosivity ◽  
The Czech Republic ◽  
Average Value ◽  
R Factor ◽  
The Usa ◽  
Time Division ◽  
R Factors

Abstract The processing of ombrographic data from 29 meteorological stations of the Czech Hydrometeorological Institute (CHMI), according to the terms of the Universal Soil Loss Equation for calculating long term loss of soil through water erosion, erosion hazard rains and their occurrence have been selected, with their relative amount and erosiveness - R-Factors determined for each month and years. By comparing the value of the time division of the R-Factor in the area of the Czech Republic and in selected areas of the USA it has been demonstrated that this division may be applied in the conditions of the Czech Republic. For the Czech Republic it is recommended to use the average value R = 40 based on the original evaluation.

scholarly journals Estimativa da erosividade da chuva por diferentes métodos e seu impacto na equação universal de perdas de solo, no semiárido pernambucano (Estimation of erosivity by different methods and their impact on the universal soil loss equation in Pernambuco semi-arid)

2019 ◽  
Vol 12 (3) ◽  
pp. 859
Author(s):  
Joaquim Pedro de Santana Xavier ◽  
Alexandre Hugo Cezar Barros ◽  
Daniel Chaves Webber ◽  
Luciano José de Oliveira Accioly ◽  
Flávio Adriano Marques ◽  
...  
Keyword(s):  
Soil Loss ◽  
Universal Soil Loss Equation ◽  
Rainfall Erosivity ◽  
R Factor ◽  
Semi Arid Region ◽  
Erosion Loss ◽  
R Factors ◽  
Semi Arid ◽  
Soil Loss Equation

Dentre os diversos métodos indiretos para estimar as perdas de solo por erosão, a Equação Universal de Perdas de Solo (EUPS) é a mais utilizada devido a sua robustez e por ser constituída de uma simples estrutura fatorial, que integra fatores naturais e antrópicos atuantes na perda de solos. A erosão é um dos fenômenos mais danosos ao solo e às atividades humanas e por isso seu estudo é importante. Para o cálculo das perdas de solo por meio da EUPS, a avaliação da erosividade das chuvas (fator R) é essencial, pois estima o fenômeno produzido pelas chuvas. O objetivo deste trabalho foi avaliar três metodologias disponíveis de obtenção da erosividade das chuvas para a região do semiárido pernambucano, avaliando sua influência nos resultados da EUPS. Os três modelos selecionados para estimar o Fator R foram desenvolvidos por Wischmeier e Smith (mais conhecido e utilizado), por Silva que estimou valores para diversas regiões do País e por Cantalice e outros que trabalharam especificamente para cada região climática do estado de Pernambuco. Os resultados indicam que as metodologias de Wischmeier e Smith e Silva obtiveram resultados de erosividade da chuva semelhantes, tendo Silva alcançado valores maiores. Cantalice e outros obtiveram os resultados mais baixos. Os resultados da EUPS indicam que, quantitativamente, os diferentes fatores R geram grande diferença nas perdas de solo, porém, qualitativamente chegam a resultados semelhantes na classificação de áreas de maior erosão, de acordo com a FAO. Logo, as três metodologias são viáveis na identificação de áreas prioritárias para a mitigação da erosão.   A B S T R A C TAmong several indirect methods to estimate soil erosion loss, the Universal Soil Loss Equation (EUPS) is the most used due to its robustness and because it is constituted of a simple factorial structure that integrates natural and anthropic factors which act in the loss of soils. Erosion is one of the most damaging phenomena to the soil and the human activities, evidencing the importance of studying it. The evaluation of rainfall erosivity (R factor) is essential for the calculation of soil loss through the EUPS, since it is possible to estimate how significant rainfall is to the occurrence of this phenomenon. The objective of this work was to evaluate three methodologies to obtain the rainfall erosivity available for the semi - arid region of Pernambuco, evaluating its influence on the results of the EUPS. The three models used to estimate the R-factor were developed by Wischmeier and Smith, the best known and used model, Silva who estimated values for several regions of the country and Cantalice and others who worked specifically for each climatic region of the state of Pernambuco. As a result, very similar results of rainfall erosivity were obtained between Wischmeier and Smith´s and Silva´s methodology, with Silva reaching higher values of energy amplitude, while Cantalice and others obtained the lowest results. The results of EUPS indicate that, quantitatively, the different R factors generate a large difference in soil loss, but qualitatively they reach similar results in the classification of areas where erosion are greater, according to the FAO. Therefore, the three methodologies are feasible in the identification of priority areas for erosion mitigation.Keywords: soil, rainfall erosivity, USLE, GIS

scholarly journals Recombination and complementation between R factors inEscherichia coliK 12

1971 ◽  
Vol 18 (3) ◽  
pp. 287-297 ◽  
Author(s):  
T. J. Foster ◽  
T. G. B. Howe
Keyword(s):  
Escherichia Coli ◽  
Specific Activity ◽  
Chloramphenicol Acetyl Transferase ◽  
Wild Type ◽  
Chloramphenicol Resistance ◽  
Low Level ◽  
R Factor ◽  
Reduced Frequency ◽  
Interallelic Complementation ◽  
R Factors

SUMMARYRecombination between chloramphenicol-sensitive (Cms) mutants of Rl, and R100, has been demonstrated inEscherichia coliK12rec+; it occurs at reduced frequency inrecBandrecC, and is not detectable inreeA, indicating that R factor recombination depends on host functions. Some mutants of R1 also recombine with an R100 mutant in a similar way.recAcells carrying an R1 and an R100 Cmsmutant (hetero-R state) have a low level of chloramphenicol-resistance, and form a chloramphenicol acetyl transferase that has lower specific activity than enzyme from hosts carrying wild-type or recombinant factors. These results suggest the occurrence of interallelic complementation between mutant R factors.

scholarly journals In vivotransfer of R factors betweenEscherichia colistrains inoculated into the rumen of sheep

1975 ◽  
Vol 75 (3) ◽  
pp. 363-370 ◽  
Author(s):  
M. G. Smith
Keyword(s):  
Population Density ◽  
Antibiotic Treatment ◽  
Intestinal Tract ◽  
Total Coliform ◽  
Starvation Period ◽  
Experimental Animals ◽  
E Coli ◽  
R Factor ◽  
R Factors

SUMMARYSubstantial transfer of R factors occurredin vivo, under certain conditions, in the rumen of adult sheep in the absence of any antibiotic treatment. A starvation period of 24–48 hr. was required to produce the conditions necessary, when even quite low inocula (ca. 103cells) of donor and recipientE. colicould grow within the rumen and reach a population density sufficient for transfer to take place. The results indicate that under the same conditions R factors may be transferred between organisms in the lower intestinal tract also. Without the starvation period, the inoculation of even massive numbers (1010cells) of the same organisms resulted in almost no detectable transfer.Some of the experimental animals on which a starvation period was imposed became carriers of either the inoculated recipientE. coli, or of R factor bearing coliforms, and these formed 1–10% of the total coliform population of the faeces for at least 6 weeks.

Occurrence of R Factors Associated with Aeromonas hydrophila Isolates from Aquarium Fish and Waters

1976 ◽  
Vol 33 (4) ◽  
pp. 736-740 ◽  
Author(s):  
E. B. Shotts Jr. ◽  
V. L. Vanderwork ◽  
L. M. Campbell
Keyword(s):  
Antibiotic Resistance ◽  
Aeromonas Hydrophila ◽  
Sulfa Drugs ◽  
Predisposing Factor ◽  
Aquarium Fish ◽  
Factors Associated ◽  
R Factor ◽  
Aquarium Water ◽  
Prophylactic Use ◽  
R Factors

Isolates obtained from aquarium fish and aquarium waters identified as belonging to the Aeromonas hydrophila complex were examined for the presence of R factors imparting conjugal transmissibility of antibiotic resistance to tetracycline and/or sulfa drugs. It was found that 25.5% of the isolates from fish which were resistant to one or more of the screening antibiotics and similarily 14.1% of the isolates from aquarium water carried such R factors. These studies suggest that the prophylactic use of tetracycline may be a predisposing factor in the emergence of R factor-carrying strains of bacteria in aquarium water.

scholarly journals Selective enrichment of R−segregants as the main mechanism of ‘curing’ of the R factor by acridine dyes

1971 ◽  
Vol 17 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Masanosuke Yoshikawa
Keyword(s):  
Shigella Flexneri ◽  
Host Cells ◽  
Bacterial Strains ◽  
Initial Inoculum ◽  
Selective Enrichment ◽  
E Coli ◽  
R Factor ◽  
Acridine Dyes ◽  
Increased Sensitivity ◽  
R Factors

SUMMARYBy the use of appropriate strains ofEscherichia coli, Shigella flexneriandSalmonella typhimuriumwith and without an R factor, R100, the mechanism of ‘curing’ of R factor by acridine dyes was examined. This R factor was shown to confer increased sensitivity to acriflavine upon the host cells.E. colistrain W-3630, once infected with R100, has never been observed to segregate R−cells. When mixtures of R+and R−cells of this strain were grown in acriflavine broth, the proportion of R−cells increased and was also correlated with the proportion in the initial inoculum. Other bacterial strains carrying R100segregate R~ cells spontaneously. Growth tests starting with varying proportion of R+and R−cells of these strains in acriflavine broth also gave a marked correlation between the initial and final proportions of R−cells, and indicated that the main cause of ‘curing’ the R factor was the selective enrichment of R−segregants present in the initial inocula or arising spontaneously during growth of the R+culture. These results suggest that the mechanisms underlying the ‘curing’ of F and R factors are different. Tests with several acridine dyes gave results similar to those with acriflavine.

scholarly journals Transmission of infectious drug resistance from animals to man

1973 ◽  
Vol 71 (1) ◽  
pp. 209-215 ◽  
Author(s):  
D. M. Wells ◽  
O. B. James
Keyword(s):  
Drug Resistance ◽  
Antibiotic Resistance ◽  
Antibiotic Treatment ◽  
Farm Animals ◽  
Antibiotic Resistant ◽  
R Factor ◽  
Resistance Patterns ◽  
Antibiotic Resistance Patterns ◽  
R Factors

SUMMARYThe antibiotic resistance patterns of coliforms in faecal specimens from pigs and their human contacts were studied. The ability of the resistant coliforms to transfer their resistance in vitro to antibiotic-sensitive recipients was examined. The results showed that pigs which had received antibiotics carried more multiply-resistant, R-factor bearing coliforms than pigs which had not been given antibiotics. Human contacts of the antibiotic-treated pigs had a higher incidence of antibiotic-resistant coliforms with R-factors than human contacts of pigs which had not been given antibiotics. It is concluded that antibiotic treatment of farm, animals may lead to acquisition of antibiotic resistance by gut coliforms of man.

scholarly journals Interaction of a colicinogenic factor with a resistance factor and with the fertility factor F inEscherichia coliK-12

1971 ◽  
Vol 17 (2) ◽  
pp. 151-159 ◽  
Author(s):  
Pearl Cooper
Keyword(s):  
Resistance Genes ◽  
Recombinant Plasmid ◽  
Resistance Factor ◽  
E Coli ◽  
Fertility Factor ◽  
Plasmid Incompatibility ◽  
R Factor ◽  
Transmissible Plasmid ◽  
K 12 ◽  
R Factors

SUMMARYThe resistance (R)-factor R538–1drdof three F-like R-factors tested can cause the transfer of the non-transmissible ColV determinant fromE. coliV. The col factor, once transferred toE. coliK-12 strains, was shown to be related to the fertility factor, F, on the basis of entry exclusion and plasmid incompatibility. The col factor was found to recombine with R538–1drd, yielding a transmissible plasmid comprised of the col determinant and the sex factor of the R-factor, but not the resistance genes. The recombinant plasmid was found to be incompatible with both R538–1drdand F, and excluded the entry of R538–1drdbut not F.

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