Molecular basis of bacterial outer membrane permeability.

DEVELOPMENTS IN THE UNDERSTANDING AND USE OF F-PRIME FACTORS ................................................................ Fertility; F+ and Hfr Strains .................................................. Sex-Factor Affinity. The First F-primes ............................................................ Deletion of Proximal or Distal Hfr Genes (or both) in the Formation of F-primes; Primary F-Prime Strains ........................................ Chromosome Mobilization. Loss of F-prime Factors; Curing .............................................. Derived F-Prime Factors and F-Prime Stability ................................ Mutations in the sexfactor. Mutations in the region of diploidy .......................................... F-prime-chromosome recombination and segregation ........................ F-prime-F-prime recombination within the F factor. Deletions of F-prime material ............................................... Transductional shortening .................................................. F-prime fusion .............................................................. Loss ofF Chromosomal Integration of F-Primes; Directed Transpositions ................ Physical Properties ofF-Primes. Regulation of F-Prime Replication, and Expression of Diploid Genes. On the Nature of F-Prime Formation. ISOLATION OF NEW F-PRIME FACTORS AND THE USE OF recA . .......... From Hfr Strains ............................................................ From Double Male Strains ..................................................... By Transduction? ............................................................. NOMENCLATURE-HFR AND F-PRIME STRAINS AND F-PRIME FACTORS HFR STRAINS .................................................................. F-PRIME FACTORS ............................................................ CAN E. COLI BE MADE DIPLOID FOR ANY LOCUS? ......................... 587 587 588 588

Escherichia coli K-12 F-prime factors, old and new.

INTRODUCTION AND DEFINITIONS ...................................... 361 SOME PROPERTIES OF BACTERIAL PLASMIDS .......................... 362 Chromosomal Integration ............... .................................... 363 Fertility Repression........................................................ 363 Incompatibility ............................................................. 364 Elimination ................................................................ 364 Replication and Segregation (Membrane Site Model) ...... ................... 365 GENETICS AND LINKAGE OF PLASMID-BORNE GENES ................. 366 MOLECULAR MODELS FOR PLASMIDS AND THEIR IMPLICATIONS FOR THE EVOLUTION OF R FACTORS.367 PHYSICAL COMPOSITION AND FORM .................................... 369 METHODS OF ISOLATION ................................................. 371 Differences from Host DNA Base Ratio ................................... 371 From Minicells ............................................................. 372 Lysis with Nonionic Detergent (Brij 58) ......... ............................ 373 Conjugal Transfer.......................................................... 373 Isolation of CCC Plasmid Molecules 374 Cellulose nitrate adsorption ............ ................................... 374 Alkaline sucrose sedimentation ........................................... 374 Ethidium bromide-cesium chloride centrifugation ...... .................... 374 METHODS OF MOLECULAR WEIGHT DETERMINATION ................. 374 Sedimentation Analysis ................. .................................... 374 Loss of Supercoil Structure by Irradiation ........ ........................... 375 Reassociation Kinetics...................................................... 376 Electron Microscopy ....................................................... 376 SIZE AND CONFIGURATION ............ .................................. 376 F and F' Sex Factors.376 Colicinogenic Factors ....................................................... 379 Drug-Resistance Factors ............... ................................... 380 Monomolecular factors ............... .................................... 380 Unstable R factors ....................................................... 381 Multimolecular R factors .............. ................................... 382 PHYSICAL INTERRELATIONSHIPS ........................................ 384 MOLECULAR STRUCTURE ..... ............................................ 385 Monomolecular Plasmids .......................... 385 A Revised Map for R222 .................... 387 Alternative Molecular Structures ofR Factors 387 Speculations on R-Factor Evolution ....... ................ 389 ASPECTS OF PLASMID REPLICATION ............ ........................ 390 Plasmid Copy Number-Relaxed and Stringent Regulation.390 Mechanism of Relaxed Replication.391 "Transition" in Drug Resistance ................ ............. 392 DNA-Protein "Relaxation Complexes"......................................... 393 Replication in Minicells ........... ............................ 394 Transfer Replication .......... ............................. 394 CONCLUSIONS ........................................... 395 LITERATURE CITED .......... ............................. 397

Molecular structure of bacterial plasmids.

The plasmid DNA content of six invasive and adhesive strains of Salmonella typhimurium was determined, and all six strains (CR8500 [S850], CR6600 [TML], W118, NY, PR, and S2204) were found to harbor at least one plasmid equivalent in size to the 60-megadalton plasmid ("cryptic" plasmid), pSLT, which is normally resident in S. typhimurium strain LT2. The role of such 60-megadalton plasmids in the adhesive and invasive properties of strain CR6600, a commonly encountered salmonella pathogen that produces type 1 fimbriae, and strain CR8500, a representative FIRN biotype which does not produce type 1 fimbriae, was studied further by obtaining derivatives of these strains that no longer harbored an autonomous 60-megadalton plasmid. Strains CR6260 and CR6190 and strains CR8100 and CR8353, which were "cured" derivatives of strains CR6600 and CR8500, respectively, were significantly less adhesive and invasive in the HeLa cell test. A 53.5-megadalton colicin plasmid harbored by strain CR6600 did not detectably influence these properties. Additionally, strain CR6260 was avirulent, and strain CR8100 was 1,000 to 10,000-fold less virulent for orally infected mice as compared with their respective parental strains. Significantly, the virulence of strain CR8100 correlated with tissue colonization by bacteria that exhibited autonomous copies of a 60-megadalton plasmid. We propose that this plasmid exists in both autonomous and integrated states and that the in vivo environment selects for bacteria with autonomous plasmid copies which can express the virulent phenotype, thus enabling such strains to survive the defense mechanisms of the host. Images

https://iai.asm.org/content/iai/38/2/476.full.pdf

Association of adhesive, invasive, and virulent phenotypes of Salmonella typhimurium with autonomous 60-megadalton plasmids.

RP4, an R factor derived from Pseudomonas aeruginosa S8 and specifying resistance to carbenicillin, neomycin, kanamycin, and tetracycline, could be isolated as an extrachromosomal satellite of covalently closed circular DNA (CCC-DNA) of molecular weight about 62 million and of buoyant density 1.719 g/cm3 (60% guanine plus cytosine). When RP4 was compared by hybridization with RP1, an R factor originating in another strain of P. aeruginosa, it was shown that RP4 contains most, if not all, of the base sequences of RP1, and also additional sequences not found in RP1.

Properties of RP4, an R Factor Which Originated in Pseudomonas aeruginosa S8

A method for effective elimination of drug resistance (R) and sex (F) factors in Escherichia coli K-12 strains by treatment with sodium dodecyl sulfate (SDS) is presented. Growth of E. coli harboring R or F factors in Penassay Broth containing SDS led to the loss of all or part of these genetic elements. Appearance of drug-susceptible or F(-) cells among survivors was observed after the culture reached the stationary phase. Drug-susceptible cells which had lost all of their resistance markers by SDS treatment could be efficiently infected with R or F factors. Among isolated segregants which came from resistant cells, tetracycline-susceptible cells were the major segregant class. Drug-susceptible cells gave no revertants to drug resistance. By treatment of F(+) cells with SDS, unusual F(+) cells which retained mating ability but showed resistance to M12 phage were also isolated, together with mutants of another type which lost mating ability but retained sensitivity to M12 phage. Since SDS is more toxic to R(+) cells than R(-) cells, the isolation of drug-susceptible or F(-) cells under these conditions may be partly attributable to selective growth of drug-susceptible or F(-) cells in SDS-Penassay Broth.

Effective Elimination of Drug Resistance and Sex Factors in Escherichia coli by Sodium Dodecyl Sulfate

Bacterial sex pili.

A specific action of sodium dodecyl sulfate (SDS) on the sex (F) factor in the integrated state of Escherichia coli K-12 Hfr H strain is reported. Growth of Hfr cells in Penassay Broth containing SDS results in the elimination of part or all of the F factor, yielding low and nonfertile variants of defective Hfr type and F+ cells and also F− derivatives. Appearance of such variants was generally observed after the culture reached stationary phase. The frequencies of F− cells then increased. F− cells were usually isolated as the major population among survivors. Some defective variants of Hfr cells with an intermediate fertility between standard Hfr and F+ cells had lost sensitivity toward the male-specific ribonucleic acid phage M12. Other defective Hfr variants with as much or less fertility than standard F+ cells had also all lost sensitivity to phage M12. On single-colony isolation, they segregated nonfertile female H cells which, when infected with F, could restore high fertility with oriented transfer of the chromosome the same as that of the original Hfr H. Also, sensitivity to phage M12 was regained. Female H cells were characterized as those lacking fertility but still retaining a small segment of F or sfa locus at the original part of the chromosome, where newly infected F could attach. Similar results were obtained with two other Hfr strains. A possible mechanism of the specific action of SDS is discussed.

Specific Action of Sodium Dodecyl Sulfate on the Sex Factor of Escherichia coli K-12 Hfr Strains

Evidence is presented for the specific role of sex pili in the eliminatory action of sodium dodecyl sulfate (SDS) on sex (F) and drug resistance (R) factors in Escherichia coli K-12 strains leading to their loss. SDS at 0.03% concentration lysed JE3100 F8+ (F-gal)/gal−fla−pil− in Penassay broth after they had grown exponentially and reached maximum growth to the extent that the agent at concentrations higher than 1% did. However, the agent was only effective in eliminating sex factors from JE3100 in high frequencies at concentrations higher than 1%. Increase of osmotic pressure of the culture with SDS at concentrations as low as 0.03 to 0.1% by addition of sucrose led to the substantial increase of elimination efficiency. Reconstruction experiments between F8+ and F− cells in the SDS culture revealed the selective growth of F− cells as well as a delay of maximum growth of F− variants derived from F8+ cells, compared with those of F8+ cells, as well as F− cells originally added to the culture. The agent was not very effective in eliminating sex factors from JE3427 F8m+5/fla−pil− cells which lack the function of production of F pili. F8m+5 cells showed a sensitivity toward SDS intermediate between those of F8+ and F− cells. SDS was further effective in eliminating R factors from KE132 R100-1+/fla−pil− cells in high efficiency; however, the action was not efficient with KE133 F100+ cells possibly with fewer sex pili than R100-1+. Action of acridine orange on these F+ or R+ strains was found to be different in some aspects from that of SDS.

Specific role of sex pili in the effective eliminatory action of sodium dodecyl sulfate on sex and drug resistance factors in Escherichia coli.

Studies on conformation and reactivity—I : The polyphosphoric acid-catalyzed ring opening of 4,5-epoxy-3-oxo steroids—the synthesis of 4-ethylthiocholest-4-EN-3-one and its analogs

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