Genetic Transfer System Research Articles

Genetic regulation of functions ofE. coli plasmid pAP42 transfer genes

Sensitivity of the genetic transfer system of F-like plasmid pAP42 marked with the transposons Tn1 and TN9 to fertility inhibitors of six reference Fin-groups was studied. It was shown that transfer function and donor-specific piliformation of the plasmid under study were inhibited by reference plasmids of FinU and FinV groups, surface exclusion by plasmids of FinU and FinQ groups. The different influence of the FinOP group plasmid on transfer functions of the marked plasmids pAP42::Tn1 and pAP42::Tn9 that is likely to be connected with the effect of incorporated transposons was determined.

Genetic transfer in Halobacterium volcanii.

Auxotrophic mutants of Halobacterium volcanii generated by chemical mutagenesis were used to demonstrate a native genetic transfer system in this extremely halophilic member of the class Archaeobacteria.

Selection of lactic acid bacteria for use in vegetable fermentations

The fermentation of brined vegetables traditionally has depended upon growth of naturally occurring lactic acid bacteria to metabolize the vegetable sugars to organic acids which, together with added salt, results in preservation. Starter cultures have been used only to a limited extent commercially. However, recent efforts to improve fermentation vessels and to develop controlled fermentation methods for fermented vegetables has resulted in an increased interest in developing cultures suitable for application in such methods. Rapid and dominant growth, type and extent of acid production, salt tolerance, temperature range, CO 2 production, cell sedimentation, bacteriophage resistance, nutritional value, and ability to survive as concentrated cultures are factors to consider in developing lactic acid bacterial cultures for use in controlled fermentation of vegetables. Recent examples of efforts to improve cultures include development of nonmalate-decarboxylating strains of lactobacilli for use in cucumber fermentation and isolation of a new species of lactobacillus that produces only the L-isomer of lactic acid from the glucose for use in sauerkraut fermentation. Further improvements in starter cultures for fermented vegetables are likely when suitable genetic transfer systems are developed for selective incorporation or deletion of specific traits.

The use of molecular techniques to study microbial determinants of pathogenicity

A variety of new methods in DNA biochemistry, molecular biology and genetics have become available for the analysis of microbial determinants of pathogenicity. It has never been easier to focus upon specific genetic determinants and to manipulate them directly to meet experimental goals. Although the principles of genetic manipulation have been used with considerable success in enteric bacteria, it is not always a straightforward matter with other microorganisms. We were unable to cloneBordetella pertussisdeterminants of pathogenicity directly inEscherichia coliK12 by selecting for their protein products. It was possible, however, to develop a genetic transfer system and methods for the identification of specificBordetellavirulence genes. These studies not only provided the basis for the eventual successful genetic cloning ofBordetella pertussisgenes but also provided an example showing that the molecular cloning of virulence genes is not always an easy task, nor even necessarily the best initial approach to take.

Genetic transfer systems in lactic acid bacteria.

Gene transfer processes (transduction, conjugation, protoplast fusion mediated exchange, transformation in protoplasts) in lactic acid bacteria are reviewed in this paper. Besides, the detailed molecular nature of lactose plasmids in the Streptococcus lactis C2, 712 and ML3 strain complex is discussed.

Utilization of a thermosensitive episome bearing transposon TN10 to isolate Hfr donor strains of Erwinia carotovora subsp. chrysanthemi.

A thermosensitive episome bearing the transposon Tn10, F(Ts)::Tn10 Lac+, has been successfully transferred from Escherichia coli to several wild strains of the enterobacteria Erwinia carotovora subsp. chrysanthemi, which are pathogenic on Saintpaulia ionantha. In one of these strains, all of the characters controlled by this episome (Lac+, Tetr, Tra+) were expressed, and its replication was stopped at 40 degrees C and above. At 30 degrees C, the episome was easily transferred between strains derived from E. carotovora subsp. chrysanthemi 3937j and to E coli. Hfr donor strains were obtained from a F' strain of 3937j by selecting clones which grew at 40 degrees C on plates containing tetracycline. One of these strains, Hfrq, was examined in more detail: the characters Lac+ and Tetr were stabilized and did not segregate higher than its parental F' strain. The mating was most efficient at 37 degrees C on a membrane. Hfrq transferred its chromosome to recipient strains at high frequency and in a polarized fashion, as evidenced by the gradient of transfer frequencies, the kinetics of marker entry (in interrupted mating experiments), and the analysis of linkage between different markers. The chromosome of Hfrq was most probably transferred in the following sequence: origin...met...xyl...arg...ile...leu...thr...cys...pan...ura...gal...trp...his. ..pur... Moreover, this genetic transfer system proved to be efficient in strain construction.

Transduction of lactose metabolism in Streptococcus lactis C2.

Ultraviolet (UV)-induced phage lysates, from lactose-positive (lac(+)) Streptococcus lactis C2, transduced lactose fermenting ability to lac(-) recipient cells of this organism. Although the phage titer could not be determined due to the absence of an appropriate indicator strain, the number of transductants was proportional to the amount of phage lysate added. Treatment of the lysate with deoxyribonuclease had no effect on this conversion, indicating the observed genetic change was not mediated by free deoxyribonucleic acid. When the lac(+) transductants were isolated and exposed to UV irradiation, lysates with higher transducing ability were obtained. The transducing ability of this lysate was about 100-fold higher than that observed in the original lysates. The lac(+) transductants were unstable since lac(-) segregants occurred at high frequency. The phage lysate from S. lactis C2 also transduced maltose and mannose metabolism to the respective negative recipient cells. The results demonstrate the transduction of carbohydrate markers by a streptococcal phage and establish a genetic transfer system in group N streptococci.

The properties of sex pili, the viral nature of "conjugal" genetic transfer systems, and some possible approaches to the control of bacterial drug resistance.

(1971). The Properties of Sex pili, The Viral Nature of “Conjugal” Genetic Transfer Systems, and Some Possible Approaches to the Control of Bacterial Drug Resistance. CRC Critical Reviews in Microbiology: Vol. 1, No. 1, pp. 105-160.

Phage and bacteriocin investigations with Pasteurella pestis and other bacteria.

PHAGE and bacteriocin investigations were conducted with Pasteurella pestis in attempts to discover a genetic transfer system in this species. Although unsuccessful in their main objective, these studies provided additional data supporting the view that certain Pasteurellae have a close taxonomic relationship to some of the Enterobacteria. These results are reported here.