Studies on the Nature of Hemophilus Influenzae Cells Susceptible to Heritable Changes by Desoxyribonucleic Acids

Abstract

In E. influenzae the highly specific desoxyribonucleic acids (DNA's) which play the role of heredity determinants of type specificity and SM resistance, have induced these traits in only a small proportion of the population exposed to their action. The evidence suggests that this small proportion, "the susceptible cells" possess a property or substance needed by the DNA in order to induce an heritable change. The size of the small proportion of susceptible cells can be influenced significantly by a number of factors; when all the factors now to be listed are operating the frequency has not exceeded 1:1000. The Type of Origin of Recipient Cells.—Type a exhibits the lowest frequency, about 1:10,000,000, and type d the highest, approximately 1 per 1000 cells exposed. This type-specific property which controls the frequency of susceptible cells is an inherited trait; repeated change to a heterologous type shows no influence on the incidence of these cells. Concentration of DNA.—Within certain limits increase in the concentration of DNA controlling streptomycin resistance can increase the size of the proportion of cells in which streptomycin resistance can be induced. However, increases in concentrations greater than 10–1 µg. per ml. have not induced streptomycin resistance in a higher proportion of cells. Phase of Growth Cycle.—Predictable fluctuations in frequency of induced heritable changes have been demonstrated in both Rb and Rd populations during growth. There is no evidence that susceptible cells reproduce their kind; they emerge in all experiments when the population reaches the end of the logarithmic period and a density of 2 to 4 x 108 cells per ml. In the early logarithmic phase it is difficult to demonstrate the presence of susceptible cells. The peak frequency of susceptible cells occurs in the early stationary phase of the growth cycle. Thereafter, the decline in frequency is a gradual one. The data suggest that in a given population the same cells are susceptible to a number of different type-specific DNA's and the DNA controlling SM resistance. Comparison of Frequency of Cells Susceptible to Different DNA's.—In a given population the frequency of cells susceptible to different type-specific DNA's and the DNA controlling streptomycin resistance is not significantly different. Competition between Type-Specific DNA's—The data suggest that DNA's of types a, b, and c compete for the same cells in Rd populations. When Rd populations are exposed simultaneously to 2 of these 3 DNA's in different concentrations the proportion which each type contributes to the total type-specific cells induced is closely correlated with the concentration of the corresponding DNA. Exclusion of DNA's.—Induction of one type specificity or streptomycin resistance can be completely prevented in a population containing susceptible cells by previous exposure for 15 minutes to a 1000-fold higher concentration of another type-specific DNA.

Delayed Multiplication of Newly Capsulated Transformants of Haemophilus influenzae Detected by Immunofluorescence

“…The response of competent bacteria to eight different concentrations of DNA was examined in experiments with DNA preparations 2 and 4. Results for both str-r and type b antigen markers corresponded to those for streptomycin resistance reported by Alexander, Leidy & Hahn (1954) and by Goodgal (1961). Capsulated bacteria were observed in tests of 0-0001 pg.…”

Genetics of Capsular Polysaccharide Production in Bacteria

“…Early studies, exploiting the natural transformability of H. injluenzae, demonstrated that a non-capsulated organism originally selected from a typed organism could be transformed to any other capsular types depending on the serotype of the organism from which the transforming DNA had been isolat~d (ALEXANDER et al 1954). Subsequent studies (CATLIN et al 1972) indicated that the locus for encapsulation (termed cap b) was located in the H. injluenzae chromosome near bio and that the cap b functions might be located over a segment of DNA as large as 50 kb.…”

Transformação genética de Xanthomonas campestris para resistência à estreptomicina e à eritromicina

“…7, fasc. 4,1968 Assim, Xanthomonas campestris mostrou ser suscetível de so frer transformação genética bacteriana, quando ácido desoxiribonucleico extraído de uma linhagem resistente à estreptomicina e à eritromicina, transferiu os dois marcos genéticos para uma li nhagem sensível aos antibióticos.…”

“…7, fase. 4,1968 MATERIAL E MÉTODOS 1) Linhagem selvagem. O isolamento foi efetuado de ma terial enegrecido de vasos de caule de couve (Brassica oleraceae var.…”