Genetic Properties of a T Factor and T‐r Recombinants

Abstract

Genetic studies have shown that one of the transfer (T) factors , T95, carries the following genetic properties: autonomous replication (rep+), conjugal transmission (tra+), transmission of the host chromosome (mat+), inhibition of F-mating (ifm+ or fi+), inhibition of superinfection with R factor (irs-), and suppression of phage proliferation (spp-). An Escherichia coli K12 strain carrying T95 factor is insensitive to male phages (f1 and f2). These facts indicated that the T95 factor is a sex factor but different from the F factors. By the interaction between T95 factor and the nontransferable resistance determinants; r21 (tet) for tetracycline resistance and r3 (kan) for kanamycin resistance, recombinants, T-tet, T-kan, and T-tet-kan, factors were obtained. These are capable of conferring drug-resistance and are conjugally transmissible as a single genetic unit. E. coli K12 strains carrying T95 or T-tet factor were insensitive to male phages and T-tet (probably T95) factor was transmitted sexually at about 10-5 transmission frequency after 1 hr of mixed culture. On the contrary, E. coli K12 strains carrying T-kan or T-tet-kan factor were found to become sensitive to male phages and their transmission frequency was 102 to 103-fold higher than that of T-tet factor. As a result of these findings, we concluded that the pili formation of T95 or T-tet factor is in a repressed state but the formation of a recombinant between T95 (or T-tet) and r3 (kan) determinants results in the derepression of pili formation.In previous papers [17,24], we presented three mechanisms involved in the acquisition of transmission of otherwise nontransferable resistance (r) determinants, 1) the resistance determinant which is integrated into the bacterial chromosome is transferred accompanying chromosomal transfer by sex factors such as F, R, and T factors, 2) acquisition of transferability of a nontransferable R factor which exists extrachromosomally, by complementation of episomic elements such as F, R, and T factors, and 3) formation of a recombinant between an r determinant and sex factors, resulting in the formation of F-r, R-r, and T-r factors [8,10,17]. This paper deals with the genetic properties of the T factors and of the recombinant T-r factors. MATERIALS AND METHODSStrains. Derivative strains of Escherichin coli K12 were used. The abbreviations and symbols of various markers were assigned according to the symbols described 339 340 M. KAMEDA ET AL.

Transmission of lac by the Sex Factor E in Erwinia Strains from Human Clinical Sources

“…It is now generally accepted that plasmid transmission is more frequent than previously thought among related bacteria sharing a common habitat (7,34,37). In addition, recombination between plasmids is known to occur under laboratory conditions (15,19,25,32,40,49) and possibly in nature (7,14). That plasmid inheritance might play a significant role in animal pathogenicity is indicated by the transmissible nature of ent (the determinant of enterotoxin production) and hly (the determinant of hemolysin production) among animal isolates of E. coli (38,41,42).…”

Naturally Occurring R Factor, Derepressed for Pilus Synthesis, Belonging to the Same Compatibility Group as the Sex Factor F of Escherichia coli K-12

“…Recombination between plasmids has often been brought about in the laboratory (1,7,9,11,12,18,19,22,26). The properties of R386 suggest that such recombination may also occur in nature.…”

Serum GDF15 Level Is Independent of Sarcopenia in Older Asian Adults

“…Given the lack of data on the association between GDF15 and sarcopenia in community-dwelling older adults, we derived the sample size from a similar human study that was performed on preoperative cardiovascular surgery patients with an available mean and standard deviation (SD) of GDF15. From the report on patients with cardiovascular disease (average age 69.9 years), the serum GDF15 levels from male and female were 2,280 ± 1,951 pg/ mL in the sarcopenia group (n = 24) and 1,286 ± 1,034 pg/mL in the non-sarcopenia group (n = 42) [25]. From this observation, the required total sample size was 80 with an alpha of 0.05 and a beta of 0.80.…”