When acetamide utilization, uridine prototrophy, phleomycin resistance, or hygromycin resistance was used to select transformants in A. awamori, average transformation frequencies of 0.2, 40, 80, and 200 transformants per 106 conidiospores were obtained (Michielse et al. 2008).
A large library also requires good electrocompetent E. coli cells with transformation frequencies of 10-10 transformants per μg plasmid DNA.
Figure 1 shows the log-transformed means (±SEM) of the transformation frequencies of serotypes 6B, 14, 19F, 9V, 23F, 3, and 18C induced by CSP-1 and CSP-2.
Gene replacement events, integrations at non-homologous sites and single-copy homologous integrations were observed, and transformation frequencies were achieved up to 6000 transformants per µg of DNA.
Transformation frequencies were in the range 36 to 87 transformants per 10 μg of vector DNA and 106 protoplasts.
In general, higher transformation frequencies were observed in E. coli O157 H7 9×1022 to 1.25×104 transformants/µg) than in Salmonella (1.2×102 to 1.4×103 transformants/µg).
Uptake of USS-containing DNA is facilitated by a number of competency proteins, resulting in transformation frequencies that can be as high as 10-3 to 10-2 transformants per CFU [ 31] and in homologous recombination with chromosomal DNA.
The transformation frequencies were expressed as the log10 value of the percentage of transformed cells.
Transformation frequencies in marker-free transformations (MF) are derived from the number of transformed shoots (transformed) and the total number of shoots minus the number of transformed shoots (non-transformed).
Many bacterial species have low transformation frequencies.
To preclude false identification of genes as essential due to low transformation frequencies, we performed experiments to optimize the transformation efficiency of S. sanguinis SK3626.
