Transformation of a type 4 encapsulated strain of Streptococcus pneumoniae

Streptococcus pneumoniae strain JNR.7/87 is a highly virulent, type 4 encap sulated Gram-positive bacterium whose transformability has not been tested previously, and whose genome is currently being sequenced. The strain was t ransformed at very low efficiency by addition of exogenous competence-stimu lating peptide: However, the efficiency was too low and irreproducible to b e useful in many genetic studies. Therefore, the effects on transformation efficiency of changing different components of competence-stimulating pepti de-induced transformation have been examined. Screening of growth media was followed by optimization of pre-induction culture acidification, glycine c oncentration, and induction time. An optimized protocol was developed where by S. pneumoniae strain JNR.7/87 was transformed reproducibly with a strept omycin resistance (Sm-R) marker at an efficiency of similar to 10(5) colony forming units per 10(8) cells. (C) 1999 Federation of European Microbiolog ical Societies. Published by Elsevier Science B.V. All rights reserved.