Improved genetic transformation by disarmament of type II Restriction-Modification system in .

UNLABELLED

, group C Streptococci, is currently used for the industrial production of hyaluronic acid (HA). However, genetic manipulation of is severely limited by its low transformation efficiency, which might be in part due to the Restriction-Modification (R-M) systems. The complete genome sequence of ATCC39920 revealed the presence of two putative R-M systems, type I and type II. The putative type I R-M system is encoded by three closely linked genes: (), , (), and the putative type II R-M system consists of two closely linked genes: and (). Inactivation of encoding the restriction endonuclease (REase) of the type I R-M system, showed no apparent effects on transformation efficiency, implying that disarmament of the type I R-M system alone is not sufficient for increasing transformation efficiency. However, inactivation of , encoding the REase of the type II R-M system, improved transformation efficiency by 4.97 folds, indicating that type II R-M system is the major barrier that restricts genetic transformation in . Furthermore, strains lacking either of the two R-M systems are phenotypically indistinguishable from the wild-type in terms of cell growth and HA production. In summary, our study revealed that the type II R-M system is the main barrier to genetic transformation in ATCC39920, and that the deletion of the type II R-M system renders more transformable, thus facilitating metabolic engineering of this industrially important microorganism.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03227-x.