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Applied and Environmental Microbiology, October 2009, p. 6340-6351, Vol. 75, No. 19
0099-2240/09/$08.00+0     doi:10.1128/AEM.00195-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Conjugative Plasmid from Lactobacillus gasseri LA39 That Carries Genes for Production of and Immunity to the Circular Bacteriocin Gassericin A{triangledown}

Yoshiyuki Ito,1* Yasushi Kawai,2 Kensuke Arakawa,2 Yoshiko Honme,1 Takashi Sasaki,1 and Tadao Saito2

Food Science Institute, Division of Research and Development, Meiji Dairies Corporation, Odawara, Japan,1 Laboratory of Animal Products Chemistry, Biological Resource Science, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan2

Received 28 January 2009/ Accepted 30 July 2009

Gassericin A is a circular bacteriocin produced by Lactobacillus gasseri strain LA39. We found a 33,333-bp plasmid, designated pLgLA39, in this strain. pLgLA39 contained 44 open reading frames, including seven genes related to gassericin A production/immunity (gaa), as well as genes for replication, plasmid maintenance, and conjugative transfer. pLgLA39 was transferred from LA39 to the type strain of L. gasseri (JCM 1131) by filter mating. The transconjugant exhibited >30-fold-higher more resistance to gassericin A and produced antibacterial activity. Lactobacillus reuteri LA6, the producer of reutericin 6, was proved to harbor a plasmid indistinguishable from pLgLA39 and carrying seven genes 100% identical to gaa. This suggests that pLgLA39 might have been transferred naturally between L. gasseri LA39 and L. reuteri LA6. The seven gaa genes of pLgLA39 were cloned into a plasmid vector to construct pGAA. JCM 1131T transformed with pGAA expressed antibacterial activity and resistance to gassericin A. pGAA was segregationally more stable than a pGAA derivative plasmid from which gaaA was deleted and even was more stable than the vector. This suggests the occurrence of postsegregational host killing by the gaa genes. pLgLA39 carried a pemIK homolog, and segregational stabilization of a plasmid by the pLgLA39-type pemIK genes was also confirmed. Thus, pLgLA39 was proved to carry the genes for at least two plasmid maintenance mechanisms, i.e., gaa and pemIK. Plasmids containing a repA gene similar to pLgLA39 repA were distributed in several L. gasseri strains.

* Corresponding author. Mailing address: Food Science Institute, Division of Research and Development, Meiji Dairies Corporation, 540 Naruda, Odawara, Kanagawa 250-0862, Japan. Phone: 81 (465) 37-5130. Fax: 81 (465) 37-3619. E-mail: yoshiyuki_itou{at}meiji-milk.com

{triangledown} Published ahead of print on 7 August 2009.

Applied and Environmental Microbiology, October 2009, p. 6340-6351, Vol. 75, No. 19
0099-2240/09/$08.00+0     doi:10.1128/AEM.00195-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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