Phenotypic and genotypic characterization of peptidoglycan hydrolases of [i]Lactobacillus sakei[/i]

Afef Najjari (1) , Houda Amairi (2) , Stephane Chaillou (3, 4) , Diego Mora (5) , Abdellatif Boudabous (6) , Monique Zagorec (7, 4) , Hadda Ouzari (1)

1 Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives
2 Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives
3 MICALIS - MICrobiologie de l'ALImentation au Service de la Santé
4 UFLEC - Unité de recherche Flore Lactique et Environnement Carné
5 Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche
6 Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives
7 SECALIM - SECurité des ALIments et Microbiologie

[i]Lactobacillus sakei[/i], a lactic acid bacterium naturally found in fresh meat and sea products, is considered to be one of the most important bacterial species involved in meat fermentation and bio-preservation. Several enzymes of Lb. sakei species contributing to microbial safeguarding and organoleptic properties of fermented-meat were studied. However, the specific autolytic mechanisms and associated enzymes involved in Lb. sakei are not well understood. The autolytic phenotype of 22 Lb. sakei strains isolated from Tunisian meat and seafood products was evaluated under starvation conditions, at pH 6.5 and 8.5, and in the presence of different carbonsources. A higher autolytic rate was observed when cells were grown in the presence of glucose and incubated at pH 6.5. Almost all strains showed high resistance to mutanolysin, indicating a minor role of muramidases in Lb. sakei cell lysis. Using Micrococcus lysodeikticus cells as a substrate in activity gels zymogram, peptidoglycan hydrolase (PGH) patterns for all strains was characterized by two lytic bands of 80 (B1) and 70 kDa (B2), except for strain BMG.167 which harbored two activity signals at a lower MW. Lytic activity was retained in high salt and in acid/basic conditions and was active toward cells of Lb. sakei, Listeria monocytogenes, Listeria ivanovii and Listeria innocua. Analysis of five putative PGH genes found in the Lb. sakei 23 K model strain genome, indicated that one gene, lsa1437, could encode a PGH (Nacetylmuramoyl-L-alanine amidase) containing B1 and B2 as isoforms. According to this hypothesis, strain BMG.167 showed an allelic version of lsa1437 gene deleted of one of the five LysM domains, leading to a reduction in the MW of lytic bands and the high autolytic rate of this strain. Characterization of autolytic phenotype of Lb. sakei should expand the knowledge of their role in fermentation processes where they represent the dominant species.

Mots clés: autolysis; lactobacillus sakei; mutanolysin; peptidoglycan hydrolase; LysM domains

Domaines: Sciences du Vivant [q-bio]

Afef Najjari, Houda Amairi, Stephane Chaillou, Diego Mora, Abdellatif Boudabous, et al.. Phenotypic and genotypic characterization of peptidoglycan hydrolases of [i]Lactobacillus sakei[/i]. Journal of Advanced Research, 2015, 7 (1), ⟨10.1016/j.jare.2015.04.004⟩. ⟨hal-01204469⟩