Genetic and biochemical approaches towards unravelling the degradation of gallotannins by Streptococcus gallolyticus

Microbial Cell Factories

Research

Natalia Jiménez¹  Félix López de Felipe¹  María Esteban-Torres¹  Rosario Muñoz¹  Inés Reverón¹  Blanca de las Rivas¹ 

[1] Laboratorio de Biotecnología Bacteriana, Instituto de Ciencia y Tecnología de Alimentos y Nutrición, ICTAN-CSIC, Juan de la Cierva 3, Madrid, Spain;

关键词: Streptococcus gallolyticus;    Tannase;    Gallate decarboxylase;    Hydrolase;    Gallotannins;   

DOI  :  10.1186/s12934-014-0154-8

 received in 2014-09-30, accepted in 2014-10-20,  发布年份 2014

来源: Springer

【 摘 要 】

BackgroundHerbivores have developed mechanisms to overcome adverse effects of dietary tannins through the presence of tannin-resistant bacteria. Tannin degradation is an unusual characteristic among bacteria. Streptococcus gallolyticus is a common tannin-degrader inhabitant of the gut of herbivores where plant tannins are abundant. The biochemical pathway for tannin degradation followed by S. gallolyticus implies the action of tannase and gallate decarboxylase enzymes to produce pyrogallol, as final product. From these proteins, only a tannase (TanBSg) has been characterized so far, remaining still unknown relevant proteins involved in the degradation of tannins.ResultsIn addition to TanBSg, genome analysis of S. gallolyticus subsp. gallolyticus strains revealed the presence of an additional protein similar to tannases, TanASg (GALLO_0933). Interestingly, this analysis also indicated that only S. gallolyticus strains belonging to the subspecies “gallolyticus” possessed tannase copies. This observation was confirmed by PCR on representative strains from different subspecies. In S. gallolyticus subsp. gallolyticus the genes encoding gallate decarboxylase are clustered together and close to TanBSg, however, TanASg is not located in the vicinity of other genes involved in tannin metabolism. The expression of the genes enconding gallate decarboxylase and the two tannases was induced upon methyl gallate exposure. As TanBSg has been previously characterized, in this work the tannase activity of TanASg was demonstrated in presence of phenolic acid esters. TanASg showed optimum activity at pH 6.0 and 37°C. As compared to the tannin-degrader Lactobacillus plantarum strains, S. gallolyticus presented several advantages for tannin degradation. Most of the L. plantarum strains possessed only one tannase enzyme (TanBLp), whereas all the S. gallolytcius subsp. gallolyticus strains analyzed possesses both TanASg and TanBSg proteins. More interestingly, upon methyl gallate induction, only the tanBLp gene was induced from the L. plantarum tannases; in contrast, both tannase genes were highly induced in S. gallolyticus. Finally, both S. gallolyticus tannase proteins presented higher activity than their L. plantarum counterparts.ConclusionsThe specific features showed by S. gallolyticus subsp. gallolyticus in relation to tannin degradation indicated that strains from this subspecies could be considered so far the best bacterial cellular factories for tannin degradation.

【 授权许可】

Unknown   
© Jiménez et al.; licensee BioMed Central Ltd. 2014. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.