title: Proteomic signature of Lactococcus lactis NCDO763 cultivated in milk.
abstract: We have compared the proteomic profiles of L. lactis subsp. cremoris NCDO763 growing in the synthetic medium M17Lac, skim milk microfiltrate (SMM), and skim milk. SMM was used as a simple model medium to reproduce the initial phase of growth of L. lactis in milk. To widen the analysis of the cytoplasmic proteome, we used two different gel systems (pH ranges of 4 to 7 and 4.5 to 5.5), and the proteins associated with the cell envelopes were also studied by two-dimensional electrophoresis. In the course of the study, we analyzed about 800 spots and identified 330 proteins by mass spectrometry. We observed that the levels of more than 50 and 30 proteins were significantly increased upon growth in SMM and milk, respectively. The large redeployment of protein synthesis was essentially associated with an activation of pathways involved in the metabolism of nitrogenous compounds: peptidolytic and peptide transport systems, amino acid biosynthesis and interconversion, and de novo biosynthesis of purines. We also showed that enzymes involved in reactions feeding the purine biosynthetic pathway in one-carbon units and amino acids have an increased level in SMM and milk. The analysis of the proteomic data suggested that the glutamine synthetase (GS) would play a pivotal role in the adaptation to SMM and milk. The analysis of glnA expression during growth in milk and the construction of a glnA-defective mutant confirmed that GS is an essential enzyme for the development of L. lactis in dairy media. This analysis thus provides a proteomic signature of L. lactis, a model lactic acid bacterium, growing in its technological environment.
authors.affiliation: Unité Biochimie et Structure des Protéines, INRA, Jouy-en-Josas, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Gitton
authors.forename: Mickael
authors.initials: M
authors.lastname: Meyrand
authors.forename: Juhui
authors.initials: J
authors.lastname: Wang
authors.forename: Christophe
authors.initials: C
authors.lastname: Caron
authors.forename: Alain
authors.initials: A
authors.lastname: Trubuil
authors.forename: Alain
authors.initials: A
authors.lastname: Guillot
authors.forename: Michel-Yves
authors.initials: MY
authors.lastname: Mistou
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D013294:Lactococcus lactis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D008892:Milk / Q000382:microbiology*; D020543:Proteome
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D020543:Proteome; D005974:Glutamate-Ammonia Ligase