title: Postgenomic analysis of streptococcus thermophilus cocultivated in milk with Lactobacillus delbrueckii subsp. bulgaricus: involvement of nitrogen, purine, and iron metabolism.
abstract: Streptococcus thermophilus is one of the most widely used lactic acid bacteria in the dairy industry, in particular in yoghurt manufacture, where it is associated with Lactobacillus delbrueckii subsp. bulgaricus. This bacterial association, known as a proto-cooperation, is poorly documented at the molecular and regulatory levels. We thus investigate the kinetics of the transcriptomic and proteomic modifications of S. thermophilus LMG 18311 in response to the presence of L. delbrueckii subsp. bulgaricus ATCC 11842 during growth in milk at two growth stages. Seventy-seven different genes or proteins (4.1% of total coding sequences), implicated mainly in the metabolism of nitrogen (24%), nucleotide base (21%), and iron (20%), varied specifically in coculture. One of the most unpredicted results was a significant decrease of most of the transcripts and enzymes involved in purine biosynthesis. Interestingly, the expression of nearly all genes potentially encoding iron transporters of S. thermophilus decreased, whereas that of iron-chelating dpr as well as that of the fur (perR) regulator genes increased, suggesting a reduction in the intracellular iron concentration, probably in response to H(2)O(2) production by L. bulgaricus. The present study reveals undocumented nutritional exchanges and regulatory relationships between the two yoghurt bacteria, which provide new molecular clues for the understanding of their associative behavior.
authors.affiliation: INRA, UR477 Biochimie Bactérienne, F-78350 Jouy-en-Josas, France.
authors.forename: Luciana
authors.initials: L
authors.lastname: Herve-Jimenez
authors.forename: Isabelle
authors.initials: I
authors.lastname: Guillouard
authors.forename: Eric
authors.initials: E
authors.lastname: Guedon
authors.forename: Samira
authors.initials: S
authors.lastname: Boudebbouze
authors.forename: Pascal
authors.initials: P
authors.lastname: Hols
authors.forename: Véronique
authors.initials: V
authors.lastname: Monnet
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Maguin
authors.forename: Françoise
authors.initials: F
authors.lastname: Rul
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000032:analysis; D018920:Coculture Techniques; D020869:Gene Expression Profiling; D007501:Iron / Q000378:metabolism*; D048668:Lactobacillus delbrueckii / Q000254:growth & development*; D008892:Milk / Q000382:microbiology*; D009584:Nitrogen / Q000378:metabolism*; D020543:Proteome / Q000032:analysis; D011687:Purines / Q000378:metabolism*; D048249:Streptococcus thermophilus / Q000737:chemistry* / Q000235:genetics* / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D020543:Proteome; D011687:Purines; D007501:Iron; D009584:Nitrogen; C030985:purine