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The capacity of FTIR spectroscopy for identification and classification of lactic acid bac- teria has been proved on brewery strains and more recently by ourselves on dairy strains. During our study, we underlined that IR spectra give very informative data which can be used for old or more recent taxonomical purposes. We tried to illustrate this aspect with two examples: the distinction between Streptococcus thermophilusand Streptococcus salivarius, the taxonomic range of Lactobacillus casei, paracasei, zeae and rhamnosus. The interest of this tool for taxonomic studies will be discussed. taxonomy / FTIR spectroscopy / Streptococcus / Lactobacillus

The potentiality of FTIR spectroscopy for the identification of lactic acid bacteria (LAB) used in the dairy industry was tested. For this purpose, spectra of different strains were recorded using standardized conditions. These strains were species of Lactobacillus (12 species, 3 sub- species), Lactococcus (4 species, 3 subspecies), Leuconostoc (3 species, 3 subspecies), Weissella (1 species) and Streptococcus (2 species) involved in the soft cheese industry . Spectral libraries were then established by statistical analysis. Reference strains were then tested on these libraries, and 100% of correct identifications were obtained at the genus and species level, 86% at the subspecies level. Well-identified strains were included in libraries. Wild isolates ( n = 48) previously identified by biochemical tests and RAPD method were then tested. We obtained 100% at the genus level and 69% at the species level of correlation between FTIR and other methods. Finally, spectra of reference strains performed in other laboratories were tested with the same method, and the results tallied with official identification in 100% of the cases at the genus level and in 41% of the cases at the species level. These results concerning a few strains allow us to plan the development of a more complete database for rapid identification of LAB.

La presence de certaines bacteries au sein d’un biofilm peut soit accelerer un processus de corrosion deja etabli, soit creer des conditions favorables a son elaboration. Les microorganismes consideres a ce jour comme les plus agressifs pour les materiaux metalliques en milieu marin sont les Bacteries Sulfato-Reductrices (BSR) et Thiosulfato-Reductrices (BTR). Des travaux preliminaires ont montre les potentialites de la spectroscopie InfraRouge a Transformee de Fourier (IRTF) pour la discrimination de ces 2 groupes. La realisation d’une bibliotheque de spectres de reference necessite la mise en place de conditions de cultures standardisees communes a l’ensemble de la flore etudiee. Une premiere bibliotheque spectrale incluant 6 BSR et 6 BTR de collection a ete elaboree. La classification hierarchique de ces 12 souches permet d’obtenir 3 clusters distincts (un de BSR, un de BTR et un mixte), et de discriminer l’ensemble de ces souches au niveau genre (11 souches sur 12) et au niveau espece (12 souches sur 12). Dix souches isolees de l’environnement ont ete testees sur cette bibliotheque, et un debut d’identification a pu etre propose. L’enrichissement de la base de donnees initiee sera poursuivi pour ameliorer les capacites d’identification des bacteries sulfurogenes isolees de l’environnement marin.