A Temporal -omic Study of Propionibacterium freudenreichii CIRM-BIA1T Adaptation Strategies in Conditions Mimicking Cheese Ripening in the Cold

Propionibacterium freudenreichii is used as a ripening culture in Swiss cheese manufacture. It grows when cheeses are ripened in a warm room (about 24°C). Cheeses with an acceptable eye formation level are transferred to a cold room (about 4°C), inducing a marked slowdown of propionic fermentation, but P. freudenreichii remains active in the cold. To investigate the P. freudenreichii strategies of adaptation and survival in the cold, we performed the first global gene expression profile for this species. The time-course transcriptomic response of P. freudenreichii CIRM-BIA1T strain was analyzed at five times of incubation, during growth at 30°C then for 9 days at 4°C, under conditions preventing nutrient starvation. Gene expression was also confirmed by RT-qPCR for 28 genes. In addition, proteomic experiments were carried out and the main metabolites were quantified. Microarray analysis revealed that 565 genes (25% of the protein-coding sequences of P. freudenreichii genome) were differentially expressed during transition from 30°C to 4°C (P<0.05 and |fold change|>1). At 4°C, a general slowing down was observed for genes implicated in the cell machinery. On the contrary, P. freudenreichii CIRM-BIA1T strain over-expressed genes involved in lactate, alanine and serine conversion to pyruvate, in gluconeogenesis, and in glycogen synthesis. Interestingly, the expression of different genes involved in the formation of important cheese flavor compounds, remained unchanged at 4°C. This could explain the contribution of P. freudenreichii to cheese ripening even in the cold. In conclusion, P. freudenreichii remains metabolically active at 4°C and induces pathways to maintain its long-term survival

Caractérisations thermodynamique et structurale de mélanges multiparaffiniques synthétiques et réels : aspects de leur cristallisation

The crystallization of normal paraffin hydrocarbons in middle distillate fuels and petroleum cuts bas been shown to be at the origin of real problems for refiners and diesel-fuel consumers in very cold regions. Thermodynamic calculations of paraffinic crude oil crystallization are based on equations of solid/liquid equilibria and the ir capacity to fit and predict experimental data depend on the choice of the best model for each phase. To understand the behaviour of these solid deposits, the aim of this study is to determine and to compare the structural and thermodynamic properties of a great number of synthetic mixtures and wax es, whose n-alkane molar concentration distributions are similar to that observed in crude and diesel oils or in petroleum waxes. First, the crystallization study of synthetic mixtures, with decreasing distribution of alkanes (as in paraffinic crude oil) allows to detlne crystallization process and to underline the influence of parameters, like temperature, length and composition of the distribution, on the number of crystallized solid solutions. Secondly, n-alkanes calorimetrie studies lead to the determination of simple analytical expressions to represent thermodynamic properties (temperatures and enthalpies of phase change, heat capacities of solid and liquid phases) as a function of carbon atom number. These relations allow to bring out the existence of excess properties for paraffinic mixtures. For ail synthetic mixtures and waxes studied, the ordered solid phase shows a great deviation to ideality, and the liquid phase, an athermal behaviour. Finally, the measurement of solid solutions formation enthalpies of multicomponent paraffinic systems permit to test the predictive capacity of the Uniquac model, for the restitution of solid phases excess properties.La présence des n-alcanes dans les effluents pétroliers pose un problème pour l'industrie pétrolière, car ils cristallisent, lors d'un abaissement de température, en formant des dépôts solides paraffiniques. La modélisation thermodynamique de la formation de ces dépôts solides repose sur l'écriture des conditions d'équilibre solide/liquide et la performance prédictive de ce modèle dépend du choix, pour chaque phase, de la meilleure représentation possible. Afin de définir le comportement des phases solides paraffiniques, cette étude s'est donc focalisée sur la caractérisation des propriétés structurales et thermodynamiques d'un grand nombre de mélanges synthétiques et réels, de distribution identique à celle des fractions paraffiniques rencontrées, soit dans les bruts pétroliers et les gazoles, soit dans les cires pétrolières et les paraffines. Dans un premier temps, l'étude de la cristallisation de mélanges n-aires synthétiques, de distribution exponentielle décroissante, a permis de cerner les processus de cristallisation et de mettre en évidence l'influence de paramètres tels que la température, le nombre de n-alcanes et la composition de la distribution sur le nombre de solutions solides cristallines formées. Dans un second temps, l'étude calorimétrique systématique de n-alcanes purs a abouti à l'établissement d'expressions analytiques simples pour représenter l'ensemble des grandeurs de changement de phase et des capacités calorifiques en phases solide et liquide en fonction de la longueur de chaîne du n-alcane considéré, expressions qui permettent de mettre en évidence des grandeurs d'excès pour les mélanges étudiés. Pour tous les mélanges complexes, on peut conclure que la phase solide ordonnée présente une 1 forte non idéalité, qui dépend des paramètres de la distribution paraffinique (fraction en non n-alcanes, nombre de n-alcanes, allure de la loi de distribution,...), et la phase liquide, un comportement athermique.Finalement, grâce aux mesures des enthalpies de formation des phases solides des mélanges multiparaffiniques, nous avons testé les aptitudes prédictives du modèle Uniquac adapté, dans la restitution des grandeurs d'excès des phases solides

Caractérisations thermodynamique et structurale de mélanges multiparaffiniques synthétiques et réels (Aspects deleur cristallisation)

NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Temperatures and enthalpies of (solid + solid) and (solid + liquid) transitions of n-alkanes

International audienc

Time-course comparison of transcriptome and proteome changes in <i>P. freudenreichii</i> CIRM-BIA1^T strain, for genes involved in metabolic categories CD, CE, DNA, E, L, Mi, Nt, and P.

a<p>Spot number (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone.0029083.s006" target="_blank">Table S4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone-0029083-g002" target="_blank">Fig. 2</a>).</p><p>Bold characters indicate genes that are differentially expressed according to microarray experiments (<i>P</i><0.05 and |fold change|>1 for at least one sampling time) and RT-qPCR (<i>P</i><0.05) experiments.</p

Time-course of <i>P. freudenreichii</i> CIRM-BIA1^T metabolic activity over a 40 h-incubation at 30°C followed by a further 9 days at 4°C.

<p>Lactate was added at 64 h (<b>↓</b>) to mimic cheese ripening conditions. <b>A</b>, growth monitored by optical density (650 nm) measurements (black circle), lactate consumption (cross), production of acetate (white triangle) and propionate (black triangle); <b>B</b>, production of pyruvate (white rhombus) and succinate (black rhombus), consumption of aspartate (white triangle) and asparagine (black triangle); <b>C</b>, production of methylbutanoate (sum of 2-methyl- and 3-methylbutanoate acids). ¥: sampling times for microarray experiments.</p

Time-course comparison of transcriptome and proteome changes in <i>P. freudenreichii</i> CIRM-BIA1^T strain, for genes involved in metabolic category CH.

a<p>Spot number (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone.0029083.s006" target="_blank">Table S4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone-0029083-g002" target="_blank">Fig. 2</a>).</p><p>Bold characters indicate genes that are differentially expressed according to microarray experiments (<i>P</i><0.05 and |fold change|>1 for at least one sampling time) and RT-qPCR (<i>P</i><0.05) experiments.</p

Time-course comparison of transcriptome and proteome changes in <i>P. freudenreichii</i> CIRM-BIA1^T strain, for genes involved in metabolic category Ph and PM.

a<p>Spot number (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone.0029083.s006" target="_blank">Table S4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone-0029083-g002" target="_blank">Fig. 2</a>).</p><p>Bold characters indicate genes that are differentially expressed according to microarray experiments (<i>P</i><0.05).</p

Figure 2

<p>Two-dimensional analysis of proteins produced during <i>P. freudenreichii</i> CIRM-BIA1^T growth (<b>A</b>) at 30°C (reference time 20 h) and then (<b>B</b>) at 4°C (3 days). Numbers identify spots which volume decreased at 4°C (<b>A</b>), or increased at 4°C (<b>B</b>). The identification by MS/MS of each spot can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone.0029083.s006" target="_blank">Table S4</a>.</p

Time-course comparison of transcriptome and proteome changes in <i>P. freudenreichii</i> CIRM-BIA1^T strain, for genes involved in metabolic categories A, AA and C.

a<p>Spot number (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone.0029083.s006" target="_blank">Table S4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029083#pone-0029083-g002" target="_blank">Fig. 2</a>).</p><p>Bold characters indicate genes that are differentially expressed according to microarray experiments (<i>P</i><0.05 and |fold change|>1 for at least one sampling time) and RT-qPCR (<i>P</i><0.05) experiments.</p