C: AHL accumulation. All samples were harvested during exponential growth at an optical density of ~2. Genes associated with quorum sensing (I), the PM production (II), and metabolism (III) are indicated. D: Cluster analysis of growth condition dependent data shown in A, B and C. The red/gray pattern indicates the degree of structural identity; components with a high structural identity (R2 > 0.98) are clustered as indicated by the coloured groups (· · ··). Cluster analysis was performed using PermutMatrix version 1.9.3. Correlation analysis of these measurements

revealed significant cluster patterns (Figure 6D). At the beginning selleck products only clusters with a structural identity >0.98 were taken into account (refer to coloured groups in Figure 6D). luxR1 click here expression was strongly correlated (R2 = 1) with both PM and C6OH-HSL levels and also with the expression level of nifK (Rru_A1012). Both nifK expression and PM production are strongly repressed in response to oxygen in R. rubrum[4, 28]. The luxR2 mRNA accumulation correlated with the initial selleck kinase inhibitor growth rate (μ) and expression of the genes

coding for phosphoenolpyruvate carboxykinase (pepck) and cytochrom oxidase cbb3 (ccoN). luxR3 expression correlates with the oxygen availability (pO2) and the expression of alpha-ketoglutarate dehydrogenase. luxR4 expression clustered with the expression of bchE and sdhD encoding Magnesium-Protoporphyrin IX monomethylesther (Mg-PPIX-mme) cyclase, an enzyme in the bacteriochlorophyll pathway, and the subunit D of the succinate dehydrogenase complex, respectively. luxR6 clustered with C10OH-HSL and genes coding for poly(R)-hydroxyalkanoic acid synthase (phaC), malic enzyme (maeB) and pyruvate carboxylase (pyc). These enzymes are involved in coordinating the metabolic fluxes of the central carbon metabolism relative to the available carbon source. C8-HSL clustered only with the availability of light. luxI

and C8OH-HSL showed no significant correlation. If the coefficient describing the structural identity in Figure 6D is relaxed to a value of 0.9, the data falls into two groups. The lower group contains luxR1 and C8-HSL along with bphP, tspO, pufL puhA and pufB which are known to be related to PM formation in other anoxgenic photosynthetic bacteria. In contrast, the upper Ceramide glucosyltransferase group contains both the remaining luxR-similar genes and genes encoding enzymes which are involved in growth modes and regulation of related metabolism. Dynamics of the quorum sensing system during Fed-Batch cultivation For a comprehensive picture of the contribution of the quorum sensing system to HCD cultivations of R. rubrum, the expression of lux genes and the kinetics of AHLs were monitored throughout the time course of a microaerobic Fed-Batch cultivation and correlated to PM expression and growth rate (Figure 7). The accumulation of the tetrapyrolle compounds PPIX and Mg-PP-mme in the culture broth was also determined.