In comparison to the non-supplemented negative control, no growth was observed for fucoidan. Decreased growth rates and longer doubling times were found for all substrates tested compared to the positive control grown on a complex medium.

The comparable or even better growth performance regarding λ-carrageenan and chondroitin sulfate given equal concentrations of substrate applied is probably a consequence of those substrates matching the natural environment of R. baltica SH1T more GSK1210151A than glucose. Both, chondroitin sulfate and λ-carrageenan occur in significant amounts in marine environments and also niches inhabited by R. baltica SH1T ( Zierer and Mourao, 2000 and Ziervogel and Arnosti, 2008). The finding, that R. baltica SH1T does not grow on fucoidan was surprising. Closely related species of R. baltica SH1T are known to dominate biofilms on the brown algae Laminaria hyperborea. These brown algae are known to secrete significant amounts of fucoidans. R. baltica SH1T features one single gene encoding for an α-l-fucoidase. Two other species of this genus (R. sallentina and R. maiorica) were found to bear more than 20 copies of this gene (not shown). Therefore, other species of this genus probably inhabit these ecosystems. In the past, it was proposed that secreted fucoidans can probably function as growth Selleckchem RAD001 substrate for present marine Planctomycetes. However, fucoidans from different algal species can strongly

differ in their structure ( Bilan et al., 2006 and Li et al., 2008). In this study fucoidan from Fucus vesiculosus was used as a growth substrate. The lack of growth during the study is probably due to structural differences between

fucoidans of different origin or due to the aforementioned lack of suitable hydrolase activities. Differently sized datasets were obtained from microarray analyses. Generally, 1000 to 1500 genes were found to be expressed, representing 14 to 20% of all genes present in the genome of R. baltica SH1T. The fucoidan-related dataset was an outlier with only 524 genes. In the context of chondroitin sulfate, approximately 10% of all expressed genes have been upregulated. 3% have been downregulated. With respect to λ-carrageenan and fucoidan, smaller fractions of the expressed genes have been upregulated (7 and 5%, respectively). Larger portions, 18% and 17% have been expressed at a lower these degree. Generally, large portions of genes expressed have been linked to the respective substrate. For instance, 611 of 1500 expressed genes in case of chondroitin sulfate were exclusively expressed regarding this substrate. The focus of the gene expression analyses was set on potentially expressed sulfatases and FGEs. Out of six predicted FGEs in R. baltica SH1T (Gene IDs: RB4229, RB5028, RB8026, RB11498, RB11811, RB11998), one, RB11998, was found to be active in the presence of all sulfated polysaccharides, but not in the glucose grown cells ( Table 3).