The Effects of the Marine-Derived Polysaccharides Laminarin and Chitosan on Aspects of Colonic Health in Pigs Challenged with Dextran Sodium Sulphate

This study examined the effects of dietary supplementation with laminarin or chitosan on colonic health in pigs challenged with dextran sodium sulphate (DSS). Weaned pigs were assigned to: (1) a basal diet (n = 22); (2) a basal diet + laminarin (n = 10); and (3) a basal diet + chitosan (n = 10). On d35, the basal group was split, creating four groups: (1) the basal diet (control); (2) the basal diet + DSS; (3) the basal diet + laminarin + DSS; and (4) the basal diet + chitosan + DSS. From d39–42, the pigs were orally challenged with DSS. On d44, colonic tissue/digesta samples were collected. The basal DSS group had reduced growth, higher pathology score and an increased expression of MMP1, IL13 and IL23 compared with the controls (p < 0.05); these parameters were similar between the DSS-challenged groups (p > 0.05). In the basal DSS group, the relative abundance of beneficial taxa including Prevotella and Roseburia were reduced while Escherichia/Shigella were increased, compared with the controls (p < 0.05). The relative abundance of Escherichia/Shigella was reduced and the molar proportions of acetate were increased in the laminarin DSS group compared with the basal DSS group (p < 0.01), suggesting that laminarin has potential to prevent pathogen proliferation and enhance the volatile fatty acid profile in the colon in a porcine model of colitis

The Family Rhodobacteraceae

The family Rhodobacteraceae can be considered a paradigm of modern taxonomy of prokaryotes. Taking into account the number of species and genera that conforms the family, together with the knowledge about their abundance and vast global distribution, it surprises that most of them have been described relatively recent to our days. Two notable exceptions are Rhodonostoc capsulatum (Molisch, Die purpurbakterien nach neuen untersuchungen, vols i–vii. G. Fischer, Jena, pp 1–95, 1907) and Micrococcus denitrificans Beijerinck and Minkman (Zentbl Bakteriol, Parasitenkd, Infektionskr Hyg. Abt II 25:30–63, 1910), early basonyms of Rhodobacter capsulatus and Paracoccus denitrificans, respectively. The fact that so many descriptions within this family are recent means that some studies have been concomitant and pose a challenge not only for pure taxonomic studies but also for interpreting other studies in which a rapidly evolving nomenclature had to be used anyway. The metabolic and ecological diversity of the group adds further complexity. In spite of all these difficulties, the picture is far from being a chaos and it can be considered an exciting and important bacterial group to study. Rhodobacteraceae are, fundamentally, aquatic bacteria that frequently thrive in marine environments. They comprise mainly aerobic photo- and chemoheterotrophs but also purple non-sulfur bacteria which perform photosynthesis in anaerobic environments. They are deeply involved in sulfur and carbon biogeochemical cycling and symbiosis with aquatic micro- and macroorganisms. One hundred genera are currently recognized as members of the family although the Stappia group, Ahrensia, Agaricicola, and Rhodothalassium do not belong, phylogenetically, to the family. The 90 other genera are distributed in 5 phylogenetic groups (the Rhodobacter, the Paracoccus, the Rhodovulum, the Amaricoccus, and the Roseobacter clades) that might be considered a family on its own