Butyrate-producing bacteria have an important role in maintaining host health. They are well studied in human and medically associated animal models; however, much less is known for other Vertebrata. We investigated the butyrate-producing community in hindgut-fermenting Mammalia (n ¼ 38), Aves (n ¼ 8) and Reptilia (n ¼ 8) using a gene-targeted pyrosequencing approach of the terminal genes of the main butyrate-synthesis pathways, namely butyryl-CoA:acetate CoA-transferase (but) and butyrate kinase (buk). Most animals exhibit high gene abundances, and clear diet-specific signatures were detected with but genes significantly enriched in omnivores and herbivores compared with carnivores. But dominated the butyrate-producing community in these two groups, whereas buk was more abundant in many carnivorous animals. Clustering of protein sequences (5% cutoff) of the combined communities (but and buk) placed carnivores apart from other diet groups, except for noncarnivorous Carnivora, which clustered together with carnivores. The majority of clusters (but: 5141 and buk: 2924) did not show close relation to any reference sequences from public databases (identity o90%) demonstrating a large 'unknown diversity'. Each diet group had abundant signature taxa, where buk genes linked to Clostridium perfringens dominated in carnivores and but genes associated with Ruminococcaceae bacterium D16 were specific for herbivores and omnivores. Whereas 16S rRNA gene analysis showed similar overall patterns, it was unable to reveal communities at the same depth and resolution as the functional gene-targeted approach. This study demonstrates that butyrate producers are abundant across vertebrates exhibiting great functional redundancy and that diet is the primary determinant governing the composition of the butyrate-producing guild.

Melanins are ubiquitous and biologically important pigments, yet the molecular mechanisms that regulate their synthesis and biochemical composition are not fully understood. Here we present a study that supports a role for serotonin in melanin synthesis in the planarian Schmidtea mediterranea. We characterize the tryptophan hydroxylase (tph) gene, which encodes the rate-limiting enzyme in serotonin synthesis, and demonstrate by RNA interference that tph is essential for melanin production in the pigment cups of the planarian photoreceptors. We exploit this phenotype to investigate the biological function of pigment cups using a quantitative light-avoidance behavioral assay. Planarians lacking eye pigment remain phototactic, indicating that eye pigmentation is not essential for light avoidance in S. mediterranea, though it improves the efficiency of the photophobic response. Finally, we show that the eye pigmentation defect observed in tph knockdown animals can be rescued by injection of either the product of TPH, 5-hydroxytryptophan (5-HTP), or serotonin. Together, these results highlight a role for serotonin in melanogenesis, perhaps as a regulatory signal or as a pigment substrate. To our knowledge, this is the first example of this relationship to be reported outside of mammalian systems.

19Schistosomes are parasitic flatworms that infect over 200 million people, causing the neglected 20 tropical disease, schistosomiasis. A single drug, praziquantel, is used to treat schistosome 21 infection. Limitations in mass drug administration programs and the emergence of 22

Schistosomes are parasitic flatworms that infect over 200 million people, causing the neglected tropical disease, schistosomiasis. A single drug, praziquantel, is used to treat schistosome infection. Limitations in mass drug administration programs and the emergence of schistosomiasis in nontropical areas indicate the need for new strategies to prevent infection. It has been known for several decades that rotifers colonizing the schistosome's snail intermediate host produce a water-soluble factor that paralyzes cercariae, the life cycle stage infecting humans. In spite of its potential for preventing infection, the nature of this factor has remained obscure. Here, we report the purification and chemical characterization of Schistosome Paralysis Factor (SPF), a novel tetracyclic alkaloid produced by the rotifer Rotaria rotatoria. We show that this compound paralyzes schistosome cercariae and prevents infection and does so more effectively than analogous compounds. This molecule provides new directions for understanding cercariae motility and new strategies for preventing schistosome infection.