Non-contiguous finished genome sequence and description of Alistipes ihumii sp. nov.

Alistipes ihumii strain AP11^T sp. nov. is the type strain of A. ihumii sp. nov., a new species within the genus Alistipes. This strain, whose genome is described here, was isolated from the fecal flora of a 21-year-old French Caucasian female, suffering from a severe restrictive form of anorexia nervosa since the age of 12 years. A. ihumii is a Gram-negative anaerobic bacillus. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,753,264 bp long genome (one chromosome but no plasmid) contains 2,254 protein-coding and 47 RNA genes, including 3 rRNA genes.     

Genome sequence and description of Alistipes senegalensis sp. nov.

Alistipes senegalensis strain JC50^T is the type strain of A. senegalensis sp. nov., a new species within the Alistipes genus. This strain, whose genome is described here, was isolated from the fecal flora of an asymptomatic patient. A. senegalensis is an anaerobic Gram-negative rod-shaped bacterium. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 4,017,609 bp long genome (1 chromosome, but no plasmid) contains 3,113 protein-coding and 50 RNA genes, including 5 rRNA genes.     

Non contiguous-finished genome sequence and description of Alistipes obesi sp. nov

Alistipes obesi sp. nov. strain ph8^T is the type strain of A. obesi, a new species within the genus Alistipes. This strain, whose genome is described here, was isolated from the fecal flora of a 26-year-old woman suffering from morbid obesity. A. obesi is an obligately anaerobic rod. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 3,162,233 bp long genome (1 chromosome but no plasmid) contains 2,623 protein-coding and 49 RNA genes, including three rRNA genes.     

Biochemical characterization of the first step in sulfonolipid biosynthesis in Alistipes finegoldii

Sulfonolipids are unusual lipids found in the outer membranes of Gram-negative bacteria in the phylum Bacteroidetes. Sulfonolipid and its deacylated derivative, capnine, are sulfur analogs of ceramide-1-phosphate and sphingosine-1-phosphate, respectively; thus, sulfonolipid biosynthesis is postulated to be similar to the sphingolipid biosynthetic pathway. Here, we identify the first enzyme in sulfonolipid synthesis in Alistipes finegoldii as the product of the alfi_1224 gene, cysteate acyl-acyl carrier protein (ACP) transferase (SulA). We show SulA catalyzes the condensation of acyl-ACP and cysteate (3-sulfo-alanine) to form 3-ketocapnine. Acyl-CoA is a poor substrate. We show SulA has a bound pyridoxal phosphate (PLP) cofactor that undergoes a spectral redshift in the presence of cysteate, consistent with the transition of the lysine–aldimine complex to a substrate–aldimine complex. Furthermore, the SulA crystal structure shows the same prototypical fold found in bacterial serine palmitoyltransferases (Spts), enveloping the PLP cofactor bound to Lys251. We observed the SulA and Spt active sites are identical except for Lys281 in SulA, which is an alanine in Spt. Additionally, SulA(K281A) is catalytically inactive but binds cysteate and forms the external aldimine normally, highlighting the structural role of the Lys281 side chain in walling off the active site from bulk solvent. Finally, the electropositive groove on the protein surface adjacent to the active site entrance provides a landing pad for the electronegative acyl-ACP surface. Taken together, these data identify the substrates, products, and mechanism of SulA, the PLP-dependent condensing enzyme that catalyzes the first step in sulfonolipid synthesis in a gut commensal bacterium.