Initiation of fatty acid biosynthesis in Pseudomonas putida KT2440.

Deciphering the mechanisms of bacterial fatty acid biosynthesis is crucial for both the engineering of bacterial hosts to produce fatty acid-derived molecules and the development of new antibiotics. However, gaps in our understanding of the initiation of fatty acid biosynthesis remain. Here, we demonstrate that the industrially relevant microbe Pseudomonas putida KT2440 contains three distinct pathways to initiate fatty acid biosynthesis. The first two routes employ conventional ß-ketoacyl-ACP synthase III enzymes, FabH1 and FabH2, that accept short- and medium-chain-length acyl-CoAs, respectively. The third route utilizes a malonyl-ACP decarboxylase enzyme, MadB. A combination of exhaustive in vivo alanine-scanning mutagenesis, in vitro biochemical characterization, X-ray crystallography, and computational modeling elucidate the presumptive mechanism of malonyl-ACP decarboxylation via MadB. Given that functional homologs of MadB are widespread throughout domain Bacteria, this ubiquitous alternative fatty acid initiation pathway provides new opportunities to target a range of biotechnology and biomedical applications.

Morphology and evolution of bioluminescent organs in the glowbellies (Percomorpha: Acropomatidae) with comments on the taxonomy and phylogeny of Acropomatiformes.

Bioluminescent organs have evolved many times within teleost fishes and exhibit a wide range of complexity and anatomical derivation. Although some bioluminescent organs have been studied in detail, the morphology of the bacterial light organs in glowbellies (Acropoma) is largely unknown. This study describes the anatomy of the bioluminescent organs in Haneda's Glowbelly (Acropoma hanedai) and the Glowbelly (Acropoma japonicum) and places the evolution of this light-producing system in the context of a new phylogeny of glowbellies and their relatives. Gross and histological examination of the bioluminescent organs indicate that they are derived from perianal ectodermal tissue, likely originating from the developmental proctodeum, contrary to at least one prior suggestion that the bioluminescent organ in Acropoma is of endodermal intestinal derivation. Additionally, anterior bioluminescent organ development in both species is associated with lateral spreading of the bacteria-containing arms of the bioluminescent organ from an initial median structure. In the context of a 16-gene molecular phylogeny, the bioluminescent organ in Acropoma is shown to have evolved within the Acropomatidae in the ancestor of Acropoma. Further, ancestral-states reconstruction demonstrates that the bioluminescent organs in Acropoma evolved independently from the light organs in related howellid and epigonid taxa which have esophageal or intestinally derived bioluminescent organs. Across the acropomatiforms, our reconstructions indicate that bioluminescent organs evolved independently four or five times. Based on the inferred phylogeny of the order where Acropoma and Doederleinia were separated from other traditional acropomatids, the familial taxonomy of the Acropomatidae was modified such that the previously described Malakichthyidae and Synagropidae were recognized. We also morphologically diagnose and describe the family Lateolabracidae.