Abstract
Iso-fatty acids (FAs) are the dominant FA family in all myxobacteria analyzed. Furthermore, it was postulated that iso-FAs or compounds derived thereof are involved in fruiting body formation in Myxococcus xanthus, since mutants with a reduced level of iso-FA due to a reduced level of the precursor isovaleryl-CoA, are delayed in aggregation and produce only few myxospores. To elucidate the function of iso-FAs and their corresponding lipids we have analyzed the developmental phenotype of mutants having different levels of iso-FAs resulting in a clear correlation between the amount of iso-FAs and the delay of aggregation and reduction in spore yield. Addition of either isovalerate or 13-methyltetradecanoic acid resulted in restoration of the wild-type FA profile and normal development. Detailed analysis of the fatty acid (FA) profile during fruiting body formation in Myxococcus xanthus wild-type revealed the specific accumulation of 13-methyltetradecanal and 1-O-13-methyltetradecylglycerol which were produced specifically in the myxospores and which are derived from 1-O-(13-methyl-1-Z-tetradecenyl)-2-O-(13-methyltetradecanoyl)-glycero-3-phosphatidylethanolamine (VEPE) and 1,2-di-(13-methyltetradecanoyl)-3-(13-methyltetradecyl)glycerol (TG-1), respectively. The structures of these unusual ether lipids have been determined by spectrometric methods and synthesis (for TG-1). Analysis of several mutants blocked at different stages of development indicated that the biosynthesis of TG-1 is developmentally regulated and that VEPE might be an intermediate in the TG-1 biosynthesis. Finally, addition of TG-1 to mutants blocked in the biosynthesis of isovaleryl-CoA could restore aggregation and sporulation emphasizing the important role of iso-branched lipids for myxobacterial development.
Highlights
Bodies are visible to the naked eye and can reach a tree-like complexity in some species
Because the wild-type fatty acid profile and the normal life cycle can be restored in the bkd mutant by adding isovalerate (IVA), it was speculated that an iso-fatty acids (FAs) or a corresponding lipid is involved in the developmental process [10, 23]
Recent analysis of a mutant that produces only trace amounts of SCFAs revealed that this FA or the corresponding PE is not required for fruiting body formation or sporulation as both occurred indistinguishable to the wild type [25]
Summary
Bkd, branched-chain keto acid dehydrogenase; FA, fatty acid; SCFA, straight-chain fatty acid; FAME, fatty acid methyl ester; IVA, isovalerate; iso15:0, 13-methyltetradecanoate; MvaS, 3-hydroxy-3-methylglutaryl-CoA synthase; kan, kanamycin; PE, phosphatidylethanolamine; di-iso15:0-PE, 1,2-di-(-O-(13-methyltetradecanoyl)glycero-3-phosphatidylethanolamine; VEPE, 1-O-(13-methyl-1-Z-tetradecenyl)-2-O-(13-methyltetradecanoyl)glycero-3-phosphatidylethanolamine; AEPE, 1-O-(13-methyltetradecyl)-2-O-(13-methyltetradecanoyl)glycero-3phosphatidylethanolamine; TG-1, 1,2-di-(13-methyltetradecanoyl)-3-(13methyltetradecyl)glycerol; TG-2, 1,2-di-(hexadecanoyl)-3-(13-methyltetradecyl)glycerol; TPG, glycerol tripalmitate; GC, gas chromatography; MS, mass spectrometry; MS/MS, tandem mass spectrometry; HPLC, high performance liquid chromatography; ESI, electrospray ionization; PR, peripheral rod. Recent analysis of a mutant that produces only trace amounts of SCFAs revealed that this FA or the corresponding PE is not required for fruiting body formation or sporulation as both occurred indistinguishable to the wild type [25]. Inactivation of the bkd locus does not lead to a complete loss of iso-FA production, which is due to the presence of a novel alternative pathway to isovaleryl-CoA (Fig. 1), branching from the well known mevalonate-dependent isoprenoid biosynthesis [18, 26]. This pathway is so far unique to myxobacteria and is highly induced in bkd mutants. 33 27 27 25 28, 34 35 31 36 myxobacterial development, because they are produced mainly in fruiting body-derived myxospores
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
