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A new cyclic peptide photoditritide (1), containing two rare amino acid d-homoarginine residues, was isolated from Photorhabdus temperataMeg1 after the nonribosomal peptide synthetase encoding gene pdtSwas activated via promoter exchange. The structure of 1was elucidated by HR-MS and NMR experiments. The absolute configurations of amino acids were determined according to the advanced Marfey’s method after hydrolysis of 1. Bioactivity testing of 1revealed potent antimicrobial activity against Micrococcus luteuswith an MIC value of 3.0 μM and weak antiprotozoal activity against Trypanosoma brucei rhodesiensewith an IC50value of 13 μM. Additionally, the biosynthetic pathway of 1was also proposed.

Seven new methionine-containing rhabdopeptide/xenortide-like peptides (1–7) were identified from Escherichia coliexpressing the rhabdopeptide/xenortide-like peptide biosynthetic gene cluster kj12ABCfrom XenorhabdusKJ12.1. Their structures were elucidated by detailed HPLC-HR-MS/MS analysis and confirmed by chemical synthesis. Bioactivity tests of these first rhabdopeptide/xenortide-like peptide derivatives (2–7) showing methionine building blocks compared to the usually found derivatives containing exclusively hydrophobic amino acids such as valine, leucine, or phenylalanine revealed good activities of 2–7against protozoan parasites and no cytotoxicity against mammalian L6 cells.

Myxobacteria are gliding bacteria of the δ-subdivision of the Proteobacteria and known for their unique biosynthetic capabilities. Two examples of a new class of metabolites, myxotyrosides A (1) and B (2), were isolated from a Myxococcussp. The myxotyrosides have a tyrosine-derived core structure glycosylated with rhamnose and acylated with unusual fatty acids such as (Z)-15-methyl-2-hexadecenoic and (Z)-2-hexadecenoic acid. The fatty acid profile of the investigated Myxococcussp. (strain 131) is that of a typical myxobacterium with a high similarity to those described for M. fulvusand M. xanthus,with significant concentrations of neither 15-methyl-2-hexadecenoic acid nor 2-hexadecenoic acid being detected.