Occasional production by genome-wide deletion through removal of linear plasmid harboring tap-tpg gene pair in Streptomyces rochei

초록

Streptomyces rochei 7434AN4 carries three linear plasmids, pSLA2-L (211 kb), pSLA2-M (113 kb), and pSLA2-S (18 kb). Genome project of this strain revealed that the linear chromosome consists of 8.36 Mb in size and carries more than 35 biosynthetic gene clusters. Three plasmidless mutants (2–39, YN-P7, and YN-P145) showed their chromosomal telomere deletion, concomitantly with a loss of plasmids. To compare the metabolic profile of plasmidless mutants, each strain was cultivated in different mediums [YM and modified oatmeal broth (OMB) medium]. Remarkably, strain YN-P145 showed two distinct UV-active spots when it was grown in OMB medium. These UV-active compounds were purified using Sephadex LH-20 and silica gel chromatographies. The UV-active compound named YN-P145A has a molecular formula of C14H16N2O2 and was characterized to be cyclo(Phe–Pro), a diketopiperazine (cyclodipeptide) that is known to have an antifungal activity. Another UV-active compound from strain YN-P145, compound YN-P145B, has a molecular formula of C8H11NO. Extensive NMR analysis revealed that YN-P145B was identical to a cyclic enamide termed as YM3163-A, 2-(cyclohex-2-en-1-ylidene)acetamide, which has been isolated from the recombinant of SARP-type activator SRO_3163 in S. rochei. Thus, genome-wide deletion occasionally leads to accumulate natural products, whose expression was weak or not at all in its parent strain. © 2026 The Society for Biotechnology, Japan

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