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Locillomycins are cyclic lipononapeptides assembled by a nonlinear hexamodular NRPS and have strong antibacterial activity. In this study, we genetically engineered Bacillus velezensis FZB42 as a surrogate host for the heterologous expression of the loc gene cluster for locillomycins. The fosmid N13 containing whole loc gene cluster was screened from the B. velezensis 916 genomic library. Subsequently, a spectinomycin resistance cassette, and the cassette fused with an IPTG inducible promoter Pspac, was introduced in the fosmid N13 using λ Red recombination system, respectively. The resulting fosmids, designated N13+Spec and N13+PSSpec, were used for the transformation of B. velezensis FZB42 to obtain derivative strains FZBNPLOC and FZBPSLOC. RT-PCR and qRT-PCR results revealed the efficient heterologous expression of the loc gene cluster in both derivative strains. Particularly, there was positive correlation between the derivative FZBPSLOC strain and the enhanced production of locillomycins upon addition of the inducer IPTG with the highest production of locillomycins at 15-fold more than that of B. velezensis 916. This overproduction of locillomycins was also related to the enhancement of antibacterial activity against methicillin-resistant Staphylococcus aureus, and exhibited moderate changes in its hemolytic activity. Together our findings demonstrate that the nonlinear hexamodular NRPS, encoded by the loc gene cluster from B. velezensis 916, is sufficient for the biosynthesis of cyclic lipononapeptide locillomycins in the surrogate host B. velezensis FZB42. Moreover, the FZBPSLOC strain will also be useful for further development of novel locillomycins derivatives with improved antibacterial activity. [ABSTRACT FROM AUTHOR]

Baphicacanthus cusia (Nees) Bremek is an herb widely used for the clinical treatment of colds, fever, and influenza in Traditional Chinese Medicine. The roots, stems and leaves can be used as natural medicine, in which indigo and indirubin are two main active ingredients. In this study, quantification of indigo, indirubin, indican and adenosine among various tissues of B. cusia was conducted using HPLC-DAD. Leaves have significantly higher contents than stems and roots (380.66, 315.15, 20,978.26, 4323.15 μg/g in leaves, 306.36, 71.71, 3,056.78, 139.45 μg/g in stems, and 9.31, 7.82, 170.45, 197.48 μg/g in roots, respectively). De novo transcriptome sequencing of B. cusia was performed for the first time. The sequencing yielded 137,216,248, 122,837,394 and 140,240,688 clean reads from leaves, stems and roots respectively, which were assembled into 51,381 unique sequences. A total of 33,317 unigenes could be annotated using the databases of Nr, Swiss-Prot, KEGG and KOG. These analyses provided a detailed view of the enzymes involved in indican backbone biosynthesis, such as cytochrome P450, UDP-glycosyltransferase, glucosidase and tryptophan synthase. Analysis results showed that tryptophan synthase was the candidate gene involved in the tissue-specific biosynthesis of indican. We also detected sixteen types of simple sequence repeats in RNA-Seq data for use in future molecular mark assisted breeding studies. The results will be helpful in further analysis of B. cusia functional genomics, especially in increasing biosynthesis of indican through biotechnological approaches and metabolic regulation. [ABSTRACT FROM AUTHOR]