FK506 is an immunosuppressant discovered from culture of the streptomycete strain “Streptomyces tsukubaensis” 9993. Since its discovery, several streptomycete strains have been found as FK506 and/or ascomycin producers at our laboratory and other institutions. Ascomycin, which is also an immunosuppressant and anti-fungal macrolide, is structurally similar to FK506. We determined almost the full sequences of 16S rDNA of seven FK506- and/or ascomycin-producing streptomycete strains using direct PCR and a direct sequencing method. A homology search and phylogenetic analysis revealed that all strains belonged to the genus Streptomyces. The FK506-producing strains formed three clusters. The first cluster included Streptomyces sp. 6260 and 49A with “S. tsukubaensis” 9993, the second included Streptomyces sp. 94128 with Streptomyces kanamyceticus KCC S-0433T, which was newly revealed to produce FK506 in this study, and the third included Streptomyces sp. ATCC 55098. The FK506-producing strains were phylogenetically suggested to belong to three different species. Furthermore, two ascomycin-producing strains phylogenetically differed from each other and the three FK506 producer clusters. The present findings confirmed that various phylogenetically different streptomycete strains produce FK506 and/or ascomycin. It is possible that the reason for this is the horizontal gene transfer of FK506 and ascomycin biosynthetic genes. Further phylogenetic investigation of these genes might therefore help further our understanding of the horizontal gene transfer and evolution of secondary metabolite genes.
Twenty actinomycete cultures were isolated from marine and mangrove areas and they were screened for the production of lignin degrading enzymes. The plate assay, using guaiacol as substrate, had been identified as an effective method for the screening of ligninolytic actinomycetes. Six isolates were found to be producing Lignin peroxidase of which four cultures were showing laccase activity too. Out of the twenty isolates screened, only one isolate produced manganese peroxidase. A newly isolated mangrove actinomycete Streptomyces psammoticus (coded NJP 49) capable of producing all the three major ligninolytic enzymes like Lignin peroxidase (LiP), Laccase and Manganese peroxidase (MnP) had been selected. Although S. psammoticus was found to be a potent producer of LiP and laccase, owing to the limited works carried out on MnP from actinomycetes, we had selected MnP for further studies and the crude characteristics of the MnP of this isolate were studied. The enzyme exhibited maximum activity at pH 7.0 and at temperature of 30 °C. The stability studies indicated that the enzyme was stable in the pH range of 7.0-7.5 and temperature range of 25 °C-40 °C.
A spore germination inhibitor was isolated from the liquid-cultured material of Streptomyces sp. B-9-1, the causal organism of root tumors in melon, and identified as anthranilic acid, which reversibly inhibited spore germination, showed no effect on hyphal growth, and was effective for other Streptomyces spp. However, anthranilic acid showed an IC50 at ca. 50 μg/ml, and its content in spores was 0.16 μg/9×108 spores, indicating that its contribution to the inhibition of spore germination was small.