Melanin production as a visual indicator of conjugal transfer in Streptomyces


To visualize transfer of plasmid in Streptomyces during conjugation, we constructed a conjugative plasmid that harbored melC operon encoding an extracellular tyrosinase and placed it in Streptomyces hosts which were defective in expressing the operon. Hyphae of these donors were mixed with hyphae of a plasmidless recipient, which could express melC, and plated on a solid medium supplemented with tyrosine. After 8 to 9 h of incubation, melanin started to appear in the mating mixture, indicating that the plasmid had entered the recipient and started to synthesize tyrosinase, which in turn catalyzed the formation of melanin. This visual monitoring system allows quick demonstration of conjugal transfer without tedious genetic or biochemical procedure commonly used. It may be applied to most Streptomyces species and may also be used for monitoring chromosome transfer.

This is a preview of subscription content, log in to check access.

Access options

Buy single article

Instant unlimited access to the full article PDF.

US$ 39.95

Price includes VAT for USA

Subscribe to journal

Immediate online access to all issues from 2019. Subscription will auto renew annually.

US$ 99

This is the net price. Taxes to be calculated in checkout.

Fig. 1
Fig. 2


  1. Chen CW (1996) Complications and implications of linear bacterial chromosomes. Trends Genet 12:192–196

  2. Crameri R, Davies JE, Hütter R (1986) Plasmid curing and generation of mutations induced with ethidium bromide in streptomycetes. J Gen Microbiol:819–824

  3. Hopwood DA (1999) Forty years of genetics with Streptomyces: from in vivo through in vitro to in silico. Microbiology 145:2183–2202

  4. Hopwood DA, Kieser T, Wright HM, Bibb MJ (1983) Plasmids, recombination, and chromosomal mapping in Streptomyces lividans 66. J Gen Microbiol 129:2257–2269

  5. Kieser T, Hopwood DA, Wright HM, Thompson CJ (1982) pIJ101, a multi-copy broad host-range Streptomyces plasmid: functional analysis and development of DNA cloning vectors. Mol Gen Genet 185:223–228

  6. Kieser T, Bibb M, Buttner MJ, Chater KF, Hopwood DA (2000) Practical Streptomyces genetics. The John Innes Foundation, Norwich

  7. Leu WM, Wu SY, Lin JJ, Lo SJ, Lee YH (1989) Analysis of the promoter region of the melanin locus from Streptomyces antibioticus. Gene 84:267–277

  8. Schrempf H, Kessler A, Brönneke V, Dittrich W, Betzler M (1989) Genetic instability in Streptomycetes. In: Hershberger CL, Queeners SW, Hegeman G (eds) Genetics and molecular biology of industrial microorganisms. American Society of Microbiology, Washington, D.C., pp 133–140

  9. Thoma L, Muth G (2016) Conjugative DNA-transfer in Streptomyces, a mycelial organism. Plasmid 87-88:1–9

  10. Thoma L, Vollmer B, Oesterhelt F, Muth G (2019) Live-cell imaging of Streptomyces conjugation. Int J Med Microbiol 309:338–343

  11. Yu TW, Chen CW (1993) The unstable melC operon of Streptomyces antibioticus is codeleted with a Tn4811-homologous locus. J Bacteriol 175:1847–1852

  12. Zhou X, Deng Z, Firmin JL, Hopwood DA, Kieser T (1988) Site-specific degradation of Streptomyces lividans DNA during electrophoresis in buffers contaminated with ferrous iron. Nucleic Acids Res 16:4341–4354

  13. Zhu D, He X, Zhou X, Deng Z (2005) Expression of the melC operon in several Streptomyces strains is positively regulated by AdpA, an AraC family transcriptional regulator involved in morphological development in Streptomyces coelicolor. J Bacteriol 187:3180–3187

Download references


T.-W. C thanks fellow students in the lab for technical assistance and advice.

Funding information

This study was supported by a student research grant to T.-W. C. and a research grant to C. W. C. from Ministry of Science and Technology, Republic of China (grant number NSC90-2312-B010-002).

Author information

Correspondence to Carton W. Chen.

Ethics declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Communicated by: Agnieszka Szalewska-Palasz

Electronic supplementary material


(DOCX 101 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Chen, T., Chen, C.W. Melanin production as a visual indicator of conjugal transfer in Streptomyces. J Appl Genetics (2020).

Download citation


  • Streptomyces
  • Conjugation
  • Plasmid transfer
  • Melanin
  • Tyrosinase