Cryptic plasmids explained

In molecular biology, a cryptic plasmid is a plasmid that doesn't appear to provide any clear advantage to its host, yet still persists in bacterial populations.^[1] These plasmids appear to lack any genetic functions of interest and do not seem to contain genes that could provide beneficial functions to their hosts. Given the lack of a clear advantage to their hosts and the likely cost of maintaining them, these plasmids are often referred to as selfish elements or genetic parasites.The maintenance of cryptic plasmids might be explained by mechanisms like horizontal gene transfer (e.g., conjugation, transduction) that balance their loss due to segregation.^[2] However, cryptic plasmids could potentially be important in antibiotic resistance, by contributing to heteroresistance in bacterial populations. ^[3]

They have been found to be highly abundant, as seen in Lactobacillus where most plasmids are cryptic. ^[4]

Notes and References

1. Fogarty EC, Schechter MS, Lolans K, Sheahan ML, Veseli I, Moore RM, Kiefl E, Moody T, Rice PA, Yu MK, Mimee M, Chang EB, Ruscheweyh HJ, Sunagawa S, Mclellan SL, Willis AD, Comstock LE, Eren AM . A cryptic plasmid is among the most numerous genetic elements in the human gut . Cell . 187 . 5 . 1206–1222.e16 . February 2024 . 38428395 . 10973873 . 10.1016/j.cell.2024.01.039 . February 28, 2025 .
2. Book: Summers DK . 1996 . Chapter 1 – The Function and Organization of Plasmids. The Biology of Plasmids. First . Osney, Oxford OX . Wiley-Blackwell . 21–22 . 978-0-632-03436-9 .
3. Nicoloff . Hervé . Hjort . Karin . Andersson . Dan I. . Wang . Helen . 2024-05-10 . Three concurrent mechanisms generate gene copy number variation and transient antibiotic heteroresistance . Nature Communications . en . 15 . 1 . 3981 . 10.1038/s41467-024-48233-0 . 2041-1723 . 11087502 . 38730266. 2024NatCo..15.3981N .
4. Wang TT, Lee BH . Plasmids in Lactobacillus . Critical Reviews in Biotechnology. 17 . 3 . 227–272 . 1997 . 10.3109/07388559709146615 . 9306650 .