Nylon-eating bacteria

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Nylon-eating bacteria are a strain of Flavobacterium that is capable of digesting certain byproducts of nylon 6 manufacture. This strain of Flavobacterium, Sp. KI72, became popularly known as nylon-eating bacteria, and the enzymes used to digest the man-made molecules became collectively known as nylonase.

Discovery[edit]

Chemical structure of 6-aminohexanoic acid

In 1975 a team of Japanese scientists discovered a strain of Flavobacterium, living in ponds containing waste water from a nylon factory, that was capable of digesting certain byproducts of nylon 6 manufacture, such as the linear dimer of 6-aminohexanoate. These substances are not known to have existed before the invention of nylon in 1935. Further study revealed that the three enzymes the bacteria were using to digest the byproducts were significantly different from any other enzymes produced by other Flavobacterium strains (or, for that matter, any other bacteria), and not effective on any material other than the manmade nylon byproducts.[1]

Later research[edit]

This discovery led geneticist Susumu Ohno to speculate that the gene for one of the enzymes, 6-aminohexanoic acid hydrolase, had come about from the combination of a gene duplication event with a frameshift mutation.[2] Ohno suggested that many unique new genes have evolved this way.

A 2007 paper that described a series of studies by a team led by Seiji Negoro of the University of Hyogo, Japan, suggested that in fact no frameshift mutation was involved in the evolution of the 6-aminohexanoic acid hydrolase.[3] However, many other genes have been discovered which did evolve by gene duplication followed by a frameshift mutation affecting at least part of the gene. A 2006 simulation found 470 examples that could potentially develop in humans alone.[4]

Scientists have also been able to induce another species of bacteria, Pseudomonas aeruginosa, to evolve the capability to break down the same nylon byproducts in a laboratory by forcing them to live in an environment with no other source of nutrients. The P. aeruginosa strain did not seem to use the same enzymes that had been utilized by the original Flavobacterium strain.[5] Other scientists were able to get the ability to generate the enzymes to transfer from the Flavobacterium strain to a strain of E. coli bacteria via a plasmid transfer.[6]

Role in evolution teaching[edit]

There is scientific consensus that the capacity to synthesize nylonase most probably developed as a single-step mutation that survived because it improved the fitness of the bacteria possessing the mutation. More importantly: The enzyme involved has been produced by a mutation completely randomizing the original gene. Despite this, the new gene still had a novel, albeit weak, catalytic capacity. This is seen as a good example of how mutations easily can provide the raw material for evolution by natural selection. [7][8][9][10]

See also[edit]

Notes[edit]

  1. ^ Kinoshita, S.; Kageyama, S., Iba, K., Yamada, Y. and Okada, H. (1975). "Utilization of a cyclic dimer and linear oligomers of e-aminocaproic acid by Achromobacter guttatus". Agricultural & Biological Chemistry 39 (6): 1219−23. doi:10.1271/bbb1961.39.1219. ISSN 0002-1369. 
  2. ^ Ohno S (April 1984). "Birth of a unique enzyme from an alternative reading frame of the preexisted, internally repetitious coding sequence". Proc Natl Acad Sci USA. 81 (8): 2421–5. doi:10.1073/pnas.81.8.2421. PMC 345072. PMID 6585807. 
  3. ^ Negoro S, Ohki T, Shibata N, et al. (June 2007). "Nylon-oligomer degrading enzyme/substrate complex: catalytic mechanism of 6-aminohexanoate-dimer hydrolase". J. Mol. Biol. 370 (1): 142–56. doi:10.1016/j.jmb.2007.04.043. PMID 17512009. 
  4. ^ Okamura K, Feuk L, Marquès-Bonet T, Navarro A, Scherer SW (December 2006). "Frequent appearance of novel protein-coding sequences by frameshift translation". Genomics 88 (6): 690–7. doi:10.1016/j.ygeno.2006.06.009. PMID 16890400. 
  5. ^ Prijambada ID, Negoro S, Yomo T, Urabe I (May 1995). "Emergence of nylon oligomer degradation enzymes in Pseudomonas aeruginosa PAO through experimental evolution". Appl. Environ. Microbiol. 61 (5): 2020–2. PMC 167468. PMID 7646041. 
  6. ^ Negoro S, Taniguchi T, Kanaoka M, Kimura H, Okada H (July 1983). "Plasmid-determined enzymatic degradation of nylon oligomers". J. Bacteriol. 155 (1): 22–31. PMC 217646. PMID 6305910. 
  7. ^ Thwaites WM (Summer 1985). "New Proteins Without God's Help". Creation Evolution Journal (National Center for Science Education (NCSE)) 5 (2): 1–3. 
  8. ^ Evolution and Information: The Nylon Bug
  9. ^ Why scientists dismiss 'intelligent design', Ker Than, MSNBC, Sept. 23, 2005
  10. ^ Miller, Kenneth R. Only a Theory: Evolution and the Battle for America's Soul (2008) pp. 80-82

References[edit]