behe.uncommondescent.comMichael Behe's Blog - Serving the Intelligent Design Community

Resources Search I am Professor of Biological Sciences at Lehigh University in Pennsylvania. I received my Ph.D. in Biochemistry from the University of Pennsylvania in 1978. My current research involves delineation of design and natural selection in protein structures. In addition to teaching and research I work as a senior fellow with the Discovery Institute’s Center for Science & Culture. In addition to publishing over 35 articles in refereed biochemical journals, I have also written editorial features in Boston Review, American Spectator, and The New York Times. My book, Darwin’s Black Box, discusses the implications for neo-Darwinism of what I call irreducibly complex” biochemical systems and has sold over 250,000 copies. The book was internationally reviewed in over one hundred publications and recently named by National Review and World magazine as one of the 100 most important books of the 20th century. I have presented and debated my work at major universities throughout North America and England. Search Recent Posts One Small Step Sideways, Two Huge Steps Back More Darwinian Degradation A Blind Man Carrying a Legless Man Can Safely Cross the Street New Work by Thornton’s Group Supports Time-Symmetric Dollo’s Law Irremediable Complexity” Archives January 2012 October 2011 August 2011 April 2011 January 2011 December 2010 March 2010 October 2009 September 2009 August 2009 May 2009 April 2009 March 2009 February 2009 January 2009 June 2008 May 2008 February 2008 November 2007 October 2007 August 2007 July 2007 June 2007 31 January 2012 One Small Step Sideways, Two Huge Steps Back Michael J Behe Recently a new paper by Richard Lenski and colleagues (Meyer et al 2012) appeared in Science ( http://www.sciencemag.org/content/335/6067/428.short )with, as usual, commentary in the New York Times . ( http://tinyurl.com/7xthu7q ) (Lenski’s lab must own a red phone with a direct line to The Gray Lady.) The gist of the paper is that a certain bacteriophage (a virus that infects bacteria) called lambda” gained the ability to bind a different protein on the surface of its host, the bacterium E. coli , than the protein it usually binds. The virus has to bind to the cell’s surface as a prelude to invading it. The protein it normally binds is called LamB. Lenski’s lab, however, used a bacterial strain that had turned off the production of LamB in 99% of E. coli cells but, crucially, 1% of cells still produced the protein. Thus the virus could still invade some cells, reproduce, and not go extinct. Under these conditions the viral binding protein (called J”) underwent several mutations, apparently to better bind LamB in the fewer cells that produced it. Then, surprisingly, after the viral gene gained a fourth mutation, the viral J protein acquired the ability to bind a different protein on E. coli , called OmpF. Now the virus could use OmpF as a platform for invading the cell. Since all cells made OmpF, the virus was no longer restricted to invading just the 1% of cells that made LamB, and it prospered. The workers repeated the experiment multiple times, and frequently got the same results. As always, the work of the Lenski lab is solid and interesting, but is spun like a top to make it appear to support Darwinian evolution more than it does. As the authors acknowledge, this is certainly not the first time a lab has evolved a virus to grow on a different strain of host. In a recent review (Behe 2010) ( http://tinyurl.com/25c422s ) there is a section entitled Evolution Experiments with Viruses: Adapting to a New Host” discussing just that topic. In general, viruses have been shown to be able to adapt to bind to related host cells which have similar surface features. In almost all cases the virus uses the same binding protein, and the same (mutated) binding site to attach to the new host cell. This seems to also be the case with Lenski’s new work. As stated above, the first several mutations apparently strengthen the ability of the J protein to bind to the original site, LamB, while the fourth mutation allows it to bind to OmpF. As the authors state, however, the mutated viral J protein can still bind to the original protein, LamB, which strongly suggests the same binding site (that is, the same location on the J protein) is being used. It turns out that both LamB and OmpF have similar three-dimensional structures, so that strengthening the binding to one fortuitously led to binding to the other. In my review (Behe 2010) I discussed why this should be considered a modification of function” event rather than a gain-of-function one. The bottom line is that the results are interesting and well done, but not particularly novel, nor particularly significant. To me, the much more significant results of the new paper, although briefly mentioned, were not stressed as they deserved to be. The virus was not the only microbe evolving in the lab. The E. coli also underwent several mutations. Unlike for lambda, these were not modification-of-function mutations — they were complete loss-of-function mutations. The mechanism the bacterium used to turn off LamB in 99% of cells to resist initial lambda infection was to mutate to destroy its own gene locus called malT , which is normally useful to the cell. After acquiring the fourth mutation the virus could potentially invade and kill all cells. However, E. coli itself then mutated to prevent this, too. It mutated by destroying some genes involved in importing the sugar mannose into the bacterium. It turns out that this mannose permease” is used by the virus to enter the interior of the cell. In its absence, infection cannot proceed. So at the end of the day there was left the mutated bacteriophage lambda, still incompetent to invade most E. coli cells, plus mutated E. coli , now with broken genes which remove its ability to metabolize maltose and mannose. It seems Darwinian evolution took a little step sideways and two big steps backwards. Literature Cited Behe, M. J., 2010 Experimental Evolution, Loss-of-function Mutations, and The First Rule of Adaptive Evolution”. Quarterly Review of Biology 85: 1-27. Meyer, J. R., D. T. Dobias, J. S. Weitz, J. E. Barrick, R. T. Quick et al. 2012 Repeatability and contingency in the evolution of a key innovation in phage lambda. Science 335: 428-432. Posted in Uncategorized | No Comments » 24 January 2012 More Darwinian Degradation Michael J Behe Recently a paper appeared by Ratcliff et al. (2012) entitled Experimental evolution of mulitcellularity” and received a fair amount of press attention, including a story in the New York Times. ( http://tinyurl.com/6va4fpp ) The authors discuss their results in terms of the origin of multicellularity on earth. The senior author of the paper is Michael Travisano of the University of Minnesota, who was a student of Richard Lenski’s in the 1990s. The paper, published in PNAS, was edited by Lenski. The gist is as follows. The authors repeated three steps multiple times: 1) they grew single-celled yeast in a flask; 2) briefly centrifuged it; and 3) took a small amount from the bottom of the flask to seed a new culture. This selected for cells that sedimented faster than most. After a number of rounds of selection the cells sedimented much faster than the beginning cells. Examination showed that the fast-sedimenting cells formed clusters due to incomplete separation of replicating mother-daughter cells. The cell clusters also were 10% less fit (that’s quite an amount) than the beginning cells in the absence of the sedimentation selection. After further selection it was seen that some cells in clusters would commit suicide” (apoptosis), which apparently made the clusters more brittle and allowed chunks to break off and form new clusters. (The beginning cells already had the ability to undergo apoptosis.) It seems to me that Richard Lenski, who knows how to get the most publicity out of exceedingly modest laboratory results, has...