page_title: Richard Lenski
section_title: E. coli experiment
hierarchical_section_title: Richard Lenski / Career / E. coli experiment
caption_attribution_description: English: Photograph of Richard Lenski's long-term evolution experiment with E. coli taken on 25 June 2008. Each flask harbors one of the 12 evolving populations. The photo was taken about 24 h after the cultures were serially transferred, hence they are at stationary phase. The populations grow in DM25 medium, which contains a relatively low glucose concentration so that the culture is not very turbid. However, one population, designated Ara-3, evolved to use the citrate that is also present in the medium. It has a much greater density of cells than the others, and it is therefore much more turbid, owing to the high concentration of citrate in the medium supporting greater cell growth.Русский: Колбы с 12 популяциями E. coli, участвующими в долговременном эколюционном эксперименте Ричарда Ленски, 25 июня 2008. Культуры перенесены в свежую питательную среду 24 часа назад и уже находятся в стационарной фазе (т.е. глюкоза уже кончилась, деление клеток прекратилось). Популяция взращиваются в питательной среде DM25, которая содержит относительно небольшое количество глюкозы, так что плотность культур не очень велика. Однако одна из популяций, обозначенная как Ara-3, приноровилась питаться цитратом, который тоже входит в состав питательной среды. Это позволило ей достигнуть большей плотности (жидкость в колбе А-3 заметно более мутная, чем в других колбах).
context_page_description: Richard Eimer Lenski is an American evolutionary biologist, a MacArthur "genius" fellow, a Hannah Distinguished Professor of Microbial Ecology at Michigan State University, and a member of the National Academy of Sciences. Lenski is best known for his still ongoing 32-year-old long-term E. coli evolution experiment, which has been instrumental in understanding the core processes of evolution, including mutation rates, clonal interference, antibiotic resistance, the evolution of novel traits, and speciation. He is also well known for his pioneering work in studying evolution digitally using self-replicating organisms called Avida.
context_section_description: The E. coli long-term evolution experiment is an ongoing study in experimental evolution led by Richard Lenski that has been tracking genetic changes in 12 initially identical populations of asexual Escherichia coli bacteria since 24 February 1988. The populations reached the milestone of 50,000 generations in February 2010.
  Since the experiment's inception, Lenski and his colleagues have reported a wide array of genetic changes; some evolutionary adaptations have occurred in all 12 populations, while others have only appeared in one or a few populations. One particularly striking adaptation was the evolution of a strain of E. coli that was able to use citrate as a carbon source in an aerobic environment.
caption: The 12 evolving E. coli populations on June 25, 2008
exif: {"Image Make": "Canon", "Image Model": "Canon PowerShot SD1100 IS", "Image Orientation": "Horizontal (normal)", "Image XResolution": "60", "Image YResolution": "60", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS3 Windows", "Image DateTime": "2008:06:25 13:30:56", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "232", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1154", "Thumbnail JPEGInterchangeFormatLength": "4614", "EXIF ExposureTime": "1/8", "EXIF FNumber": "14/5", "EXIF ISOSpeedRatings": "200", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2008:06:25 13:00:02", "EXIF DateTimeDigitized": "2008:06:25 13:00:02", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "3", "EXIF ShutterSpeedValue": "3", "EXIF ApertureValue": "95/32", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "95/32", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "31/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1038", "EXIF ExifImageLength": "423", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "Interoperability RelatedImageWidth": "3264", "Interoperability RelatedImageLength": "2448", "EXIF InteroperabilityOffset": "1004", "EXIF FocalPlaneXResolution": "43520/3", "EXIF FocalPlaneYResolution": "2448000/169", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard"}