Carl Hirschie Johnson is an American-born biologist who researches the chronobiology of different organisms, most notably the bacterial circadian rhythms of cyanobacteria. Johnson completed his undergraduate degree in Honors Liberal Arts at the University of Texas at Austin, and later earned his PhD in biology from Stanford University, where he began his research under the mentorship of Dr. Colin Pittendrigh. Currently, Johnson is the Stevenson Professor of Biological Sciences at Vanderbilt University.
Personal life
Carl Johnson was born in Washington D.C. When he first began college at the University of Texas at Austin, he planned to go to medical school rather than pursue research. However, he quickly developed a passion for research after working as an undergraduate student in a chronobiology lab directed by Dr. Michael Menaker. Johnson asserts that "music led [him] to science," as he originally began his research job with Menaker to pay for classical voice lessons. Classical music has remained a major avocation, as he continues to sing music with the chorus of the Nashville Symphony Orchestra. Also in his free time, he enjoys yoga.
Scientific career
Early career and education
Johnson graduated with a B.A. in Honors Liberal Arts (the Plan II Honors program ) at the University of Texas at Austin in 1976. During this time, he became involved in undergraduate research under the mentorship of Dr. Michael Menaker, whose lab was studying biological clocks in birds and rodents. Johnson's exposure to the practice of experimental research in Dr. Menaker's lab inspired him to go to graduate school instead of following his original plan to become a physician. He went on to earn his Ph.D. in biology in 1982 at Stanford University, first working under the renowned leader in chronobiology, Colin Pittendrigh and then moving to David Epel's laboratory to finish his degree. Subsequently, Johnson conducted postdoctoral work in Cell & Developmental Biology at Harvard University, which he completed in 1987, with Dr. J.W. 'Woody' Hastings (John Woodland Hastings), a biologist famous for his work on bioluminescence in many organisms, including algae. Hastings became a close friend and mentor to Johnson. In 1987, Johnson came to Vanderbilt University to initiate an independent research program, and he has been a biology professor at Vanderbilt since then.
Research beginnings
Johnson's initial foray into research was as an undergraduate in Menaker's lab, which was working on the pineal gland in birds and other chronobiology projects in vertebrates. In graduate school at Stanford under Colin Pittendrigh, Johnson attempted to discover circadian rhythms in a variety of organism such as leeches and cockroaches. He also worked with earthworms to see whether they would completely recover circadian rhythms upon regeneration of lesioned parts of their brains. He also developed a method to measure the pH levels inside cells in search of rhythmic acid/base relationships. However, only one of these projects ultimately resulted in a publication, namely a paper about the clock's control over the pH in the bread mould Neurospora crassa. Johnson switched to David Epel's marine biology lab in his fourth year of graduate school, because their work on the pH change in sea urchin and starfish eggs upon fertilization was an excellent system in which to apply the method he had developed earlier to measure the pH levels inside cells. He successfully published a number of papers on this topic. In his postdoctoral studies with Hastings, Johnson returned to the biological clocks field and worked mainly on rhythms in the bioluminescent alga Gonyaulax polyedra and later in the algal model system for genetics, Chlamydomonas reinhardtii.