Rockefeller University Digital Commons @ RU Rockefeller University Research Profiles Campus Publications Fall 1986 The urS face of a Small Cell: [Dr. Alexander Tomasz] Fulvio Bardossi Judith N. Schwartz Follow this and additional works at: http://digitalcommons.rockefeller.edu/research_profiles Part of the Life Sciences Commons Recommended Citation Bardossi, Fulvio and Schwartz, Judith N., "The urS face of a Small Cell: [Dr. Alexander Tomasz]" (1986). Rockefeller University Research Profiles. Book 24. http://digitalcommons.rockefeller.edu/research_profiles/24 This Article is brought to you for free and open access by the Campus Publications at Digital Commons @ RU. It has been accepted for inclusion in Rockefeller University Research Profiles by an authorized administrator of Digital Commons @ RU. For more information, please contact [email protected]. THE ROCKEFELLER UNIVERSITY RESEARCH Bacterial "suicide. I! A pneumococcal cell explosion PROFILES triggered by penicillin. FALL 1986 The Surface ofa Small Cell To the naked eye it is a milky liquid in a test tube. But when a droplet of it is seen through the thousandfold magnifying power of the microscope in Alexander Tomasz's laboratory, the field of vision suddenly becomes filled with hundreds of foot­ ball-like objects, remarkably uniform in shape and size, some of them arranged in pairs, some aligned tip-to-tip like a necklace. "You are looking at pneumococci," explains Dr. Tomasz, "bacteria that are among the most dangerous agents of human disease. You are also looking at the microbe that provided the clues to what many consider the most important discovery of biology in this century: the identification of DNA as the mat­ erial ofthe genes." In the preantibiotic era, up to the 1940s, pneumococcal infection was a leading cause of death, surpassing heart disease Pneumococcus surrounded by its and cancer. Even with the introduction of penicillin, the protective wall. pneumococcus has remained a major killer of children. Not surprisingly, many of the first generation of biologists and chemists at what was originally known as The Rockefeller Insti­ tute for Medical Research concentrated on learning more about the pneumococcus. Their efforts were rewarded with some of the most important landmarks of microbiology, including the chemical characterization of the first polysaccharide antigen, the sugary "coat" that enables bacteria to evade a host's immune Alexander Tomasz defenses. The crowning achievement to emerge from Page 2 The circledareas represent specific chemical groupings on the bacterial cell wall that are "recognized" by an invaded host and that: Elaine Tuomanen reading a (1) provoke capillary bleeding and inflammation; computer printout that shows the Simplified diagram of the pneumococcal cell wall, layers offibers (2) trigger the immune system; growth ofpneumococcal cultures composed ofchains ofsugars (G andM), interlinkedby short peptides (3) serve as an attachment sitefor proteins ofcomplement, a substance and their death by penicillin. (made ofamino acids), shown in orange. (G = glucosamine. important in host defense; M = muramic acid.) (4) activate complement before attachment; The small black balls represent other types ofsugar chains, an (5) react with the so-calledC-reactive protein, which is produced in important component of which is choline, essential to normal cell large amounts in the blood during infection but the function of growth. which is still unclear. This part ofthe wall also contains choline, PBPs, penicillin-binding proteins. Responsible for building cell the receptorjorautolysin, the enzyme which, when activated by walls, these proteins are the targets ofpenicillin action. penicillin, causes the pneumococcus to explode. pneumococcal research at The Rockefeller-the demonstration "Ironically," Dr. Tomasz remarks, "the original question ad­ that DNA was the molecular carrier ofheredity-was reported dressed by the early studies, namely, how do as few as a hundred by Oswald Avery, Colin Macleod, and Maclyn McCarty in of these tiny bacteria kill a child, has remained unanswered." 1944. For the past several years, Dr. Tomasz's laboratory has been Page 3 readdressing this question. 'Tm convinced," he says, "that the Sloan-Kettering Institure and a small flat, I invested my first answers lie in a better understanding of the chemistry of the paycheck in some clothes, a record player, and two favorite pneumococcal surface, specifically, the outermost layer called recordings-the Bach double concerto for violins and the Mass the cell wall. in B Minor. Furniture came later." "What fascinates me about the cell wall," he says, "is the Resuming his scientific education, he earned a Ph. D. in improbable nature and number of tasks it has to perform. It biochemistry at Columbia University. "My mind was only vag­ has to be rigid enough to maintain the integrity of the cell. uely set as to what 1 wanted to do nexr. I was interested in It has to reproduce itself, in perfect replicas, in each cell divi­ two subjects, molecular genetics and the surfaces of cells." sion. And it has to regulate tbe opening and closing of its The pneumococcus has the capacity, rare among bacteria, to many gates, doors, and windows to allow the orderly traffic of take up free-floating strands of DNA from its environment. thousands of nutrient molecules in and out of the cell every This capacity was dubbed "competence" by the investigators second. It also serves as the cell's communication center, receiv­ who took advantage of it in studying the mechanisms by which ing and transmitting signals from and to the outside world. " nonvirulent pneumococci are transformed by absorbing DNA A slender band measuring about a thousandth ofa millimeter molecules from virulent neighbor pneumococci (which led to and visible only through the electron microscope, the cell wall the recognition of DNA as the genetic bearer). is, in fact, an enormous molecular envelope, conforming to Through his reading, Dr. Tomasz came upon the perfect " , , the size and shape of the cell and surrounding the entire cell problem to engage both his interests: how pneumococci capture 1 \ , ~ -~ with an uninterrupted protective network of chemical bonds. DNA molecules during the process of genetic transformation. '~. ~ Bacterial walls represent the largest molecules in nature. Bac­ It was clear that the place to approach it was The ,Rockefeller - teria can reproduce these "miniature architectural master­ University laboratory of Rollin Hotchkiss, whose group had -'""~-"", pieces," as Dr. Tomasz calls them, with speed and precision in made enormous advances in refining the discovery of Avery, 'l) . ., ...". \,"" . each cell division. He notes: "I often watch and admire the Macleod, and McCarty. logistics that go into the construction of a building in New "The reputation of the place was formidable," says Dr. To­ ~ ~.~\ .\~ York. Imagine a house already inhabited and yet under continu­ masz. "I still remember my interview with Hotchkiss. At the ous expansion with such miraculous efficiency that a new, iden­ end of it 1 was so excited that 1 inadvertantly put on his. ,~?~;\~~ tical twin structure arises every halfhour without inconveniencing somewhat oversized galoshes instead of my own. Hotchkiss "~., •.. ? the tenants." observed with quiet amusement and then asked, 'How does it ~,)I ., "'"'-#. feel to be in my shoes?'" The work on competence started out with "a lot of frustra­ tion," Dr. Tomasz recalls. "Most people in the field were in­ Scanning electron micrograph of BAcrERIA TALKING TO ONE ANarHER terested in it simply as a technique to assess the quality of the pneumococcal cells stuck together in long chains. The inhibition of Hungarian-born Alexander Tomasz briefly considered a career DNA molecule. I was at heart a cell biologist. I was interested in music before deciding to study biology and chemistry at the in the competent cell itself. 1 wanted to know what special normal cell division is one ofthe University of Budapest. He fled to Austria after the Soviet properties of the pneumococcus enable it to recognize bare consequences 'when the bacteria are grown in a medium containing suppression of the Hungarian uprising in 1956, crossing the DNA floating by. Are there special entry points, special doors border hidden in a canvas-covered farm truck. Shortly after, he on the cell surface? Could one see them?" the abnormal compound ethanolamine in place ofcholine. came to New York. Soon after his arrival, he consulted with Walther Stoeckenius, "Like so many other refugees," he says, "I came with only now a professor of biophysics at the University of California, Another consequence is penicillin the clothes 1 wore. After 1 had found a job as a technician at San Francisco, who showed him how to mix pneumococci with tolerance. Page 4 DNA molecules and, by means of a special technique new at pen and wrote on a reprint of it, 'To Alex Tomasz, Avery's the time, see both cells and molecules in the electron micro- grandson.' When I reminded him that Avery had never married, scope. , he promptly corrected the dedication, 'To Alex Tomasz, Avery's "I will never forget my excitement and amazement when, illegitimate grandson.' " after searching and searching in vain, I suddenly saw the contour With activator in hand, Dr. Tomasz started a series ofexper­ of a long, slender fiber of DNA attached to the side of a iments to understand, in biochemical terms, what this sub­ pneumococcus. I knew that I was fortunate to have caught a stance actually does to cells. It was clear that activator was cell at the moment of uptake. I ran into the hall and called some sort of a key that opened a door on the cell wall through everyone in to look." (The micrograph has since appeared in which DNA molecules could now move inward and attach to several microbiology textbooks.) receptors located somewhere deeper under the cell surface. Despite his thrill and "aesthetic satisfaction" he still hadn't found the "door" he was looking for. ':As it turned out," he SUICIDAL ENZYMES says, "I was soon to find the 'key' for the door, but the nature While searching for the DNA receptor, Dr.