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Tom Mullins, Ph.D.

Emeritus Professor of Botany

• (352) 392-1095 (Voice)
• (352) 392-3993 (Fax)
• mullins@botany.ufl.edu

Biography

Tom Mullins was born and raised in Highland Springs, Virginia. While a student in chemistry at the University of Richmond he had the good fortune of taking biology courses with Drs. Robert F. Smart (a mycologist) and John C. Strickland (an algologist) and was thereby introduced to the wonderful world of lower plants. His interest in fungi continued to develop with the opportunity to pursue doctoral studies with Dr. John N. Couch at the University of North Carolina. Professor Couch was one of the early leaders in the development of fungal species as model systems for understanding fundamental aspects of biology. This was the beginning of my research interest in model systems, and this theme was continued with an early collaboration with Dr. John R. Raper at Harvard, and more recently with Dr. Enrico Cabib at the NIH. Both my teaching and research is centered in the concept that structural and functional similarities are the most fascinating aspect of organisms. Finally, Professor Mullins has devoted and continues to devote time and effort to the development of graduate studies in the Department of Botany. He was a member of the faculty when the graduate program was initiated and still feels that this aspect remains a major basis for maintaining our department.

Education

• Ph.D., University of North Carolina (Botany), 1960

• M.S., University of Richmond (Biology), 1957

• B. S., University of Richmond (Chemistry), 1955

• M.S. Thesis Title: A critical study of chromosomes in two species of Myxophyceae.

• Ph.D. Dissertation Title: Studies on the life history and development of Pringsheimella dioica

Academic Positions

• Assistant Professor, University of Florida, 1959-64

• NIH Special Fellow, Harvard University, 1964-65

• Associate Professor, University of Florida, 1965-73

• Professor, University of Florida 1973-present

• NRS Fellow, NIH, 1988-89

Research Interests / Major Research Achievements:

My research interests have as their central theme the understanding of how growth and development is regulated. A major achievement has been a series of studies that defined the fundamental aspects of the biology of the aquatic fungus Achlya. This broadly based program has included nutrition, physiology, biochemistry, enzymology, and ultrastructure. The University of Florida has the special distinction of having a broadly based scientific faculty and this has allowed us to exploit the best techniques and skilled people in addressing these fundamental questions. Most recently we have determined the molecular structure of a unique food reserve which occurs in a number of organisms, including Achlya. This molecule stores not only glucose, but also phosphate by utilizing the phosphodiester chemical linkage. This linkage allows a small neutral molecule to aggregate into a very large acidic one. This demonstrates that carbohydrates, as well as nucleic acids, have taken advantage of the unique chemical bonding of the phosphoric acid molecule. When appropriate we are also interested in the applied aspects of our research results. In this light we have contributed to a better understanding of the fundamental biological aspects of fuel ethanol production from Florida crops, and the microbiology of composting of yard wastes.

Present Research

We are currently interested in the biosynthesis and structure of the cell wall of Achlya as it relates to the classical problem of hyphal tip growth. The central issue here and in plant cell walls in general is to identify the chemical linkages which distinguish a growing cell wall from a non-growing one. We view the wall composition of Achlya as another variation of the central theme of a cellulose microfibrillar component embedded in a matrix of (1->3)-beta-glucans and proteins. Our first goal is to determine if there is a qualitative difference between growing and on-growing areas of the cell wall. Using a combination of labeling techniques including antibodies or enzymes coupled to colloidal gold and electron microscopy, we have found qualitative difference in growing versus non-growing areas of the wall. This is in contrast to prevailing models which suggest only quantitative differences. We are also investigating possible linkages between cellulose and (1->3)-beta-glucans using a technique of enzyme digestion of cell walls with (1->3)-beta-glucanase, followed by labeling of the exposed reducing ends with borotritide, and finally enzymatic hydrolysis of the cellulose. The radioactive glucose oligosacchaides should contain the linkages(s) of interest if they exist. Proton and 13C NMR spectra of these purified compounds can then be used to identify the linkages present in the labeled molecules. Such data will allow us to begin to understand the differences in chemical linkages which distinguish the growing cell wall from the non-growing cell wall, and thus to appreciate the fundamental basis of growth in plant and fungal cells.

Courses Taught:

• BCH 3023 Organic & Biological Chemistry; Cell, Organisms and Genetics
• BOT 6566 Plant Growth and Development; Fungal Genetics & Physiology
• BSC 2010 Integrated Principles of Biology

Membership in Professional Organizations:

• American Association for Advancement of Science
• Botanical Society of America
• Mycological Society of America
• American Society of Plant Physiologists
• Sigma Xi

Grants received

• My research has been supported by grants from NIH; USDA, ARS; NSF; Brown-Hazen Fund, Research Corporation; Governorís Energy Office; and the Center for Biomass Energy Systems. Current support is being provided by a CLAS Research Initiative Projects grant.

Selected Publications

1999. Du, Xin and J. T. Mullins. Glucan 1,3-$-glucosidase activities of Achlya bisexualis: synthesis and properties. Mycologia 91: 353-358.

1998. Du, Xin and J. T. Mullins: Ca2+-induced sporulation in Achlya bisexualis: reserve (1->3)-$-glucans provide both carbon and phosphorus. Mycologia 90: 990-994.

1997. Shapiro, A. and J. T. Mullins. Localization of cytoplasmic water-soluble reserve (1->3)-$-glucans in Achlya with immunostaining. Mycologia 89: 89-91.

1996. Lee, J.-H., J. T. Mullins, and J. E. Gander. Water-soluble reserve polysaccharides from Achlya are (1->3)-$-glucans. Mycologia 88: 264-270.

1994. Mol, P. C., H.-M. Park, J. T. Mullins and E. Cabib. A GTP-binding protein regulates the activity of (1->3)-$-glucan synthase, an enzyme directly involved in yeast cell wall morphogenesis. J. Biol. Chem. 269: 31267-31274.

1994. Mullins, J. T. Hormonal control of sexual dimorphism. In: The Mycota. Vol. I. Growth, Differentiation and Sexuality. J. G. H. Wessels and F. Meinhardt (eds.) Pp. 413-421. Springer-Verlag, Berlin.

1994. Lee, J. H. and J. T. Mullins. Cytoplasmic water-soluble $-glucans in Achlya: response to nutrient limitation. Mycologia 86: 235-241.

1991. Cabib, E., S. Silverman, A. Shaw, S. Das Gupta, H. E. Park, J. T. Mullins, P. Mol and B. Bowers. Carbohydrates as structural constituents of yeast cell wall and septum. Pure and Appl. Chem. 63: 483-489.

1990. Mullins, J. T. Regulatory mechanisms of $-glucans synthases in baterica, fungi, and plants. Physiologia Plantarum 78: 309-314.

1988. Mullins, J. T. and C. C. NeSmith. Nitrogen levels and yeast viability during ethanol fermentation of grain Sorghum containing condensed tannins. Biomass 16: 77-87.

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