3258 TAMU
College Station, TX 77843-3258

Office:
Biological Sciences Building West
Room 103A
979-845-2187

Lab:
Biological Sciences Building West
Room 103
979-845-8470

Fax: 979-845-2891
Email: cop@mail.bio.tamu.edu

The work in my lab focuses on understanding molecular-level events in bioenergetic mechanisms and pathways of nutrient utilization in microalgae. Photosynthetic light reactions and electron flow are obligately membrane-bound processes. Nutrient uptake and retention are strongly influenced by the physical state of the cytoplasmic membrane. We are therefore interested in membrane chemistry and in physiological responses of membranes to stress. Photosynthetic microbes including cyanobacteria, diatoms, chrysophytes, and green algae are the preferred organisms of investigation.

My students and I have shown that the fatty-acid composition of algal membranes changes in response to culture conditions. In membranes of the cyanobacterium Anacystis (Synechococcus) nidulans, ratio of saturated and unsaturated fatty acids changes in response to presence of exogenous solvents such as alcohols. In the chlorophyte Tetraselmis, the diatom Chaetoceros, and the chrysophyte Isochrysis, similar alterations in fatty acid composition are observed following exposure of cells to volatile aromatic hydrocarbons. Using fluorescent membrane probe techniques, we are exploring effects of solvents (hydrocarbons, alcohols, etc.) on the viscosity/fluidity of both intact and isolated membranes. We are especially interested in the mechanisms whereby cells detect and respond to changes in membrane integrity.

In collaboration with an electrochemical research group at a local biotechnology firm, I have developed techniques for depositing colloidal particles of elemental platinum directly onto thylakoid membranes of intact cyanobacterial cells. This diverts photosynthetic electron flow away from reduction of NADP and results in production of gaseous hydrogen. Illuminated platinized cells produce both gaseous oxygen and gaseous hydrogen, each of which we can measure polarographically. Electron microscopy allows us to determine the positions of platinum particles on thylakoid membrane faces. This provides an experimental tool to study intra-membrane topology of the Photosystem 1 reaction center complex.

In cyanobacteria, membrane-bound phycobilins serve as photosynthetic antenna pigments. We have shown that Spirulina platensis adjusts its phycobilin levels in response to light and nutrient levels, while chlorophyll content remains largely unchanged. Regulatory mechanisms and effects on membrane structure are presently topics of investigation.

In carrying out the studies mentioned above, we needed large quantities of cells grown under uniform and reproducible conditions. Batch cultures of a few hundred milliliters were not sufficient, so we developed continuous mass-culture techniques. My graduate students and I have designed and constructed computer-managed photobioreactors which allow us to maintain algal cultures in continuous exponential growth for months with less than 1% variation in growth rates. This technology provides a powerful tool for studies of stress responses in photosynthetic microbes. Improvement of such technologies remains an ongoing focus in the lab.

Hitchens, G.D., T.D. Rogers, O.J. Murphy, and C.O. Patterson. 1991. A new photocatalytic material based on algal cells. Biochemical and Biophysical Research Communications 175:1029-1035.

Holtzapple, M., F.E. Little, W. Moses and C.O. Patterson. 1989. Analysis of an algae-based closed ecological life support system, Part II, Options and Weight Analysis. Acta Astronautica 19:365-375.

Holtzapple, M., F.E. Little, M.E. Makela and C.O. Patterson. 1989. Analysis of an algae-based closed ecological life support system, Part I, Model Development. Acta Astronautica 19:353-364.

Patterson, C.O., M. Holtzapple, and B.D. Etter. 1988. Advances in experimental apparatus for algal growth. In Conceptual Designs for a Food Production, Water and Waste Regeneration Module. O.W. Nicks, ed., SRC Report 4-5873-2 NASA Johnson Space Center, NAG9-253. pp 125-130.