The bacterium Asticcacaulis biprosthecum is to be used as a system for studying mechanisms of membrane transport and for studying the nature of a biological adhesive. The specialized appendages called prosthecae produced by this organism appear to be organelles whose function is to concentrate nutrients from low-nutrient environments. Purified prosthecae possess systems for the active transport of solutes. The transported solutes are concentrated in prosthecae against a gradient and are not metabolized. The systems of transport are respiration linked and must depend on the cytoplasm of the cell proper for the reducing power required to drive transport, since transported solutes are not metabolized in prosthecae. Two systems for transport of glucose in prosthecae appear to require periplasmic glucose-binding proteins in order to function. I propose to determine how reducing power generated in the cell drives transport in prosthecae. This is to be done with the use of specific TCA-cycle mutants and by determining the fates of TCA-cycle intermediates in mutants and in wild-type cells growing on (14C)-glucose and by determining the effects of such mutations on prosthecal transport. Also, glucose-binding proteins will be purified and their role in glucose transport in prosthecae will be determined. The ability of prosthecae to transport other solutes (organic and inorganic) will be determined, and the mechanisms of transport will be characterized. Prosthecae isolated from cells of Caulobacter crescentus will also be examined to see if their function is the same as those of A. biprosthecum. A method for isolating holdfast-negative (hf-) mutants of A. biprosthecum has been developed, and many hf- mutants are now available. Some hf- mutants are resistant to phages to which wild-type cells are sensitive, suggesting that those phages might attach to holdfast material. The mutants and wild-type cells will be used to identify and characterize holdfast material, and the kinds of defects that result in the holdfast negative condition will be determined. BIBLIOGRAPHIC REFERENCES: Larson, R.J., and J.L. Pate. 1976. Glucose transport in isolated prosthecae of Asticcacaulis biprosthecum. J. Bact. 126, 282-293. Larson, R.J. and J.L. Pate. 1976. Growth and morphology of Asticcacaulis biprosthecum in defined media. Arch. Microbiol. 106, 147-157.
NIH ExPorter
NIH ExPorter