Coregulation of {beta}-galactoside uptake and hydrolysis by the hyperthermophilic bacterium Thermotoga neapolitana
- Univ. of Connecticut, Storrs, CT (United States)
Regulation of the {beta}-galactoside transport system in response to growth substrates in the extremely thermophilic anaerobic bacterium Thermotoga neapolitana was studied with the nonmetabolizable analog methyl-{beta}-D-thiogalactopyranoside (TMG) as the transport substrate. T. neapolitana cells grown on galactose or lactose accumulated TMG against a concentration gradient in an intracellular free sugar pool that was exchangeable with external galactose or lactose and showed induced levels of {beta}-galactosidase. Cells grown on glucose, maltose, or galactose plus glucose showed no capacity to accumulate TMG, though these cells carried out active transport of the nonmetabolizable glucose analog 2-deoxy-D-glucose. Glucose neither inhibited TMG uptake nor caused efflux of preaccumulated TMG; rather, glucose promote TMG uptake by supplying metabolic energy. These data show that {beta}-D-galactosides are taken up by T. neapolitana via an active transport system that can be induced by galactose or lactose and repressed by glucose but which is not inhibited by glucose. Thus, the phenomenon of catabolite repression is present in T. neapolitana with respect to systems catalyzing both the transport and hydrolysis of {beta}-D-galactosides, but inducer exclusion and inducer expulsion, mechanisms that regulate permease activity, are not present. Regulation is manifest at the level of synthesis of the {beta}-galactoside transport system but not in the activity of the system. 29 refs., 2 figs., 2 tabs.
- DOE Contract Number:
- FG02-93ER20122
- OSTI ID:
- 518322
- Journal Information:
- Applied and Environmental Microbiology, Vol. 63, Issue 3; Other Information: PBD: Mar 1997
- Country of Publication:
- United States
- Language:
- English
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