Na/sup +/ requirement for growth, photosynthesis, and pH regulation of the alkalotolerant cyanobacterium Synechococcus leopoliensis
It was found that Na/sup +/ is required for all the alkalotolerance of the cyanobacterium Synechococcus leopoliensis. Cell division did not occur at any pH in the absence of Na/sup +/, but cells inoculated into Na/sup +/-free growth medium at pH 6.8 did continue metabolic activity, and over a period of 48 h, the cells became twice their normal size. Many of these cells remained viable for at least 59 h and formed colonies on Na/sup +/-containing medium. Cells grown in the presence of Na/sup +/ and inoculated into Na/sup +/-free growth medium at pH 9.6 rapidly lost viability. An Na/sup +/ concentration of ca. 0.5 milliequivalents x liter/sup -1/ was required for sustained growth above pH 9.0. The Na/sup +/ requirement could be only partially met by Li/sup +/ and not at all by K/sup +/ or Rb/sup +/. Cells incubated in darkness in growth medium at pH 6.8 had an intracellular pH near neutrality in the presence or absence of Na/sup +/. When the external pH was shifted to 9.6, only cells in the presence of Na/sup +/ were able to maintain an intracellular pH near 7.0. The membrane potential, however, remained high (-120mV) in the absence or presence of Na/sup +/ unless collapsed by the addition of gramicidin. Thus, the inability to maintain a neutral intracellular pH at pH 9.6 in the absence of Na/sup +/ was not due to a generalized disruption of membrane integrity. Even cells containing Na/sup +/ still required added Na/sup +/ to restore photosynthetic rates to normal after the cells had been washed in Na/sup +/-free buffer at pH 9.6. This requirement was only partially met by Li/sup +/ and was not met at all by K/sup +/, Rb/sup +/, Cs/sup +/, Mg/sup 2 +/, or Ca/sup 2 +/. The restoration of photosynthesis by added Na/sup +/ occurred within 30 s and suggests a role for extracellular Na/sup +/. Part of our results can be explained in terms of the operation of an Na/sup +//H/sup +/ antiporter activity in the plasma membrane, but some results would seem to require other mechanisms for Na/sup +/ action. 30 references, 7 figures.
- Research Organization:
- Queen's Univ., Kingston, Ontario
- OSTI ID:
- 5972805
- Journal Information:
- J. Bacteriol.; (United States), Vol. 159:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
Bioaccumulation of 2,2{prime},5,5{prime}-tetrachlorobiphenyl and pyrene by picoplankton (Synechococcus leopoliensis, Cyanophyceae): Influence of variable humic acid concentrations and pH
ACCUMULATION OF RUBIDIUM-86 BY THE RABBIT LENS
Related Subjects
CALCIUM COMPOUNDS
MEMBRANE TRANSPORT
CESIUM COMPOUNDS
CYANOBACTERIA
GROWTH
METABOLISM
LITHIUM COMPOUNDS
MAGNESIUM COMPOUNDS
POTASSIUM COMPOUNDS
RUBIDIUM COMPOUNDS
SODIUM COMPOUNDS
CATIONS
CELL DIVISION
CULTURE MEDIA
NUTRIENTS
PH VALUE
PHOTOSYNTHESIS
TOLERANCE
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHARGED PARTICLES
CHEMICAL REACTIONS
IONS
MICROORGANISMS
PHOTOCHEMICAL REACTIONS
SYNTHESIS
560302* - Chemicals Metabolism & Toxicology- Microorganisms- (-1987)