TY - JOUR
T1 - Permeability studies of lipid vesicles from alkalophilic Bacillus firmus showing opposing effects of membrane isoprenoid and diacylglycrol fractions and suggesting a possible basis for obligate alkalophily
AU - Clejan, Sanda
AU - Krulwich, Terry A.
N1 - Funding Information:
This work was supported in part by research grants GM28454 from the National Institu~.es of Health and DMB8504395 from the National Science Foundation, and contract DEACO181ER 10871 from the Department of Energy.
PY - 1988/12/8
Y1 - 1988/12/8
N2 - Previous studies of the membrane lipids of extremely alkalophilic bacilli had indicated that both facultative and obligate alkalophiles contained a substantial fraction of isoprenoid lipid as well as high concentrations of cardiolipin. Facultative alkalophiles differed from obligate strains in having a phospholipid fatty acid composition that would be expected to result in a more ordered membrane structure. Current studies of ion permeability in vesicles prepared from lipids from obligately alkalophilic Bacillus firmus RAB and its facultatively alkalophilic strain, OF4, support the suggestion that membranes of the latter strain form a tighter barrier structure, with the difference especially pronounced at near neutral pH values. The water permeability of whole cells and the reflection coefficients for acetamide in vesicles were also consistent with a tighter membrane in the facultatively alkalophilic strain than in the obligately alkalophilic strain. The permeability properties of vesicles prepared from phospholipids from these organisms were studied as a function of the addition of either homologous membrane isoprenoid or diacylglycerol. For each permeability parameter that was assayed, in lipids from both strains, the isoprenoid fraction decreased the permeability, whereas the diacylglycerol fraction increased the permeability of the vesicles to solute.
AB - Previous studies of the membrane lipids of extremely alkalophilic bacilli had indicated that both facultative and obligate alkalophiles contained a substantial fraction of isoprenoid lipid as well as high concentrations of cardiolipin. Facultative alkalophiles differed from obligate strains in having a phospholipid fatty acid composition that would be expected to result in a more ordered membrane structure. Current studies of ion permeability in vesicles prepared from lipids from obligately alkalophilic Bacillus firmus RAB and its facultatively alkalophilic strain, OF4, support the suggestion that membranes of the latter strain form a tighter barrier structure, with the difference especially pronounced at near neutral pH values. The water permeability of whole cells and the reflection coefficients for acetamide in vesicles were also consistent with a tighter membrane in the facultatively alkalophilic strain than in the obligately alkalophilic strain. The permeability properties of vesicles prepared from phospholipids from these organisms were studied as a function of the addition of either homologous membrane isoprenoid or diacylglycerol. For each permeability parameter that was assayed, in lipids from both strains, the isoprenoid fraction decreased the permeability, whereas the diacylglycerol fraction increased the permeability of the vesicles to solute.
KW - (B. firmus)
KW - Alkalophilic bacillus
KW - Lipid vesicle
KW - Permeability
UR - http://www.scopus.com/inward/record.url?scp=0024282197&partnerID=8YFLogxK
U2 - 10.1016/0005-2736(88)90455-5
DO - 10.1016/0005-2736(88)90455-5
M3 - Article
C2 - 3145017
AN - SCOPUS:0024282197
SN - 0005-2736
VL - 946
SP - 40
EP - 48
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 1
ER -