Affiliation:
1. Department of Biochemistry and Molecular Biology, Saitama University, 255 Shimo-ohkubo, Sakura, Saitama, Saitama 338-8570, Japan
Abstract
ABSTRACT
Recently, use of the cardiolipin (CL)-specific fluorescent dye 10-
N
-nonyl-acridine orange (NAO) revealed CL-rich domains in the
Escherichia coli
membrane (E. Mileykovskaya and W. Dowhan, J. Bacteriol.
182:
1172-1175, 2000). Staining of
Bacillus subtilis
cells with NAO showed that there were green fluorescence domains in the septal regions and at the poles. These fluorescence domains were scarcely detectable in exponentially growing cells of the
clsA
-disrupted mutant lacking detectable CL. In sporulating cells with a wild-type lipid composition, fluorescence domains were observed in the polar septa and on the engulfment and forespore membranes. Both in the
clsA
-disrupted mutant and in a mutant with disruptions in all three of the paralogous genes (
clsA
,
ywjE
, and
ywiE
) for CL synthase, these domains did not vanish but appeared later, after sporulation initiation. A red shift in the fluorescence due to stacking of two dye molecules and the lipid composition suggested that a small amount of CL was present in sporulating cells of the mutants. Mass spectrometry analyses revealed the presence of CL in these mutant cells. At a later stage during sporulation of the mutants the frequency of heat-resistant cells that could form colonies after heat treatment was lower. The frequency of sporulation of these cells at 24 h after sporulation initiation was 30 to 50% of the frequency of the wild type. These results indicate that CL-rich domains are present in the polar septal membrane and in the engulfment and forespore membranes during the sporulation phase even in a
B. subtilis
mutant with disruptions in all three paralogous genes, as well as in the membranes of the medial septa and at the poles during the exponential growth phase of wild-type cells. The results further suggest that the CL-rich domains in the polar septal membrane and engulfment and forespore membranes are involved in sporulation.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
236 articles.
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