Cells of two smooth Salmonella typhimurium strains (SL696 and SH4247) were treated with ethylenediaminetetraacetic acid (EDTA) and the polycations poly(L-lysine) and protamine to monitor both quantitatively and qualitatively the release of [ 14C] galactose-labelled lipopolysaccharide into the medium to find out whether these effector substances caused selective release of certain fractions from the initially heterogenous lipopolysaccharide population. Each one of the substances released considerable amounts of lipopolysaccharide into the medium. Analysis by sodium dodecyl sulphate/polyacrylamide gel electrophoresis followed by autoradiography showed that the total lipopolysaccharide (from isolated membranes) and the released materials produced coincident banding patterns, each with a high degree of 0 side-chain length heterogeneity. Densitometric scans of the autoradiograms were analyzed for possible differences in the distribution and relative abundance of lipopolysaccharide molecules with different 0 chain lengths. It was found that in SL696 the released materials were identical to the total lipopolysaccharide; in SH4247 subtle deviations from the total lipopolysaccharide were seen. We conclude from these results that lipopolysaccharide molecules with short and long 0 side chains are linked to and stabilized in the outer membrane by similar mechanisms equally susceptible to the effects of EDTA and polycations.In smooth gram-negative bacteria the outermost cell surface (the outer membrane; for a recent review see [I]) is covered by lipopolysaccharide (LPS). LPS consists of a lipophilic moiety termed lipid A (embedded in the outer membrane), an oligosaccharide core, and an 0-specific chain containing repeating oligosaccharide units (protruding outside from the cell surface). Recent studies employing sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) have revealed that the LPS of smooth bacteria are highly heterogenous with respect to the degree of polymerization of the 0-specific chain. For instance, Salmonella typhimurium LPS separated in SDS-PAGE and visualized either by silver staining or autoradiography typically appears to contain two predominant populations: one consisting of molecules having long 0 chains with even up to 50 repeating units, and the other having only a few or no repeating units (2 -61. The biological significance of these two populations is unclear; it is not known whether or not the different species of LPS molecules have different functions or separate location in the outer membrane.Leive and coworkers have shown that treatment of smooth bacteria with EDTA releases approximately half of their LPS into the surrounding medium [7-91. On this basis it was suggested [9] that LPS exists in the outer membrane in two distinct fractions, one being held there by divalent cations and releasable with EDTA, and the other organized by some other unspecified mechanism which is resistant to EDTA. On the other hand, it has been reported [lo] that EDTA does not release significant amoun...
The lipopolysaccharide (LPS) of 3 recently identified antibiotic‐supersensitive mutants of Salmonella typhimurium was analyzed and compared to the parent. The amounts of glucose, galactose, heptose, 2‐keto‐3‐deoxyoctonate, total phosphorus, total amino groups, and fatty acids were similar in all of the LPS preparations, and typical of the chemotype Rb2 of the rfaJ parent. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) did not reveal any differences between the mutants and the parent. Ethylenediaminetetraacetic acid and polycations, which partially release LPS from intact cells (presumably by replacing or removing divalent cations between molecules in the outer membrane), liberated similar amounts of [14C]alactose‐labelled LPS from the mutants and the parent.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.