A new class of outer membrane lipid (OML) was isolated from the oral spirochete Treponema denticola strain ATCC 33521 using a phenol/chloroform/light petroleum procedure normally applied for lipopolysaccharide extraction. In addition to chemical analysis, Fourier transform infrared (FTIR) spectroscopy was applied to compare the biophysical properties of OML with lipopolysaccharides (LPS) and lipoteichoic acids (LTA). Isolated OML fractions represent 1.4% of the total dry cell weight, are about 4 kDa in size, and contain 6% amino sugars, 8% neutral sugars, 14% phosphate, 35% carbazol-positive compounds, and 11% fatty acids (containing iso-and anteiso-fatty acyl chains). Rare for outer membrane lipids, OML contains no significant amount of 3-deoxy-D-manno-octulosonic acids, heptoses, and -hydroxy fatty acids. The fatty acyl chain composition, being similar to that of the cytoplasmic membrane, is quite heterogeneous with anteiso-pentadecanoic acid (12%), palmitic acid (51%), and iso-palmitic acid (19%) as the predominant fatty acids present. Findings of a glycerol-hexose unit and two glycerol-hexadecanoic acid fragments indicate a glycolipid membrane anchor typically found in LTA. There was also no evidence for the presence of a sphingosine-based lipid structure. The results of FTIR measurements strongly suggest that the reconstituted lipid forms normal bilayer structures (vesicles) expressing a high membrane state of order with a distinct phase transition as typical for isolated LPS. However, in contrast to LPS, OML of T. denticola has a lower T m near 22°C and a lower cooperativity of the phase transition. The results suggest a different kind of permeation barrier that is built up by this particular OML of T. denticola, which is quite different from LPS normally essential for Gram-negative bacteria.
The occurrence of small (diameter 0.125 micrometers) and large (diameter 0.27 micrometers) treponemal species on expanded polytetrafluoroethylene membranes were demonstrated in vivo. In the apical part of the expanded polytetrafluoroethylene membrane only the smaller treponemes were colonizing, while in other parts a mixed population of different bacterial species including large treponemes was seen. Only the smaller treponemes were able to form spherical bodies in the occlusive part of the membrane. All morphological characteristics of spherical bodies such as common outer sheath, randomly distributed axial flagella, sheathless protoplasmic cylinders and central bodies could be differentiated. Possible causes for the formation of spherical bodies are discussed.
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.