The chemical composition of oral anaerobes has several characteristic features. Some of these are plasmalogens and sphingolipids which are polar lipids restricted mainly to anaerobes. Increasing attention has been paid to these atypical phospholipids over recent years. This paper is a short overview of plasmalogens and sphingolipids with emphasis on oral anaerobes. Ether lipids are major components of most of these organisms. Plasmalogens in their natural form are mainly found as 1-O-alkenyl-2-acyl glycerophosphatides. Their distribution is characterized by species specificity. Plasmalogens are found in lactic acid fermenting species: Veillonella parvula, Megasphaera elsdenii, Selenomonas ruminantium, in butyric acid-producing clostridia, e.g. Clostridium butyricum, in Bacteroides, Peptostreptococcus, Propionibacterium, Treponema, Desulfovibrio, Butyrivibrio and Ruminococcus. Plasmalogens have specific roles in membrane organization and stability. Sphingolipids are still an elusive class of lipids. Ceramide serves as an intracellular second messenger for tumour necrosis factor-α, interleukin (IL)-1β, and other cytokines. Inhibition of cerebroside synthase has indicated a role for ceramide in cellular stress responses including heat shock. Sphingolipids have been useful for defining the genus Bacteroides and have been found also in Prevotella, Porphyromonas, Fusobacterium, Sphingomonas, Sphingobacterium, Flavobacterium and Bdellovibrio. Plasmalogens and sphingolipids should be examined further for their potential in the taxonomy of anaerobes and for their ability to fill the gap in our knowledge about anaerobe membrane lipids.
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