A Glycoprotein Surface Layer Covers the Pseudomurein Sacculus of the Extreme Thermophile Methanothermus fervidus
With a temperature maximum of 97°C, Methanothermus is the most thermophilic methanogenic genus. Only members of this archaebacterial genus possess a double-layered cell envelope composed of a pseudomurein sacculus and an S-layer (Fig.1a; Stetter et al. 1981). Each layer could be specifically removed: the S-layer with detergent or pronase (Stetter et al. 1981) and the pseudomurein sacculi of freshly harvested cells with a pseudomurein endopeptidase from Methanobacterium wolfei (Fig.1d). The cells are bipolar polytrichous flagellated. Up to 10 flagella with a length of 8–10 μm and a thickness of 13–15 nm could be found at each pole. The channels at the two poles of the pseudomurein sacculi are probably the passage holes of the flagella, since the diameter corresponds with the thickness of the flagella (Fig.1a,b). The thickness and the rigidity of the cell envelopes varied with the culture conditions. The cell envelope layers became thicker and more rigid in autotrophically than in heterotrophically grown cells. The thickness of the pseudomurein and the S-layer increased from 14 nm and 10 nm to 22 nm and 16 nm, respectively.
KeywordsOligosaccharide Galactose Mannose Pentose Glucosamine
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