The pterin lumazine inhibits growth of methanogens and methane formation

The pterin compound lumazine [2, 4-(1H, 3H)-pteridinedione] inhibited the growth of several methanogenic archaea completely at a concentration of ≤ 0.6 mM and was bacteriocidal for Methanobacterium thermoautotrophicum strain Marburg. In contrast, growth of two non-methanogenic archaea, several eubacteria, and one eukaryote was not strongly affected at much higher concentrations. In washed-cell suspensions, methanogenesis from H₂ and CO₂ by Mb. thermoautotrophicum or from H₂ and methanol by Methanosarcina barkeri was inhibited by addition of lumazine. In cell-free extracts of Mb. thermoautotrophicum, H₂-driven methane production from CO₂ or CH₃-S-CoM was completely inhibited by 0.6 mM lumazine. The results suggest that the compound may be useful in probing the methanogenesis pathway or in selecting against methanogens. Received: 30 January 1996 / Accepted 15 May 1996     

Glycogen utilization in isolated frog muscle: an effect of passive mechanical stretch

The effect of passive mechanical stretch on glycogen utilization and total protein maintenance in paired sartorii muscles from small male frogs has been investigated, in vitro. Glycogen content of stretched muscles decreased 72.6% over a 24-hr incubation period, compared to a 23.1% decline in unstretched control muscles. Stretched muscles retained 54.7% of their total protein content over a 24-hr period, compared to 38.4% in the unstretched control muscles. Unstretched muscles demonstrated a significant (11.1%) increase in wet weight following 24 hr of incubation, presumably due to increased water retention. There were no significant changes in the wet wts of stretched muscles.     

Folic acid and pteroylpolyglutamate contents of archaebacteria.

Cell extracts of methanogens and the thermoacidophile Sulfolobus solfataricus contained little or no folic acid (pteroylglutamate) or pteroylpolyglutamate activity (less than 0.1 nmol/g [dry weight]). However, the halophile Halobacterium salinarum contained pteroylmono- or pteroyldiglutamates, and Halobacterium volcanii and Halobacterium halobium contained pteroyltriglutamates at levels equivalent to those in eubacteria (greater than 1 nmol/g [dry weight]).