Intracellular potassium concentration and relative acidity of the ribosomal proteins of methanogenic bacteria

Abstract

The intracellular potassium concentration and percentage of acidic ribosomal proteins were determined for nine methanogenic bacteria representing diverse phylogenetic groupings. Representatives of the Methanobacteriaceae family possessed very high internal potassium concentrations: Methanobrevibacter arboriphilus, 1225 mM; Methanobrevibacter smithii, 1065 mM; Methanobacterium thermoautotrophicum, 1103 mM; Methanobacterium bryantii, 861 mM; and Methanobacterium strain G2R, 886 mM. Members of other families tested maintained much lower internal concentrations of potassium. Methanosarcina barkeri (family Methanosarcinaceae) and Methanospirillum hungatei (family Methanomicrobiaceae) maintained approximately 200 mM internal potassium, while Methanococcus voltae (family Methanococcaceae) possessed an intermediate concentration of 725 mM. Those organisms maintaining the highest internal potassium concentrations also had the largest number of acidic ribosomal proteins. There appeared to be a correlation among the phylogenetic placement of the organism (based on 16S rRNA sequence data), its content of intracellular potassium, and the percentage of acidic ribosomal proteins. Those methanogens most closely related to extreme halophiles possessed the highest concentrations of internal potassium and had an increased percentage of acidic ribosomal proteins, both properties of halophilic bacteria.

The presence of H+ and Na+‐translocating ATPases in Methanobacterium thermoautotrophicum and their possible function under alkaline conditions

“…With respect to the evolutionary aspects of these observations we assume that sodium energetics in these cells might reflect the observed portion of their halophilic nature. Methanobacteriaceae, as already been suggested, is the methanogenic group most closely related to the extreme halophilis [29]. We also speculate that magnesium ions, which occur in high concentrations in various saline biotopes (e.g.…”

Purification and characterization of d‐glyceraldehyde‐3‐phosphate dehydrogenase from the thermophilic archaebacterium Methanothermus fervidus

“…Unlike the specific stabilization by the coenzyme, the salt concentration necessary for a sufficient stabilization is possibly too high for claiming a physiological relevance. However, as shown by Jarrell et al [61] especially the members of Methanobacteriaceae, which are phylogenetically related to the Methanothermaceae, exhibit nearly halophilic intracellular potassium concentrations (up to 1.2 M). Considering in addition the high portion of acidic proteins within the fraction of ribosomal proteins of these organisms [61] one might assume that M. fervidus also posesses a higher portion of acidic proteins, which can lead in vivo to a respective reduction of the N terminus and three tryptic peptides of the M. fervidus-o-glyceraldehyde-3-phosphate dehydrogenase to the sequences of the o-glyceraldehyde-3-phosphate dehydrogenases from T. aquaticus 1211 .…”

Hydrolysis and reduction of factor 390 by cell extracts of Methanobacterium thermoautotrophicum (strain delta H)

“…Exposure of Methanobacterium cells to oxygen leads to the complete elimination of AX (1), which causes a rapid efflux of potassium from the cells (18). This oxygen-induced decline in the internal potassium concentration, which is normally very high (600 to 1,100 mM) (10,18), again favors synthesis of F390. In addition, efflux of potassium might be accompanied by H+ influx, lowering the internal pH.…”