ISSN:
1432-072X
Keywords:
Methanobacterium thermoautotrophicum
;
Na+ dependent methanogenesis
;
Na+/H+ antiporter
;
pH regulation
;
Membrane potential
;
pH gradient
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Methane formation from H2/CO2 by methanogenic bacteria is dependent on Na+ ions. In this communication it is shown with Methanobacterium thermoautotrophicum that a Na+/H+ antiporter plays a role in methane formation from H2 and CO2 and in the regulation of the ΔpH. This is based on the following findings: (i) Li+ ions, an alternative substrate of Na+/H+ antiporters, could replace Na+ in stimulating methanogenesis from H2 and CO2. (ii) Harmaline, amiloride, and NH 4 + , which are inhibitors of Na+/H+ antiporters, inhibited methanogenesis; inhibition was competitive to Na+ or Li+. (iii) Addition of Na+ or Li+ rather than of other cations to cell suspensions resulted in an acidification of the suspension medium. The rate and extent of acidification was affected by those inhibitors, which inhibited methanogenesis competitively to Na+ or Li. (iv) During methane formation from H2 and CO2 the generation of a ΔpH (inside alkaline) was dependent on the presence of Na+ or Li+. However, methanogenesis was also dependent on Na+ or Li+ under conditions where ΔpH was zero. (v) ATP synthesis driven by an electrogenic potassium efflux was significantly enhanced in the presence of Na+ or Li+. Na+ or Li+ were shown to prevent acidification of the cytoplasm under these conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00491903
