No abstract

The effect of Ca 21 ions on methanogenesis and growth of Methanothermobacter thermautotrophicus was investigated. The calcium chelator ethylene glycol bis(2aminoethylether)-N,N,N 0 ,N 0 -tetra-acetic acid, calcium ionophore A23187 and ruthenium red all inhibited growth of this strain. Methane formation was strongly dependent on the external Ca 21 concentration in a resting cell suspension. In addition, methanogenesis of Ca 21 preloaded cells was stimulated by 400%. Inhibitor studies revealed that Co 21 and Ni 21 , inorganic antagonists of Ca 21 transport, strongly inhibited methanogenesis in these cells. Interestingly, our findings imply that one of the enzymes of methanogenesis might catalyse a Ca 21dependent step and allow a direct activation of methanogenesis by Ca 21 ions.

A spontaneous mutant of Methanothermobacter thermautotrophicus resistant to the Na(+)/H(+) antiporter inhibitor harmaline was isolated. The Na(+)/H(+) exchange activity in the mutant cells was remarkably decreased in comparison with wild-type cells. Na(+)/H(+) antiport activity of wild-type cells grown in the high Na(+) concentration (125 mmol/l) was significantly increased as compared to the cells grown under low Na(+) concentration (6.25 mmol/l) conditions. In contrast, harmaline resistant mutant showed almost the same Na(+)/H(+) antiport activity under both these conditions. While harmaline profoundly inhibited methanogenesis in the wild-type, increased methanogenesis was observed both in the presence and absence of harmaline in the mutant strain. ATP synthesis driven by methanogenic electron transport was significantly enhanced in the mutant cells. The experimental data revealed the differential expression of A flavoprotein and molybdenum-containing formylmethanofuran dehydrogenase 1 subunit C in harmaline-resistant mutant. The overexpression of these proteins might contribute to harmaline resistance. Taken together the results indicate that harmaline resistance in this mutant has arisen as a consequence of mutation(s) in antiporter gene(s) or protein(s) linked to antiporter activity. Moreover this work provides the evidence that Na(+)/H(+) exchanger deficiency in harmaline-resistant mutant can induce overexpression of several proteins participating in methanogenesis.

In today's well-resistant pathogens and excessive use of antibiotics which weake and undermine the immune system the importance of pre- and probiotics is more desired. Probiotics - lactic acid bacteria - our intestinal symbiotes, has significant affect on our intestinal tract and brings us to number of positive physiological effects – inhibit the development of pathogenic microflora and serious stimulate the immune system, which subsequently leads to secondary health benefits - efficient use of energy from food, better resorption of minerals and vitamins by intestinal epithelium, suppression of diseases and inflammatory processes in the human intestine and many others. This article discusses the impact of prebiotics (essential substrate for probiotic bacteria), but also natural occurrence and important of prebiotics. Galactooligosaccharides (GOS) as prebiotic are the most suitable and therefore their commercial application is discussed.

doi:10.5219/251