The aim of this research was to study the dissimilatory sulfate reduction process by various Desulfovibrio sp. strains of the human intestine, such as bacterial growth, sulfate-and lactate usage, production of sulfide and acetate by the strains, and carry out cluster and correlation analyses of this process. Methods. Microbiology methods of the study for bacterial strains cultivation and photometric methods for determination of bacterial biomass and hydrogen sulfide concentration were used, sulfate ions concentration was determined by turbidymetric method, lactate concentration was carried out by lactate dehydrogenase. Acetate ions accumulation by the strains was determined by titration. Using the experimental data, the methods of statistical analysis have been also used. Results. The various Desulfovibrio sp. strains accumulated different biomass for ten days of cultivation in modified Kravtsov-Sorokin's medium. The highest biomass (up to 3.89 g/l) was accumulated by Desulfovibrio sp. strain Vib-7 on the sixth day of cultivation. Clustering of bacterial growth parameters has showed the greatest similarity between strains Desulfovibrio sp. strain Vib-7 and Desulfovibrio sp. strain Vib-9. After using all of the sulfate and lactate from the medium, the bacteria stopped growing and the stationary growth phase began. Clustering of the parameters of sulfate usage has showed that strains Desulfovibrio sp. Vib-1 and Desulfovibrio sp. Vib-2 were combined in one cluster, and the strains Desulfovibrio sp. Vib-7 and Desulfovibrio sp. Vib-9 were in another cluster. The strong correlation between all parameters of dissimilatory sulfate reduction (growth, reduction of sulfate, accumulation of sulfide, use of lactate and accumulation of acetate) by the Desulfovibrio sp. strains has been determined. Thus, the obtained results may be promising for further study, in particular for creating ulcerative colitis models, prediction and prevention of human inflammatory bowel disease. K e y w o r d s : sulfate-reducing bacteria, Desulfovibrio, intestinal microbiocenosis, inflammatory bowel diseases. Sulfate-reducing bacteria (SRB) of the intestine use different nutrient substances that a human consumes. Human intestinal microbiocenosis is formed by the hundreds of bacterial species and subspecies [2, 4, 5, 9, 17].

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Viable counts and activities of sulfate-reducing bacteria were determined in the oral cavities of 12 healthy volunteers. Of these, 10 harboured viable sulfate-reducing bacteria populations. Six separate sites were sampled: the posterior tongue, anterior tongue, mid buccal mucosa, vestibular mucosa, supragingival plaque and subgingival plaque. Sulfate-reducing bacteria occurred in all areas, with the highest incidence in supragingival plaque. Viable counts and sulfate-reducing activities in each of the regions varied from 0 to 10(8) cfu (g wet weight)-1 and from 0 to 50 nmol (g wet weight)-1 h-1, respectively. As sulfate-reducing bacteria can be detected in the oral cavity, they may potentially be involved in terminal oxidative processes carried out by the microflora of the mouth.

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1. Potassium secretion by the distal colon before and during intravenous infusion of a potassium load was measured in vivo in groups of rats treated in various ways: A, normal control; B, adrenalectomized; C, sodium depleted; D, on potassium‐rich diet for 7 days; E, after 72 h aldosterone (1 microgram/h); F, after 72 h aldosterone (10 micrograms/h). 2. Potassium infusion produced no increase of secretion in the adrenalectomized rats but in all the other groups it increased by 2‐ to 3‐fold. Secretion during infusion correlated well with the basal (pre‐infusion) rate and in groups C and D reached 140 +/‐ 15 and 173 +/‐ 17 nmol min‐1 cm‐1 respectively compared with 28 +/‐ 6 nmol min‐1 cm‐1 in the controls (A). The passive paracellular pathway for potassium was unaffected by the infusion. Amiloride (100 mumol/l) did not significantly affect potassium secretion rate either before or during the acute potassium infusion. The potassium channel blocker, tetraethylammonium chloride, reduced both basal and the secretion rate during infusion. 3. Transepithelial potential difference (PD), active sodium absorption and sodium fluxes were similar in normal controls and rats fed the potassium‐rich diet. However, the PD was partially amiloride sensitive in the latter group although amiloride insensitive in the normal group. In sodium‐depleted rats, the PD was elevated and totally amiloride insensitive. 4. In both aldosterone‐treated groups (E and F), basal potassium secretion rate was high and similar, and during potassium infusion rose 3‐fold to 114 +/‐ 24 (E) and 105 +/‐ 5 (F) nmol min‐1 cm‐1. However, the PD was not elevated significantly in group E and was only partially amiloride sensitive, whereas in those infused at the higher rate (F) the PD was increased and was totally amiloride sensitive. 5. The high potassium secretion rates developed by this epithelium in sodium‐restricted and potassium‐enriched dietary states appear to depend on the presence of an amiloride‐insensitive transcellular potassium pathway which is induced at a lower level of aldosterone stimulation than is the amiloride‐sensitive transcellular sodium pathway.