Shifts in methanogenic subpopulations measured with antibody probes in a fixed-bed loop anaerobic bioreactor treating sulfite evaporator condensate

A fixed-bed loop, high-rate anaerobic bioreactor treating sulfite evaporator condensate was sampled when it reached steady state and afterwards following perturbations during a 14-month period. By using immunotechnology, it was observed that shifts in methanogenic subpopulations occurred in association with perturbations, such as restarting and relocating the biomass into a different tank. Methanogens related to Methanobacterium bryantii MoHG and Methanobrevibacter smithii ALI were numerous throughout the observation period, while Methanosarcina mazei S6 and Methanosarcina thermophila TM1 were found in the early and late samples, respectively. Also, Methanobacterium formicicum was more numerous at the top portion of the bioreactor, while Methanobrevibacter arboriphilus AZ and DC were at the bottom. Sample formalinization required for prolonged storage proved suitable for antigen preservation.

Quantitative Microbiological Analysis of Bacterial Community Shifts in a High-Rate Anaerobic Bioreactor Treating Sulfite Evaporator Condensate

The bacterial population of a high-rate, anaerobic, fixed-bed loop reactor treating sulfite evaporator condensate from the pulp industry was studied over a 14-month period. This period was divided into seven cycles that included a startup at the beginning of each cycle. Some 82% of the total biomass was immobilized on and between the porous glass rings filling the reactor. The range of the total number of microorganisms in these biofilms was 2 × 10 9 to 7 × 10 9 cells per ml. Enumeration and characterization by microbiological methods and by phase-contrast, epifluorescence, and electron microscopy showed that the samples consisted mainly of the following methanogens: a Methanobacterium sp., a Methanosarcina sp., a Methanobrevibacter sp., and a Methanothrix sp., as well as furfural-degrading sulfate-reducing bacteria resembling Desulfovibrio furfuralis. Viable counts of hydrogenotrophic methanogens were relatively stable (mostly within the range of 3.2 × 10 8 to 7.5 × 10 8 cells per ml), but Methanobrevibacter cells increased from <5 to 30% of the total hydrogenotrophic count after transfer of the fixed bed into a second reactor vessel. Acetotrophic methanogens reached their highest numbers of 1.3 × 10 8 to 2.6 × 10 8 cells per ml in the last fermentation cycles. They showed a morphological shift from sarcinalike packets in early samples to single coccoid forms in later phases of the fermentation. Furfural-degrading sulfate reducers reached counts of 1 × 10 7 to 5.8 × 10 7 cells per ml. The distribution of the chief metabolic groups between free fluid and biofilms was analyzed in the fifth fermentation cycle: 4.5 times more furfural degraders were found in the free fluid than in the biofilms. In contrast, 5.8 times more acetotrophic and 16.6 times more hydrogenotrophic methanogens were found in the biofilms than in the free liquid. The data concerning time shifts of morphotypes among the trophic groups of methanogens corroborated the trends observed by using immunological assays on the same samples.

Synergistic internal carotid vasodilator effects of human alpha-calcitonin gene-related peptide and nimodipine in conscious rats

1. In a first series of experiments, male Long Evans rats were chronically instrumented for the measurement of internal carotid blood flow and systemic arterial blood pressure; cardiovascular changes were assessed during and after 30 min infusions of human alpha-calcitonin gene-related peptide (CGRP) (0.06 and 0.6 nmol h-1), or nimodipine (60 and 600 nmol h-1) or human alpha-CGRP plus nimodipine. The effects of human alpha-CGRP or nimodipine on internal carotid vasoconstriction induced by endothelin-1 were also measured. 2. Human alpha-CGRP (0.06 nmol h-1) caused a small (+15%), transient increase in internal carotid blood flow and a tachycardia (+33 beats min-1), but no change in mean blood pressure. Nimodipine (60 nmol h-1) caused a brief internal carotid hyperaemia (+16%) but no changes in blood pressure or heart rate. However, concurrent administration of human alpha-CGRP (0.06 nmol h-1) and nimodipine (60 nmol h-1) caused a sustained increase in internal carotid blood flow (+40%) unaccompanied by significant changes in heart rate or blood pressure. 3. Human alpha-CGRP at a dose of 0.6 nmol h-1 or nimodipine at a dose of 600 nmol h-1 caused substantial reductions in internal carotid vascular resistance (-43 and -40%, respectively); concurrent administration of these doses did not have an additive vasodilator effect. 4. Infusion of endothelin-1 (1.2nmolhV1) for 20min caused incremental constriction of the internal carotid vascular bed; human alpha-CGRP infusion (0.6 and 6.0nmolh-1) begun tOmin after the onset of endothelin-1 infusion reversed this effect (dose-dependently); nimodipine (600nmolh-1) also caused a substantial attenuation of the effects of endothelin-1. 5. In a second series of experiments the haemodynamic effects of human alpha-CGRP and/or nimodipine were assessed in rats chronically instrumented for the measurement of renal, superior mesenteric and hindquarters blood flow together with systemic arterial blood pressure. 6. Administration of human alpha-CGRP (0.06 nmol h-') alone or in conjuction with nimodipine (60nmolh-1) had no significant effects on renal or superior mesenteric vascular resistances, although there was a slight hindquarters vasodilatation. Human alpha-CGRP at a dose of 0.6 nmol -1 caused hypotension, tachycardia and reductions in renal and superior mesenteric blood flows, together with a marked (+31% maximum) hindquarters hyperaemia. Nimodipine at a dose of 600 nmol h-1 caused hypotension, tachycardia and a reduction (-34%) in renal blood flow; mesenteric blood flow was unchanged and there was an increase in hindquarters flow (+ 59%). 7. Concurrent administration of human alpha-CGRP (0.6 nmol h 1) and nimodipine (600 nmol h') did not have an additive hypotensive effect or an enhanced hindquarters hyperaemic effect, but was associated with a marked impairment of renal blood flow (-48%). 8. The present results indicate that concurrent administration of low doses of human alpha-CGRP and nimodipine might be particularly helpful in the acute treatment of patients with cerebral vasospasm and impaired renal perfusion, since this intervention improved internal carotid blood flow without compromising blood flow to the kidney.