Inhibition of propionate degradation by acetate in methanogenic fluidized bed reactors

Summary The degradation of acetate, propionate and butyrate was monitored during start-up of five lab-scale methanogenic fluidized bed reactors on an artificially prepared waste water. The acetate concentration in the reactor content was found to influence the degradation of propionate but not of butyrate. In general, at acetate levels over 200 mg/l the degradation of propionate was below 60%, whereas the degradation was complete at acetate levels under 100 mg/l. The rationale of the inhibition of propionate degradation by acetate is discussed.     

Glucose-6-phosphate dehydrogenase activity in individual rat hepatocytes of different ploidy classes. I. Developments during postnatal growth

The glucose-6-phosphate dehydrogenase (G6PDH) activity of isolated male rat hepatocytes has been investigated in relationship to the ploidy classes of the cells during the first 20 weeks of postnatal growth. The G6PDH activity in the individual cells was measured with an improved quantitative cytochemical method. The data obtained showed that throughout the whole period of postnatal growth there existed a proportional relationship between the genome copies per cell and the amount of G6PDH activity per cell for binuclear diploid (BD), mononuclear tetraploid (MT) and binuclear tetraploid (BT) cells but not for mononuclear diploid (MD) cells. In the MD cells, which are the stem cells of the liver parenchyma, the activity measured was 1.5 times higher than expected. Furthermore, during postnatal growth, the G6PDH activity per hepatocyte was low at the age of 2 weeks, increased somewhat after weaning (5 weeks) and then more dramatically after 8 weeks to reach a maximum between 12 and 16 weeks. This development occurred in MT and BT cells at an earlier age than in MD and BD cells, in which the increase in enzyme activity followed some 3 weeks later. Castration of the rats before puberty did not influence the development of the amount of G6PDH activity per cell of any of the ploidy classes.     

Endosymbiotic interactions in anaerobic protozoa

Several aspects of the endosymbiosis of methanogenic archaea with anaerobic protozoa are reviewed. Special attention is payed to the role of hydrogenosomes and plastid-like organelles that seem to provide the substrates for the methanogenic endosymbionts. Evidence is presented that hydrogenosomes evolved several times in the various protoctistan taxa. Hydrogenosomes are seemingly different, and their common denominator is the production of hydrogen. The absence of nucleic acids and a protein-synthesizing machineny hampers the analysis of their divergent evolutionary history, and molecular genetic data argue not only for different but even a chimeric origin of the hydrogenosomes.     

Influence of waste water composition on biofilm development in laboratory methanogenic fluidized bed reactors

Summary The influence of the volatile fatty acid composition of waste waters on biofilm development and on the time course of reactor start-up was investigated in laboratory scale fluidized bed reactors. It was found that biofilm development proceeded in a similar way with either acetate, butyrate, propionate or a mixture of these compounds as carbon source in the waste water. Startup was retarded, however, with propionate as sole carbon source. Scanning electron microscopic examination revealed that immobilization of bacteria on the sand used as adhesive support initially occurred in crevices and that thereupon the surface of the sand particles became colonized. The composition of the newly developed biomass was determined when reactors reached steady state. Significant differences in the relative substrate spectra and in the amounts of hydrogenotrophic and acetotrophic methanogenic bacteria were measured. The differences reflected the differences in the composition of the waste waters. The results obtained emphasize the role of the structure of the carrier surface in start-up of methanogenic fluidized bed reactors.Abbreviations used Aw ash weight - COD chemical oxygen demand - EB fluidized bed - hbi vitamin B₁₂-HBI - spt sarcinapterin - UASB upflow anaerobic sludge blanket - VFA volatile fatty acid - VSS volatile suspended solids - Ww wet weight     

Isolation and characterization of thermophilic methanogenic bacteria from mushroom compost

Abstract During the first stage of the preparation of mushroom compost oxygen is believed to be readily available. However we measured methane in the evoking air above the compost piles and were able to isolate thermophilic methanogenic bacteria from this compost. The isolates grow only on H₂ and CO₂ as energy and carbon source and do not require complex factors for growth. On the basis of nutritional and morphological characteristics these methanogens were identified as strains of Methanobacterium thermoautotrophicum .     

Personality profiles of youngsters with velo-cardio-facial syndrome

The personality profile of 48 youngsters (24 males and 24 females, mean age 8 years, 5 months) with Velo-Cardio-Facial Syndrome (VCFS) was compared with a group of 240 non VCFS control youngsters (matched on age and gender), and, in addition, with groups of youngsters with Prader-Willi (PWS), Fragile X (FXS), and Williams Syndromes (WS). Personality characteristics of each youngster were rated by both parents, using the California Child Q-set (CCQ). The scores on eight personality dimensions were compared, i.e., Extraversion, Agreeableness, Conscientiousness, Emotional Stability, Openness, Motor Activity, Irritability, and Dependency. Moreover, Individual differences in personality of VCFS youngsters were related to IQ level, presence or absence of cardiac defects, and de novo versus familial origin of VCFS. The personality profile of VCFS youngsters was markedly different from all non-VCFS groups. Compared to the 240 control children, they were equally extravert and agreeable, less conscientious and emotional stable and more Irritable and dependent. Some personality characteristics in youngsters with VCFS were related to IQ and Age, but not to cardiac defects or de novo versus familial genetic origin of the 22q11 deletion.     

The velocardiofacial syndrome: a review

The Velocardiofacial syndrome is characterised by a complex clinical behavioural phenotype, resulting from the imbalance of normal dosage genes located on 22q11. Low copy repeat gene clusters are known to flank the microdeleted region and predispose to unequal crossing over events resulting in the interstitial 22q11 deletion. Involvement of multiple disease genes is strongly suspected and traditional positional cloning techniques as well as mouse models are used to identify the involved genes.