Organization of telomeric and subtelomeric chromatin in the higher plant Nicotiana tabacum

We have examined the structure and chromatin organization of telomeres in Nicotiana tabacum. In tobacco the blocks of simple telomeric repeats (TTTAGGG)_n are many times larger than in other plants, e.g., Arabidopsis thatiana or tomato. They are resolved as multiple fragments 60–160 kb in size (in most cases 90–130 kb) on pulsed-field gel electrophoresis (PFGE) of restriction endonuclease-digested DNA. The major subtelomeric repeat of the HRS60 family forms large homogeneous blocks of a basic 180 by motif having comparable lengths. Micrococcal nuclease (MNase) cleaves tobacco telomeric chromatin into subunits with a short repeat length of 157±5 bp; the subtelomeric heterochromatin characterized by tandemly repeated sequences of the HRS60 family is cut by MNase with a 180 by periodicity. The monomeric and dimeric particles of telomeric and subtelomeric chromatin differ in sensitivity to MNase treatment: the telomeric particles are readily digested, producing ladders with a periodicity of 7 bp, while the subtelomeric particles appear to be rather resistant to intranucleosomal cleavage. The results presented show apparent similarities in the organization of telomeric chromatin in higher plants and mammals.     

Anaerobic digestion of palm oil mill effluent and condensation water waste: an overall kinetic model for methane production and substrate utilization

The process of anaerobic digestion is viewed as a series of reactions which can be described kinetically both in terms of substrate utilization and methane production. It is considered that the rate limiting factor in the digestion of complex wastewaters is hydrolysis and this cannot be adequately described using a Monod equation. In contrast readily assimilable wastewaters conform well to this approach. A generalized equation has thus been derived, based on both the Monod and Contois equations, which serves extreme cases. The model was verified experimentally using continuous feed anaerobic digesters treating palm oil mill effluent (POME) and condensation water from a thermal concentration process. POME represents a complex substrate comprising of unhydrolyzed materials whereas the condensation water is predominantly short chain volatile fatty acids. Substrate removal and methane production in both cases could be predicted accurately using the generalized equation presented.List of Symbols A (=K_skY/K_h) Kinetic parameter - B Specific methane yield, 1 of CH₄/g of substrate added B₀ Maximum specific methane yield, 1 of CH₄/g of substrate added at infinity - C Empirical constant in Contois equation - F Volumetric substrate removal rate, g/l day - k Hydrolysed substrate transport rate coefficient, 1/days - K (=YC) Kinetic parameter in Chen-Hashimoto equation - K _h Substrate hydrolysis rate coefficient, 1/days - K _s Half-saturation constant for hydrolysed substrate, g/l - M _v Volumetric methane production rate, 1 of CH₄/l day - MS Mineral solids, g/l - MSS Mineral suspended soilds, g/l - POME Palm oil mill effluent - R (=S_r/S_T0) Refractory coefficient - S _h Concentration of hydrolysed substrate, g/l - S _u Intracellular concentration of hydrolysed substrate, g/l - S ₀ Input biodegradable substrate concentration, g/l - S Biodegradable substrate concentration in the effluent or in the digester, g/l - S _r Refractory feed substrate concentration, g/l - S _T0 (=S₀+S_r) Total feed substrate concentration, g/l - S _T (S+S_r) Total substrate concentration in the effluent, g/l - TS Total solids, g/l - TSS Total suspended solids, g/l - VFA Total volatile fatty acids, g/l - VS Volatile solids, g/l - VSS Volatile suspended solids, g/l - X Biomass concentration, g/l - Y Biomass yield coefficient, biomass/substrate mass - Hydraulic retention time, days. - Specific growth rate of microorganisms, l/days - _m Maximum specific growth rate of microorganisms, l/days The authors wish to express their gratitude to the Departamento de Postgrado y Especialización del CSIC and to the Consejería de Educación y Ciencia de la Junta de Andalucia for their financial support of this work.     

A Field Study on Group Housing of Lactating Sows with Special Reference to Sow Health at Weaning

Four farms that group-housed sows from 2 weeks of lactation until weaning (G-farms) and 3 farms that kept the sows individually penned throughout the 5 to 6-week-long lactation period (C-farms), were compared in terms of sow health. All sows were crossbred Swedish Yorkshire × Swedish Landrace. The daily food ration was similar on all farms except during the group-housing period, when G-farm sows were fed ad libitum. Sows were grouped in the breeding section and kept grouped on deep litter in the dry sow section on all farms. Individual health examinations were performed at the time of weaning (±4 days) on 179 G-farm sows and on 167 C-farm sows. Teat- and udder skin wounds occurred less frequently (p<0.001) in G-farm sows than in C-farm sows. In addition, preweaning atrophy of all mammary glands occurred in 6.6% of the G-farm-sows but not in a single C-farm sow (p<0.001). This indicates that sow-piglet interactions decrease when sows are group housed. However, these differences did not occur in primiparous sows, suggesting that the relation between the primiparous sow and her litter is not affected. Mastitis frequency was the same in the 2 systems. Moreover, the frequency of locomotor disorders was the same in the 2 groups, and hoof overgrowth was common in both systems. These similarities could be due to the fact that all farms group housed dry sows on deep litter. A strong relation (p<0.001) between hoof overgrowth and locomotor disorders was evident. Low access to food due to low rank among primiparous group-housed sows was indicated by a lower (p<0.05) backfat thickness compared with multiparous sows, and a higher (p<0.001) frequency of skin wounds compared with individually housed primiparous sows.     

Mycoplasma hyopneumoniae and Mycoplasma hyosynoviae Infection in Cases of Fibrinous Pericarditis in Slaughter Pigs

Pericarditis, acute or subacute, is found at post mortem meat inspection of baconers in about 0.02 to 0.04% of slaughtered pigs in Denmark. The pathological findings are usually restricted to the pericardial sac. The pericardial sac is filled with a fibrinous exudate, which may be blood stained. In some cases massive granulation tissue formation is seen underlying the fibrinous exudate. Other constantly occurring, but less aggravating lesions, are chronic catarrhal bronchopneumonia and increased volume of serosanguinous synovial fluid in the large joints of the limbs. Lesions usually seen as sequelae to septicaemia have not been observed. The lesions seem to be part of a pathological entity which may be involved in the pathogenesis of fibrinous pericarditis in baconers.     

Advantages and limitations in the use of hairy root cultures for the production of tropane alkaloids: Use of anti-auxins in the maintenance of normal root morphology

Summary Brugmansia candida hairy roots, obtained by infection withAgrobacterium rhizogenes LBA 9402, exhibit, after subculturing in liquid media, a tendency towards dedifferentiation. It has been found that the following strategies can be applied to inhibit this dedifferentiation and preserve normal root morphology: (a) lowering both the mineral and sucrose concentration in the media employed so as to diminish osmotic stress (a condition to which these roots appear to be particularly susceptible); (b) employing antiauxins in appropriate concentrations; and (c) maintaining the hairy roots on solid media prior to use in production processes in liquid media. The first strategy suggested does not favor alkaloid productivity, but in this case a two-step method could be attempted: biomass with normal root morphology could be obtained in a first stage using low sucrose concentrations, and in a second stage, sucrose could be increased in order to achieve higher productivity. In all the clones ofB. candida obtained, alkaloid production was biased towards scopolamine.     

Ecological requirements and recent European distribution of the aquatic carnivorous plantAldrovanda vesiculosa L.—A review

Aldrovanda vesiculosa, a critically endangered aquatic carnivorous plant, is a species rapidly vanishing from Europe. A map of its recent European distribution is given. Of its earlier distribution area covering a substantial part of Europe, only a few native sites in Hungary, Poland, Romania, Russia and Ukraine remain. On the basis of the literature, field research inAldrovanda habitats, and experience of its cultivation both in culture and in the field, its ecological requirements and habitat characteristics are reviewed. The most important requirements appear to be a high CO₂ concentration, a medium concentration of humic acids in the water, warm water of high transparency, and a very low biomass of accompanying aquatic plants. The possibility of forming new substitute localities ofAldrovanda is discussed.     

Studies on homoveratric acid transformation by the ligninolytic fungus Pleurotus eryngii

Homoveratric acid (HVA) degradation was observed in cultures of Pleurotus eryngii lacking lignin peroxidase (LiP) activity. Extracellular enzymes seemed responsible for this transformation, and the lack of activity after ultrafiltration of the culture liquid suggests that the presence of some low-molecular-size compounds is required. This hypothesis is supported by rapid HVA transformation after addition of the synthetic laccase substrate 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) to the ultrafiltered liquid. HVA transformation by the extracellular enzymes from P. eryngii takes place via C-C breakdown and formation of veratryl alcohol, which is further transformed into veratraldehyde. The same major compounds were found during HVA transformation by LiP from Phanerochaete chrysosporium, but this reaction was not stimulated by ABTS. Although the involvement of other enzymes cannot be ruled out, purified laccase from Pleurotus eryngii caused the same HVA transformation pattern in presence of ABTS. Moreover, veratryl alcohol oxidation by P. eryngii laccase was demonstrated in the presence of ABTS. These results suggest that enzymatic systems lacking LiP could be responsible for natural degradation of lignin.     

Preservation of Xanthomonas campestris on agar slopes: effects on xanthan production

Xanthomonas campestris NRRL B-1459 and a variant E2, when preserved on agar slopes (transferred monthly) over 11 months did not deteriorate in their ability to produce xanthan in quantity and quality, as determined by culture in 500-ml baffled flasks. Variations between 8 and 14% (with respect to the average) in the final xanthan concentration were observed for the E2 and B-1459 strains, respectively. A wide range of final viscosities was obtained; these were consistent with the changes in gum concentration. Differences were more likely associated with differences in fermentation kinetics rather than being inherent to the strains. The rheological quality of both polysacharides was relatively constant throughout the time of culture maintenance. Preservation of these bacteria on agar slopes was an adequate method, in contrast to previous reports. In the period studied, strain E2 produced higher gum titres and slightly lower gum quality compared to strain B-1459. Correspondence to: E. Galindo     

Continuous limonin degradation by immobilizedRhodococcus fascians cells in K-carrageenan

Limonin can be effectively degraded byRhodococcus fascians cells. These bacteria can be entraped in -carrageenan, and used in a continuous stirred tank reactor to degrade limonin in a continuous process. The effects of temperature limonin concentration, dilution rate, and aeration on the reactor behaviour have been tested, and the results correlated with changes in limonin conversion, substrate degradation rate, and free and immobilized biomass. Results showed that the immobilized cells were able to debitter limonin-containing media and the immobilized biomass was quite stable throughout the operational conditions tested. A population of free biomass was present in the reactor, the quantity of which was dependent on dilution rate. The immobilized bacteria increased its limonin-degrading capability when the substrate concentration was increased. The aeration was not strictly necessary for limonin degradation. Additionally, the immobilized cells were active and stable for more than 2 months of continuous operation, and were able to recover their limonin-degrading capability when used intermittently. Finally, none of the main components of a juice was noticeably altered during limonin degradation, so the reactor response was good enough to consider its application.