Effect of biomass concentration and mycelial morphology on fermentation broth rheology

The effect of biomass concentration and mycelial morphology on fungal fermentation broth rheological properties has been investigated. In previous work it had been shown that commonly used rheological parameters, such as the power law consistency and flow behavior indices, could be correlated successfully with the broth biomass concentration and clump morphological parameters of roughness and compactness. More recent work on a broader range of data showed a correlation between roughness and compactness; consequently, it was not correct to use both of these morphological variables simultaneously in rheological parameter correlations. Furthermore, earlier correlations were only made using clump morphological parameters, as clumps were found to be around 90% of the biomass in batch fermentations. In the present work it was found that the percentage of clumps fell to around 30% to 40% of a sample during the later stages of fed-batch fermentations. No clear relationship between the flow behavior index and biomass concentration was found, at least for those phases of the fermentation in which the viscosities were high enough for the rheology to be characterized by a disk turbine rheometer. The mean value of the flow behavior index was found to be 0.35 +/- 0.1 (standard deviation) throughout both batch and fed-batch fermentations, although some significant deviations from this value were observed early and very late in the fermentations. Correlations for the consistency index, measured using a disk turbine rheometer, were based on the biomass concentration and the mycelial size (represented by the mean projected area or the mean maximum dimension of all the mycelia). These correlations were reasonably successful for both fed-batch and batch fermentations. The correlation using the mean maximum dimension was preferred to that using the mean projected area, as the former is independent of magnification. The proposed correlation is: where K is the consistency index (Pa. s(n>)), C(m) is the biomass concentration as dry cell weight (g L(-1)), and D is the mean maximum dimension (microm). It should be noted that small changes in the exponent on the biomass concentration (alpha) may dramatically affect any predictions. Consequently, caution in the use of this correlation (and that based on mean projected area) is advocated, although its accuracy may be suitable for operational or design purposes.     

Involvement of matrix metalloproteinases 2 and 9, tissue inhibitor of metalloproteinases and apoptosis in tissue remodelling in the sheep placenta

Placental growth and development is crucial for successful pregnancy. The aim of this study was to characterize the activity and localization of the matrix metalloproteinase 2 (MMP-2) and MMP-9, which are capable of degrading basement membrane collagen (predominantly collagen type IV), and their endogenous tissue inhibitor of matrix metalloproteinases (TIMPs), in amniotic fluid and in the developing ovine placenta. Cell deletion by apoptosis during placental development was also examined. Zymography with gelatin as substrate indicated that MMP-2 (72 kDa gelatinase A; predominantly latent form) was present in increasing amounts in amniotic fluid from day 70 of gestation to labour (days 140-145), and MMP-9 (92 kDa gelatinase B; predominantly latent form) was detectable from day 125 to labour; there was no increase in MMP-2 or -9 in labour. A broad range of TIMPs was detected in amniotic fluid; the molecular masses corresponded to TIMP-1, -2 and -3. Immunohistochemical techniques localized MMP-2, MMP-9 and TIMP-3 in the sheep placenta, predominantly in the trophoblast layer in uninucleate, but not binucleate, cells. However, MMP-2 and -9 activated proteins in placental homogenates were low throughout pregnancy. Apoptosis was identified by morphological criteria and also by TdT-mediated dUTP nick end labelling. Apoptosis was present in discrete regions in the placenta, predominantly in trophoblast cells near the tips and the basal regions of the fetomaternal interdigitations. During pregnancy the sheep placenta becomes more complex and the area of the fetomaternal interface increases. MMP-2 and -9 are likely to be involved in breaking down basement membranes to allow cell migration during this process. It is suggested that digestion of supporting extracellular matrix may trigger apoptosis and in some way increase the branching pattern in the villi.     

Survival of Plasmid-Containing Bacillus subtilis Released into Mushroom Compost

Abstract The survival of a plasmid-containing Bacillus subtilis released into mushroom compost was investigated. The indigenous Bacillus population of mushroom compost exhibited an antibiotic-resistance profile that was distinguished by almost complete absence of chloramphenicol resistance. Bacillus subtilis containing the chloramphenicol-resistance plasmid pC194 was released into mushroom compost microcosms and populations were monitored at different incubation temperatures. The organism colonized both sterile and untreated compost at 37°C, and to a lesser extent at 50°C, but was eliminated after 30 d at 65°C. Although sporulation of the B. subtilis population occurred within compost, the population was maintained for up to 13 weeks at 50°C, largely as vegetative cells. Experiments in which the B. subtilis host strain, without plasmid, was released demonstrated that plasmid carriage had no effect on the ability of the bacterium to colonize and survive in compost. Furthermore, the size and composition of the indigenous bacterial population was unaffected by the presence of the introduced B. subtilis strain. Virtually no loss of plasmid pC194 from the B. subtilis population in compost was observed, and experiments at low growth rates in chemostats confirmed the stability of this host/vector system in the absence of positive selection pressure. Received: 9 July 1997; Accepted: 20 October 1997     

Effect of storage at 4 degrees on prepared Salmonella/microsome test plates

Salmonella/microsome soft-agar overlay ('Ames' test) plates were prepared using the previously published 'York' method. Plates treated with either added 3-methylcholanthrene (3MC) or 3,3'-dichlorobenzidine (DCB) and Aroclor-induced rat-liver S9 were stored at 4 degrees after preparation and removed at time intervals thereafter for incubation at 37 degrees. The number of 3MC-induced mutants in TA100 fell within 24 h of storage by 50% but then remained at this level until 96 h. Storage for a total of 336 h still showed some residual mono-oxygenase activity. On the other hand the ability to convert DCB to a mutagen for TA98 appeared to increase with storage, reaching a peak by 96 h. After this time the number of induced mutants fell until by 336 h the numbers were approximately equal to those plates which had not been stored in the cold.     

Magnetic particles associated with the lateral line of the European eel Anguilla anguilla

Magnetization measurements of the European eel Anguilla anguilla demonstrated the presence of magnetic material concentrated in the region of the mandibular canals of the lateral line system. The data suggest that the material is magnetite, has a size suitable for magnetoreception and is of biogenic origin. The presence of magnetic particles in the lateral line system is discussed in relation to their possible role in allowing the fish to orientate with respect to the geomagnetic field during their extensive oceanic spawning migrations.     

DED or alive: assembly and regulation of the death effector domain complexes

Death effector domains (DEDs) are protein–protein interaction domains initially identified in proteins such as FADD, FLIP and caspase-8 involved in regulating apoptosis. Subsequently, these proteins have been shown to have important roles in regulating other forms of cell death, including necroptosis, and in regulating other important cellular processes, including autophagy and inflammation. Moreover, these proteins also have prominent roles in innate and adaptive immunity and during embryonic development. In this article, we review the various roles of DED-containing proteins and discuss recent developments in our understanding of DED complex formation and regulation. We also briefly discuss opportunities to therapeutically target DED complex formation in diseases such as cancer.