Calcium uptake and survival of Bacillus stearothermophilus

The calcium transport in resting vegetative cells of Bacillus stearothermophilus was studied by determining the retention of ⁴⁵Ca in a membrane filter assay. The kinetics of death by vegetative cells, when suspended in buffer at 55°C, was also investigated. The calcium influx required the presence of an energy source, e.g. glucose-1-phosphate and the system exhibited saturation kinetics. The requirements for survival of the thermophilic cells reflected those of the calcium transport system. Thus, cells treated with nitrogen gas showed an increased thermal stability and a decreased efflux of calcium. The initial velocity of calcium influx correlated linearly with the survival of the cells after 1 min heating at 55° C. Lanthanum inhibited calcium influx and reduced survival. Magnesium did not inhibit calcium influx but could replace calcium as a stabilizing agent. The results suggest that the thermophilic cells are not intrinsically heat stable but survive due to a high cellular concentration of divalent ions.Abbreviations CFU colony forming units - CPM counts per min - NCA National canners association - CCCP carbonyl cyanide m-chlorophenylhydrazone - PMS phenazine methosulfate     

Soil recovery after removal of the N2-fixing invasive Acacia longifolia: consequences for ecosystem restoration

Invasion by Acacia longifolia alters soil characteristics and processes. The present study was conducted to determine if the changes in soil C and N pools and processes induced by A. longifolia persist after its removal, at the São Jacinto Dunes Nature Reserve (Portugal). Some areas had been invaded for a long time (>20 years) and others more recently (<10 years). For each type of invasion, (i.e., long-invaded and recently invaded), three treatments were used: (1) A. longifolia left intact; (2) A. longifolia was removed; and (3) both A. longifolia and litter layer were removed. Soil samples were collected once a year for four and half years and analysed for chemical and microbial properties. In general, microbial parameters responded faster than C and N pools. In long-invaded areas, two and half years after removal of plants and litter, basal respiration and microbial biomass had already decreased >30%, β-glucosaminidase activity (N mineralization index) >60% and potential nitrification >95%. Removal of plants and litter resulted in a >35% decrease in C and N content after four and half years. In recently invaded areas, β-glucosaminidase activity and potential nitrification showed a marked decrease (>54% and >95%, respectively) after removal of both A. longifolia and litter. Our results suggest that after removal of an N₂-fixing invasive tree that changes ecosystem-level processes, it takes several years before soil nutrients and processes return to pre-invasion levels, but this legacy slowly diminish, suggesting that the susceptibility of native areas to (re)invasion is a function of the time elapsed since removal. Removal of the N-rich litter layer facilitates ecosystem recovery.     

Protease Activation in Apoptosis Induced by MAL

The proteolytic caspase cascade plays a central role in the signaling and execution steps of apoptosis. This study investigated the activation of different caspases in apoptosis induced by MAL (a folding variant of human alpha-lactalbumin) isolated from human milk. Our results show that the caspase-3-like enzymes, and to a lesser extent the caspase-6-like enzymes, were activated in Jurkat and A549 cells exposed to MAL. Activated caspases subsequently cleaved several protein substrates, including PARP, lamin B, and alpha-fodrin. A broad-range caspase inhibitor, zVAD-fmk, blocked the caspase activation, the cleavage of proteins, and DNA fragmentation, indicating an important role for caspase activation in MAL-induced apoptosis. Since an antagonistic anti-CD95 receptor antibody, ZB4, did not influence the MAL-induced killing, we conclude that this process does not involve the CD95-mediated pathway. While MAL did not directly activate caspases in the cytosol, it colocalized with mitochondria and induced the release of cytochrome c. Thus, these results demonstrate that caspases are activated and involved in apoptosis induced by MAL and that direct interaction of MAL with mitochondria leads to the release of cytochrome c, suggesting that this release is an important step in the initiation and/or amplification of the caspase cascade in these cells.     

Proteases in Fas-mediated apoptosis

Involvement of a unique family of cysteine proteases in the multistep apoptotic process has been documented. Cloning of several mammalian genes identifies some components of this cellular response. However, it is currently unclear which protease plays a role as a signal and/or effector of apoptosis. We summarize contributions to the data concerning proteases in Fas-mediated apoptosis. J. Cell. Biochem. 64:43–49. © 1997 Wiley-Liss, Inc.     

Microbial changes during oil decomposition in soil

An examination has been made of the changes in bacterial and fungal populations during the decomposition of oil in contaminated soil. The number of aerobic and anaerobic bacteria and the length of mycelium increased in the oily soil whereas the number of CFU (= colony forming units) of fungi was highest in a control soil. The percentage of oil-utilizing fungi increased from 60% to 82%, while the bacterial utilization figure increased from 3% to 50%. The important oil-utilizing fungus Scolecobasidium appeared only in the oily soil, but otherwise the composition of the fungal flora changed only little after addition of oil. In laboratory experiments the chemical Pajab FI was shown to increase microbial activity.