Production and charactization of toxins of bacillus cereus and its mutants

The crude toxin from three standard Bacillus cereus strains [NRRL 569, ATCC 11778 and KllS] was found to contain hemolysin, phospholipase C and mouse lethality factor. Mutant 88 which results from U.V. induction to the type strain B. cereus NRRL 569 could not produce hemolysin in its crude toxin[s]; it also failed in causing lethality to mice. Mutants 318, 431 and 486 failed in producing phospholipase C in their crude toxins. Gamma irradiation has not obvious effect on the properties of the crude toxin [s] up to 20 kGy. The most suitable temperature for storage of B. cereus crude toxin [s] was found to be 4 deg. Mouse lethal toxin was found to be inactivated by heat treatment/denaturation at 65C for 5 minutes

Influence of different calcium and boron salts on cell wall degradation of melon plants caused by erwinia carotovora var. carotovora

The effect of different 10-6-103 M calcium nitrate, calcium sulfate, calcium chloride, calcium hypophosphate or calcium carbonate as well as 10-100 ppm sodium tetraborate on the activity of cellulase, pectinase, cell wall degrading enzymes and proteases was studied applying the colorimetric methods of assay. The results showed that raising the salts concentration was accompanied by a concomitant reduction in the activity of such enzymes. Furthermore, calcium nitrate, calcium sulfate and calcium hypophosphate were more effective inhibitors than the other test salts. In the meantime, using mixtures of calcium salts and sodium tetraborate revealed that borate + calcium nitrate or borate + calcium sulfate were more effective than the other mixtures

Reducing the severity of bacterial soft rot of melon by applying calcium and boron mixtures

Applying borate + calcium nitrate + calcium sulfate in moderate concentrations [in vitro or in vivo] definitely attenuated the extracellular cell wall degrading enzymes produced by Erwinia carotovora var. Carotovora. The obvious decrease in the activities may be associated with the presence of both calcium and borate. The results indicated that the disease severity was reduced to the maximum value of 10% by using 5 x 104 M borate + 105 M calcium sulfate plus 10-5 M calcium nitrate. This effective mixture significantly increased radicle and hypocotyl lengths and decreased the fresh of the whole seedling, whereas the dry weights were insignificantly affected. The results indicated that the average pH remained close to alkalinity by the end of the incubation period. The resistance of melon seedling may be attributed to the presence of high levels of calcium which form calcium complex with pectic substances rendering the resistance to hydrolysis

Salinity stress and enzymatic activities during seeds germination

The germination and water uptake by wheat and pea seeds were suppressed following the sodium chloride concentration with a concomitant increase in their proteins. Polyphenol oxidase and amylase activities of germinated pea seeds also decreased. In wheat the former enzyme was stimulated whereas the latter was suppressed by salt concentration. Protein and isoenzyme patterns were also affected by soaking seeds for 5 days in 10-2 M NaCl which arrested germination