Zentralblatt fur Bakteriologie, Parasitenkunde, Infektionskrankheiten und Hygiene. Zweite naturwissenschaftliche Abt.: Allgemeine, landwirtschaftliche und technische Mikrobiologie最新文献

In three profiles of a semi-gley soil under the floodplain forest, variations were studied in the activities of invertase, amylase, cellobiase, cellulase, proteases, and phosphatases. In the surface soil layer, enzymatic activity was found affected by the soil moisture at a significant level, whereas in the deeper soil layers the influence of aeration was more effective. Moreover, significant correlations could be detected between the amount of available nitrogen and protease activity, while the water-soluble phosphorus acted as a represeive agent on the activity of phosphatases. Existence of correlations between the numbers of microbes and enzymes could be demonstrated for invertase and protases only.

In order to investigate the decomposition of 46 organic and anorganic compounds by Bac. mycoides, the behaviour of four strains was tested by means of plate counting technique (after Koch) and the Warburg method. Mostly intensive substances containing protein were decomposed by all strains. Furthermore amino acid, sugar, alcohols, and ammonium salts are used by the bacteria, but there were large differences between strains tested. Urea and nitrates have not been decomposed.

Erysimum latent virus (ELV) proved to be transmissible by Phyllotreta atra, P. nemorum, P. nigripes, and P. undulata. From them P. nemorum is a new discovered vector. The acquisition of the virus by the beetles was possible within a feeding time of less than 10 minutes. Because virus transmission could be performed within 30 to 60 minutes immediately after virus uptake there exists apparently no latent period in the vector. The retention or persistence of ELV in the Phyllotreta species amounted up to 3 days. Trials to induce infectivity of Phyllotreta species by injection of the virus were unsuccessful. ELV was transmissible by Aphis frangulae gossypii, Brevicoryne brassicae, and Myzus persicae neither in short nor in long feeding times. Field tests showed that the Phyllotreta species are able to spread ELV under natural conditions.

Results of a field experiment on the effect of three years irrigation on the population dynamic of migratory nematodes of the cereals are described. In case of constant high moisture content the Pratylenchus spec. were inhibited. A cumulation of this effect during three years was not observed. The influence was only low on the species of the genus Tylenchorhychus, Paratylenchus, on the species of the families Aphelenchoididae/Aphelenchidae, Dorylaimidae, and on the saprophytic nematodes of the order Rhabditida.

Lactobacilli isolated from grass silage were shown to belong to Lb. plantarum, Lb. casei and Lb. brevis. In studies on the degradation of fructosanes significant differences among the three species were found. While all strains of L. casei were able to degrade fructosanes from Dactylis glomerata or Phleum pratense regardless of the degree of polymerization, no nember of Lb. plantarum or Lb. brevis could attack these polysaccharides.

By means of manometric technique the influence of X-ray-repairsubstances on the growth and respiration of Micrococcus denitrificans, Micrococcus radiodurans and Saccharomyces cerevisiae was investigated. Though these substances are stimulating the development of higher plants, there is no effect on growth and respiration of these microorganisms.

The influence of calcium-cyanamide upon the microbiological activity was tested in pot experiments under controlled conditions in two Portuguese soils (sandy and loamy) after the addition of rice or wheat straw (rice straw 0.275% N, wheat straw 0.307% N). The amount of straw was equalled to 100 dz/ha, the application of calcium-cyanamide to 25, 50 and 100 kg N/ha. In the containers treated with straw the total amount of microorganisms (Koch-method) was higher in sandy than in loamy soil after 30 days, but after 70 days it was higher in loamy soil. The content of active nitrogen (NH4 + NO3) increased, when calcium-cyanamide was added, but decreased after the application of straw. After 70 days sandy soil again showed an increase of active nitrogen. Straw increased the rates of CO2-production considerably, wheat straw was superior to rice straw. Calcium-cyanamide increased the CO2-production more in sandy than in loamy soil or German loess, which was also used for this experiment. Only in the case of rice straw higher doses of calcium-cyanamide had a positive effect. After 70 days the CO2-production rose only when rice straw was applied. The dehydrogenase-activity was increased in both soils, but a superiority of wheat straw occurred in sandy soil only. The microbiological activity in the pots with straw was higher in sandy than in loamy soil, the addition of calcium-cyanamide accelerated it. Doses of 25-50 kg N/ha are sufficient generally. The period of the formation of insoluble organic N-compounds, usually connected with the application of organic matter with a wide N:C-ratio, seems to be reduced by the addition of calcium-cyanamide.

Biochemical properties of the crystalline delta-endotoxin of Bacillus thuringiensis, such as stability and solubility in different solvents, were investigated. The dissolved compounds were characterized by gel-electrophoresis and gel-filtration. Covalent and non-covalent bonds are responsible for the crystallisation of the protein molecules. The solubilisation of crystals with non-enzymatic solvents led to high molecular weight products (MW greater than or equal to 800,000) and to components with a molecular weight less than or equal to 10,000. Only the high molecular weight compounds showed toxic activity. The enzymatic degradation of the protein crystals yielded components with molecular weights of greater than or equal to 800,000, 250,000, 100,000, and less than or equal to 10,000. Again, the fraction less than or equal to 10,000 showed no toxic activity. Digestion of the crystals with proteases isolated from the gut juice of Pieris brassicae resulted in a highly toxic fraction with a molecular weight of 100,000. This component, which is resistant to further degradation, appears to be the toxic unit of the protein crystal.