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

In a 10-year field experiment, the influence of fertilizing, cultivating, and crop rotation measures on the C-content of the soil, humus quality of the organic soil substance, and the yield was investigated. With cultivation of fodder plants only, the C-content of the soil can be improved by increased mineral and increased organo-mineral fertilization at any depth of cultivation. When in the same location there was a turn between cereals and green crops, a decrease of C-rate can only be prevented by increased organo-mineral fertilization. Continuous cultivation of root crops resulted in a decrease of the C-content. Deeper tillage of the soil generally decreased C-content. Within the years, a variability of the pure humin substances could be detected, depending on the rotation of crops and C-content. The composition of the fulvic acids is differentiated in dependence on the factors "time" and "cultivation". The effect of fertilization variants on the yield was different. Fertilization in that location with manure only, compared with mineral fertilization, caused in most cases depression in yield. Decrease on yield by deeper ploughing had the least influence with root crops.

The influence of 544 biocides on soil-microflora was investigated by a special plate-test and by a soil-test. Fungi were particularly sensitive to active substances. They were more inhibited by a greater number of substances, by lower concentrations and by a larger time-interval than bacteria. A differentiated sensitivity of fungi becomes apparent. The pseudomonads, a species of Agrobacter (AIA), flavobacteria and some coryneforme bacteria were relatively resistant. Actinomyces responded similar to fungi. The plate-test is suitable as preliminary test for the selection of substances retarding the degradation of straw. These organisms already favoured by treatments with active substance locate in higher quantities in such soils where the biological balance was disturbed in after the injection. Therefore, the effect of the active substance exceeds that of the injection. The displacement-effect by bacteria resistant to active substances and little active against cellulose plays a minor role in opposite to bacteria active against cellulose, because bacteria don't develop any homogeneous protective coat. A priority effect is therefore excluded.

During three years serological tests (latex test) were run from Novemeber till April to detect Prunus ring spot viruses in forced buds of Prunus avium L., P. avium L. var. avium, and P. cerasus L. It was found that Prunus necrotic ring spot virus (NRV) could be detected reliably during the winter in all infected trees. In contrary the detection of Prune dwarf virus (PDV) was affected by temperatures below zero. In 1971 a low percentage of positive reacting trees was pointed out after the frost periods in January and March. This result was started after the low temperatures in January 1972. The mild winter 1972/73 hardly influenced the reliability of the PDV-test.

Several strains of Pseudomonas aeruginosa were investigated for pathogenicity to plant tissue. Inoculations into the intercellular spaces of leaves of Vicia faba (28 degrees C) and Vinca rosea (36 degrees C) showed negative results. In leaves of Nicotiana tabacum (32 degrees C) the bacteria multiplied; the tissue reacted to form partial lesions and necrosis. Neither in culture filtrates of the bacteria nor in eluates of inoculated leaves pectolytic and cellulolytic enzymes or breakdown products of these could be obtained. Whilst the proteolytic activity was high, symptoms for effects on the plant tissue, however, were not observed. Although this bacterium may be able to multiply after injection into tobacco leaf, the general question about pathogenicity to plants must be denied.

1. Active ingredients retarding the carbon-transformation of straw (TCP, Thiuram, TBTO) also retard the nitrification. Their active period depends on the concentration and on the presence of organic matter. High doses of urea can inhibit the nitrification as well. 2. The activity of urease and the ammonification could not be influenced by adequate doses of the tested active ingredients. 3. The species of bacterium Azotobacter fixing the nitrogen from the air were inhibited by TCP, urea and D-chloramphenicol and promoted by Thiuram and WTZ II 277 after a short period of inhibition. 4. The fungi are very important in the biological nitrogen fixation after manuring straw and in prevention of nitrogen leaching in the autumn. 5. The sufficient concentration of the active ingredients to inhibit the nitrification are lower than the fungicidal concentrations. The soil bacteria could even not be restrained by doses of 5000 ppm. The bacilli were more retarded in presence of organic matters than in a not manured soil.

According to earlier studies the strains of the rhizobia could be put into three biochemical groups (A, B, C) independently of the nodules of which kind of plants having been isolated from. The aim of our experiments has been the determination of the antigenic structure of these rhizobia strains. Regarding the agglutination tests only 24 strains from the 47 ones were agglutinated by A sera, one B strain from the 3 B ones, and 2 C strains from the C ones gave positive reaction with B and C sera, respectively.

Microscopic analysis of longitudinal sections of feeder roots of apple seedlings from soil with experimentally prepared different degrees of soil sickness led to the following results: 1. A colonization of root-barks by actinomycetes could be pointed out in injured and in macroscopic not visible injured feeder roots of apple seedlings from sick soil. 2. The frequency of the colonization of root-pieces of the two highest root classes was in the sick soil at 47.3% and in the two soils with a less degree of soil sickness at 32.4%. In the non-sick soil the root were at a frequency of 0.3% nearly free from actinomycetes. 3. Feeder roots colonizated by actinomycetes showed injuries in the cell-bandage. Increasing injuries of the roots were obtained with increasing intensity of colonization by actinomycetes. In heavy injured feeder roots the proof of actinomycetes was difficult or no more possible. As the share of heavy injured roots was increasing with increasing degree of soil sickness can be supposed that the real frequency of root colonization by actinomycetes is substantially higher than it was observed in roots seeming to be healthy macroscopically. 4. The results obtained support our hypothesis that soil sickness of apple trees is caused by actinomycetes. The injuries of the roots appearing as a consequence of the colonization may explain both, the soil sickness in the case of replanting and the development of soil sickness in growing apple plantations. 5. Since until now there is no proof that actinomycetes cause injuries in roots of fruit-trees further examinations have to be aspired to confirm our results.

The production of sorbose by Acetobacter suboxydans (4) is closely related to the concentration of sorbit in the medium. An increasing concentration of sorbit gives rise to the inhibition of cell reproduction; followed by a decrease of sorbose content in the culture medium. The decrease of sorbose yield in concentrations of about 15% sorbit in medium indicates the decreasing metabolism rate of the total population of Acetobacter suboxydans (4) culture and does not refer to the ability of the individual bacterium cell to produce sorbose. Relevant research work showed, that sorbose production for each bacterium cell distinctly increased with the decrease of the number of cells in a population of Acetobacter suboxydans (4) as a consequence of the application of an increased sorbit concentration. An unrestrained reproduction of bacteria could be obtained by exluding all factors involved in the contamination of sorbit and exhibiting toxic effects. Therefore the organisms could be offered a greater concentration of sorbit for conversion into sorbose. Thus sorbose yield would be increased, respectively. The total conversion of the C-source into sorbose could not be obtained with Acetobacter ruboxydans (4).