Acta microbiologica Polonica. Series B: Microbiologia applicata最新文献

The production of gibberellin-like substances by bacteria and fungi was investigated. A considerable number of the microorganisms studied produced these substances (55 and 86% of bacterial and fungal isolates respectively). Most of the organisms tested synthesized biologically active substances located on the chromatograms with the solvent system benzene, acetic acid (10:3 v/v) at Rf 0.05--0.3. The ammount of gibberellin-like substances produced varied in the range 0.00007--0.00065 GA3 equivalents mug/ml in bacteria and 0.00014--0.00118 mug/ml in fungi.

A change of the N/S ratio in the reaction medium affects the degree of the microbial reduction of sulphates to sulphides (x'). The time interval between the initial and the log phase of the process (t0) also varies, depending on the N/S ratio. It was demonstrated that optimal reduction conditions by the studied strain of Desulfovibrio desulphuricans exist in media of N/S=0.33.

The abundance and activity of certain groups of soil microorganisms were estimated in the rhizosphere of 13 plants from four different habitats at several dates. An additional study was made of the rhizosphere microflora of Ledum palustre from a peat-bog. Numbers of proteolytic, nitrate assimilating, denitrifying, and cellulolytic bacteria were estimated. The intensity of ammonification, nitrification and Clostridium growth was estimated. The studies have revealed that the abundance and the activity of all the groups of bacteria studied depended on the habitat. Within one habitat, however, the influence of the plant was sometimes more pronounced than that of the habitat itself, particularly on the abundance of proteolytic bacteria (Fig. 1). The date of sampling had very little effect on the abundance of all the bacterial groups studied except the cellulolytic bacteria.

Biological activity of some vitamin B12 forms for Escherichia coli 113-3 and the effect of methionine on the assay of these compounds by E. coli 113-3 were studied. It was found that the coenzymatic form had the highest biological activity and that under experimental conditions methionine was an interfering factor in determination of the coenzymatic form and the methyl derivative of B12 only. Otherwise, metionine did not affect the determination of cyanocobalamin an hydroxycobalamin even when the methionine and vitamin B12 ratio was 32 000 : 1.

The influence of salt mixtures consisting of Ca(H2PO4)2, trace elements, CaSO4, CaCO3, Na2CO3, NaCl and K2SO4 in different combinations on the nitrifying power, evolution of carbon dioxide and the total number of bacteria was studied in arid soils (sandy and alluvial) and semi-humid ones (chernozem and rendzina). Salt mixtures comprising of either mono-calcium phosphate or sodium chloride showed highly inhibiting action on the studied microbial activities in sandy, alluvial and chernozem soils, whilst mono-calcium phosphate stimulated the heterotrophs of rendzina. Trace elements stimulated the autotrophs of the clay soils. The other different salts mixtures acted according to the salt combination and nature of the microbial activity.

The physiology and growth kinetics of Aspergillus niger B-64-5 in shaken culture were studied, five successive phases of citric acid fermentation being distinguished. Growth was found to be diauxic, spore germination being followed by an exponential growth phase, then a period of growth disturbance, and last of all a phase of secondary growth, characterized by a constant coefficient of growth decline appeared. The citric acid production started in the phase of growth disturbance. The chief increase in citric acid concentration took place in the production phase, i.e. in the last fermentation phase.