Solubilization of potassium containing minerals by high temperature resistant Streptomyces sp.isolated from earthworm's gut

A potassium solubilizing bacterial strain des- ignated EGT, which is tolerant of high temperature, was isolated from an earthworm＇s gut to obtain a bacterium that can weather potassium-bearing rock effectively through solid-state fermentation. Molecular phylogeny and 16S rRNA gene sequence analysis demonstrated the bacterial strain was a member of the Streptomyces genus. To assess its potential to release potassium from silicate minerals, this strain was used to degrade potassium-bearing rock powder by solid-state fermentation. After fermentation, the amount of water-soluble A1, Fe and K of the substrate with active inoculum was higher than those of the control, which had autoclaved inoculum, and those of the fresh substrate. The result indicated that the strain had the ability to weather potassium-bearing rock and could be used as an inoculum in the production of potassium bio-fertilizer, due to its potassium release activity from rock and tolerance to high temperature.

Isolation and Selection of Beneficial Microorganism Used for Peanut Growing in Sandy Soil of Binhdinh Province, Vietnam

With the aim to apply the beneficial microorganisms to peanut （groundnut （Arachis hypogaea）） growing in sandy soil of Binhdinh province in Vietnam, the paper was conducted to study the isolation, selection of N-fixing, phosphate, potassium solubilizing and slime producing microorganism from sandy soil and peanut root samples, and evaluate the capability of selected isolates to adapt to the sandy soil condition. The isolation and selection of beneficial microbes were based on the biological activity of isolates, which was determined by acetylene reduction assay and nodulation on the peanut for Rhizobium spp., by testing the capability to solubilize Ca3（PO4）2 or fenspat in the growth medium for phosphate, potassium solubilizing microbes, and by measurement of the viscosity of Hansen medium for slime producing microorganism. All isolates were evaluated for the effectiveness on the nutrition uptake and growth of peanut by carrying out at the greenhouse and field experiments. To evaluate the adaptation of selected isolates to the sandy soil condition, the experiments were carried out in the laboratory to determine the microbial density in suitable medium, containing different NaCI concentrations or with different pH or at different temperatures. The results showed that rhizobial strain RA18 had an N-fixing activity value of 3,458 ＋ 10.95 nmol C2H2/plant and can supply 30% of N required for peanut. The bacterial strain P 1107 is able to solubilize phosphate and can increase phosphorus uptake by 30% in peanut. Further, inoculation of peanut with the bacterial strain S3.1 can save 30% required mineral potassium, and the Lipomyces strain PT5.1 can produce the slime, which can provide the sandy soil to keep moisture for 15 d longer than the control without the inoculation. All selected isolates are able to grow at temperatures from 20 ℃ to 35 ℃, pH from 4.5 to 6.0 and the salinity of 0.2%o-0.6%o NaCI, and can well adapt to the sandy soil conditions.