Mineral Phosphate Solubilizing Bacteria Isolated from Various Plant Rhizosphere under Different Aluminum Content

The objectives of this study was to isolate and characterize the mineral phosphate solubilizing bacteria from rhizosphere and evaluate their potential as plant growth promoting bacteria in Al-toxic soils. The halo    zone formation method was used to isolate PSB using the media containing insoluble phosphates (Ca-P or Al-P) as a source of phosphate. Eight of acid and Al-tolerant PSB isolates that were able to solubilize Ca-P were obtained from rhizosphere of clover, wheat, corn, and sunflower grown in Al-toxic soil. Identification of the isolates based on the 16S rRNA gene sequence analysis demonstrated that the isolates were strains of Burkholderia (5 strains), Pseudomonas (1 strain), Ralstonia (1 strain), and unidentified bacterium (1 strains). All PSB isolates showed the capability to dissolve Ca-P, and only 1 strain (Ralstonia strain) was able to dissolve Al-P in agar plate medium. The P-solubilization by these isolates was correlated with pH of medium. Inoculation of the bacterial strains on clover on Al-toxic medium showed that all isolates increased the plant dry weight compared with uninoculated treatment. Our results showed that those PSB isolates have potential to be developed as a biofertilizer to increase the efficiency of P-inorganic fertilizer used in Al-toxic soils

Mineral Phosphate Solubilizing Bacteria Isolated from Various Plant Rhizosphere under Different Aluminum Content

The objectives of this study was to isolate and characterize the mineral phosphate solubilizing bacteriafrom rhizosphere and evaluate their potential as plant growth promoting bacteria in Al-toxic soils. The halozone formation method was used to isolate PSB using the media containing insoluble phosphates (Ca-P or Al-P)as a source of phosphate. Eight of acid and Al-tolerant PSB isolates that were able to solubilize Ca-P wereobtained from rhizosphere of clover, wheat, corn, and sunflower grown in Al-toxic soil. Identification of theisolates based on the 16S rRNA gene sequence analysis demonstrated that the isolates were strains of Burkholderia(5 strains), Pseudomonas (1 strain), Ralstonia (1 strain), and unidentified bacterium (1 strains). All PSB isolatesshowed the capability to dissolve Ca-P, and only 1 strain (Ralstonia strain) was able to dissolve Al-P in agar platemedium. The P-solubilization by these isolates was correlated with pH of medium. Inoculation of the bacterialstrains on clover on Al-toxic medium showed that all isolates increased the plant dry weight compared withuninoculated treatment. Our results showed that those PSB isolates have potential to be developed as a biofertilizerto increase the efficiency of P-inorganic fertilizer used in Al-toxic soils

Presence of linA-Homologous DNA Sequences in Different Types of Soil and Their Sequence Diversity

linA is a gene encoding γ-hexachlorocyclohexane dehydrochlorinase identified in a γ-HCH-degrading Sphingobium japonicum UT26 that had been isolated from soil of an experimental field treated with γ-HCH. The presence of linA-homologous nucleotide sequences and their sequence diversity was investigated by linA-targeted PCR amplification of DNA obtained from different soils in the field and in Japan. linA-homologous sequences were obtained from almost all the soils some of which had never been treated with γ-HCH. Deduced amino acid sequences suggested that they can be regarded as fragments of linA that encode LinA. Some common, natural function of LinA in soil was suggested

Isolation of Oligotrophic Denitrifiers Carrying Previously Uncharacterized Functional Gene Sequences▿ †

Oligotrophic denitrifying bacteria, including those belonging to the genera Herbaspirillum, Azospirillum, and Bradyrhizobium, were obtained using a single-cell isolation technique. The taxonomic composition of the denitrifier population was similar to those assessed by previous culture-independent studies. The sequencing of nitrite reductase and N2O reductase genes of these strains revealed previously unknown links between 16S rRNA and the denitrification-functional gene phylogenies. In particular, we identified Bradyrhizobium strains that harbor nirS sequences previously detected only in culture-independent studies

Microbial regulation of nitrogen dynamics along the hillslope of a natural forest

Topography affects the soil physicochemistry, soil N dynamics, and plant distribution and growth in forests. In Japan, many forests are found in mountainous areas and these traits are often highly variable along steep slopes. In this study, we investigated how the microbial population dynamics reflected the bioavailable N dynamics with the physicochemical gradient along the slope in soils of a natural forest in Japan. We measured the gross rates of NH[+4] production, nitrification, and NH[+4]/ NO[−3] immobilization using the N isotope dilution method to analyze the N dynamics in the soils. We also determined the abundance of the bacterial 16S rRNA gene and bacterial and archaeal ammonia monooxygenase gene (amoA) using qPCR to assess the populations of total bacteria and nitrifiers. We found that gross rates of NH[+4] production and nitrification were higher in the lower part of the slope, they were positively correlated with the abundance of the bacterial 16S rRNA gene and archaeal amoA, respectively; and the availability of N, particularly NO[−3], for plants was higher in the lower part of the slope because of the higher microbial nitrification activity and low microbial NO[−3]immobilization activity. In addition, path analysis indicated that gross rates of NH[+4] production and nitrification were regulated mainly by the substrate (dissolved organic N and NH[+4]) concentrations and population sizes of total bacteria and nitrifiers, respectively, and their population sizes were strongly affected by the soil physicochemistry such as pH and water content. Our results suggested that the soil physicochemical gradient along the slope caused the spatial gradient of gross rates of NH[+4] production and nitrification by altering the communities of ammonifiers and nitrifiers in the forest slope, which also affected plant distribution and growth via the supply of bioavailable N to plants

Prokaryotic Community Structure of Long-Term Fertilization Field Andisols in Central Japan

Long-term fertilization experiments are a useful way to elucidate the impacts of fertilization on soil ecosystems. Here, we report the prokaryotic community structure in experimental field soil after 80 years of successive fertilization. Our 16S rRNA gene sequencing detected 20,996 amplicon sequence variants, including major phyla such as Proteobacteria, Acidobacteria, and Actinobacteria.ArticleMicrobiol. Resour. Announc. 8:e01551-18 (2019)journal articl

Phosphorus-mineralizing Communities Reflect Nutrient-Rich Characteristics in Japanese Arable Andisols

Elucidating the soil phosphorus cycle driven by soil microbes is a vital question in soil microbial ecology. The Japanese arable Andisols, occupying half of the Japanese cropland, are known for their high phosphorus sorption capacity. However, limited information is currently available on microbially driven phosphorus mineralization in arable Andisols. We herein report that the phosphorus-mineralizing community in the Japanese arable Andisols showed characteristic distribution and composition patterns, from those in other types of soils. We performed a chemical analysis and microbial community analysis of 43 amble Andisols along the Japanese archipelago. Soil phosphomonoesterase activities measured at pH 11 were approximately 70% of those at pH 6.5, which indicates that alkaline phosphatase contributes to phosphorus cycling, although most soil samples were acidic. Functional gene predictions based on 16S rRNA gene sequencing indicated that the alkaline phosphatase gene phoD was more abundant than other alkaline phosphatase genes and, thus, plays major roles. Hence, amplicon sequencing targeting phoD was performed and the results obtained showed that alphaproteobacterial phoD was dominant. This is in contrast to previously reported phoD compositions in other soils and may be attributed to the nutrient conditions in arable Andisols, which favor copiotrophic Alphaproteobacteria. Furthermore, the composition of phoD correlated with soil pH and bioavailable phosphorus concentrations rather than carbon or nitrogen concentrations. These results were partly different from previous findings, varying in the soil types and geographic ranges of sampling sites. Collectively, the present results indicate that the phosphorus-mineralizing community in the Japanese arable Andisols is regulated differently from those in other soil types.ArticleMICROBES AND ENVIRONMENTS. 33(3):282-289 (2018)journal articl