Characterization of Cu-resistant bacterial communities in Cu-contaminated soils

Bacterial communities in a spoil heap in a copper mine, a forest soil with high Cu contamination, and an agricultural soil with low Cu contamination were characterized in terms of Gram-staining, plasmid frequency, pigmentation, Cu-resistance system, and predominant Cu-resistant bacterial species. Similarity existed in that the ratio of green colonies for sorbing Cu and Gram-negative bacteria increased with the increase of the Cu content of the medium regardless of the characteristics of the bacterial communities. It was found that the plasmid was not present in most of the Cu-resistant bacteria of the soils. Curesistant genera including Burkholderia, Alcaligenes, and Methylobacterium species were isolated from the Cu contaminated soils using YG agar plates treated with 2 mM Cu. Furthermore, the bacterium with the highest Cu resistance (MIC = 5.5 mm Cu) was identified as a Gram-positive bacterium Bacillus sp., though most of the Cu-resistant bacteria were Gram-negative.     

Importance of 2,4-DAPG in the biological control of brown patch by Pseudomonas fluorescens HP72 and newly identified genes involved in 2,4-DAPG biosynthesis

The Pseudomonas fluorescens strain HP72 used as biocontrol agent was isolated from the roots of creeping bentgrass on brown patch-suppressive soil. This strain can suppress brown patch disease caused by Rhizoctonia solani. The analysis of secondary metabolites from strain HP72 revealed that it produced known antifungal compounds, 2,4-diacetylphloroglucinol (2,4-DA-PG), HCN, and a fluorescent siderophore. In the present study, the Tn5inserted mutants of strain HP72, which did not show any antifungal activity, were selected. None of the mutants produced 2,4-DA-PG but they produced a fluorescent siderophore, while some strains produced HCN. Therefore, it is suggested that 2,4-DA-PG plays a major role in the biological control of brown patch disease caused by R. solani. In the genomic region where Tn5 was inserted, two open reading frames (ORFs A and B), which are not included in the 2,4-DAPG gene cluster of HP72, were detected. It was demonstrated that ORFs A and flare involved in the regulation of 2,4-DAPG biosynthesis.     

Arbuscular mycorrhizal fungal communities associated with some pioneer plants in the lahar area of Mt. Pinatubo,Philippines

An extensive area has been buried due to the repeated occurrence of mud flows (lahars) derived from volcanic deposits during the eruption of Mt. Pinatubo in the Philippines. Most of the area was covered with sparse vegetation consisting of only a few gramineous pioneer plants such as Saccharum spontaneum (site SV). However dense vegetation consisting of wild leguminous plants such as Calpogonium mucunoides showed a patch distribution (site DV). In 1999, we investigated the community composition of AMF at these two sites. S. spontaneum at both sites was slightly colonized with AMF while the leguminous plants were highly colonized. Spores of AMF were collected from the rhizosphere of these plants. Eight spore morphotypes were identified; one each for Acaulospora and Entrophospora colombiana, two for Glomus, one for Paraglomus, and three for Scutellospora. Part of the 18S rRNA gene of AMF colonizing the plant roots was amplified with AMF-specific primers, NS31 and AM1, cloned and sequenced. Fifty-three AMF clones were phylogenetically classified into 8 phylotypes as follows: one each for Acaulospora and E. colombiana, five for Glomus, and one for Scutellospora. Both molecular and morphological examinations showed that the diversity of AMF was comparable to that in other temperate ecosystems with abundant vegetation and did not differ significantly between sites SV and DV, regardless of the vegetation cover. Furthermore, S. spontaneum supported diverse AMF species in spite of its scant growth at site SV. E. colombiana was mostly associated with C. mucunoides. Significance of AMF for the primary plant succession in the lahar area was analyzed.     

Modeling the growth,transport, and feeding migration of age-0 Pacific saury Cololabis saira

Fisheries Science - In this study, we developed an individual-based model for age-0 Pacific saury Cololabis saira focusing on the winter-spawned cohort to advance our understanding of the dynamic...