Linear 3-Hydroxybutyrate Tetramer (HB4) Produced by Sphingomonas sp. Is Characterized as a Growth Promoting Factor for Some Rhizomicrofloral Composers

Sphingomonas spp. of α-proteobacteria often play a role in assisting the development of microfloral communities under adverse soil conditions. Using a Frateuria sp. as an indicator for bacterial growth assay, we investigated the bacterial growth-promoting factor in the culture fluids of Sphingomonas sp. EC-K085. This factor was successfully isolated and identified as linear (R,R,R,R)-3-hydroxybutyrate tetramer (HB4), having a hydroxy-end and a carboxy-end group. When 28 μg of HB4 was charged on a paper disc, impregnated Frateuria sp. cells in modified Winogradsky agar medium exhibited a promoted cell growth to form a clear colony emerging zone after a 2-day incubation

Necessity of particular seed-borne fungi for seed germination and seedling growth of Xyris complanata, a pioneer monocot in top soil-lost tropical peatland in Central Kalimantan, Indonesia

Hawaii yellow-eyed grass (Xyris complanata: Xyridaceae) inhabits infertile, acidic peat soil in the rainy tropical zone in Southeast Asia, and this monocot plant produces a large number of dormant seeds to make a large deposit to seed bank in the soil. Under laboratory conditions, surface-sterilized X. complanata seeds were rarely able to germinate on sterilized peat moss bed, while they required inoculation with either seed epiphytic or soil fungi to facilitate active seed germination. In the present study, three different genera of seed epiphytic fungi were isolated, and two common fungal genera, Fusarium sp. (strain R-1) and Penicillium sp. (strain Y-1), were found to promote the seed germination of this plant. In the sterile peat moss beds, the germination-stimulating fungi also showed growth-promoting effects on X. complanata seedlings growing. These results suggested that the seed germination-promoting fungi likely function as genuine partners for X. complanata in tropical, open peat lands

Screening of rhizobacteria from dipterocarp seedlings and saplings for the promotion of early growth of Shorea selanica seedlings

Low-cost forest management using highly effective microorganisms to promote seedling and tree growth is an important issue in reforestation in Indonesia and other tropical rain forest zones. To survey effective plant growth-promoting rhizobacteria (PGPR) for dipterocarp seedlings and/or saplings, forty-four bacterial strains were isolated from rhizoplane of several Dipterocarpaceae seedlings and saplings in Carita plantation forest located in the western part of Java Island followed by test for their effectiveness on the growth of Shorea selanica. Some isolated rhizobacteria demonstrated growth-promoting activity on dipterocarp seedlings. In the primary bioassay, these rhizobacteria indicated positive, negative or no effect on the plant growth, and 16S rRNA gene sequences of some important isolates were determined for their tentative identification. The most prominent strain isolated from Shorea leprosula was Erwinia. Other effective isolates were tentatively identified as, Rhizobium, Enterobacter, Duganella, an Alcaligeneceae bacterium, an Oxalobacteraceae bacterium, and some yeasts