Screening and Assessment of Potential Plant Growth-promoting Bacteria Associated with Allium cepa Linn.

Plant growth-promoting bacteria (PGPB) are beneficial microbes that increase plant growth and yield. However, limited information is currently available on PGPB in onion (Allium cepa Linn.). The aims of the present study were to isolate and identify PGPB in onion and examine the effects of isolated PGPB on germination and growth during the vegetative stage in onion, pak choy (Brassica chinensis), and sweet pepper (Capsicum annuum). Twenty-three strains of PGPB were isolated from the roots, bulbs, and rhizosphere soil of onion. All isolated bacterial strains showed one or more PGP traits, including indole acetic acid production, phosphate solubilization ability, and 1-aminocyclopropane-1-carboxylate deaminase and nitrogenase activities; most of these traits were derived from Bacillus sp., Microbacterium sp., and Pseudomonas sp. Eight bacteria that exhibited strong abilities to produce indole acetic acid were selected for a Petri dish trial, soil pot test, and vermiculate pot test. The Petri dish trial showed that strains ORE8 and ORTB2 simultaneously increased radicle and hypocotyl lengths in onion, but inhibited growth in sweet pepper after 7 d. The soil pot experiment on onion revealed that strains ORE5, ORE8, and ORTB2 strongly promoted growth during the vegetative stage with only a half dose of chemical fertilizer. The present results indicate that ORE8 (Bacillus megaterium) and ORTB2 (Pantoea sp.) are the most promising biofertilizers of onion and may simultaneously inhibit the seedling growth of other plants.

Exploration of Root-associated Bacteria from the Medicinal Plant Platycodon grandiflorum.

The present study was performed to investigate root-associated bacteria from Platycodon grandiflorum, a medicinal plant commonly grown in East Asia. Isolates were obtained from the rhizosphere or root interior with various culture media, and phylogenetic analyses were performed based on their 16S rDNA sequences. In consideration of practical applications, traits related to plant growth promotion and niche adaptation were assessed in several endophytic strains with fewer biosafety concerns. The effects of a bacterial inoculation on seedling and mature plant growth were evaluated. Seventeen genera that encompassed more than 30 bacterial lineages were successfully retrieved from the roots, the majority of which have not been reported as P. grandiflorum-associated bacteria, particularly for non-negligible Proteobacteria. Although nitrogen-fixing or phosphate-solubilizing and indole acetic acid-producing activities were recorded in all of the strains selected, these strains were beneficial or detrimental to plant growth as evidenced by their influence on the length of seedlings and biomass of mature plants. Among the 4 endophytic Rhizobium species tested in the present study, the potentially novel Rhizobium sp. BF-E16, which was more compatible with the non-leguminous medicinal plant P. grandiflorum, was identified. Other than plant growth-promoting traits, characteristics such as plant constituent-hydrolyzing activities need to be taken into consideration and their roles clarified when investigating plant growth-promoting rhizobacteria.

The second type of transglutaminase regulates immune and stress responses in white shrimp, Litopenaeus vannamei.

The total haemocyte count (THC), differential haemocyte count (DHC), phenoloxidase activity, respiratory bursts (release of superoxide anion), superoxide dismutase activity, and phagocytic activity and clearance efficiency to the pathogen Vibrio alginolyticus were measured when white shrimp, Litopenaeus vannamei, (7.5 ± 0.5 g) were individually injected with diethyl pyrocarbonate-water (DEPC-H2O) or different dsRNA at 3 days of injection. In addition, haemolymph glucose and lactate, and haemocytes crustacean hyperglycemic hormone (CHH), transglutaminase I (TGI), transglutaminase II (TGII) and clottable protein (CP) mRNA expression were determined for the shrimp that received DEPC-H2O and different dsRNA after 3 days, and then transferred to 22 and 28 °C from 28 °C. Results showed that respiratory burst, phagocytic activity and clearance efficiency significantly decreased, but hyaline cells significantly increased in the shrimp received LvTGII dsRNA after 3 days. In hypothermal stress studies, LvTGI and CHH were significantly up-regulated in LvTGII-depleted shrimp following exposure to 28 and 22 °C, and haemolymph glucose and lactate were significantly enhanced in LvTGII-depleted shrimp. The injection of LvTGII dsRNA also significantly increased the mortality of L. vannamei challenged with the pathogen V. alginolyticus. These results suggest that LvTGII is an important component on the immune resistance of shrimp, and is involved in the regulation of some immune parameters and carbohydrate metabolites, as well as has a complementary effect with LvTGI in immunological and physiological response of shrimp.

A new phenolic and a new lignan from the roots of Juniperus chinensis.

A new phenolic, (4-hydroxy-2-isopropylphenyl)ethanoic acid and a new lignan, epi-calocedrin were obtained from the roots of Juniperus chinensis Linn. The structures were elucidated on the basis of spectroscopic analysis and chemical evidence.