Volatile 1-octanol of tea (Camellia sinensis L.) fuels cell division and indole-3-acetic acid production in phylloplane isolate Pseudomonas sp. NEEL19.

Tea leaves possess numerous volatile organic compounds (VOC) that contribute to tea's characteristic aroma. Some components of tea VOC were known to exhibit antimicrobial activity; however, their impact on bacteria remains elusive. Here, we showed that the VOC of fresh aqueous tea leaf extract, recovered through hydrodistillation, promoted cell division and tryptophan-dependent indole-3-acetic acid (IAA) production in Pseudomonas sp. NEEL19, a solvent-tolerant isolate of the tea phylloplane. 1-octanol was identified as one of the responsible volatiles stimulating cell division, metabolic change, swimming motility, putative pili/nanowire formation and IAA production, through gas chromatography-mass spectrometry, microscopy and partition petri dish culture analyses. The bacterial metabolic responses including IAA production increased under 1-octanol vapor in a dose-dependent manner, whereas direct-contact in liquid culture failed to elicit such response. Thus, volatile 1-octanol emitting from tea leaves is a potential modulator of cell division, colonization and phytohormone production in NEEL19, possibly influencing the tea aroma.

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.

Molecular detection and phylogenetic characterization of Gordonia species in heavily oil-contaminated soils.

This study was undertaken to assess genetic diversity among Gordonia species present in heavily oil-contaminated sites using both a culture-dependent and a culture-independent (PCR-denaturing gradient gel electrophoresis (DGGE)) approach. Soil samples for this purpose were collected from 8 different heavily (crude) oil-contaminated industrial park sites located around Kaohsiung County, Taiwan. Using Gordonia-specific PCR-DGGE, a significant increase in Gordonia species diversity was noted in 1% heavily oil-enriched soil. A total of 67 strains were scored and identified as Gordonia after genus-specific PCR amplification and sequencing. BOX-PCR fingerprinting of culturable Gordonia showed wide strain diversity. A total of 33 different strains were identified from most of the sampling sites. Based on gyrB gene sequence analysis, all Gordonia strains could be segregated into five major clusters. Gordonia amicalis was the predominant species in all oil-amended soil samples. Isolates sharing <98.5% gyrB gene sequence similarities with Gordonia type strains represent indigenous novel Gordonia species. Variations in phenotypic characteristics further confirm the presence of a wide range of species and strain diversity among Gordonia isolates. Based on the genotypic and phenotypic details obtained here, we conclude that heavily oil-contaminated soil supports diverse indigenous Gordonia strains.

Arenimonas malthae sp. nov., a gammaproteobacterium isolated from an oil-contaminated site.

A Gram-negative, rod-shaped bacterium (CC-JY-1(T)) was isolated on nutrient agar from a soil sample collected from an oil-contaminated site located in Chyai county, Taiwan. 16S rRNA gene sequence analysis demonstrated that this isolate is unique, showing 96.7 % sequence similarity to the type strain of Arenimonas donghaensis and similarities of 93.0-93.8 % to species of the genera Thermomonas, Lysobacter and Silanimonas. The presence of ubiquinone Q-8, a polar lipid profile consisting of the major compounds diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine and the fatty acid profile were in accordance with the phylogenetic affiliation of CC-JY-1(T). DNA-DNA reassociation experiments between CC-JY-1(T) and A. donghaensis KACC 11381(T) resulted in a mean relatedness value of 32 %, indicating that strain CC-JY1(T) represents a novel species in the genus Arenimonas, for which we propose the name Arenimonas malthae sp. nov. The type strain is CC-JY-1(T) (=CCUG 53596(T) =CIP 109310(T)).

Pseudoxanthomonas spadix sp. nov., isolated from oil-contaminated soil.

A bacterial isolate from a sample of oil-contaminated soil was characterized using a polyphasic taxonomic approach. Comparative analysis of the 16S rRNA gene sequence showed that this isolate constituted a distinct phyletic line within the genus Pseudoxanthomonas, displaying >3.7 % sequence divergence with respect to recognised Pseudoxanthomonas species. The genus assignment was confirmed by a chemotaxonomic analysis, which revealed the presence of a fatty acid profile characteristic of members of the genus Pseudoxanthomonas (straight-chain saturated, unsaturated and branched-chain fatty acids of the iso/anteiso type and 3-hydroxylated fatty acids) and the presence of a ubiquinone with eight isoprene units (Q-8) as the predominant respiratory quinone. The novel isolate was distinguishable from other members of the genus Pseudoxanthomonas on the basis of a combination of phenotypic properties. The genotypic and phenotypic data show that the strain represents a novel species of the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas spadix sp. nov. is proposed. The type strain is IMMIB AFH-5(T) (=DSM 18855(T)=CCUG 53828(T)).

Williamsia serinedens sp. nov., isolated from an oil-contaminated soil.

The taxonomic status of a bacterium designated strain IMMIB SR-4(T) isolated from an oil-contaminated soil sample was characterized by using a polyphasic approach. Chemotaxonomic investigations revealed the presence of cell-wall chemotype IV, short-chain mycolic acids that co-migrated with those extracted from members of the genus Williamsia and that on pyrolysis GC produce C(16 : 0) and C(18 : 0) fatty acids, and dihydrogenated menaquinone with nine isoprene units as the predominant menaquinone. The generic assignment was confirmed by 16S rRNA gene sequence analysis. Comparative analysis of the 16S rRNA gene sequence showed that strain IMMIB SR-4(T) formed a distinct phyletic line within the genus Williamsia, displaying sequence similarities of 95.5-98.1 % with the type strains of recognized Williamsia species. Strain IMMIB SR-4(T) was distinguished from the type strains of recognized species of the genus Williamsia based on a set of phenotypic features. The genotypic and phenotypic data indicated that strain IMMIB SR-4(T) represents a novel species of the genus Williamsia, for which the name Williamsia serinedens sp. nov. is proposed. The type strain is IMMIB SR-4(T) (=DSM 45037(T)=CCUG 53151(T)).