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.

Non-cephalosporin-susceptible, glucose non-fermentative Gram-negative bacilli meningitis in post-neurosurgical adults: clinical characteristics and therapeutic outcome.

OBJECTIVE: The clinical and laboratory characteristics of non-cephalosporin-susceptible (non-CS) glucose non-fermentative Gram-negative (G(-)) infections in adults with postneurosurgical meningitis are rarely examined solely in the literature. METHODS: The data of 28 post-neurosurgical adults meningitis with glucose non-fermentative G(-) infections, collected during a study period of 5 years (2006-2010), were reviewed. The clinical and laboratory data between the non-cephalosporin-susceptible groups and the cephalosporin-susceptible groups were compared. RESULTS: A total of 30 G(-) strains were collected from the 28 enrolled cases. Among the implicated glucose non-fermentative G(-) strains, 18 strains, belonging to 17 cases, were non-CS. Among the 18 non-cephalosporin-susceptible strains, Acinetobacter spp. (39%, 7/18) was the most common, followed by Pseudomonas spp. (22%, 4/18), Stenotrophomonas maltophilia (22%, 4/18) and Elizabethkingia meningoseptica (11%, 2/18). With a comparative analysis, there were no significant difference between the non-cephalosporin-susceptible and cephalosporin-susceptible glucose non-fermentative G(-) groups. The clinical and laboratory data were also of no statistical significance between the fatal (n=4) and non-fatal (n=13) non-cephalosporin-susceptible groups. CONCLUSION: Sixty percent (18/30) of implicated glucose non-fermentative G(-) strains of post-NS meningitis in adults are non-cephalosporin-susceptible. Among the non-cephalosporin-susceptible glucose non-fermentative G(-) strains, Acinetobacter spp., Pseudomonas spp., S. maltophilia and E. meningoseptica are the commonly implicated pathogens, and their emergence in this specific group of meningitis has caused a therapeutic dilemma. The clinical manifestations of non-cephalosporin-susceptible glucose non-fermentative G(-) meningitis were not unique; therefore, only bacterial culture and antimicrobial susceptibility test are the methods for identification confirmation.

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)).