A Gram-negative, non-spore-forming, rod-shaped bacterial strain, AR20T, was isolated from anodic biofilms of an acetate-fed microbial fuel cell in Japan and subjected to a polyphasic taxonomic study. Strain AR20T grew optimally at pH 7.0−8.0 and 25°C. It contained Q-8 as the predominant ubiquinone and C16:0, summed feature 3 (C16:1ω7c and/or iso-C15:02OH), and C18:1ω7c as the major fatty acids. The DNA G+C content was 67.1 mol%. A neighbor-joining phylogenetic tree revealed that strain AR20T clustered with three type strains of the genus Hydrogenophaga (H. flava, H. bisanensis and H. pseudoflava). Strain AR20T exhibited 16S rRNA gene sequence similarity values of 95.8−97.7% to the type strains of the genus Hydrogenophaga. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain AR20T is considered a novel species of the genus Hydrogenophaga, for which the name Hydrogenophagaelectricum sp. nov. is proposed. The type strain is AR20T (= KCTC 32195T = NBRC 109341T).
According to the traditional view, establishment and maintenance of critical population densities in the rhizosphere was the premise of PGPR to exert growth-promoting effects. In light of the facts that soil bacterial community structures can be changed by some PGPR strains including Bacillus pumilus WP8, we hypothesize that regulation of soil bacterial community structure is one of the plant growth-promoting mechanisms of B. pumilus WP8, rather than depending on high-density cells in soil. In this study, denaturing gradient gel electrophoresis (PCR-DGGE) was performed to evaluate the relationship between changes in soil bacterial community structure and growth-promoting effect on the seedling growth of fava beans (Vicia faba L.) during three successive cultivations. We found that B. pumilus WP8 lacks capacity to reproduce in large enough numbers to survive in bulk soil more than 40 days, yet the bacterial community structures were gradually influenced by inoculation of WP8, especially on dominant populations. Despite WP8 being short-lived, it confers the ability of steadily promoting fava bean seedling growth on soil during the whole growing period for at least 90 days. Pseudomonas chlororaphis RA6, another tested PGPR strain, exists in large numbers for at least 60 days but less than 90 days, whilst giving rise to slight influence on bacterial community structure. In addition, along with the extinction of RA6 cells in bulk soils, the effect of growth promotion disappeared simultaneously. Furthermore, the increment of soil catalase activity from WP8 treatment implied the ability to stimulate soil microbial activity, which may be the reason why the dominant population changed and increased as time passed. Our study suggests that regulation of treated soil bacterial community structure may be another possible action mechanism.
Current studies of the antioxidant activity of fungal resources are mainly focused on the fruiting bodies of edible mushrooms. To access the potential of basidiomycetes in culture-state applications, extracts of solid cultures of 83 basidiomycetous fungi newly isolated from woody materials were prepared at the same concentration (10 mg/ml), and their antioxidant activities were measured using ABTS (2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assays. Among the basidiomycetes tested, Cryptoporus volvatus, Daedalea dickinsii, Gloeophyllum abietinum, G. trabeum, Pseudomerulius curtisii and Stereum hirsutum exhibited good antioxidant activities. The EC50 value for the removal of free radicals was lowest (i.e., most effective) in the crude extract of S. sanguinolentum (19.61 g/ml), and reduced DNA damage based on a DNA nicking assay was observed for the extracts from the six basidiomycetous species above.
Streptococcus uberis is a common cause of dairy cow mastitis throughout the world. The failure to control bovine mastitis caused by S. uberis is largely attributed to the little known about the epidemiology of this bacteria, especially strain differences in the same area. To define the local epidemiology of S. uberis in the south of Xinjiang, China, we explored the genetic diversity of 28 bovine subclinical mastitis field isolates of S. uberis, collected from 3 Chinese farms during 2009 and 2010, which was examined by using pulsed-field gel electrophoresis (PFGE) for clustering of the isolates and multilocus sequence typing (MLST) to assess the relationship between PFGE patterns and to identify genetic lineages. The 28 isolates were grouped into 13 pulsotypes (U1 to U13), and 1 PFGE type (U1) accounted for almost half of the isolates (13/28, 46.4%). This major type was herd specific, indicating either cow-to-cow transmission or infection with isolates from the same environmental reservoirs. The remaining 12 PFGE types of isolates were from different herds, strongly suggesting environmental sources of S. uberis infection. All 28 isolates were analyzed by MLST and clustered into 8 sequence types (STs), of which 7 STs were found to be novel, either with 5 new alleles of 6 housekeeping and virulence genes (ST158, ST159) or with different combinations of previously assigned alleles (ST153, ST154, ST155, ST156, ST157). To our knowledge, this is the first report that documents molecular typing studies of bovine isolates of S. uberis from southern Xinjiang Province, China, which were shown to represent novel genomic backgrounds of this pathogen.
Organic farming is gaining popularity all over the world as it avoids the use of synthetic chemicals. Plant production in organic farming mainly depends on nutrient release as a function of mineralization processes in soils. In the present study, efficient phosphate mineralizing bacteria were isolated and their efficacy tested in plant mineral uptake and soil fertility of an organic field. Amongst 12 P-solubilizing bacteria (PSB) isolated from an organic field, two isolates were selected for field inoculation based on their rock phosphate (RP) solubilzing ability, exudation of organic acids, phosphatase and phytase activity and production of indole acetic acid and siderophores. On the basis of biochemical characterization and 16S rRNA sequence analysis, these isolates were identified as Pantoea cypripedii (PSB-3) and Pseudomonas plecoglossicida (PSB-5). These isolates significantly increased yield and total P uptake in maize. Soil analysis showed that available P, organic carbon and soil enzyme activities were significantly increased. Present study results suggested that inoculation of these bacteria has great application potential in improving the crop yield and soil fertility in organic farming.