To examine the in vivo effects of macrolide antibiotics on mucus hypersecretion, we induced hypertrophic and metaplastic changes of goblet cells in rat nasal epithelium by intranasal instillation of ovalbumin (OVA) in OVA-sensitized rats and by intranasal LPS instillation. Oral administration of clarithromycin (CAM) (5-10 mg/kg) significantly inhibited OVA- and LPS-induced mucus production and neutrophil infiltration, whereas josamycin and ampicillin showed no effect. In vitro effects of macrolide antibiotics on airway epithelial cells were examined using NCI-H292 cells and human nasal epithelial cells cultured in air-liquid interface. Mucus secretion was evaluated by ELISA using anti-mucin monoclonal antibodies (anti-MUC5AC and HCS18). CAM and erythromycin significantly inhibited spontaneous and tumor necrosis factor-alpha (20 ng/ml)-induced mucus secretion from NCI-H292 cells at 10-6 to 10-7 M and from human nasal epithelial cells at 10-4 to 10-5 M. MUC5AC messenger RNA expression was also significantly inhibited. These results indicate that the 14-member macrolide antibiotics, CAM and erythromycin, exert direct inhibitory effects on mucus secretion from airway epithelial cells and that they may be useful for the treatment of mucus hypersecretion caused by allergic inflammation and LPS stimulation.
Bradyrhizobium sp. S23321 is an oligotrophic bacterium isolated from paddy field soil. Although S23321 is phylogenetically close to Bradyrhizobium japonicum USDA110, a legume symbiont, it is unable to induce root nodules in siratro, a legume often used for testing Nod factor-dependent nodulation. The genome of S23321 is a single circular chromosome, 7,231,841 bp in length, with an average GC content of 64.3%. The genome contains 6,898 potential protein-encoding genes, one set of rRNA genes, and 45 tRNA genes. Comparison of the genome structure between S23321 and USDA110 showed strong colinearity; however, the symbiosis islands present in USDA110 were absent in S23321, whose genome lacked a chaperonin gene cluster (groELS3) for symbiosis regulation found in USDA110. A comparison of sequences around the tRNA-Val gene strongly suggested that S23321 contains an ancestral-type genome that precedes the acquisition of a symbiosis island by horizontal gene transfer. Although S23321 contains a nif (nitrogen fixation) gene cluster, the organization, homology, and phylogeny of the genes in this cluster were more similar to those of photosynthetic bradyrhizobia ORS278 and BTAi1 than to those on the symbiosis island of USDA110. In addition, we found genes encoding a complete photosynthetic system, many ABC transporters for amino acids and oligopeptides, two types (polar and lateral) of flagella, multiple respiratory chains, and a system for lignin monomer catabolism in the S23321 genome. These features suggest that S23321 is able to adapt to a wide range of environments, probably including low-nutrient conditions, with multiple survival strategies in soil and rhizosphere.
T is a nitrogen-fixing oligotrophic bacterium isolated from paddy field soil that is able to grow in extra-low-nutrient environments. Here, the complete genome sequence of S58 was determined. The S58 genome was found to comprise a circular chromosome of 8,264,165 bp with an average GC content of 65.1% lacking nodABC genes and the typical symbiosis island. The genome showed a high level of similarity to the genomes of Bradyrhizobium sp. ORS278 and Bradyrhizobium sp. BTAi1, including nitrogen fixation and photosynthesis gene clusters, which nodulate an aquatic legume plant, Aeschynomene indica, in a Nod factor-independent manner. Although nonsymbiotic (brady)rhizobia are significant components of rhizobial populations in soil, we found that most genes important for nodule development (ndv) and symbiotic nitrogen fixation (nif and fix) with A. indica were well conserved between the ORS278 and S58 genomes. Therefore, we performed inoculation experiments with five A. oligotrophica strains (S58, S42, S55, S72, and S80). Surprisingly, all five strains of A. oligotrophica formed effective nitrogen-fixing nodules on the roots and/or stems of A. indica, with differentiated bacteroids. Nonsymbiotic (brady)rhizobia are known to be significant components of rhizobial populations without a symbiosis island or symbiotic plasmids in soil, but the present results indicate that soil-dwelling A. oligotrophica generally possesses the ability to establish symbiosis with A. indica. Phylogenetic analyses suggest that Nod factor-independent symbiosis with A. indica is a common trait of nodABC-and symbiosis island-lacking strains within the members of the photosynthetic Bradyrhizobium clade, including A. oligotrophica.
Bacteria were isolated from soil on a 100-fold dilution of nutrient broth agar, a 10-fold dilution of alubumin yeast extract agar, or agar without additional nutrient. Their growth was severely suppressed by full strength nutrient broth but well supported by a 100-fold dilution of nutrient broth and these organisms were proposed to be called dilute nutrient broth (DNB) organisms. One percent each of peptone and meat extract, and 1 ° o or 2 % casamino acids severely suppressed growth of most of them. Glycine, arginine, serine, or lysine (10 mM), yeast extract (0.1 %), nicotinic acid or thiamine (20 ,ug/ml), and sodium succinate (20-50 mM) inhibited growth of many organisms though sensitivity of each organism to organic compounds was of a great variety. They were also highly sensitive to NaCI and KC1. Growth inhibition of some isolates by serine was recovered by coexisting threonine, alanine, or leucine and valine. Inhibitive effect of serine was also influenced by NaCI, KC1, CaC12, or MgC12.It was shown by MlsHusTIN (1) that organic compounds such as peptone and meat extract were inhibitive to the growth of many soil bacteria. These organisms were thought to be difficult to be isolated and their physiological characters have not been studied well. HATTORI (2) showed that such organisms could be isolated on a diluted nutrient agar and that sodium chloride at concentration of usual use was inhibitive to them, as well as peptone and meat extract. Since the growth of these organisms is severely suppressed by full strength nutrient broth (NB) but well supported by a 100-fold dilution of nutrient broth (NB/100), we propose to call them dilute nutrient broth (DNB) organisms. In the present work, the growth of DNB organisms on diluted nutrient broth or a synthetic medium supplemented with various organic and inorganic compounds was studied. It was found that these organisms were highly sensitive to these compounds and that their sensitivity depended on the concentration of other coexisting organic or inorganic compounds.
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