No abstract

We constructed a mesophilic anaerobic chemostat that was continuously fed with synthetic wastewater containing propionate as the sole source of carbon and energy. Steady-state conditions were achieved below the critical dilution rate of 0.3 d (-1) with almost complete substrate degradation. The propionate-degrading methanogenic communities in the chemostat at dilution rates of 0.01, 0.08, and 0.3 d (-1) were analyzed using molecular biological techniques. Fluorescence in situ hybridization with archaeal and bacterial domain-specific probes showed that archaeal cells predominated throughout the three dilution rates. Archaeal-16S rRNA gene clone library analysis and quantitative real-time polymerase chain reaction studies showed that hydrogenotrophic methanogen rRNA genes closely related to Methanoculleus was detected at a dilution rate of 0.01 d (-1) , whereas rRNA genes closely related to the Methanoculleus and Methanospirillum genera were detected at dilution rates of 0.08 and 0.3 d (-1) . The aceticlastic methanogen, Methanosaeta , was detected throughout the three dilution rates. Bacterial-rRNA gene clone library analysis and denaturing gradient gel electrophoresis demonstrated that rRNA genes affiliated with the genus Syntrophobacter predominated at the low dilution rate, whereas rRNA genes affiliated with the phylum Firmicutes predominated at the higher dilution rates. A significant number of rRNA genes affiliated with the genus Pelotomaculum were detected at dilution rate of 0.3 d (-1) . The diversity of genes encoding acetate kinase agreed closely with the results of the rRNA gene analysis. The dilution rates significantly altered the archaeal and bacterial communities in the propionate-fed chemostat.

Three new polyphenols, together with 14 known compounds, were isolated from a hot water extract of mangosteen (Garcinia mangostana L.) pericarp, a plant that has been used medicinally in Southeast Asia. The three new polyphenols were characterized as a 4-aryl-2-flavanylbenzopyran derivative (tentatively named GM-1), 1, 3,4,3',5'-tetrahydroxy-5-methoxybenzophenone (GM-2), 2, and 2,3-dihydrochromone derivative (GM-3), 3 on the basis of NMR and MS data. The relative stereostructure of GM-1 was assigned to have 2,3-cis-3,4-trans- and 2″,3″-cis configurations on the basis of the coupling constants of heterocyclic ring protons in the (1)H NMR spectrum along with nuclear Overhauser effect correlations. The HPLC analysis indicated that major polyphenolic components in the hot water extract of mangosteen pericarp were epicatechin and procyanidin B2 (epicatechin dimer).

No abstract

A new insertion sequence from Corynebacterium glutamicum ATCC 14999 was isolated and characterized. This IS element, designated IS14999, comprised a 1149 bp nucleotide sequence with 22 bp imperfect terminal inverted repeats. IS14999 carries a single open reading frame of 345 amino acids encoding a putative transposase that appears to have partial homology to IS642, an IS630/Tc1 superfamily element, at the C-terminal region in the amino acid sequence. This indicated that IS14999 belonged to the IS630/Tc1 superfamily, which was first identified in C. glutamicum. IS14999 has a unique distance of 38 amino acid residues between the second and third amino acids in the DDE motif, which is well known as the catalytic centre of transposase. This suggested that IS14999 constituted a new subfamily of the IS630/Tc1 superfamily. A phylogenetic tree constructed on the basis of amino acid sequences of transposases revealed that this new transposable element was more similar to eukaryotic Tc1/mariner family elements than to prokaryotic IS630 family elements. Added to the fact that IS14999 was present in only a few C. glutamicum strains, this implies that IS14999 was probably acquired by a recent lateral transfer event from eukaryotic cells. Analysis of the insertion site in C. glutamicum R revealed that IS14999 appeared to transpose at random and always caused a target duplication of a 59-TA-39 dinucleotide upon insertion, like the other IS630/Tc1 family elements. These findings indicated that IS14999 could be a powerful tool for genetic manipulation of corynebacteria and related species.