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Responses of Active Bacterial and Fungal Communities in Soils under Winter Wheat to Different Fertilizer and Pesticide Regimens. Martina S. Girvan, 2004.The composition of the active microbial (bacterial and fungal) soil community in an arable wheat field subjected to different management practices was examined at five times during a 1-year period . Field sections were fertilized either at good agricultural practice (GAP) levels or at reduced levels (0.5x GAP) and were inoculated with vesicular arbuscular mycorrhizae (VAM) at the same time . Field subsections were treated either with or without pesticides . Changes in the active microbial communities were investigated by denaturing gradient gel electrophoresis analysis of reverse transcription-PCR-amplified 16S and 18S rRNA . Microbial community structure was primarily determined by season, and the seasonal trends were similar for the fungal and bacterial components . Between-sample microbial heterogeneity decreased under a mature crop in the summer but increased following harvesting and plowing . Although similar overall trends were seen for the two microbial components, sample variability was greater for the fungal community than for the bacterial community . The greatest management effects were due to GAP fertilization, which caused increases in the bacterial numbers in the total and culturable communities . Microbial biomass similarly increased . GAP fertilization also caused large shifts in both the active bacterial community structure and the active fungal community structure and additionally resulted in a decrease in the heterogeneity of the active bacterial community . Pesticide addition did not significantly affect bacterial numbers or heterogeneity, but it led to major shifts in the active soil bacterial community structure . PCR primers specific for Glomales 25S rRNA genes were used to monitor the VAM population following inoculation . Glomales were detected initially only in VAM-inoculated field sections but were subsequently detected in noninoculated field sections as the season progressed . After plowing, the level of Glomales was reduced in noninoculated field sections but remained high in VAM-inoculated field sections . Inoculation of VAM correlated with elevated soil phosphate and carbon levels . Cloning and Characterization of the Bile Salt Hydrolase Genes (bsh) from Bifidobacterium bifidum Strains. Geun-Bae Kim, 2004.Biochemical characterization of the purified bile salt hydrolase (BSH) from Bifidobacterium bifidum ATCC 11863 revealed some distinct characteristics not observed in other species of Bifidobacterium . The bsh gene was cloned from B . bifidum, and the DNA flanking the bsh gene was sequenced . Comparison of the deduced amino acid sequence of the cloned gene with previously known sequences revealed high homology with BSH enzymes from several microorganisms and penicillin V amidase (PVA) of Bacillus sphaericus . The proposed active sites of PVA were highly conserved, including that of the Cys-1 residue . The importance of the SH group in the N-terminal cysteine was confirmed by substitution of Cys with chemically and structurally similar residues, Ser or Thr, both of which resulted in an inactive enzyme . The transcriptional start point of the bsh gene has been determined by primer extension analysis . Unlike Bifidobacterium longum bsh, B . bifidum bsh was transcribed as a monocistronic unit, which was confirmed by Northern blot analysis . PCR amplification with the type-specific primer set revealed the high level of sequence homology in their bsh genes within the species of B . bifidum . Isolation and Characterization of Thermophilic Bacilli Degrading Cinnamic, 4-Coumaric, and Ferulic Acids. Xue Peng, 2003.Thirty-four thermophilic Bacillus sp . strains were isolated from decayed wood bark and a hot spring water sample based on their ability to degrade vanillic acid under thermophilic conditions . It was found that these bacteria were able to degrade a wide range of aromatic acids such as cinnamic, 4-coumaric, 3-phenylpropionic, 3-(p-hydroxyphenyl)propionic, ferulic, benzoic, and 4-hydroxybenzoic acids . The metabolic pathways for the degradation of these aromatic acids at 60°C were examined by using one of the isolates, strain B1 . Benzoic and 4-hydroxybenzoic acids were detected as breakdown products from cinnamic and 4-coumaric acids, respectively . The ß-oxidative mechanism was proposed to be responsible for these conversions . The degradation of benzoic and 4-hydroxybenzoic acids was determined to proceed through catechol and gentisic acid, respectively, for their ring fission . It is likely that a non-ß-oxidative mechanism is the case in the ferulic acid catabolism, which involved 4-hydroxy-3-methoxyphenyl-ß-hydroxypropionic acid, vanillin, and vanillic acid as the intermediates . Other strains examined, which are V0, D1, E1, G2, ZI3, and H4, were found to have the same pathways as those of strain B1, except that strains V0, D1, and H4 had the ability to transform 3-hydroxybenzoic acid to gentisic acid, which strain B1 could not do .
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