Two strains 333 to 339 of Enterobacter agglomerans were selected in the present study to evaluate the response of increasing concentrations of NaCl on growth, N2-fixation, and nitrogenase activity/synthesis. E. agglomerans strains 333 and 339 showed optimum growth and acetylene-reducing activity with 0.5 to 1.0% NaCl in a nitrogen-free minimal medium (NFDM) with glucose, respectively, in 28 h incubation, although both strains displayed better growth and acetylene-reducing activity with 3.0% and 2.0% NaCl after 52 h and 100 h incubation periods than the 28 h culture did. Our experiments with shiftings of salt concentrations in NFDM medium indicated that a synthesis of nitrogenase enzyme was generally more sensitive to higher concentrations of NaCl than nitrogenase activity was.
Stereoisomers of lactic acid produced by lactic acid bacteria were determined by HPLC by using an enantiomeric resolution column. In general, the ratios of L-form to D-form (the type of stereoisomer) obtained were compared with those in references. Values of the type of stereoisomer of lactic acid were discussed from the viewpoint of identification of lactic acid bacteria.
The features and the constitution of the microbial population of fresh feces were compared between pigs fed a diet supplemented with dietary microbes and pigs given nonsupplemented diets. The former were reared on farm C and the latter on farms A and B. The concentrations of ammonia-N, indole, and skatole of fresh feces were not significantly different between pigs reared on farm C and those raised on farms A and B, but the concentrations of ammonia-N and the skatole of fresh feces were significantly different between pigs reared on farms A and B. The total VFA (volatile fatty acids) concentration of fresh feces in pigs on farm C was slightly lower than in those on farms A and B. Moreover, the molar proportion of the acetic acid in feces in pigs on farm C was lower; inversely, that of propionic and butyric acids was higher in comparison with those on farms A and B. No differences were evident in the total viable counts of feces among pigs reared on the three different farms. Clostridium perfringens was abundant in feces of pigs raised on farms A and B, but it was not detected in pigs reared on farm C. Megasphaerae, bifidobacteria, and clostridia except for C. perfringens were more abundant in the feces of pigs fed a diet supplemented with dietary microbes on farm C, compared with pigs given the nonsupplemented diets on farms A and B.
Even though fungal phosphatases are widely used to study ambient-regulated gene expression, little is known about these enzymes in the agriculturally important genus Colletotrichum. We have therefore identified several phosphatase activities in endophytic isolates of Colletotrichum musae grown under conditions of nutritional sufficiency or starvation for sources of phosphorus (P), nitrogen (N), carbon (C), and sulphur (S). These enzyme forms could be distinguished by substrate specificity, optimum pH, activation and inhibition by some substances, response to nutritional starvation, and pattern of migration in native gel electrophoresis. At least four individual phosphatase activities were identified under the growth conditions employed. A pH 5.0 acid phosphatase and an Mg2+-dependent pH 7.5 phosphodiesterase were expressed under all growth conditions at constant rates. Under conditions of P-starvation, derepression of a major pH 6.0-acid phosphatase was observed in cell-free extracts and the culture medium. A synthesis of alkaline phosphatase activities followed a more distinct pattern. Under conditions of nutritional sufficiency of P- or N-starvation, only a single intracellular enzyme form (optimum pH 10) was observed, which was resolved as a single electrophoretic activity band. However, in media lacking C or S sources additional alkaline phosphatase forms were derepressed with a concomitant increase in the overall enzyme activity level measured at pH 10. To our knowledge, this report represents the most detailed study of phosphatases in Colletotrichum and the first partial characterization of the phosphatase system in an endophytic fungus.
Acetyl esterase was found to be widely distributed in ammonia fungi in a screen comprising 26 species (71 strains). No great differences appeared in enzyme production for acetyl esterase, β-xylosidase, α-arabinosidase, or β-glucosidase between different strains of the same species, but differences were detected between different genera. Acetyl esterase of Coprinus phlyctidosporus and Lyophyllum tylicolor may act cooperatively with β-glucosidase. An increase in urea concentration significantly affected enzyme activity. It was supposed that urea used as 20 mg/g litter may solubilize leaf nutrients. At 20 mg urea added/g litter, a sizable increase in β-glucosidase activity of C. phlyctidosporus and L. tylicolor was found, whereas a decrease in enzyme production of α-arabinosidase and β-xylosidase was detected in some strains. Acetyl esterase and β-glucosidase of C. phlyctidosporus, L. tylicolor, C. leucocephala 589, and C. rhombisperma 248 were most active in acidic conditions (pH 5.3–6.3), whereas acetyl esterase of L. nuda 561 and L. tarda 564 was most active in alkaline conditions (pH 8.3).
The internal transcribed spacer (ITS) region of rDNA was used for taxonomic inferences in ascomycetous yeasts. The Debaryomyces species had a 640–690 ITS size. The analyzed Candida species can be differentiated by its distinct ITS size. The enzymatic digestion of the ITS region show large homogeneity in Debaryomyces, with polymorphism for only two enzymes. The ITS size and the enzymatic restriction method were used in Brazilian isolates, detecting some Debaryomyces misidentifications in cultures previously identified by conventional methods.
The effects of growth conditions and chemical or physical treatments on the production of extracellular ice nucleators (ECINs) by Erwinia herbicola cells were investigated. The spontaneous release of ECINs, active at temperatures higher than −4°C, into the environment depended on culture conditions, with optimal production when cells were grown in yeast extract to an early stationary phase at temperatures below 22°C. ECINs were vesicular, released from cell surfaces with sizes ranging from 0.1 to 0.3 μm as determined by ultrafiltration and transmission electron microscopy. Protein profiles of ECIN fractions during bacterial growth were examined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and Ina proteins were detected by Western blotting. ECIN production was enhanced 5-fold when cells were treated with EDTA and 20- to 30-fold when subjected to sonication. These conditions provide a means for large-scale preparations of ECINs by E. herbicola.