Syncephalastrum racemosum Cohn. produces an extracellular xylanase that was shown to potentially bleach pulp at pH 10 and 50°C. The enzyme was found to be a dimer with an apparent molecular weight of 29 kDa as determined by SDS-PAGE. The optimum activity was found at two pH values 8.5 and 10.5; however the activity sharply decreased below pH 6 and above pH 10.5. The enzyme was stable for 72 h at pH 10.5 and at 50°C. Kinetic experiments at 50°C gave Vmax and Km of 1,400 U/ml min−1 mg−1 protein and 0.05 mg/ml respectively. The enzyme had no apparent requirement for cofactors, and its activity was strongly inhibited by group II b metal ions like Zn2+, Hg2+, etc. Xylan completely protected the enzyme from being inactivated by N-bromosuccinimide.
VY-68, a ballistoconidiogenous yeast strain, isolated from a plant leaf at Cuc Phuong National Park of Ninh Binh Province, Vietnam, was assigned to the genus Bullera based on morphological and chemotaxonomical characteristics. Based on the sequence analyses of 18S rDNA, D1/D2 region of 26S rDNA, and internal transcribed spacer regions (ITS), VY-68 was phylogenetically closely related to Bullera pseudoalba and Cryptococcus cellulolyticus. DNA-DNA reassociation experiments among VY-68, B. pseudoalba and C. cellulolyticus revealed that strain VY-68 is a distinct species, and the latter two are conspecific. Bullera hoabinhensis is proposed for VY-68.
Vibriosis in penaeid species cultured in the Philippines results in massive mortalities and consequently in severe economic losses in the shrimp industry. Rapid and accurate detection of the causative agent of the disease is imperative. In this study, toxR gene sequence analysis of ten Vibrio isolates (from several provinces of the Philippines) implicated in disease affecting the penaeid shrimp (Penaeus monodon) was performed in order to develop a toxR-targeted PCR detection of similar strains of shrimp pathogens. Analysis of the partial toxR gene revealed 97–100% sequence similarity among the ten Philippine Vibrio isolates. Distinct sequence variation of the toxR gene, however, was observed between the Philippine Vibrio isolates and the type strains, with the Philippine isolates exhibiting only 92–93% and 74–75% sequence similarity with the type strain V. campbellii (NBRC 15631T) and V. harveyi (NBRC 15634T), respectively. The use of a PCR primer set that was designed based on toxR sequences of the Philippine Vibrio isolates amplified the expected 226-bp toxR fragment using templates from all ten Philippine Vibrio isolates. No amplified product was observed in PCR using templates from type strains of V. harveyi, V. campbellii, and other non-target bacteria, suggesting that the primers were specific for the Philippine Vibrio isolates. The toxR-targeted PCR primers reported in this study could be useful in the detection of Philippine Vibrio isolates associated with mortalities in the shrimp industry, which could not be detected in PCR using primers designed for type strains of V. harveyi and V. campbellii.
Fifteen mesophilic bacteria with high Cx cellulase activities were isolated and purified from a mixed-culture enriched from a flower stalks-vegetable waste co-composting system. A CMCase test showed that the enzyme activity of these isolates ranged from 7.9 to 28.0 U ml−1. Although filter paper degrading capability was low in single culture, significant synergetic cellulose degradation were detected in four groups of mixed cultures, their degradation rates were 23.5%, 26.3%, 19.4% and 24.5%, respectively. Study of morphological and physiological characters of five predominant isolates which possess high CMCase and had positive effect on synergetic cellulose degradation in mixed culture system showed that two of them were closely related to Bacillus pasteurii and Bacillus cereus, whereas the rest belong to the genus Halobacillus, Aeromicrobium and Brevibacterium, respectively.
The changes in composition and structure of fecal coliforms (FC) and enterococci (ENT) populations, as well as the elimination of spores of sulphite-reducing bacteria (SRB), were compared between municipal sewage and their derived sludge in a biological treatment plant in order to determine any selective reduction or adsorption to sludge during the treatment process. Additionally, the persistence of antibiotic-resistant enterococcal populations in two kinds of sludge was also considered to evaluate their potential elimination in the treatment process. Microbial indicators, vancomycin-resistant and erythromycin-resistant enterococci were enumerated. The structure and composition of FC and ENT populations were determined by biochemical fingerprinting and clustering analyses. Raw and treated sewage showed a concentration of FC 1 log unit higher than ENT and nearly 2 log units higher than spores of SRB. However, the three studied indicators showed similar concentrations in both types of sludge. Consequently, FC were eliminated in higher proportion than ENT and spores of SRB in sludge. FC and ENT populations showed high diversity and similarity population indexes for all kinds of samples. Antibiotic-resistant enterococci persisted in a similar proportion in respect to total enterococci not only in treated sewage but also in sludge. The persistence of antibiotic-resistant strains in sludge as well as in treated sewage should be considered if they are used for land disposal or for water reutilization, respectively.
DNA polymorphism among 36 Astragalus cicer nodule isolates and 9 reference mesorhizobia was evaluated by a simplified PstI based AFLP procedure with three selective primers: Pst-A, Pst-G, and Pst-GC. The DNA profiles were found to be highly specific for nearly each strain, although DNA bands characteristic for most A. cicer microsymbionts were also noted. The overall topologies of dendrograms, generated by AFLP patterns in PCR reaction with three primers, were very similar to one another and to that constructed by phenotyping. Also the strain compositions in the particular clusters on pheno- and genomograms were in good agreement. The obtained results indicate that AFLP technique can be a useful tool for typing of A. cicer rhizobia as well as for studying their diversity.