Cause of abnormal acidity of lysozyme ionogenic active center groups at cell wall lysis

pH-Dependence of the kinetic parameters of Micrococcus lysodeicticus cell lysis under the action of the protein hen egg lysozyme at the pH 6.9-10.0 at 25 and 37 degrees C has been investigated. The pKb effective values for the lysozyme catalytic activity controlling group have been calculated. The DeltaHion value indicates that this group is the carboxyl one though its pK (9.15 at 25 degrees C) is found far for the limit of the carboxyl groups pK values. The cause of this abnormal pK values is supposed to be the strong negative charge of the bacterial cell wall. As a result the enzyme that catalyzes the hydrolysis ofcopolymer N-acetylglucosamine--N-acetylmuramic acid acts in the high acidity microenvironment.     

Chromosome numbers and meiotic analysis in the pre-breeding of <Emphasis Type="BoldItalic">Brachiaria decumbens</Emphasis> (Poaceae)

A total of 44 accessions of Brachiaria decumbens were analysed for chromosome count and meiotic behaviour in order to identify potential progenitors for crosses. Among them, 15 accessions presented 2n = 18; 27 accessions, 2n = 36; and 2 accessions, 2n = 45 chromosomes. Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number and meiotic stability, the present study indicates the apomictic tetraploid accessions that can act as male genitor to produce interspecific hybrids with B. ruziziensis or intraspecific hybrids with recently artificially tetraploidized accessions.     

Patterns of genetic variability at individual minisatellite loci in minke whale Balaenoptera acutorostrata populations from three different oceans

The genetic variability at six cloned minisatellite loci was analyzed in minke whale populations from the North Atlantic, North Pacific, and Antarctic Oceans. Three loci displayed only a few different alleles in each of the three populations, with heterozygosity ranging from 0.00 to 0.47, and three loci revealed many different alleles in at least two fo the three populations, with heterozygosity ranging up to 0.98. Using small sample sizes, samples from two adjacent Antarctic Management Areas were not found to differ significantly in allele frequencies at any of the six loci. The use of principal coordinate analysis to detect multilocus disequilibria was explored. No significant evidence was found of intrapopulation heterogeneity within the pooled Antarctic sample. Pronounced interoceanic differences were observed at every locus, confirming the existence of genetic isolation found earlier using more conventional marker systems. The populations from the three oceans appear to have diverged to such a degree that the hypervariable loci have had time to evolve independently and arrive at different evolutionary stages in different populations. The frequency of undetected "null" alleles is remarkably high in minke whale populations compared to human populations and is probably a result of the cloning protocol used. Minisatellite loci are shown to provide a powerful population genetic tool, supplying levels of resolution appropriate to different degrees of evolutionary divergence.      

Taxonomic diversity of aerobic organotrophic bacteria from clean vietnamese soils and their capacity for oxidation of petroleum hydrocarbons

The dominant species and abundance of the cultured aerobic organotrophic bacteria were determined in the clean soils of the Republic of Vietnam. The total number of organotrophs varied from 2.0 × 10⁵ to 5.8 × 10⁸ CFU/g soil. A considerable fraction of the bacterial population (1.1 × 10⁵–9.5 × 10⁶ CFU/g soil) was able to utilize petroleum hydrocarbons as the sole carbon and energy source. Most of the organisms obtained in pure cultures were gram-positive bacteria; over 70% were hydrocarbon-oxidizing organisms. Analysis of 16S rRNA gene sequences resulted in tentative determination of the taxonomic position of 22 strains, with 12 belonging to the Firmicutes, 4, to the Proteobacteria, and 6 to the Actinobacteria. The most common bacteria capable of hydrocarbon oxidation belonged to the genera Acinetobacter, Bacillus, Brevibacillus, Chromobacterium, Cupriavidus, Gordonia, Microbacterium, Mycobacterium, and Rhodococcus. Some of the isolated Bacillus and Staphylococcus strains, as well as one Pseudomonas and one Sinomonas strain, did not utilize hydrocarbons. Gram-positive degraders, especially members of the order Actinomycetales, which exhibited high hydrocarbon-oxidizing activity, gained competitive advantage in the presence of hydrocarbons. This microbial group probably plays an important role in hydrocarbon degradation in tropical soils. Thus, Vietnamese soils, which had no history of petroleum contamination, support numerically significant and taxonomically diverse populations of h ydrocarbon-oxidizing bacteria.     

Adsorption chromatography of proteins

A method for adsorption chromatography of proteins is proposed. A protein solution is passed through a cellulose column at a pH value corresponding to an isoelectric point of the protein. Depending on the charge of unwanted proteins, they either remain at the origin (if charges of protein and ion-exchanger are opposite) or are released from the column (if charges of protein and ion-exchanger coincide). Elution volume of the purified protein is higher than for the second group of unwanted proteins because movement of the uncharged protein of interest includes its adsorption on cellulose followed by subsequent desorption caused by the elution buffer. Problems of optimization of buffers and adsorbents are discussed. Applicability of the method of adsorption chromatography is illustrated using purification of horseradish peroxidase as an example.     

Transgenic tobacco plants expressing Tarin 1 inhibit the growth of Pseudomonas syringae pv. tomato and the development of Spodoptera frugiperda

The protein Tarin 1, from Colocasia esculenta, was expressed in Nicotiana tabacum. Bioassays were done on plants expressing Tarin 1 at different levels using Spodoptera frugiperda larvae, various bacteria and fungi and the root‐knot nematode Meloidogyne javanica. It was found that S. frugiperda larvae fed on transformed plants had retarded and lower pupation, lower accumulated biomass and higher mortality rate than larvae fed on control plants. Also, Tarin 1 was found to inhibit the growth in vitro of Pseudomonas syringae pv. tomato. For Meloidogyne javanica, both relative replication and root damage were greater in control plants than in transformed plants, but the results were not statistically significant. This work illustrates the effects of plants expressing Tarin 1, on the growth and development of insects and bacteria, and shows its potential for pest management.     

卤虫染色体倍性组成的研究

本文报道了我国4个地理品系卤虫的染色体倍性组成及卵径分布,分析了卤虫染色体的非整倍性,讨论了卤虫种的分布。 天津卤虫有2倍体(2n=42),占33.3％和5倍体,占16.2％;染色体数的波动为21—108;卵径为262±17μm。 海南卤虫有2倍体(2n=42),占8％;4倍体,占17.7％;5倍体,占18.3％;染色体数的波动为16—111;卵径为285±15μm。 新疆卤虫有2倍体(2n=42),占39.2％;染色体数的波动为17—106;卵径为269±15μm。 山西卤虫有2倍体(2n=42),占45.1％,染色体数的波动为17—84;卵径为234±13μm。     

Microbiological processes in a high-temperature oil field

Thermophilic sulfate-reducing bacteria (SRB) oxidizing lactate, butyrate, and C12-C16 n-alkanes of oil at a temperature of 90 degrees C were isolated from samples of water and oil originating from oil reservoirs of the White Tiger high-temperature oil field (Vietnam). At the same time, no thermophiles were detected in the injected seawater, which contained mesophilic microorganisms and was the site of low-temperature processes of sulfate reduction and methanogenesis. Thermophilic SRB were also found in samples of liquid taken from various engineering reservoirs used for oil storage, treatment, and transportation. These samples also contained mesophilic SRB, methanogens, aerobic oil-oxidizing bacteria, and heterotrophs. Rates of bacterial production of hydrogen sulfide varied from 0.11-2069.63 at 30 degrees C and from 1.18-173.86 at 70 degrees C micrograms S/(1 day); and those of methane production, varied from 58.4-100 629.8 nl CH4/(1 day) (at 30 degrees C). The sulfur isotopic compositions of sulfates contained in reservoir waters and of hydrogen sulfide of the accompanying gas indicate that bacterial sulfate reduction might be effective in the depth of the oil field.