Antagonism of Lactic Acid Bacteria against Phytopathogenic Bacteria

A variety of lactic acid bacteria, isolated from plant surfaces and plant-associated products, were found to be antagonistic to test strains of the phytopathogens Xanthomonas campestris, Erwinia carotovora, and Pseudomonas syringae. Effective “in vitro” inhibition was found both on agar plates and in broth cultures. In pot trials, treatment of bean plants with a Lactobacillus plantarum strain before inoculation with P. syringae caused a significant reduction of the disease incidence.     

高效脱硫诱变菌株降硫性能的研究

目的:筛选具有脱硫功能的细菌,为采用生物法脱硫奠定理论基础.方法:从大庆石化废水曝气池中采集5个活性污泥样本,经过富集培养、分离、纯化获得具有典型特征的菌株,采用碘量法对这些菌株进行降硫能力测定,从中选择降硫效率较高的菌株进行诱变.结果:在30℃、转速160r/min的条件下,Z39ay1菌株的最佳生长pH值为7.0,对数生长期为12～32h,当硫离子为102.24mg/L时,该菌株对硫化物的降解率达42.60％,将其置于2000Gry的60Co射线下照射,从存活菌细胞中进行筛选获得1株诱变菌株Z39a,当硫离子浓度为60mg/L时,对硫化物的降解率达98.58％.结论:从大庆石化废水中分离纯化出1株代号为Z39ay1菌株,经鉴定为赖氨酸芽孢杆菌,诱变后获得菌株Z39a,其降硫效果比出发菌株有大幅度的提高.     

Bacteria decomposing alpha-methylstyrol

Two bacterial strains assimilating alpha-methylsterene as a sole carbon and energy source were isolated from the sewage of an industrial plant producing synthetic rubber. The morphological, cultural and physiologo-biochemical properties of the strains were studied and their taxonomic position was determined. One of the cultures was classified as Bacillus cereus and the other as Pseudomonas aeruginosa. The rate of alpha-methylsterene destruction in the chemically defined medium was shown to depend on the conditions of cultivation.     

Milky Disease Bacteria

A comparative study was made of all available milky-disease species and strains that have been isolated around the world from beetle larvae (family Scarabaeidae). Included in the study were Bacillus popilliae Dutky, B. lentimorbus Dutky, and B. lentimorbus var. maryland from the United States; B. euloomarahae Beard and B. lentimorbus var. australis Beard from Australia; B. fribourgensis Wille from Switzerland; and New Zealand milky disease (Dumbleton). The organisms were classified into three groups: (i) those containing parasporal bodies, including B. popilliae Dutky, B. fribourgensis Wille, and New Zealand milky disease (Dumbleton); (ii) those without a visible parasporal body and with spore morphology similar to B. lentimorbus Dutky, including B. lentimorbus var. australis Beard; and (iii) those with very tiny spores and no parasporal body, including B. euloomarahae Beard and B. lentimorbus var. maryland. All available milky-disease species and strains were cultivated in vitro on Brain Heart Infusion Agar plates. However, the most fastidious organisms—B. euloomarahae and B. lentimorbus var. maryland—could not be grown until they were passed through a life cycle in larvae of a large scarabaeid beetle infesting rotting wood. Then they remained stable for only one or two subcultures. All the milky-disease organisms produced larger cells in vitro than they did in vivo. The pattern of sugar fermentations was similar for all milky-disease species. It appears that there is a very low percentage of strains of B. popilliae, B. lentimorbus, and the other milky-disease organisms that have the inherent genetic makeup to permit them to sporulate on artificial media, if conditions are favorable. Among these conditions are a sufficiently high cell population and a reduced oxygen tension. Spores produced in vitro may have a low virulence via the normal ingestion pathway, even though they show apparent virulence when injected directly into the hemocoel.     

Staining Iron Bacteria

A modification of Perls's reaction for hemosiderin in tissue is described for staining iron bacteria. The procedure involves the formation of either Prussian blue (ferric ferrocyanide) or Turnbull's blue (ferro ferricyanide) where iron is present on the surface of the bacterium or in the sheath enclosing the bacterium. The counterstain, safranin, imparts a pink color to the noniron-bearing portions of the bacterial cell. Excellent results have been obtained using this technique for staining Clenothrix and Gallionella. The procedure is a valuable aid for the rapid detection of iron bacteria in water samples and for the study of the microscopic morphology and biochemical activities of these organisms.     

Acyltransferases in Bacteria

SUMMARY

Long-chain-length hydrophobic acyl residues play a vital role in a multitude of essential biological structures and processes. They build the inner hydrophobic layers of biological membranes, are converted to intracellular storage compounds, and are used to modify protein properties or function as membrane anchors, to name only a few functions. Acyl thioesters are transferred by acyltransferases or transacylases to a variety of different substrates or are polymerized to lipophilic storage compounds. Lipases represent another important enzyme class dealing with fatty acyl chains; however, they cannot be regarded as acyltransferases in the strict sense. This review provides a detailed survey of the wide spectrum of bacterial acyltransferases and compares different enzyme families in regard to their catalytic mechanisms. On the basis of their studied or assumed mechanisms, most of the acyl-transferring enzymes can be divided into two groups. The majority of enzymes discussed in this review employ a conserved acyltransferase motif with an invariant histidine residue, followed by an acidic amino acid residue, and their catalytic mechanism is characterized by a noncovalent transition state. In contrast to that, lipases rely on completely different mechanism which employs a catalytic triad and functions via the formation of covalent intermediates. This is, for example, similar to the mechanism which has been suggested for polyester synthases. Consequently, although the presented enzyme types neither share homology nor have a common three-dimensional structure, and although they deal with greatly varying molecule structures, this variety is not reflected in their mechanisms, all of which rely on a catalytically active histidine residue.     

Glutathione in Bacteria

Glutathione metabolism and its role in vital functions of bacterial cells are considered, as well as common features and differences between the functions of glutathione in prokaryotic and eukaryotic cells. Particular attention is given to the recent data for the role of glutathione in bacterial redox-regulation and adaptation to stresses.