Pleiotropic consequences of mutations towards antibiotic-hypersensitivity in Serratia marcescens

Various mutants (oxa ^s ) were isolated from Serratia marcescens SM-6 by selecting for hypersensitivity towards oxacillin. All mutants found are highly pleiotropic and able to yield spontaneous revertants which behave like the wild-type. Mutant W 1421 mostly studied shows the following phenotypic properties not found in the wild-type: (1) The growth is hypersensitive to various antibiotics, detergents and dyes which differ remarkably in their chemical structure and antibacterial action-mechanism, (2) the cells can be easily solubilized by 0.05% Sodium-dodecylsulfate, (3) the cells allow the adsorption of the roughmutant specific Salmonella phage 6SR, (4) strong cellular binding of crystal violet, (5) agglutination of the cells in 0.3% auramin solution and (6) reduced formation of red pigment. Strain W 1421 is assumed to be a lipopolysaccharide-defective mutant. The outer membrane of mutant W 1421 analyzed by Sodiumdodecylsulfate-polyacrylamide gel electrophoresis possesses a single protein less than that of the wild-type. Mutant W 1421 is further characterized by its low exolipase activity; exoprotease and exonuclease activities are as in the wild-type. This specific exoenzyme deficiency can be overcome either by backmutation to oxacillin-resistance or by growing mutant W 1421 in a medium supplemented with certain non-metabolizable polysaccharides, e.g. glycogen or pectin B. Both polysaccharides increase the exolipase activity of the wild-type too.List of Abbreviations amp ampicillin - LPS lipopolysaccharide - MIC minimal inhibitory concentration - NB nutrient broth - oxa oxacillin - str streptomycin - TBY tryptone broth with yeast extract - SDS sodium-dodecylsulfate - OD optical density This paper is dedicated to Prof. Dr. R. W. Kaplan, University of Frankfurt/M., on the occasion of his 65th birthday     

A contaminant,Erwinia carotovora,affecting commercial plant tissue cultures

Summary Commercial plant tissue cultures of several ornamental plants exhibiting reduced vigor and chlorosis in stage II were found to contain bacterial contaminants. In most cases, visible evidence of the contaminants in the tissue-culture medium was not easily discernible. Physiological and pathological tests employing pure cultures proved 5 of the 10 isolates obtained to beErwinia carotovora, an important pathogen of many horticultural plants. The tissue cultures from whichE. carotovora was isolated were of plant types nonsusceptible under normal commercial production methods. These results indicate nonhost plants may serve as carriers ofE. carotovora during tissue-culture propagation and also possibly under normal methods of commercial production. Florida Agricultural Experiment Stations Journal Series No. 883. This investigation was supported in part by The Fred C. Gloeckner Foundation.     

耐药菌感染的噬菌体治疗专利技术

耐药菌,尤其是多重耐药菌的出现和持续进化给人类健康带来了巨大的威胁。在抗生素逐渐失去特效作用的情况下,科学界和医药界又把眼光重新投向了抗菌的天然生物-噬菌体,并在一些研究中证明了噬菌体可以作为新的武器去替代抗生素治疗耐药菌感染。通过对噬菌体治疗及衍生的裂解酶治疗的世界专利申请进行统计及分析,获得了专利发展趋势、申请人分布特点及主要专利申请人等信息,详细分析了噬菌体及裂解酶治疗的主要专利技术路线和研发热点。     

DNA Throughout the Single Mitochondrion of a Kinetoplastid Flagellate: Observations on the Ultrastructure of Cryptobia vaginalis (Hesse, 1910)

SYNOPSIS. Cryptobia vaginalis (Hesse 1910) occurs as long thin and short broad forms in the vagina of the gnathobdelliform leeches Haemopis sanguisuga (Linnaeus) and Hirudo medicinalis Linnaeus. Cytochemical staining for DNA and transmission electron microscopy of sectioned material indicate that in the thin forms the kinetoplast DNA (kDNA) is dispersed irregularly through the mitochondrial network ( pankinetoplastic condition) rather than concentrated in the adbasal region of the mitochondrion ( eukinetoplastic condition) as in trypanosomatids and most other kinetoplastid flagellates. Light-microscopic studies on the rare broad forms, however, suggest that these have conventional adbasal location of the kinetoplast. Binary fission appears to occur in the thin forms, suggesting that the dispersed kinetoplast is either highly polyenergid or lacks a genetic function. In other features of its microanatomy, C. vaginalis is a conventional kinetoplastid. The flagellate has an incomplete corset of pellicular microtubules which may have a role in the cortical contractility characteristic of the genus Cryptobia . Feeding is by pinocytosis of vaginal colloids through a microtubule-lined cytopharynx, possibly after binding to a prominent filament-coated preoral ridge. A pulsatile (contractile) vacuole is present and appears to be responsible for defecation as well as osmoregulation. Some individuals have elongate bacterial epibionts attached to the body in parallel with the cortical microtubules. All individuals have 2–8 spheroplast-like endobiotic bacteria in the prenuclear cytoplasm.     

Aphid transmission and a polypeptide are specified by a defined region of the cauliflower mosaic virus genome

Infection of young turnip leaves with an aphid-transmissible isolate, Cabb B-JI, of cauliflower mosaic virus (CaMV) causes synthesis of an Mr 18 000 polypeptide (p18) which co-purifies with virus inclusion bodies. This polypeptide is not detectable in leaves infected with either of two aphid non-transmissible isolates. Campbell and CM4-184. Construction in vitro, of hybrid genomes between Cabb B-JI and Campbell isolates demonstrates that aphid transmissibility and presence of p18 is dependent on the small genome fragment from the BstEII site to the XhoI site. A deletion made in this fragment within open reading frame (ORF) II causes loss of aphid transmissibility and also terminates production of p18. We conclude that aphid transmissibility and the presence of p18 are related to the expression of ORF II of the CaMV genome.     

Stable integration of foreign DNA into the chromosome of the cyanobacterium Synechococcus R2

The blue-green alga, Synechococcus R2, is transformed to antibiotic resistance by chimeric DNA molecules consisting of Synechococcus R2 chromosomal DNA linked to antibiotic-resistance genes from Escherichia coli. Chimeric DNA integrates into the Synechococcus R2 chromosome by homologous recombination. The efficiency of transformation, as well as the stability of integrated foreign DNA, depends on the position of the foreign genes relative to Synechococcus R2 DNA in the chimeric molecule. When the Synechococcus R2 DNA fragment is interrupted by foreign DNA, integration occurs through replacement of chromosomal DNA by homologous chimeric DNA containing the foreign insert; transformation is efficient and the foreign gene is stable. Mutagenesis in some cases attends integration, depending on the site of insertion. Foreign DNA linked to the ends of Synechococcus R2 DNA in a circular molecule, however, integrates less efficiently. Integration results in duplicate copies of Synechococcus R2 DNA flanking the foreign gene and the foreign DNA is unstable. Transformation in Synechococcus R2 can be exploited to modify precisely and extensively the genome of this photosynthetic microorganism.     

Biotechnology applied to mining of metals

The present review describes the advances achieved during the last two years in the application of biotechnological principles in the extraction of metals from ores and minerals. Despite the fact that this branch of science is very young and many details are yet to be understood, the microbes are applied at commercial levels especially for the extraction of copper and uranium from low-grade ores. The technique is far from being developed to its full potential and it is generally recognized to be a technology of the future. The studies involved are complex and multidisciplinary in nature.     

Immunosuppressive properties of leukotriene D4 and E4 in vitro

Leukotrienes D₄ and E₄ whose physiological function has been associated with smooth muscle contraction, are demonstrated to be potent suppressors of immunocompetent cell function. In concentrations as low as 10^?12 M both leukotriene D₄ and E₄ can inhibit mitogen-induced lymphocyte transformation. Higher concentrations of leukotrienes E₄ and D₄ will inhibit appearance of antibody-forming cells in tissue culture. These data suggest another role for the leukotrienes in addition to their function as slow-reacting substances.     

不同胃疾患胃内微生态变化的研究

本文对75例不同胃疾患胃液内的菌群及影响胃内微生态环境的因素进行了研究,发现健康胃内基本无菌或只有少量口腔细菌,未发现厌氧菌。而不同胃疾患胃内均分离到细菌(log10~n/ml),慢性萎缩性胃炎:3.89±0.99,残胃炎:4.45±0.16,胃癌:4.23,十二指肠球部溃疡治疗前(2.8±0.62)与抗酸治疗后(4.35±0.61)差别显著,慢性浅表性胃炎:3.39±0.98,胃溃疡:3.42±0.29。所分离到的细菌既有来自于口腔的细菌,也有来自于肠道的细菌。影响胃内细菌增殖的主要因素是胃液的PH值,幽门功能失调及幽门切除亦可使胃内细菌过度生长。本研究提示对胃病的治疗亦应进行生态防治。