摘要:

AbstractMutants ofRhodobacter capsulatus, blocked at different steps of bacteriochlorophyll a (BChl) synthesis between protoporphyrin IX and 2‐hydroxyethyl bacteriochlorophyllide a, were induced to synthesize the photosynthetic apparatus by lowering of oxygen tension in dark cultures. The cells were pulse‐labeled with [35S]methionine and the radioactivity chased after dilution of [35S]. The specific radioactivity in the pigment‐binding proteins of light‐harvesting and reaction center proteins of the wild‐type strain was not lowered during the chase period of three hours but in the BChl‐free mutants the label disappeared within five to thirty minutes. The polypeptides were inserted into the membrane but did not remain stably incorporated. In the mutant strain NK9 the synthesis of the carotenoid spheroidenone/spheroidene was inhibited by insertion of Tn5 in thecrtIgene (phytoene desaturase), which blocked completely the formation of the light‐harvesting (LH) complex II (B800–850) but not of the LHI (B870) complex. In this mutant the polypeptides of the LH complexes were synthesized in a lower amount than in the wild‐type cells and were inserted into the membrane. The LHIIα poly‐peptide disappeared after 60 min of chase while the LHIIβ was more stable. It was concluded that the pigments are not only necessary for absorption of photons and efficient transfer of excitation energy but have a structural role by stabilizing the oligomeric LH complexes. This is in accordance with the crystal structure d

ISSN:0233-111X    

DOI:10.1002/jobm.3620370402

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe Staph‐Zym and the Rosco Set methods were used to assign species to 142 strains of staphylococci isolated from the milk of sheep with subclinical intramammary infection or teat skin, mouth of lambs or milking machine teat cups. One hundred eleven of the same strains were also tested by Standard Laboratory Culture Media. The Rosco Set assigned species to all strains tested, but the other two methods were unable to assign species to a similar proportion of isolates. Seventy six (68.5%) of the strains tested with all three methods were not assigned the same species, each method shown a preference for particular species. The Staph‐Zym and the Rosco Set identified most of the strains as members of the ‘epidermidis’ group with the ‘aureus’ second, while the reverse was observed with the Standard Laboratory Culture Media. Only in the caseof Staphylococcus epidermidisall methods were in close agreement. When the results of the Staph‐Zym and the Rosco Set are compared, although they agree on the predominant group, they disagree on the predominant species within t

ISSN:0233-111X    

DOI:10.1002/jobm.3620370403

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractRelationship between intrinsic thermal resistance, thermotolerance and heat shock proteins (hsp) synthesis is studied inEnterococcus faecalis. We showed that an impressive phenotypic heat resistance was induced by mild heat and a slight thermotolerance was developed by various sublethal pretreatments such as NaCl, SDS and bile salts. Hydrogen peroxide, acid and alkalin shifts or ‘thermomimetic’ agent such as ethanol, did not enhance the survival of adapted cells against the lethal thermal shock (62 °C). The inhibition of protein synthesis by chloramphenicol or rifampin abolished thermotolerance. The immunological identification of the DnaK and GroEL proteins inE. faecalisallowed to study induction of these molecular chaperones under various conditions. Heat was the most efficient inductor of DnaK and GroEL synthesis. However, it was surprising that ethanol did not strongly induce these proteins. We also show that amplification of these hsp is not correlated to acquired thermotolerance with a linear relationship. A weak thermotolerance is not coupled from increased synthesis of DnaK and GroEL. So, we postulate that the high synthesis of the major hsp is not obligatory in the thermal cross‐protection but thatde novoprotein synthesis is an absolute necessity inE. faecalis. Activation of preformed hsp or other factors depending or not on protein synthesis may be also necessary to enhance thermal resi

ISSN:0233-111X    

DOI:10.1002/jobm.3620370404

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractUltraviolet‐B and heat shock (HS)1) induced changes in growth kinetics, NO−3reductase (NR), glutamine synthetase (GS), NO−3uptake and NO−2efflux activities, have been studied in the wild typeAnacystis nidulansand its UV‐HS1strain. The application of UV‐B and HS stresses either used separately or in combination shows a drastic changes in growth rates of wild type, and insignificant effect on the growth of the UV‐HStstrain. The wild type cells, in contrast to its UV‐HStstrain exhibits insignificant effect on NR and GS activities upon UV‐B radiation followed by heat shock treatment. Similar treatments to the wild type cells resulted in maximum reduction of NR and GS activities. The NO−3uptake and NO−2efflux activities are found to be lower in the UV‐HStstrain than in the wild type counterpart and both the systems consisted of an initial rapid phase followed by a slower one. NH+4grown cells when transferred to NO−3medium in presence of streptomycin showed significant inhibition in the development of both the NO−3uptake and NO−2efflux systems indicating thatde novoprotein synthesis is required for the development of NO−3uptake and NO−2efflux systems. Whereas the same cells in the presence of L‐methionine‐DL‐sulfoximine (MSX) showed marginally higher NO−3uptake but, exhibits only 42% NO−2efflux to that of MSX‐devoid both the cells. It is suggested that NH+4assimilation via GS is necessarily re

ISSN:0233-111X    

DOI:10.1002/jobm.3620370405

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractMethanol dehydrogenase (MDH) fromMethylocystissp. GB 25, which belongs to the group II of methanotrophic bacteria, is able to catalyse the oxidation of methanol to formate directly. The enzyme was purified 20‐fold by a 5 step procedure to electrophoretic homogeneity. After cell disruption by French press, about 95% of MDH‐activity was found in the soluble fraction. The relative molecular mass of the native enzyme has been estimated to be 122 kDa by gel filtration and 115 kDa by the method of HEDRICKand SMITH(1968). It seems to be composed of two identical subunits with a relative molecular mass of 62 kDa (estimated by SDS gel electrophoresis). The isoelectric point was found to be about 8.3. The amino terminal sequence shows a strong similarity to the α‐chain of MDH from the facultative methylotrophic bacteriumMethylobacterium extorquensAM1. PQQ, the probable prosthetic group of MDH, could be detected in the supernatant of the culture by using the apoenzyme of a membrane‐bound glucose dehydrogenase fromPseudomonas aeruginosabut not absolutely in the absorption spectra of the enzyme after DEAE‐chromatography. The purified MDH has an optimum activity at pH 9.0 and at 45 °C. MDH ofMethylocystissp. GB 25 oxidises only primary alcohols from methanol to heptanol and aldehydes from formaldehyde to propionaldehyde and the glutaraldehyde, respectively. The estimatedKm‐values show no dependence upon the chain length

ISSN:0233-111X    

DOI:10.1002/jobm.3620370406

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractPseudomonas aeruginosaGS3 produced rhamnolipid biosurfactants during growth on carbohydrates, higher chain lengthn‐alkanes and l‐alkenes, petroleum crude oil and vegetable oils. With glucose as the substrate, maximum surfactant production (0.44 g/l) was observed during the stationary phase of growth. Partially purified rhamnolipids showed excellent surface‐active properties in terms of reduction in the interfacial tension between them and a variety of hydrocarbons, hydrocarbon mixtures and vegetable oils and formation of stable emu

ISSN:0233-111X    

DOI:10.1002/jobm.3620370407

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe white‐rot fungusNematoloma frowardiiwas examined for the ability to degrade [ring U‐14C]‐phenanthrene and [4,5,9,10‐14C]pyrene in liquid and solid (straw) cultures in a period of 63 days. 3.2% phenanthrene and 8.6% pyrene were mineralized to14CO2in liquid cultures, respectively. A considerable higher mineralization of 11.2% (phenanthrene) and 46.5% (pyrene) was detected in straw cultures. Metabolites were identified by their UV absorption spectra.N. frowardiitransformed phenanthrene to phenanthrene 9,10‐dihydrodiol. Pyrene 4,5‐dihydrodiol was identified as major metabolite in pyrene

ISSN:0233-111X    

DOI:10.1002/jobm.3620370408

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

摘要:

AbstractTrehalase (THA) activity fromS. cerevisiaespores and vegetative cells could be differentiated in cell‐free extracts. THA from the vegetative cells has an optimal activity at neutral pH whereas biphase pH optimum in the spores was observed. The enzyme from the spores exhibited higher thermostability than that from the vegetative cells. The presence of magnesium ions was necessary mainly for THA activity from the vegetative cells. The effect of the other metal ions studied: Hg2+, Ag2+, Cu2+, Fe3+, Ni2+, Cd2+etc. (Table II), on THA from both sources was almost the same, however, the spores THA was resistant to Pb2+and especially to Zn2+. Moreover, the influence of inorganic polyphosphates and polyamines was also quite dissimilar. Polyphosphates inhibited THA from the vegetative cells and to a smaller extent from the spores. On the other hand, polyamines stimulated highly THA activity from vegetative yeast cells in contrast to spores one. The effect of these ions modulators would facilitate differentiating of THA activity in the cell‐free extracts from both sources. These data could be interpreted as phenotypic reflections of trehalase genes expression in theS. cerevisiaece

ISSN:0233-111X    

DOI:10.1002/jobm.3620370409

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620370401

出版商:Wiley‐VCH    

年代:1997

数据来源: WILEY