摘要:

AbstractA systematic study of transformation reactions of the genusStreptomyceswith respect to the progesterone molecule was undertaken. The types of transformation reactions by differentStreptomycesspecies were evaluated from the point of view of taxonomy. The isolates tested were divided according to the transformation types into six groups: (1) a group of species transform progesterone to 16α‐hydroxyprogesterone; (2) a group of species transform progesterone to 6β‐hydroxyprogesterone; (3) a group of species transform progesterone to 6β, 11α‐dihydroxyprogesterone; (4) a group of species dehydrogenate progesterone in C1 ‐ 2position; (5) a group of species transform progesterone to 3 derivatives namely 6β‐hydroxyprogesterone, 6β, 11α‐dihydroxyprogesterone and dehydrogenation in position C1 ‐ 2; (6) a group of species with no capacity to transform progesterone into another steroid derivative. From the point of view ofStreptomycesclassification, the transformation reaction of progesterone fulfil all the requirements of taxonomic feature ofStreptomyces.These appear to be specific properties and common to all the strains of individualStrept

ISSN:0233-111X    

DOI:10.1002/jobm.3620350102

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620350104

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

摘要:

AbstractHot springs located in a geothermal area of central Italy were investigated with respect to the total number of thermophilic microorganisms as well as to the presence of amylolytic and pullulolytic bacteria. A number of motile thermophilic spore‐forming bacteria were isolated from different sites. The aerobic organisms grew optimally at 60 −65°C on yeast extract‐trypticase and/or xylose‐starch supplemented mineral medium and spores were mostly observed on agar plates after prolonged incubation. According to the results based on phenotypic characterization, G + C% and lipid analyses all the aerobic isolates belong to the genusBacillusand are characterized by an unusual G + C content ranging between 33.4 ‐ 38.8. A limited number of anaerobic organisms were also isolated and investigated for the presence of amylolytic and pullulolytic activity. According to physiological tests these isolates were identified asClostridium thermohydrosulfuricum; when grown on starch, they produced thermostable α‐amylases, pullulanases and

ISSN:0233-111X    

DOI:10.1002/jobm.3620350105

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620350106

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

摘要:

AbstractA periplasmic insulin‐cleaving proteinase (ICP)1), purified to its electrophoretic homogeneity in the SDS‐PAGE from the Gram‐negative bacteriumAcinetobacter calcoaceticus, was examined and compared in its properties with the protease III (protease Pi, pitrilysin, EC 3.4.99.44) ofEscherichia coliand the insulin‐destroying proteinase (IDE, insulinase, EC 3.4.99.45) from eucaryotes. The enzyme was proven to be a metalloprotease like protease III and IDE, as was shown by the inhibitory effects exerted by EDTA and o‐phenanthroline. Furthermore, dialysis against EDTA and o‐phenanthroline led to a complete loss of activity, which could be restored by addition of Co2+, and, to a lesser extent, but at a lower metal ion concentration by Zn2+Similar to protease III and IDE, ICP prefers the cleavage of small polypeptides (insulin, insulin B‐chain, glucagon) to the cleavage of proteins (casein, human serum albumin, globin) and was inactive against synthetic amino acid derivates (esters,p‐nitranilides, and furoylacroleyl substrates) of subtilisin, thermolysin, trypsin, and chymotrypsinThe peptide‐bond‐specificity of the ICP in the cleavage of the oxidized insulin B‐chain was investigated and the results were compared to the specificity of protease III ofE. coli, IDE, protease‐24,11, and thermolysin. Cleavage sites in the oxidized insulin B‐chain generated by ICP are Asn3‐Gln4, His10‐Leu11, Ala14‐Leu15, Leu17‐Vall8, Gly23‐Phe24, Phe24‐Phe25, and Phe25‐Tyr26. Principally, ICP cleaves between hydrophobic amino acids and amides. The ICP shares one of the only two cleavage sites with the p

ISSN:0233-111X    

DOI:10.1002/jobm.3620350107

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620350109

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe plasmids harbouring therelA gene under an inducible promoter allowed us to increase the guanosine 5′‐diphosphate‐3′‐diphosphate (ppGpp) concentration inEscherichia colicells without any starvation and thus, to directly investigate the effect of ppGpp on DNA replication. We studied all types of replicons which were investigated previously in amino acid‐starved bacteria and found that ColE1,oriC, λ plasmid and pSC101 but not RK2 replicons are sensitive to high ppGpp level. To our knowledge, this paper presents the first direct evidence that replication of most, but not all, replicons is dependent on ppGpp concentration and thus, is under strin

ISSN:0233-111X    

DOI:10.1002/jobm.3620350110

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620350111

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

摘要:

AbstractEscherichia colicells exposed to high temperatures exhibit a progressive loss of viability. We observed two mechanisms of cell death induced by lethal temperatures: with and without lysis. The number of cells lysed by heat decreased at later stages of the growth curve, when cells were pre‐treated at lower temperatures for 10 minutes and when cells were pre‐treated with novobiocin, nalidixic acid and cadmium chloride. Cell lysis was similar in wild type,rpoH,groE anddnaK mutant cells as well as in cells which overproduce heat shock proteins GroE or DnaK. Results using cells aligned for cell division and cells growing at 42°C, 45°C and 47°C suggest that cells near division are more sensitive to lysis and that a high concentration of heat‐shock proteins increases their resistance

ISSN:0233-111X    

DOI:10.1002/jobm.3620350112

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of different salts on the nitrate reductase (NR) activity ofRhodobacter sphaeroidesSW was studied. An increase of the activity in the presence of monovalent cations was observed (90, 80 and 77% with Na+, K+and NH 4+, respectively), whereas divalent cations inhibited the enzyme activity (30 and 85% with Ca2+and Mg2+). Both activation or inhibition of the NR activity were reversible. These results could be explained by the interaction of cations with negatively charged amino acids. On the other hand, several anions were also effective in stimulating NR activity (Cl−>NO 3−>Br−>I−>SCN−), suggesting that the degree of hydration of the enzyme molecule might influence its activity. Finally, the effect of salts on the NR activity ofR. sphaeroidesSW can be atributed to both electrostatic and hydrophobic

ISSN:0233-111X    

DOI:10.1002/jobm.3620350113

出版商:Wiley‐VCH    

年代:1995

数据来源: WILEY