摘要:

AbstractExcision of Tn917 from chromosomal sites inB. subtilisis characterized by reversion studies. We propose different modes of excision depending on the site of transposon insertion. Excision takes place as precise excision in one step which results in reversion of the mutant phenotype, or by a two‐step process where nearly precise excision of the transposon moiety is followed by precise excision of the nearly precise excision remnants. For this type of transposons a minor pathway or nonreplicative transposition is proposed to be connected with precise exsisio

ISSN:0233-111X    

DOI:10.1002/jobm.3620300602

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

摘要:

AbstractForty‐eight species of wood‐destroying basidiomycetous fungi which are represented by 74 strains were examined for their dependence on exogenous vitamin sources such as thiamine and biotin. In a series of up to 11 consecutive transfers to vitamin‐free glucose‐salt medium batches in a 4‐week rhythm it was shown that (i) the level of vitamin heterotrophy did not depend on whether the fungus was a parasite or a saprophyte, (ii) among both parasites and saprophytes vitamin‐independent and highly vitamin‐dependent isolates could be detected, (iii) almost 70% of the brown‐fungi, but only 30% of the white‐rot fungi dependend comparatively little on exogenous vitamin sources, (iv) the degree of vitamin heterotrophy varied in part dramatically among several strains of a given fungal species, (v) under permanent vitamin starvation none of the 74 fungal strains completely ceased growing, but several strains suffered an irreversible physiological collapse whose nature is still unknown. It is concluded that on natural timber resources both vitamin‐dependent and vitamin‐independent fungal strains can probably develop their normal pathovirulence and kratovirulence properties. Under conditions of vitamin starvation the equilibrium between the vitamin‐dependent decay fungus and the vitamin‐independent competitor may neve

ISSN:0233-111X    

DOI:10.1002/jobm.3620300603

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe presence of the essential growth factor thiamine in timber was ascertained with the determination of the mycelial growth figures of several indicator fungi on the respective timber substrates. The behaviour of the absolutely thiamine‐dependent phycomycete,Phycomyces blakesleeanusBURGEFF (Pb), as well as of 6 strains of basidiomycetous wood‐decay fungi (WBF) that did or did not depend on exogenous vitamin supply proved in accordance that (i) both sapwood and heartwood material of 14 native timber species examined were able to furhish fungi with any degree of vitamin dependence with the essential growth factor(s); (ii) both fresh timber and timber pre‐colonized by bacteria, ascomycetous discolouration fungi, and WBF contained thiamine resources above the saturation level of 50 μg per kg; (iii) neither a thiamine supply of 2 to 20 mg per kg total weight nor the residues of microbial pre‐colonizers added to the vitamin pool of timber in that the growth of the test fungi could be further stimulated; (iv) the depressive growth of WBF on vitamin‐free liquid media was not observed on vitamin‐free solid media such as fertilized builder's sand. A vitamin supply did not improve the vigour of WBF of any degree of vitamin dependence, but it was a prerequisite for the growth of Pb on these substrates.It is concluded that vitamins in timber have, on their permanent excessive presence, no ecological significance. They do not add to host wood specificity, to the election of the fungus' host range, to the specialization for gymnosperm wood, to the preference for sapwood or heartwood within the stem, to the establishment of pathogenesis on standing timber, and to the preference for fresh or pre‐colonized

ISSN:0233-111X    

DOI:10.1002/jobm.3620300604

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

摘要:

AbstractGrowth ofEscherichia coli044 K 74 in liquid medium of raised osmotic strength was stimulated by exogenous L‐carnitine, crotonobetaine and γ‐butyrobetaine, respectively. L‐Carnitine was accumulated within the cells in dependence on the salt concentration of the media. Osmotic stress during aerobic or anaerobic growth with glucose triggered the L‐carnitine uptake inE. coli044 K 74 whereas L‐carnitine uptake by cells of this organism grown anaerobically on glycerol/fumarate was only slightly modified. Synthesis of the enzymes metabolizing L‐carnitine to γ‐butyrobetaine in glycerol/fumarate growing bacteria was found to be completely repressed by high NaCl‐concentrations. Together, these results indicate that most likely the L‐carnitine metabolization sequence does not play a role in osmoregulatio

ISSN:0233-111X    

DOI:10.1002/jobm.3620300605

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620300606

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

摘要:

AbstractFifteen nocardioform bacteria strains, capable of transforming steroid compounds were investigated with regard to their range of inducible steroid‐1‐dehydrogenase (St1DH)1activities. The St1DHs of these bacteria were compared due to their immuno reactivity in Western blot experiments with a rabbit antiserum raised against the purified St1DH ofRhodococcus rhodochrous7030. Four strains exhibited a strong immuno reactivity, irrespective of differences in the electrophoretic mobility of the enzymes. Fivestrains revealed significantly diminished reactivities, and in five strains with a very low St1DH content, no reactivity was found. One strain, designated asNocardiaspec. 7151, exhibited a high, inducible St1DH activity, but no immuno reaction was found. The absence of immuno reactivity is discussed in connection with the considerably diminished electrophoretic mobility of this enz

ISSN:0233-111X    

DOI:10.1002/jobm.3620300608

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620300610

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the phytopathogenicPseudomonas syringaepv.phaseolicolaan amidinotransferase was detected and characterized which catalyzes the amidinotransfer from arginine to lysine producing the phaseolotoxin precursors homoarginine and ornithine. The enzyme was purified 419‐fold by affinity chromatography on homoarginine‐Sepharose. It had an apparent mol. wt. of 200 000 and exhibited MICHAELIS‐MENTEN kinetics withKm7.7 mM for arginine andKm4.2 mM for lysine. Ornithine competitively inhibited the enzyme with aKiof 0.8 mM. During cultivation of the pseudomonad the highest enzyme activity corresponds with the highest production rate of phaseolotoxin. At low toxin production, mutants exhibit a low enzyme activity and vice versa. Only those strains of different pathovarieties which are able to produce phaseolotoxin contain the enzyme. At 30 °C cultivation temperature, the enzyme activity was 50% of that at 18 °C, and toxin production decreased with increasing temperature. When microbes were grown on ribose, their enzyme activity was 60% lower than grown on glucose or glycerol. Toxin production was decreased to about 10% when growing on ribose. Amidinotransferase is considered to be one of the key enzymes of phaseolotoxin biosy

ISSN:0233-111X    

DOI:10.1002/jobm.3620300611

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620300613

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY

摘要:

AbstractVarious non‐ionic surfactants affect the SOS‐inducing potency (SOSIP)1of the model genotoxin, 4‐nitroquinoline‐1‐oxide, inEscherichia coliPQ37 to varying degrees, as measured by an automated version of the SOS chromotest. While there is little effect on the SOSIP value and other test parameters from Tween 20 and 80 and, with some reservation, Triton X305 and Tyloxapol, over the critical micelle concentration range, the SOSIP value increases in the presence of comparable concentrations of Triton X15, 45 and 100. A possible dependence of the tester strain's β‐galactosidase production and its growth inhibition on the HLB of the non‐ionic surfactants adde

ISSN:0233-111X    

DOI:10.1002/jobm.3620300614

出版商:Wiley‐VCH    

年代:1990

数据来源: WILEY