摘要:

AbstractTwenty‐five identified and 3 unidentified species in addition to one variety belonging to ten genera of aquatic fungi were recovered from 20 surface water samples collected from different aquatic sites in Tübingen region (Baden‐Württemberg, Germany) during July‐September 1992 using sesame seeds as baiting substances. Three genera were of high occurrence;Saprolegnia(8 species),Aqualinderella(one species) andPythium(6 species) and two genera namelyAchlya(2 species) andDictyuchus(one species) were of moderate occurrence.Allomyces(3 species + one variety) andAphanomyces(one species) were of low occurrence whereasOlpidiopsis, Phytophthora, PythiopsisandThraustothecawere of rare occurrence (one species each).Saprolegniacontributed the broadest spectrum of species (8 species). The richest water samples inSaprolegniaspecies (7 species) and the aquatic fungal species (15 species) was number one which collected from the river Neckar while this group of fungi disappeared completely in sample number (16). It seems that the most effective factor in the occurrence and distribution of this group of fungi during this study was the water temp

ISSN:0233-111X    

DOI:10.1002/jobm.3620340202

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

摘要:

AbstractProlonged adaptation of Ca‐alginate immobilized cells ofPseudomonas acidovoransCA28 to a mixture of 3‐chloroaniline (3‐CA)1) and 2‐CA and subsequently to 2‐CA as sole substrate led to the isolation of another strain, termed CA50 with the additional capability of utilizing 2‐CA as sole source of carbon, nitrogen, and energy. Batch‐degradation of 190 mg/l of 2‐CA at pH 6.1 by this newly isolated strain was achieved within 3 days, at higher concentrations up to 0.6 g/l increasing lag‐phases and degradation periods were observed. Except chloride and ammonium no further metabolites were detectable in the medium. Mineralization of 2‐CA proceeds via the modifiedortho‐cleavage pathway as demonstrated by the presence of catechol 1,2‐dioxygenase (C120) activity, which is characterized by its substrate specificity and elution beha

ISSN:0233-111X    

DOI:10.1002/jobm.3620340203

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

摘要:

Abstractα‐Galactosidases (α‐gal) from six strains ofLeuconostoc mesenteroidessubsp.mesenteroides, which were isolated from four different ecological niches, have been characterized. The enzymes have an optimum pH ranging from 5.5 to 6.4. Strain 19A possesses a pH optimum close to neutral. The optimum temperature varied with the strains, ranging from 37 to 43 °C. TheKmvalues of the enzymes for substratep‐nitrophenyl‐α‐D‐galactopyranoside (PNPG) varied from 2.15 to 22.70 mM. α‐Gal from strain 23A had the lowest affinity for substrate PNPG. An increase of the affinity for PNPG in the presence of 10 mM lactose was observed for strains 6M, 19A, 23A, 19M, while this higher affinity for PNPG was also observed in the presence of 10 mM galactose for strains 6M, 23A, 19M. The activation energy of the enzyme from different strains was calculated to be about 62.9–72.8 kJ/mol. Ca2+ions have a strong inhibitive effect on the enzyme activity. Appearance of α‐gal activity band and protein profiles under the same conditions of SDS‐PAGE allowed an estimation of the apparent molecular weight of α

ISSN:0233-111X    

DOI:10.1002/jobm.3620340204

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

摘要:

AbstractSeeds of faba bean cultivar Giza 3 were screened for natural presence of mycotoxins. Eleven out of 100 samples were contaminated. Aflatoxins B1and B2were found in 7 samples while aflatoxins B1, B2, G1and G2and ochratoxin A were each detected twice in separate samples. Mycotoxins at concentrations of 100 or 200 μg kg−1soil significantly decreased nodule number, nodule fresh weight and total nitrogenase activity, leading to reductions in dry matter accumulation and nitrogen yield of the bean. Mycotoxins also suppressed specific nitrogenase activity. NADH‐dependent glutamate dehydrogenase (NADH‐GDH) as well as glutamate synthase (NADH‐GOGAT) activities. In addition, mycotoxins inhibited synthesis of leghaemoglobin, carbohydrated and protein in the nodule cytosol. Of the mycotoxins tested, aflatoxin B1was the most toxic. The decline in nitrogenase activity and total N concentration in the plants could be attributed to mycotoxins interference with normal nodule physiology and

ISSN:0233-111X    

DOI:10.1002/jobm.3620340205

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

摘要:

AbstractA 1,3 kb DNA fragment of the IncM plasmid R446, if cloned in a multicopy plasmid, inhibitsin transthe expression of conjugation pili by IncM plasmid‐harbouring host bacteria as indicated by their insensitivity to the IncM pilus‐dependent bacteriophage ϕM (Iml, insensitivity to ϕM‐mediated lysis). Determination of the nucleotide sequence of this DNA fragment, the introduction of deletions and the analysis of transposon insertions reveal two determinants,imlA andimlB, responsible for the Iml phenotype. A stretch of 80 bp of DNA containingimlA and about 450 bp of adjacent DNA comprisingimlB, together, bring about inhibition of the typical expression of conjugation pili at 30 °C. The introduction of a transposable promoter probe and the construction of respectivelacZ fusions indicate transcription of complementary strandsin vivooverlapping in the region comprisingimlA andimlB. Moreover, the expression of reporter genes discloses temperature‐dependent transcription of theimlA‐imlB‐region in one direction.A particular subfragment of the 1.3 kb IncM plasmid‐derived DNA does not inhibit conjugation pilus expression at 30 °C but stimulatesin transthe formation of pili at 42 °C to give rise to untypical sensitivity to ϕM at 42 °C in addition to 30 °C. Other subfragments reveal vital interferences with IncM plasmid‐harbouring host cells.The putative nature of the cloned determinants interfering with the normal expression of IncM p

ISSN:0233-111X    

DOI:10.1002/jobm.3620340206

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

摘要:

AbstractIt is known that two gluconokinases are inducibly expressed during the utilization of gluconate byE. coli. One is thermoresistant (activity stable for 3 h at 30 °C) and the other thermosensitive (losses 75% or more of its activity under the above conditions). The thermoresistant gluconokinase (EC 2.7.1.12) was isolated, purified and characterized for the first time from theE. colimutant Ca26, a K12 derivative which lacks the thermosensitive activity. The enzyme was purified 43 fold with a recovery of 11%. TheMrof the enzyme was 100 kDa with three equal subunits of approximately 29.5 kDa. The enzyme exhibited Michaelis‐Menten kinetics and theKmvalues for gluconate and ATP were 0.02 mM and 0.045 mM respective

ISSN:0233-111X    

DOI:10.1002/jobm.3620340207

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

摘要:

AbstractBiodegradation of phloroglucinol (1,3,5‐trihydroxybenzene) and other polyphenolic compounds by microbes may occur by aerobic and anaerobic metabolic pathways. Aerobic microbes may initiate the mineralization of phloroglucinol or other polyphenolics by either a reductive pathway, epoxide formation, or a specific hydroxylating mechanism. Cleavage of the various intermediates of phloroglucinol and polyphenolic degradation may occur by intradiol and extradiol mechanisms. The reductive pathway in contrast to other mechanisms utilized by aerobic microbes, seems both cumbersome and energy wasteful. The degradation of lignin and its associated phenolics follows an enzymatic combustion process which resembles a nonspecific enzyme‐catalyzed burning. Anaerobic mineralization of phloroglucinol and its associated polyphenolics by several microbes seems to favour the reductive formation of a dihydrophloroglucinol (1,3‐dioxo‐5‐hydroxycyclohexane), which is cleaved by a specific hydrolase. Mineralization of numerous other polyphenolic compounds by anaerobes seems to utilize phloroglucinol as a central m

ISSN:0233-111X    

DOI:10.1002/jobm.3620340208

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY

ISSN:0233-111X    

DOI:10.1002/jobm.3620340201

出版商:Wiley‐VCH    

年代:1994

数据来源: WILEY