bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of the steroid 1‐dehydrogenase in Rhodococcus erythropolis IMET 7030 by immunoelectron microscopy
Authors: Wagner B. , Atrat P. G. , Clark‐Curtiss J. E. , Wagner M.
Published: February 2007

The steroid 1‐dehydrogenase of Rhodococcus erythropolis IMET 7030, an active steroid‐transforming strain, was localized by immunogold labelling both in cells induced with 17‐alpha‐methyl‐testosterone and in noninduced cells. The labelling intensity was much higher in induced cells than in noninduced cells, indicating increased enzyme production in the case of induction.

Using the postembedding procedure, the main portion of the enzyme was found in the peripheral region of the cytoplasm. A considerable amount was bound in clusters to the inner side of the cytoplasmic membrane. The enzyme was also detected in channels connecting the cytoplasm with the cell surface.

By means of the preembedding labelling, a few gold clusters could be detected on the cell surface. The significance of this observation was discussed.
Invasion of wood by basidiomycetous fungi VI. Quantitative but not qualitative differences in the pathovirulence of pathogenic and saprophytic decay fungi
Authors: Gramss G.
Published: February 2007

Wood dowels sterilely overgrown with test mycelia of pathogenic and saprophytic basidiomycetous wood‐decay fungi, respectively, were inserted into drill holes in the stems of 3 hardwood (Fagus sylvatica, Betula verrucosa, Sorbus aucuparia) and 1 softwood tree species (Picea abies). The host trees 40‐120 mm in diameter were part of the light‐starved understory of a timber forest. Eighteen to 52 months after inoculation the trees were dissected and the colonized stemwood was microbio‐logically examined. Extension growth and survival of the test mycelia in trees of known vitality were taken as a basis for fungal pathovirulence rating. Basidiomycetous wood‐decay fungi reach at best the status of physiologically facultative pathogens. They only colonized trees of the lowest vitality classes in the understory. For the expected range of pathovirulence, an appropriate host tree to be chosen had a proper range of vitality which expressed itself in a crown volume of 5 to 70% that of the crown of a free‐standing tree and a width of the current annual growth ring from 0.5 to 2.5 mm in dependence of the tree species. Increasingly moribund trees with low crown volumes and narrow growth rings favoured an unlimited mycelial expansion and survival, while in vital trees fungal expansion gradually came to a standstill within 18 to 52 months, frequently combined with an active killing of both the pathogenic and saprophytic mycelia. Development of pathogenic test mycelia much more depended on the choice of an appropriate host tree species than did development of saprophytic test mycelia. The stem colonization by several late saprophytes was nearly as extensive and durable as the stem colonization by notorious tree pathogens. Pathosism in wood‐decay basidiomycetes appeared thus to be a quantitative rather than a qualitative feature. For the dieback of the basidiomycetous test mycelia in the live stem reasons such as wood substrate depletion or antagonistic microbial activities could be excluded. The dieback rate of the test mycelia however was clearly enhanced in trees of increasing vitality, and it was enhanced with prolonged host‐fungus interaction times. In comparison with sound dominant trees, the endophyte incidence in the sapwood of moribund P. abies trees was not increased. At the instant of tree death or crown decapitation however a severe colonization with blue stain and soft rot fungi was observed that exerted considerable antagonism on test mycelia low in kratovirulence. The implication of this antagonistic action for the colonization of dying trees by pathogenic decay fungi are discussed.
Application of newly synthesized detergents in the side chain degradation of plant sterols by Mycobacterium fortuitum
Authors: Atrat P. G. , Koch B. , Szekalla B. , Hörhold‐Schubert C.
Published: February 2007

Newly synthesized detergents of polyoxyethylene polyoxypropylene co‐polymers (o‐EOPO), polyoxyethylene polyoxypropylene adducts of the diethylene triamine (DETA‐EOPO), and steroidal detergents (SDD) stimulate significantly side chain degradation of plant sterols referring to both the sterol degradation and the formation of the product, 9α‐hydroxy‐androsta‐4‐ene‐3,17‐dione (9 OH‐AD), by Mycobacterium fortuitum NRRL‐B‐8119. Highest stimulative effects were observed with derivatives of the DETA‐EOPO group. Using compounds of the Co‐EOPO group optimal sterol transformation rates were found for polymers with a polyoxypropylene domain of 1400–2000 in molecular weight and with a polyoxyethylene content of 20–50%. Mostly efficient steroidal detergents tested were the 4‐cholesten‐3‐(O‐carboxymethyl)‐oxime and the amino acid adducts of sterol‐3β‐chlorocarbonates.

Detergents were favourably applied as pre‐formed sterol‐detergent complexes (9:1/w:w) in submers fermentation procedures. By treating harvested resting cells of M. fortuitum with derivatives of Co‐EOPO or DETA‐EOPO a considerable activation of the cells takes place concerning the sterol degradation and the formation of 9 OH‐AD at a high yield in subsequent transformation process on buffer.

In solubilization experiments we revealed that there is no correlation between the detergent mediated solubilization of the hydrophobic sterol substrate in the aqueous medium and the transformation activity of the bacterial cells.

The detergents are assumed to interact with a multicomponent mesophase (FMCM) which is placed between cells and sterol surface and mediates the transport.
Effect of cosubstrates on the dechlorination of selected chlorophenolic compounds by Rhodococcus erythropolis 1CP
Authors: Gorlatov S. N. , Golovleva L. A.
Published: February 2007

Effects of aromatic and nonaromatic cosubstrates on the rate of 2,4‐dichlorophenol degradation by R. erythropolis 1CP were studied under growth and nongrowth conditions. Glucose and maltose were found to accelerate 2,4‐dichlorophenol (initial conc. 50 mg/l) dechlorination from 11 days to 24 and 20 h, respectively. The stimulating effect was observed within the range of glucose concentration of 0.5 – 2.0 g/l in the medium. Ascorbic acid at a concentration of 10–70 mg/l as a nongrowth substrate also increased the decomposition of 2,4‐dichlorophenol, though at a lower degree than glucose. Experiments with washed cells showed the limiting stage of chlorophenol degradation by R. erythropolis 1CP to be, possibly, aromatic ring dechlorination after its hydroxylation. As an additional source of electrons, glucose introduced into suspensions of washed cells grown on 3‐hydroxybenzoate made it possible to eliminate the bottleneck in 2,4‐dichlorophenol metabolism by significantly accelerating dechlorination of 3,5‐dichlorocatechol. Based on the experimental and literature data, the enzyme systems involved in 2,4‐dichlorophenol degradation by the culture R. erythropolis 1CP are assumed to be nonspecific.
Neighbour restoration: A possible explanation for some “broken” survival curves of UV‐irradiated Escherichia coli K12 cells
Authors: Bernardo‐Filho M. , Leitao A. C. , Alcantara‐Gomes R.
Published: February 2007

Survival curves for UV irradiation of five non‐filamenting strains of E. coli K12 decrease exponentially at moderate levels of radiation but are broken at high levels of radiation. That is, it appears a change in the slope of survival curves, featuring a tail.

As this phenomenon was observed with strains bearing uvrA and recA mutations it must be independent of the products of these genes.

Experiments with isolated surviving colonies and synchronized cultures eliminated genetic and phenotypic heterogeneity as reasons for the tails in the survival curves.

UV survival increased 10‐ to 15‐fold when UV‐irradiated cells were plated either with cells unable to grow in the plating medium or with bacterial cell‐free extracts.

We suggest that factors related to the high cell densities used to obtain survival curves at high radiation levels (neighbour restoration) could be responsible for the survival increases, generating the tailed survival curves.
Immunoelectronmicroscopic study of the nucleoid structure of hydrogen bacteria
Authors: Mogilnaya Olga A. , Kiselyova Elena V. , Medvedeva Svetlana E. , Puzir Alexey P. , Guseynov Oleg A. , Kulyba Natalia N. , Kozlov A. V.
Published: February 2007

Electron microscopical studies of the nucleoid structure of hydrogen bacteria using ultrahin sections and spread DNA from bacterial cell lysates revealed a different DNA packaging in the cell. A compact state of the major part of DNA at all growth stages and stability of nucleosome‐like structures were shown. The use of antibodies to HU protein of E. coli labelled by protein A‐colloidal gold demonstrated the immunological relationship between HU protein of E. coli and histone‐like proteins of Alcaligenes eutrophus and their possible role in the nucleosome‐like DNA packaging in procariotic genome.
Coagulation autolysis in microorganisms and its relation to coagulase production
Authors: Zaslavskaya P. L. , Chekalina I. V. , Nys P. S. , Bartoshevich Yu. E.
Published: February 2007

The phenomenon of coagulation autolysis was observed in two model microorganisms, i.e., a bacterial culture and an imperfect fungus. It was characterized by impairment of the cell membranes, followed by condensation and dehydration of the cytoplasm and long‐term preservation of the cells in the form of coagulated cytoplasm. In this respect, it was similar to coagulation necrosis of human tissues. The autolysis in the microorganisms was accompanied by increase of their coagulase activity, the substrate specificity of the enzyme rather broad. The coagulase activity of the microorganisms was detected during the culture period between the lag‐phase and the exponential growth phase, i.e., the phase of their active growth. It served as a signal to induce biosynthesis of peptidohydrolase and cleavage of proteins. We believe that the phenomenon of coagulation autolysis in these microorganisms is rather typical and can be considered as an adaptative reaction, inducing a cascade of events from synthesis of coagulase to overproduction of peptidohydrolases with proteolytic activity.
Morpho‐physiologic characteristics of Escherichia coli and Shigella flexneri 2a carrying the htpR15 gene
Authors: Tetz Victor V. , Rybalchenko Oksana V. , Savkova Galina A.
Published: February 2007

Electron microscopic examination of the morphology of normal Escherichia coli MC4100 and Shigella flexneri cells and their htpR‐defective recombinants has shown the presence in the latter of noncrystalline granules after growth at 37 °C. The defect of the htpR gene leads to some changes in ultrastructure of bacterial colonies and the intensification of the processes of development and aging of colonies as integral structures. These phenomena are manifested by early formation of intercellular contacts and thick surface films as well as the enhanced destruction of microorganisms. The recombinant Shigella strain grown at 30 °C retained its ability to provoke keratoconjunctivitis.
Cellulase from Humicola spp.
Authors: Ali Md. Showkat , Akhand Anwarul Azim , Gomez Paul Fabrian , Sarker Rafiqul Islam
Published: February 2007

The newly isolated Humicola strain secreted cellulases in the culture medium supplemented with 1% water hyacinth as carbon source. Of the nitrogen sources investigated, ammonium sulphate (0.5%) and yeast extract (4%) produced the highest amount of the enzyme complex. Maximal cellulases were synthesized at pH 6.0 and temperature 35 °C. The culture filtrate from this organism was used to study the saccharification of lignocellulosic wastes and adsorption onto avicel. About 48% saccharification was achieved with rice straw after a period of 24 h hydrolysis. The endoglucanase in the culture filtrate was adsorbed onto avicel to the extent of 13%.
Different factors affecting growth and amylase production by fungi inhabiting poultry feeds
Authors: Mahmoud A.‐L. E.
Published: February 2007

Extracellular amylase synthesis by Aspergillus flavus and A. fumigatus, isolated from poultry feeds, was studied in stationary liquid medium. Maximum mycelium and extracellular amylase were produced after 7 days of incubation at 30 °C and after 5 days at 35 °C by A. flavus and A. fumigatus, respectively. Optimal amylase yield was obtained at pH 8 and 6 by the two fungi, respectively. Amylase production did not depend on the presence of starch in the growth medium but its inclusion in the medium enhanced amylase production by A. fumigatus. Sucrose appeared to be a poor carbon source for amylase synthesis by the test fungi. Growth on varying nitrogen sources showed that glycine promoted amylase production by A. flavus while yeast extract achieved maximum enzymatic yield by A. fumigatus.
Production of cell wall‐degrading enzymes by three isolates of Aspergillus niger under different cultivation conditions
Authors: Mehta A. , Chopra S. , Mehta P.
Published: February 2007

Three strongly pathogenic isolates of Aspergillus niger were capable of producing pectolytic, cellulolytic and proteolytic enzyme activities in various culture media, extracellularly, indicating the positive correlation between in vitro enzyme production and virulence of the pathogens.
Dodecylguanidine monoacetate (dodine) causes severe membrane damage in Pseudomonas syringae above the critical micelle concentration
Authors: Cabral João P. S.
Published: February 2007

The release of K + from Pseudomonas syringae cells treated with dodecylguanidine monoacetate (dodine) was followed with a K+‐selective glass electrode. Treatment of the cells with 5–15 μmol/1 dodine resulted in low levels of K+ release, but higher surfactant concentrations caused extensive and rapid K+ efflux. Dodine concentrations that caused high K+ release also induced significant leakage of inorganic phosphate. The addition of 5–10 μmol/1 dodine also caused an increase in the rate of oxygen consumption in the presence of glycerol or succinate, but an increase in concentration from 10 to 40 μmol/1 resulted in a concomitant decrease in O2 consumption. The results from this and previous work suggest that dodine inhibits respiration firstly by causing drainage of coenzymes, and then by a direct interaction with the components of the respiratory chain.

Previous work showed that above 25 μmol/1, dodine molecules aggregate to form micelles. The results therefore suggests that, in contrast with other cationic amphiphiles, the micellar form of dodine is more damaging to the cytoplasmic membrane than the free molecules.
The formation of N‐acetyl‐β‐D‐hexosaminidase is repressed by glucose in Penicillium chrysogenum
Authors: Pócsi István , Pusztahelyi Tünde , Bogáti Magdolna sz. , Szentirmai Attila
Published: February 2007

The formation of N‐acetyl‐β‐D‐hexosaminidase is under carbon catabolite repression in growing Penicillium chrysogenum. The enzyme accumulates inside the cells during the stationary phase of growth and is released into the culture fluid when the cell‐wall lysis has started and progressed. The time‐course of enzyme formation strongly supports the suggestion that fungal N‐acetyl‐β‐D‐hexosaminidase may have a role in the degradation of intermediate cell‐wall breakdown products during starvation. Regarding that analogous enzymes from other fungi have been shown to be able to liberate GlcNAc monomers from different glycoproteins and glycopeptides a possible participation in the orderly destruction of cellular glycoprotein components cannot be excluded. The physical and enzyme kinetic properties of both intracellular and extracellular N‐acetyl‐β‐D‐hexosaminidase are essentially the same indicating that the enzyme is probably released into the culture fluid without modification.
Periplasmic aminopeptidases in Acinetobacter calcoaceticus and Pseudomonas aeruginosa
Authors: Fricke Beate , Aurich Harald
Published: February 2007

The greater part of the intracellular aminopeptidases in Pseudomonas aeruginosa and Acinetobacter calcoaceticus is soluble. The localization of aminopeptidases in the cells was examined using the osmotic shock method with some modifications. When the cells of A. calcoaceticus and P. aeruginosa of the logarithmic phase were subjected to an osmotic shock, all aminopeptidases investigated were mainly localized in the sucrose supernatants and in the periplasm. Acid phosphatase as marker enzyme for periplasm showed a similar distribution between the fractions as the aminopeptidases.

The periplasmic aminopeptidases of both microorganisms were separated by FPLC on Superose 12 and their molecular masses were determined. The results obtained show that at least four different aminopeptidases occur in the periplasm, a leucyl aminopeptidase (LAP, cleaving Leu‐NH‐NH2. 400 kDa), a glutamyl aminopeptidase (GAP, 200 kDa), an alanyl aminopeptidase (AAP, 80 kDa) and a prolyl aminopeptidase (PAP, 65 kDa). The results are in agreement for both species.

Our results show clearly that aminopeptidases of these typical members of Gram‐negative bacteria are mainly periplasmic like degrading enzymes (alkaline and acid phosphatases, 5′‐nucleotidase, cyclic phosphodiesterase), detoxifying enzymes and binding proteins for amino acids and sugars.
Numerical taxonomy of Monascus species based on the electrophoretic analysis of intracellular enzymes
Authors: Nishikawa Jiro , Iizuka Hiroshi
Published: February 2007

Four isozymes in fifteeen species of Monascus were analyzed using polyacrylamide gel electrophoresis. A numerical analysis was carried out on the basis of similarity values obtained from the electrophoretic mobilities of the enzymes. Non‐specific esterase and lactate dehydrogenase showed clearly distinguishable mobilities amont two clusters. From these results obtained, the strains used were divided into two clusters of Group‐I and Group‐II. Both groups were further subdivided into two subclusters. The type strain, M. ruber VAN TIEGHEM MR MO‐10 (IAM 8009) and M. kaoliang MR MO‐F2 were found to belong to the Group‐I. M. pilosus SATO MR MO‐4 (IAM8003) and M. pubigerus SATO MR MO‐8 (IAM 8004) were found to belong to the Group‐II. Nearly 100% similarity values were found between M. anka SATO MR MO‐6 (IAM 8001) and M. rubiginosus SATO IFO 4484, between M. anka var. rubellus SATO MR MO‐5 (IAM 8081) and M. purpureus WENT MR MO‐9 (IAM 8010), and, moreover, among M. vitreus SATO MR MO‐3 (IAM 8007), M. fuliginosus SATO IFO 4483 and M. serorubescens SATO 4487, respectively.

Therefore, it was concluded that electrophoretic analysis of enzymes may be useful in presenting a new classification system of Monascus spp.
Occurrence of antimicrobial activities of bacteria from soybean leaf spots
Authors: Völksch B. , Ullrich M. , Fritsche W.
Published: February 2007

Bacteria were isolated from leaf spots of field grown soybeans during two growing seasons. The leaf spots yielded up to 4 different species and a total population size of about 107–108 bacteria/cm2. The majority of the 192 isolates belonged to the species Pseudomonas syringae pv. glycinea (55%), causing leaf spots of bacterial blight on soybeans, and Erwinia herbicola (22%). The remaining isolates included bacteria from other genera, but occurred occasionally.

The determination of biological activity of the isolates demonstrated that a high percentage of strains from the group Erwinia/Enterobacter produced biological active substances against Escherichia coli (69%) and against Chlorella pyrenoidosa (88%). The majority of P. syringae pv. glycinea strains failed to do so. None of the isolates affected the growth of Geotrichum candidum. The E. herbicola strains showed clear antagonistic properties against a wide range of isolated bacteria. Four E. herbicola strains inhibited the growth of nearly all other E. herbicola isolates and 6 other strains were active against most of the P. syringae pv. glycinea isolates. However, antagonistic interactions among strains isolated from a distinct leaf spot were very rarely.
Isolation and characterization of the thermoresistant gluconokinase from Escherichia coli
Authors: Vivas Eugenio I. , Liendo Andreina , Dawidowicz Karl , Istúriz Tomás
Published: February 2007

It is known that two gluconokinases are inducibly expressed during the utilization of gluconate by E. 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 the E. coli mutant Ca26, a K12 derivative which lacks the thermosensitive activity. The enzyme was purified 43 fold with a recovery of 11%. The Mr of the enzyme was 100 kDa with three equal subunits of approximately 29.5 kDa. The enzyme exhibited Michaelis‐Menten kinetics and the Km values for gluconate and ATP were 0.02 mM and 0.045 mM respectively.
Optimization of alkaline amylase production by thermophilic Bacillus stearothermophilus AN 002
Authors: Bezbaruah R. L. , Gogoi B. K. , Pillai K. R.
Published: February 2007

Bacillus stearothermophilus AN 002 secreted thermostable alkaline amylase into a liquid growth medium containing 2 g/l starch. Amylase activity was highest at early stationary phase of growth. Among the various carbohydrates tested maximum amylase production was obtained with starch. When starch was replaced by other carbon sources, amylase production was reduced. Peptone and corn steep liquor (CSL) were the ideal nitrogen sources for amylase production by this strain. Of the phosphate sources tested, (NH4)2HPO4 showed best restults. Amylase production was highest in a laboratory fermenter at a initial pH of 6.5 and at a constant pH of 7.0. The optimum aeration and agitation for amylase production were 0.66 v/v/m and 400 rev/min, respectively. Maximum growth was obtained at 55 °C and maximum amylase was produced at 50 °C. The amylase was found to be stable between pH 6.0 to 11.0.
Growth response of the cyanobacterium Microcystis aeruginosa to herbicides and pesticides
Authors: Swain N. , Rath B. , Adhikary S. P.
Published: February 2007

Growth response of the planktonic cyanobacterium Microcystis aeruginosa to various concentrations of the herbicides and pesticides viz. CuSO4, DCMU (analytical grade Diuron), Karmex (commercial grade Diuron), 2,4‐D, Fernoxone, BHC and bleaching powder (CCH) was studied in laboratory culture. The organism was sensitive to very low concentrations of CuSO4, DCMU and Karmex. Lethal concentration of Karmex and CuSO4 were found to be 0.1 μg · ml−1 and 5.0 μg · ml−1 respectively. The cyanobacterium could tolerate the other chemicals tested up to a concentration of over 500 μg · ml−1. On culturing the organism in the CuSO4 containing media, toxic effect of the chemical was reduced to a significant extent. This indicated that CuSO4 was accumulated or detoxified in the Microcystis cells. Toxic effect of Karmex on the organism was not reduced under similar experimental conditions.
A method for screening diacetyl and acetoin‐producing bacteria on agar plates
Authors: Phalip V. , Schmitt P. , Diviès C.
Published: February 2007

A simple method for screening bacteria for diacetyl and acetoin production was developed. This method is based on the ability of diacetyl and acetoin to form a red insoluble complex with α‐naphthol in the presence of creatine. Addition of carboxymethyl‐cellulose containing calcium citrate in the medium allowed discrimination between citrate utilizing and non‐utilizing bacteria.
Radiation sensitivities of Acinetobacter strains isolated from clinical sources
Authors: Nishimura Yukimasa , Uchida Kazuyuki , Tanaka Kunio , Ino Takeshi , Ito Hitoshi
Published: February 2007

For twelve clinical strains genetically grouped together with Acnetinobacter radioresistens FO‐1T, the radiation sensitivity was measured. Their D10 values in γ‐ray irradiation under N2‐equilibrium were 0.24 to 0.93 kGy and about 1/10 to 1/3 of that of the radiation‐resistant strain FO‐1. The results showed that the genospecies A. radioresistens contained some radiation‐sensitive strains.
Inhibition of nitrite reductase and urease by arginine and proline in the cyanobacterium Anabaena cycadeae
Authors: Singh Surendra , Bisen P. S.
Published: February 2007

The arginine and proline inhibition of nitrite reductase and urease activities have been studied in the cyanobacterium Anabaena cycadeae and its mutant strain lacking glutamine synthetase (GS)1) activity. Arginine and proline inhibited the nitrite reductase and urease activities in the parent strain, however, they could not do so in the mutant strain. The level of arginine‐ and proline‐dependent NH production in the outer medium was several fold higher in the mutant strain as compared to its parent strain. These results suggest that (1) nitrite reductase and urease activities are arginine‐ and proline‐repressible; (2) the catalytic function of GS is necessarily required for the arginine and proline inhibition of nitrite reductase and urease systems; and (3) the NH resulting from the catabolism of arginine and proline should be metabolized via GS for repression of nitrite reductase and urease to occur.
Transformation reactions of progesterone by different species of Streptomyces
Authors: Atta F. M. , Zohri A. A.
Published: February 2007

A systematic study of transformation reactions of the genus Streptomyces with respect to the progesterone molecule was undertaken. The types of transformation reactions by different Streptomyces species 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 ‐ 2 position; (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 of Streptomyces classification, the transformation reaction of progesterone fulfil all the requirements of taxonomic feature of Streptomyces. These appear to be specific properties and common to all the strains of individual Streptomyces species tested.
Effect of salts on the activity of nitrate reductase from the photosynthetic bacterium Rhodobacter sphaeroides SW
Authors: Paggi Roberto A. , De Castro Rosana E. , Kerber Norma L. , Garcia Augusto F.
Published: February 2007

The effect of different salts on the nitrate reductase (NR) activity of Rhodobacter sphaeroides SW was studied. An increase of the activity in the presence of monovalent cations was observed (90, 80 and 77% with Na+, K+ and NH, 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 > 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 of R. sphaeroides SW can be atributed to both electrostatic and hydrophobic interactions.
Seasonal fluctuations of aquatic fungi recovered from Egyptian soil (Delta Region)
Authors: Khallil A. M. , El‐Hissy Farida T. , Ali E. H.
Published: February 2007

One hundred and eleven identified and seven unidentified species in addition to 5 varieties belonging to forty‐three aquatic fungal genera were recovered from 452 soil samples collected randomly from different localities in Nile Delta and Suez canal regions including eleven governorates. The investigated soil samples were collected seasonally during the period from autumn 1990 to summer 1991 (113 samples each season). The richest season (85 identified and 5 unidentified species in addition to 2 varieties) in aquatic fungi was the winter season (10.0‐15.5°C) whereas the poorest (32 identified and 5 unidentified species in addition to one variety) was summer (24.0‐27.5°C). The richest soil samples in aquatic fungi were those of low or moderate temperature seasons, high contents of organic matter and considerably poor in total soluble salts. The pH value did not show any regular seasonal variation and did not exhibit any considerable influence on fungal populations. Some aquatic fungal genera and species were disappeared completely in certain seasons and vice versa.

The most dominant aquatic fungal genera were Pythium, Allomyces, Aqualinderella and Nowa‐kowskiella. The commonest aquatic fungal species were Allomyces anomalus, Aqualinderella fermentans, Nowakowskiella elegans, Blastocladiopsis parva and Dictyuchus sterilis.
Effect of acetic acid on xylose fermentation to xylitol by Candida guilliermondii
Authors: Felipe Maria G. A. , Vieira Délia C. , Vitolo Michele , Silva Silvio S. , Roberto Ines C. , Manchilha Ismael M.
Published: February 2007

The effect of acetic acid concentration on xylose fermentation to xylitol by Candida guilliermondii FTI 20037 was evaluated in semisynthetic medium containing different concentrations of the acid. Increasing acetic acid concentration up to 1.0 g/1 favored xylitol yield and productivity, with maximum values of 0.82 g/g and 0.57 g/.h1, respectively. The presence of acetic acid reduced cell production at all concentration. Furthermore, acetic acid was assimilated by the yeast together with the sugars and was depleted from the medium at concentrations of less than 3.0 g/1. The ability of this yeast to assimilate acetic acid suggests that these cells act as agents of medium detoxification. This behavior may lead to a viable microbiological process of xylitol production by C. guilliermondii FTI 20037 using xylose‐rich lignocel‐lulosic hydrolysates in which acetic acid is commonly present, causing inhibition of fermentative activity.
Improved contrast by a simplified post‐staining procedure for ultrathin sections of resin‐embedded bacterial cells: Application of ruthenium red
Authors: Vogt Beate , Berker Ruth , Mayer Frank
Published: February 2007

High contrast can be obtained in ultrathin sections of bacterial cells embedded in the low‐temperature resin Lowieryl by post‐staining of the sections on an aqueous ruthenium red solution. Post‐staining with lead citrate can be omitted. Combination with post‐staining with uranyl acetate results in further improvement of contrast. This is shown for Gram‐positive, Gram‐negative, and methanogenic bacteria. Improved visibility is demonstrated for wall layers including slime and capsule, cytoplasmic membrane, nucleoid, envelope of PHB inclusion bodies, polyphosphate, and intracellular defective bacteriophages. The procedure is suited as post‐staining for immunocytochemical analyses.
The effects of culture media on the production of xyIan‐degrading enzymes by Streptomyces chattanoogensis UAH 23
Authors: Fernández C. L. López , Rodríguez J. , Soliveri J. , Copa‐Patiño J. L. , Pérez‐Leblic M. I. , Arias M. E.
Published: February 2007

The production of 4 extracellular xylanolytic enzymes, arabinofuranosidase, endoxylanase, β‐xylosidase and acetyl esterase during the growth of Streptomyces chattanoogensis UAH 23 in basal salts media containing different carbon sources was examined. The highest enzyme activities were generally detected when arabinoxylan was used as the carbon source, with the exception of acetyl‐esterase where greatest activity was detected when ball‐milled straw was used as carbon source. A comparison of enzyme activities revealed that the specific activity of endoxylanase (3.15 U/mg protein) was greater than those of the other three enzyme activities (44.11,5.77 and 2.04 mU/mg protein for acetyl‐esterase, a‐L‐arabinofuranosidase and β‐xylosidase, respectively). Cellulase activity could not be detected throughout the study

Characterization of the endoxylanase activity revealed that two optima pH could be detected (7.0 and 8.0) and was stable at alkaline pH values between 6.5 and 8.5. The optimum temperature was 55°C with the enzyme stable for one hour at 60°C. Activity staining of non denatured polyacrylamide gels containing culture supernatants revealed the presence of two active endoxylanase bands. The result suggest that two endoxylanase enzymes with different pH optimas are secreted by Streptomyces chattanoogensis UAH 23.
Microbial transformation of isoprenoid systems by means of fungi of Zoophthora genus — Microbial transformation of compounds with α‐campholenic system by means of fungus Zoophthora (Neopandora) sp.
Authors: Zabża Andrzej , Greb‐Markiewicz Beata , Sodano Guido , De Riccardis Francesco
Published: February 2007

Unsaturated ketones (4 and 10) and epoxides (2–3 and 8–9) were the main products of biotransformation performed by means of Zoophthora (Neopandora) phyllobii. Enantiospecificity of both reactions leading to these compounds strongly depends on the distance of reacting fragment of molecule from the chiral center at C‐1′.
Effect of medium components and metabolic inhibitors on β‐galactosidase production and secretion by Penicillium notatum 1
Authors: Fiedurek J. , Gromada A. , Jamroz J.
Published: February 2007

Factors affecting the β‐galactosidase production by Penicillium notatum 1 were studied using fermentation media of different chemical composition. The medium containing lactose, salts, peptone and yeast extract with intitial pH 2.5 was selected as the best for enzyme production. Monobasic ammonium phosphate (0.9%) was found to be the best inorganic nitrogen source for lactase production. Various extraction media and metabolic inhibitors were examined for effective releasing of β‐galactosidase from the fungal cells. Using a simple method of mycelium extraction with 0.1 Triton X‐100, it was possible to obtain about 4‐fold higher amounts of enzyme in the cell free extracts, than those excreted into the post‐culture liquid.
Biological and molecular characterisation of potential biocontrol strains of Trichoderma
Authors: Turóczi György , Fekete Csaba , Kerényi Zoltán , Nagy Richárd , Pomázi Andrea , Hornok László
Published: February 2007

Thirty‐four strains of seven species of Trichoderma isolated from various fungal sources were compared for direct mycoparasitic activity (MPA), chitinase production and antibiotic activity (ANA) in order to choose the most appropriate partners for a strain‐breeding programme. Within species genetic differences were also assesses in T. hamatum, T. harzianum and T. viride by means of random amplification of polymorphic DNA (RAPD). Endochitinase activities of the Trichoderma strains ranged between 20.4 and 1264.5 units/g dry weight of mycelium. The correlation between MPA and chitinase activity was not unambiguous and no correlation existed between MPA and ANA. The RAPD patterns of T. viride strains were highly variable, while isolates of T. harzianum proved to be more uniform; T. hamatum revealed remarkable intraspecific divergence. All these three comprised certain pairs of strains that are promising participants of a strain‐improving programme, since their strong genetic affinities offer good changes for combining their contrasted biocontrol traits.
Bacillus subtilis α‐amylase, lichenase, β‐mannanase and xylanase: Screening for their induction by agro‐industrial byproducts and precipitation by organic solvents
Authors: El‐Helow Ehab R. , El‐Gazaerly Magda A.
Published: February 2007

Current research focuses on the utilization of low value agro‐industrial byproducts for targeting B. subtilis towards different exoenyzeme lines. This includes α‐amylase, β‐mannanase, xylanase, and lichenase. As an orientation step, growth and α‐amylase activity were monitored in three different nutritional media. A medium which showed low levels of catabolite repression and spore development was selected as a basal fermentation medium. Different patterns of exoenzyme induction were obtained when beet pulp, corn cob, rice husk, wheat bran, and wheat straw were separately used to partially replace the nutrient contents of the selected medium. α‐Amylase and lichenase were maximally expressed in the presence of corn cob or beet pulp. On the other hand, considerable levels of the four polysaccharide hydrolyzing enzymes were induced by wheat bran. β‐mannanase and xylanase expression responded more significantly towards inducers than α‐amylase and lichenase. The effects of five different organic solvents as precipitative agents on these exoenzymes were also studied.
Characterization and chillproofing activity of two enzymes from Streptomyces species
Authors: Etok C. A. , Eka O. U.
Published: February 2007

Two enzymes, amylase and protease of Streptomyces species were purified by a combination of ion exchange chromatography and gel filtration and characterized. The amylase had an exoaction on starch yielding maltose as a major end product and was identified as β‐amylase. The purified amylase had a molecular weight of 48,000 and was maximally active at 35 °C and at pH 6.0. On the other hand, protease had a molecular weight of 21,000 and was most active at pH 10.0 and at a temperature of 30 °C. The Km or MICHAELIS constant of amylase for maize starch was 0.333 mg/ml while that of protease for casein was 2.5 mg/ml. The feasibility of using the purified protease for various industrial application especially in the chillproofing of beer is discussed.
Investigations on the cell volumes of Azotobacter vinelandii by scanning electron microscopy
Authors: Efuet Ekem T. , Pulakat Lakshmidevi , Gavini Narasaiah
Published: February 2007

Previous experiments by other investigators on the DNA content of Azotobacter vinelandii have demonstrated that the DNA content in these cells is several folds higher than that of E. coli. On the basis of this observation, it was hypothesized that A. vinelandii has at least 40 to 80 identical chromosomes per cell. However, the gene dosage analysis in A. vinelandii cells suggested that many genetic operations can be performed in these cells without the constraints expected in a polyploid bacterium. In an attempt to explain this apparent discrepancy, we have done systematic analysis of the relationship between the DNA content and the cell volume of this bacterium. Since a linear correlation is observed between the DNA content and the cell size in many other cell types, we hypothesized that if A. vinelandii is polyploid in nature, it should have a much larger cell volume to accommodate such a large amount of DNA. Our scanning electron microscopic analysis revealed that the cell volume of the vegetative cells of A. vinelandii is about 16 times larger than the cell volume of E. coli. This result is apparently consistent with the concept that the A. vinelandii is a polyploid bacterium. It was also reported that the encysted cells of A. vinelandii contain about 25% of the DNA content of the vegetative cells. This would mean that an encysted cell of A. vinelandii could contain about 10 copies of its chromosome. Since the estimated molecular weight of A. vinelandii chromosome is very similar to that of E. coli chromosome, the DNA content of the encysted cells also should be about 10 times higher than that of E. coli cells. If we assume that the relationship between the DNA content and the cell size is linear, then the encysted cells should have a cell volume larger than that of E. coli and smaller than that of the vegetative cells of A. vinelandii. However our scanning electron microscopic analysis showed that the cell volume of the encysted cells of A. vinelandii is in fact very similar to the cell volume of E. coli.
Properties of lysophospholipase in Mycobacterium leprae
Authors: Prabhakaran K. , Harris E. B. , Randhawa B.
Published: February 2007

Lysophospholipids are key intermediates in the metabolism of phospholipids. Cytoplasmic membranes of both eukaryotes and prokaryotes are made of phospholipid bilayers. Phospholipases are activated during phagocytosis. Lysophospholipids generated by phospholipase A2 or A1 degrade cell membranes and can cause cell lysis. An active lysophospholipase, that hydrolyzes lysophospholipids, was detected by the radioisotope technique in Mycobacterium leprae. About two‐thirds of the enzyme was particulate and one‐third cytoplasmic. Optimum activity was at 37 °C, and at pH 6.0. Temperatures above 70 °C completely inactivated the enzyme. The compound AACOCF3, a trifluromethylketone analog of arachiodonic acid, inhibited the activity; the inhibition appeared to be of the uncompetetive type. The Km of the enzyme was 2.5 × 10−4 M, suggesting a fairly strong affinity for the substrate. Lysophospholipids have been shown to be microbicidal to invading organisms. Possession of lysophospholipase by M. leprae is apparently one of the methods by which the bacilli overcome the defense mechanisms of the host.
Permeability of mycobacterial cell envelopes to sterols: Peptidoglycan as the diffusion barrier
Authors: Lisowska Katarzyna , Korycka Małgorzata , Hadław‐Klimaszewska Olga , Ziółkowski Andrzej , Sedlaczek Leon
Published: February 2007

Vancomycin, an inhibitor of peptidoglycan synthesis, depressed the growth of Mycobacterium sp. NRRL B 3805 and MB 3683, but not the β‐sitosterol side chain degradation and androstane derivatives accumulation. As a result, the specific activity (products formed/cell weight unit × h) increased threefold in the peptidoglycan‐deficient cells, indicating faster crossing of the sterol through the cell water barrier.

Cell wall preparations: crude cell wall (CCW), purified cell wall (PCW), and peptidoglycan — enriched PCW — residue (PEPCW) were obtained and analysed in order to find a relationship between the vancomycin — induced chemical changes and the permeation rate of the sterol.

The amounts of CCW, PCW and PEPCW, produced from 8 g lyophilised control cells were 445, 170 and 28 mg respectively. The respective figures were 176, 61, and 4.8 mg for vancomycin — treated cells. In addition to the lower content of the rigid layer, a distinct shift in the molar ratios of the peptidoglycan constituents: alanine, glutamic, diaminopimelic and muramic acids, and glucosamine was observed under the action of the murein inhibitor. The most significant change was that of muramic acid: diaminopimelic acid molar ratio, the compounds which are markers of glycan strands and tetrapeptides, respectively. In control cells it was approximately 1:1, and increased to 1.34–1.43: 1 in the compared preparation, which indicated a marked decrease in the tetrapeptide moieties crosslinking the main glycan strands. Together with the general lower content of murein, this modification may be responsible for the enhanced sterol permeation through the cell wall.
Regulation of L‐lysine biosynthesis in prototrophic revertants of Corynebacterium glutamicum
Authors: Hilliger Matthias , Hertel Waltraud
Published: February 2007

The regulation pattern of L‐lysine biosynthesis has been investigated in protrophic revertant derived from an initially homoserine‐auxotrophic strain of Corynebacterium glutamicum and, additionally, in antimetabolite‐resitant mutants. The influence of regulatory important amino acids of the aspartate family on growth and L‐lysine biosynthesis and especially on the activity of aspartate kinase was studied. Furthermore the activity of homoserine dehydrogenase in dependence on the growth phase was estimated.

From a total number of ninety nine L‐lysine forming, homoserine‐prototrophic, and S‐(2‐aminoethyl)‐L‐cysteine‐resistant (AEC) strains the best lysine producers were selected by an emerse cultivation assay as a preselection. Strain No. 132 forming 10 g · 1−1 lysine was selected for the derivation of α‐amino‐β‐hydroxyvaleric acid (AHV)‐ and lysine‐resistant strains. From 121 double resistant mutants (hse−rev, AECr, AHVr) sixty two strains (=51.2%) were isolated producing lysine. The best producer, strain 132‐IV‐37, reached 19.8 g · 1−1 after 8 optimization steps of the growth medium in comparison to 9.2 g · 1−1 as the initial value. This higher potential for lysine synthesis in the mutant 132‐IV‐37 could be attributed to changed regulation of the homoserine dehydrogenase and aspartate kinase.

As was shown by the action of threonine or threonine + lysine on the activity of aspartate kinase, a general desensibilization of this key enzyme exists in the mutant strain 132‐IV‐37, but not in the AEC‐resistant parent strain. In addition to isoleucine none of several amino acids tested showed any significant influence on the aspartate kinase. This agrees with the increased lysine formation by this strain in comparison to the parent strain 132.
Location of xylanolytic enzymes in Chaetomium globosum
Authors: Gandhi Jagruti P. , Rao K. Koteshwara
Published: February 2007

Localisation of endo β‐1‐4‐xylan xylanohydrolase and β‐xylosidase was studied in Chaetomium globosum when the fungus was grown on 1% (w/v) birchwood xylan. Although both enzymes are present in the soluble fraction of the cell, xylanase activity was membrane bound whereas β‐xylosidase activity was associated with the cell wall. Xylanase and β‐xylosidase acted synergistically on the xylan backbone with the appearance of xylo‐oligosaccharides, xylobiose and xylose.
Characterization of cellulase complex of Streptomyces albaduncus
Authors: Harchand R. K. , Singh S.
Published: February 2007

Exoglucanase and endoglucanase (glucanases) enzymes of S. albaduncus were found to be very stable, showing only 36% and 8% loss in activities respectively after 3 days of incubation at 50 °C. In contrast, β‐glucosidase was significantly less stable retaining only 22.30% activity after 30 min incubation at 40 °C. The glucanases manifested maximum stability in pH range of 5.5–6.0 whereas β‐glucosidase was completely stable over a broad pH range of 6.5–9.0. Both glucanases were enhanced by some cations whereas β‐glucosidase did not require any cation for activity. Km values for crude exoglucanase, endoglucanase and β‐glucosidase were 40.00 mg/ml, 92.30 mg/ml and 1.714 mM with maximum reaction velocities (Vmax) of 0.606, 33.330 and 0.109 IU/mg of protein, respectively. The enzymes were subject to end‐product inhibition, with exo‐ and endo‐glucanases decreasing by 20% and 70% respectively, in the presence of 0.3% glucose. However, β‐glucosidase showed marked resistance to glucose inhibition, retaining 59% of residual activity even in the presence of 30% glucose in the reaction mixture. This characteristic may be advantageous in the commercial exploitation of enzyme system. An activation of β‐glucosidase at lower concentrations of glucose suggests competitive inhibition.
Chemicals and heat generate different protein patterns in Acinetobacter calcoaceticus
Authors: Benndorf Dirk , Loffhagen Norbert , Babel Wolfgang
Published: February 2007

The effect of exposing Acinetobacter calcoaceticus 69‐V to DNP1‐stress and heat shock was examined by two‐dimensional gel electrophoresis of proteins, which were detected either by autoradiography or by silver staining. Both DNP stress and heat shock led to altered patterns of protein synthesis or concentration. About 10% of the proteins which were synthesized newly or at an increased rate and about 25% of those which were found newly or with an increased concentration after DNP treatment were identified after heat shock, too.