Propagation and Growth Cycle of Rickettsia quintana in a New Liquid Medium

The growth cycle of Rickettsia quintana was studied for the first time in liquid culture. Growth of the microorganism in a transparent broth medium was made possible by the finding that fetal calf serum (FCS), but not calf serum (CS), satisfied the requirement of R. quintana (Fuller strain) for red blood cell lysate. The three constituents of the medium, other than FCS, were autoclavable. The growth cycle was characterized by a lag phase of approximately 24 hr, an exponential growth phase of 72 hr, and a doubling time of approximately 4.5 hr. In FCS medium, titers increased 10(5)-fold over starting titers and reached a peak after 5 days of greater than 10(8) colony-forming-units (CFU)/ml. Optical density readings at 520 nm (OD(520)) served as useful estimates of the titers only during the last 30 hr of exponential growth. Before this time, titers were below 3 x 10(7) CFU/ml and could not be detected at OD(520). The growth-promoting activity of FCS appeared to be a normal serum component widely distributed among fetal calves. FCS from five commercial suppliers supported growth of R. quintana. The active factor(s) was: (i) non-dialyzable, (ii) resistant to heating at 56 C for 30 min, and (iii) partially inactivated at 100 C in 2 min and completely lost at 100 C in 10 min. The results emphasize the presence of erythrocyte and serum factors other than hemoglobin which stimulate the growth of R. quintana.     

Fate of enterohemorrhagic Escherichia coli O157:H7 in apple cider with and without preservatives.

A strain of enterohemorrhagic Escherichia coli serotype O157:H7 isolated from a patient in an apple cider-related outbreak was used to study the fate of E. coli O157:H7 in six different lots of unpasteurized apple cider. In addition, the efficacy of two preservatives, 0.1% sodium benzoate and 0.1% potassium sorbate, used separately and in combination was evaluated for antimicrobial effects on the bacterium. Studies were done at 8 or 25 degrees C with ciders having pH values of 3.6 to 4.0. The results revealed that E. coli O157:H7 populations increased slightly (ca. 1 log10 CFU/ml) and then remained stable for approximately 12 days in lots inoculated with an initial population of 10(5) E. coli O157:H7 organisms per ml and held at 8 degrees C. The bacterium survived from 10 to 31 days or 2 to 3 days at 8 or 25 degrees C, respectively, depending on the lot. Potassium sorbate had minimal effect on E. coli O157:H7 populations, with survivors detected for 15 to 20 days or 1 to 3 days at 8 or 25 degrees C, respectively. In contrast, survivors in cider containing sodium benzoate were detected for only 2 to 10 days or less than 1 to 2 days at 8 or 25 degrees C, respectively. The highest rates of inactivation occurred in the presence of a combination of 0.1% sodium benzoate and 0.1% potassium sorbate. The use of 0.1% sodium benzoate, an approved preservative used by some cider processors, will substantially increase the safety of apple cider in terms of E. coli O157:H7, in addition to suppressing the growth of yeasts and molds.     

Enhancing the antimicrobial effects of bovine lactoferrin against Escherichia coli O157:H7 by cation chelation, NaCl and temperature

AIM: To evaluate the effect of NaCl, growth medium and temperature on the antimicrobial activity of bovine lactoferrin (LF) against Escherichia coli O157:H7 in the presence of different chelating agents. METHODS AND RESULTS: LF (32 mg ml(-1)) was tested against E. coli O157:H7 strain 3081 in Luria broth (LB) and All Purpose Tween (APT) broth with metal ion chelators sodium bicarbonate (SB), sodium lactate (SL), sodium hexametaphosphate (SHMP), ethylene diamine tetraacetic acid (EDTA) or quercetin at 0.5 and 2.5% NaCl at 10 and 37 degrees C. LF and the chelators were tested against four other E. coli O157:H7 strains in LB at 2.5% NaCl and 10 degrees C. LF alone was bacteriostatic against strains 3081 and LCDC 7283 but other strains grew. Antimicrobial effectiveness of LF was reduced in APT broth but enhanced by SB at 2.5% NaCl and 10 degrees C where 4.0 log(10) CFU ml(-1) inoculated cells were killed. EDTA enhanced antimicrobial action of the LF-SB combination. SL alone was effective against E. coli O157:H7 but a reduction in its activity at 2.5% NaCl and 10 degrees C was reversed by LF. The combinations LF-SHMP and LF-quercetin were more effective at 37 degrees C and NaCl effects varied. CONCLUSIONS: LF plus SB or SL were bactericidal toward the same 3/5 E. coli O157:H7 strains and inhibited growth of the others at 2.5% NaCl and 10 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of LF with either SL or SB shows potential for reducing viability of E. coli O157:H7 in food systems containing NaCl at reduced, but growth permissive temperature.     

Purification and properties of heme-deficient hepatic soluble guanylate cyclase: effects of heme and other factors on enzyme activation by NO, NO-heme, and protoporphyrin IX

Purified hepatic soluble guanylate cyclase (EC 4.6.1.2) had maximal specific activities in the unactivated state of 0.4 and 1 μmol cyclic GMP min^?1 mg protein^?1, when MgGTP and MnGTP, respectively, were used as substrates. The apparent K_m for GTP was 85 or 10 μm in the presence of excess Mg²⁺ or Mn²⁺, respectively. Guanylate cyclase purified as described was deficient in heme but could be readily reconstituted with heme by reacting enzyme with hematin and excess dithiothreitol at 4 °C and pH 7.8. Unpurified guanylate cyclase was activated 20- to 84-fold by NO, nitroso compounds, NO-heme, and protoporphyrin IX. The purified enzyme was only slightly (2- to 3-fold) activated by NO and nitroso compounds but was markedly (50-fold) activated by NO-heme and protoporphyrin IX, achieving maximal specific activities of 10 μmol cyclic GMP min^?1 mg protein^?1. Enzyme activation by NO and nitroso compounds was restored by addition of hematin or by reconstitution of guanylate cyclase with heme. Excess hematin, however, inhibited enzyme activity. A partially purified heat-stable factor (activation-enhancing factor) was found to enhance (2- to 35-fold) enzyme activation without directly stimulating guanylate cyclase. In the presence of optimal concentrations of hematin, enzyme activation was still increased (2-fold) by the activation-enhancing factor but not by bovine serum albumin. Guanylate cyclase was markedly inhibited by SH reactive agents such as cystine, o-iodosobenzoic acid, periodate, and 5,5′-dithiobis (2-nitrobenzoic acid). In addition, CN^? and FMN inhibited enzyme activation by NO-heme, but not by protoporphyrin IX, and did not affect basal enzymatic activity. Hepatic soluble guanylate cyclase appears to possess SH groups required for catalysis and to require heme and/or other unknown factors for the full expression of enzyme activation by NO and nitroso compounds.     

Isolation and enumeration of Campylobacter jejuni from poultry products by a selective enrichment method

A direct selective enrichment procedure was developed for the isolation of Campylobacter jejuni from poultry products. The selective enrichment medium (ATB) consisted of (per liter) tryptose (20 g), yeast extract (2.5 g), sodium chloride (5 g), FBP supplement (ferrous sulfate [0.25 g], sodium metabisulfite [0.25 g], sodium pyruvate [0.25 g]), bicine (10 g), and agar (1 g). Hematin solution (6.25 ml; prepared by dissolving 0.032 g of bovine hemin in 10 ml of 0.15 N sodium hydroxide solution and autoclaving at 0.35 kg/cm2 for 30 min), rifampin (25 mg), cefsulodin (6.25 mg), and polymyxin B sulfate (20,000 IU) were added after the medium was sterilized. The pH was adjusted to 8.0. Samples were enriched in the above medium at 42 degrees C for 48 h under an atmosphere of 5% O2, 10% CO2, and 85% N2. Enrichment cultures were streaked on a plating medium composed of Brucella agar, hematin solution, FBP supplement, and the above antibiotics. Plates were incubated under the same conditions as above. Suspect colonies from the plates were confirmed to be C. jejuni by morphological examination, growth characteristics, and biochemical tests. The above method yielded 25 isolates of C. jejuni from 50 samples of retail cut-up chicken and chicken parts, whereas a more complex method involving filtration, centrifugation, selective enrichment under a flowing atmosphere, and membrane filtration yielded only 6 positives from the same samples. The new isolation procedure was particularly effective in isolating C. jejuni in the presence of large numbers of Pseudomonas aeruginosa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation and enumeration of Campylobacter jejuni from poultry products by a selective enrichment method.

A direct selective enrichment procedure was developed for the isolation of Campylobacter jejuni from poultry products. The selective enrichment medium (ATB) consisted of (per liter) tryptose (20 g), yeast extract (2.5 g), sodium chloride (5 g), FBP supplement (ferrous sulfate [0.25 g], sodium metabisulfite [0.25 g], sodium pyruvate [0.25 g]), bicine (10 g), and agar (1 g). Hematin solution (6.25 ml; prepared by dissolving 0.032 g of bovine hemin in 10 ml of 0.15 N sodium hydroxide solution and autoclaving at 0.35 kg/cm2 for 30 min), rifampin (25 mg), cefsulodin (6.25 mg), and polymyxin B sulfate (20,000 IU) were added after the medium was sterilized. The pH was adjusted to 8.0. Samples were enriched in the above medium at 42 degrees C for 48 h under an atmosphere of 5% O2, 10% CO2, and 85% N2. Enrichment cultures were streaked on a plating medium composed of Brucella agar, hematin solution, FBP supplement, and the above antibiotics. Plates were incubated under the same conditions as above. Suspect colonies from the plates were confirmed to be C. jejuni by morphological examination, growth characteristics, and biochemical tests. The above method yielded 25 isolates of C. jejuni from 50 samples of retail cut-up chicken and chicken parts, whereas a more complex method involving filtration, centrifugation, selective enrichment under a flowing atmosphere, and membrane filtration yielded only 6 positives from the same samples. The new isolation procedure was particularly effective in isolating C. jejuni in the presence of large numbers of Pseudomonas aeruginosa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Formation of hydroxanthommatin-derived radical in the oxidation of 3-hydroxykynurenine.

Using ESR, a radical (g = 2.004) was detected in the reaction mixture of 3-hydroxykynurenine (3-HKY), H2O2, and horseradish peroxidase. The radical was stable and was detected even after 5 h. On HPLC analysis of the reaction mixture, two radical peaks (Peak-1 and Peak-2) were detected using ESR. The ESR spectra of Peak-1 and Peak-2 radicals were the same and identical with that of the original radical in the reaction mixture. The retention times of Peak-1 and Peak-2 corresponded to those of authentic xanthommatin (XA) and hydroxanthommatin (Hydro-XA), respectively, XA being formed in the oxidation of 3-HKY by potassium ferricyanide and Hydro-XA being formed in the reduction of XA by sodium metabisulfite. The absorbance spectra of Peak-1 and Peak-2 were nearly identical with those of authentic XA and Hydro-XA. The absorbance spectrum of Peak-2 changed from that of Hydro-XA to that of XA, indicating that Hydro-XA auto-oxidized to XA in the air. The ESR signal intensity of the Peak-2 radical developed in accordance with the progress of this auto-oxidation of Hydro-XA to XA. It was supposed that the Peak-2 radical was generated in the auto-oxidation of Hydro-XA after its elution from the HPLC column. Thus, the radical seemed to be the one-electron oxidized form of Hydro-XA. The Peak-1 radical appeared to be the true retention of the radical on the column and to be eluted with a much larger amount of XA. The separation of the radical from XA was impossible on the column. Hemoglobin (Hb) or hematin also induced the same radical in the reaction mixture of 3-KHY, H2O2, and Hb or hematin.     

Effects of nutritional characteristics of Streptococcus agalactiae on inhibition of growth by lactoperoxidase-thiocyanate-hydrogen peroxide in chemically defined culture medium.

Five cultures of Streptococcus agalactiae have an absolute requirement for L-cystine to grow in a chemically defined medium. The L-cystine could be replaced with cysteine, glutathione, or the disulfide form of glutathione. Dithiothreitol could not substitute for the sulfur-containing amino acids of glutathione; hence, the growth requirement appears to be truly nutritional. Growth was maximum with 4 to 5 mug of L-cystine per ml. If the concentration of L-cystine was no greater than 4 to 5 mug/ml, complete growth inhibition could be obtained by the addition of lactoperoxidase, thiocyanate, and H2O2. The growth inhibition, however, was nullified by additions of L-cystine 10-fold or more in excess of the concentration needed for maximum growth. During the aerobic degradation of glucose by cell suspensions, H2O2 accumulation could be shown with cultures 317 and 11-13, the only cultures the growth of which was inhibited without addition of exogenous H2O2. All of the cultures had varying degrees of peroxidase activity. The balance between H2O2 generation and peroxidase activity of the culture evidently determined whether growth could be inhibited with lactoperoxidase and thiocyanate without H2O2 addition. The growth yeilds per 0.5 mol of the disulfide forms (cystine and oxidized glutathione) were 1.5 and 1.9 times greater than that per 1 mol of the sulfhydryl forms (cysteine and glutathione).     

Reaction of hematin with allylic fatty acid hydroperoxides: identification of products and implications for pathways of hydroperoxide-dependent epoxidation of 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene

Reaction of 10-hydroperoxyoctadec-8-enoic acid (10-OOH-18:1) (50 microM) with hematin (0.5 microM) in sodium phosphate buffer containing Tween 20 (200 microM) generates 10-oxooctadec-8-enoic acid, 10-oxodec-8-enoic acid (10-oxo-10:1), and 10-hydroxyoctadec-8-enoic acid in relative yields of 79, 4, and 17%, respectively. The product profile and relative distribution are unaffected by 1 mM butylated hydroxyanisole. Approximately 5% of the hydroperoxide isomerizes from the 10- to the 8-position. 10-Oxo-10:1 most likely arises via beta-scission of an intermediate alkoxyl radical to the aldehyde and the n-octyl radical. To test this, 10-hydroperoxyoctadeca-8,12-dienoic acid was reacted with hematin under identical conditions. 10-Oxooctadeca-8,12-dienoic acid, 10-oxodec-8-enoic acid, and 10-hydroxyoctadeca-8,12-dienoic acid are formed in relative yields of 50, 45, and 5%, respectively. The product ratios are constant with time and hydroperoxide to catalyst ratio and unaffected by inclusion of phenolic antioxidants. The higher yield of 10-oxo-10:1 from 10-OOH-18:2 compared to 10-OOH-18:1 is due to the higher rate of beta-scission of the intermediate alkoxyl radical from the former to the resonance-stabilized octenyl radical. Two products of reaction of the 2-octenyl radical with O2, octenal and octenol, were detected in 10% yield relative to 10-oxo-10:1. Inclusion of 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) led to epoxidation by both 10-OOH-18:1 and 10-OOH-18:2. Studies with isotopically labeled hydroperoxide or O2 indicated approximately 65% of the epoxide oxygen was derived from O2 and 35% from hydroperoxide oxygen, consistent with the involvement of peroxyl free radicals as the oxidizing agents. The available evidence indicates that hematin reduces the fatty acid hydroperoxides homolytically to alkoxyl radicals that are oxidized to ketones, reduced to alcohols, or undergo beta-scission to aldehydes. Carbon radicals generated during these reactions couple to O2, generating peroxyl free radicals that epoxidize BP-7,8-diol. The smaller percentage of epoxidation that results from hydroperoxide oxygen may arise from oxidation of the hydroperoxide group to peroxyl radicals or from heterolytic cleavage of the hydroperoxide to alcohol and an iron-oxo complex.     

Inactivation of Bacillus anthracis spores by liquid biocides in the presence of food residue

Biocide inactivation of Bacillus anthracis spores in the presence of food residues after a 10-min treatment time was investigated. Spores of nonvirulent Bacillus anthracis strains 7702, ANR-1, and 9131 were mixed with water, flour paste, whole milk, or egg yolk emulsion and dried onto stainless-steel carriers. The carriers were exposed to various concentrations of peroxyacetic acid, sodium hypochlorite (NaOCl), or hydrogen peroxide (H(2)O(2)) for 10 min at 10, 20, or 30 degrees C, after which time the survivors were quantified. The relationship between peroxyacetic acid concentration, H(2)O(2) concentration, and spore inactivation followed a sigmoid curve that was accurately described using a four-parameter logistic model. At 20 degrees C, the minimum concentrations of peroxyacetic acid, H(2)O(2), and NaOCl (as total available chlorine) predicted to inactivate 6 log(10) CFU of B. anthracis spores with no food residue present were 1.05, 23.0, and 0.78%, respectively. At 10 degrees C, sodium hypochlorite at 5% total available chlorine did not inactivate more than 4 log(10) CFU. The presence of the food residues had only a minimal effect on peroxyacetic acid and H(2)O(2) sporicidal efficacy, but the efficacy of sodium hypochlorite was markedly inhibited by whole-milk and egg yolk residues. Sodium hypochlorite at 5% total available chlorine provided no greater than a 2-log(10) CFU reduction when spores were in the presence of egg yolk residue. This research provides new information regarding the usefulness of peroxygen biocides for B. anthracis spore inactivation when food residue is present. This work also provides guidance for adjusting decontamination procedures for food-soiled and cold surfaces.     

Interactions of quinoline antimalarials with hematin in solution

Quinoline antimalarial drugs such as chloroquine and related compounds are believed to act by targeting ferriprotoporphyrin IX (Fe(III)PPIX) in the form of hematin (H(2)O/HO-Fe(III)PPIX), its mu-oxo dimer ([Fe(III)PPIX](2)O) or crystalline beta-hematin ([Fe(III)PPIX](2)) in the malaria parasite. Fe(III)PPIX is formed when the parasite digests host hemoglobin during its intraerythrocytic blood stage. This has led to a number of studies on the interaction of Fe(III)PPIX with quinoline antimalarials and related compounds. This article reviews the spectroscopy, thermodynamics and structures of Fe(III)PPIX-quinoline complexes in solution.     

Generation of IgG aggregates by the myeloperoxidase-hydrogen peroxide system

Incubation of native human 125I-IgG with polymorphonuclear neutrophil (PMN) peroxidase-containing granules or with purified myeloperoxidase (MPO) in the presence of H2O2 and a suitable hydrogen donor such as catechol generated large amounts of heavy IgG aggregates. Short-term incubation (15 to 60 min) of native 125I-IgG (400 microgram) with MPO-containing granules or with purified MPO (1.5 microgram) in the presence of H2O2 (0.036 to 0.36 mumol) and catechol (0.2 mumol) resulted in the generation of 8 to 100 microgram of heavy IgG aggregates (3 X 10(5) to 4 X 10(6) daltons). Aggregate formation was completely abolished by the omission of H2O2 or catechol, and by the addition of catalase, sodium azide, or cyanide. IgG aggregates were also generated with tyrosinase, tyrosine, and atmospheric oxygen. These results indicate that aggregation was due to MPO-H2O2-mediated oxidation of catechol to orthoquinone, which was deemed to be directly responsible for cross-linking by non-enzymic biochemical reactions. The IgG aggregates generated were shown to behave as typical immune complexes in that they consumed C, were detected by the solid-phase C1q and Raji cell assays, and were precipitable by monoclonal rheumatoid factor. This nonspecific oxidative protein-aggregation reaction may play an important role in the pathogenesis of tissue injury in acute and chronic inflammatory processes and in drug reactions. It could also provide an explanation for the frequent detection of circulating immune complex-like material in a large variety of acute and chronic inflammatory states.     

Ameliorative role of nitric oxide on H2O2 toxicity to a chlorophycean alga Scenedesmus obliquus

A concentration-dependent toxicity of hydrogen peroxide (H(2)O(2)) was observed on growth yield, chlorophyll a content and chlorophyll fluorescence characteristics of the green microalga Scenedesmus obliquus under laboratory batch culture conditions. The addition of sodium nitroprusside, a nitric oxide (NO) donor, in combination with H(2)O(2) prevented chlorophyll losses, and the inhibition level of growth yield, maximum quantum yield of photosystem II (PSII) and the light-adapted quantum yield of PSII were significantly reduced. The antioxidant compounds, penicillamine and thiourea also reduced the damage caused by H(2)O(2) exposure. The protective actions of sodium nitroprusside were, however, arrested in cultures where sodium nitroprusside was supplemented in combination with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO), a specific scavenger of NO. The NO(3)(-)-grown Scenedesmus depicted less sensitivity to H(2)O(2) toxicity with respect to the quantum yields of PSII as compared to its NH(4)(1)-grown counterpart. The role of NO in providing protection against H(2)O(2) toxicity to the processes under study was discussed.     

Dexamethasone-mediated regulation of death and differentiation of muscle cells. Is hydrogen peroxide involved in the process?

The hypothetical involvement of H2O2 in dexamethasone-mediated regulation of muscle cell differentiation and elimination was studied. Rat L6 myoblasts and mouse C2C12 satellite cells were chosen for acute (24 h) and chronic (5 or 10 day) experiments. Mitogenicity and anabolism were both affected by H2O2. Micromolar concentrations of H2O2 inhibited DNA while stimulating protein synthesis. At the millimolar level, H2O2 led to cell death by apoptosis.Synthetic glucocorticoi - dexamethasone (Dex) was shown to effect muscle cell fate similarly to H2O2. Chronic treatment with H2O2 or Dex dose-dependently accelerated either the formation of myotubes or cell elimination. Dex-induced cell death slightly differed from classical apoptosis and was featured by the symptoms of cell senescence such as extensive cytoplasm vacuolisation, accumulation of inclusion-bodies and lack of low molecular weight oligonucleosomal DNA fragmentation but chromatin condensation. Antioxidants (sodium ascorbate, N-acetyl-L-cysteine, catalase) abrogated Dex-dependent cell death. We conclude that H2O2 directly influences myogenesis and muscle cell elimination. Moreover, H2O2 can be considered as the potent mediator of glucocorticoid-dependent effects on muscle cells.     

Low doses of selenium specifically stimulate the repair of oxidative DNA damage in LNCaP prostate cancer cells

Epidemiological studies have demonstrated an inverse relationship between selenium (Se) intake and cancer incidence and/or mortality. However, the molecular mechanisms underlying the cancer chemopreventive activity of Se compounds remain largely unknown. The objective of this study was to investigate the effect of low doses of Se on the stimulation of DNA repair systems in response to four different qualities of DNA damage. P53-proficient LNCaP human prostate adenocarcinoma cells were grown either untreated or in the presence of low concentrations of two Se compounds (30° nM sodium selenite, or 10 μM selenomethionine) and exposed to UVA, H2O2, methylmethane sulfonate (MMS) or UVC. Cell viability as well as DNA damage induction and repair were evaluated by the alkaline Comet assay. Overall, Se was shown to be a very potent protector against cell toxicity and genotoxicity induced by oxidative stress (UVA or H2O2) but not from the agents that induce other types of deleterious lesions (MMS or UVC). Furthermore, Se-treated cells exhibited increased oxidative DNA repair activity, indicating a novel mechanism of Se action. Therefore, the benefits of Se could be explained by a combination of antioxidant activity, the reduction in DNA damage and the enhancement of oxidative DNA repair capacity.     

Anaerobic c(1) metabolism of the o-methyl-C-labeled substituent of vanillate

The O-methyl substituents of aromatic compounds constitute a C(1) growth substrate for a number of taxonomically diverse anaerobic acetogens. In this study, strain TH-001, an O-demethylating obligate anaerobe, was chosen to represent this physiological group, and the carbon flow when cells were grown on O-methyl substituents as a C(1) substrate was determined by C radiotracer techniques. O-[methyl-C]vanillate (4-hydroxy-3-methoxy-benzoate) was used as the labeled C(1) substrate. The data showed that for every O-methyl carbon converted to [C]acetate, two were oxidized to CO(2). Quantitation of the carbon recovered in the two products, acetate and CO(2), indicated that acetate was formed in part by the fixation of unlabeled CO(2). The specific activity of C in acetate was 70% of that in the O-methyl substrate, suggesting that only one carbon of acetate was derived from the O-methyl group. Thus, it is postulated that the carboxyl carbon of the product acetate is derived from CO(2) and the methyl carbon is derived from the O-methyl substituent of vanillate. The metabolism of O-[methyl-C]vanillate by strain TH-001 can be described as follows: 3CH(3)OC(7)H(5)O(3) + CO(2) + 4H(2)O --> CH(3)COOH + 2CO(2) + 10H + 10e + 3HOC(7)H(5)O(3).     

The effect of hydrogen peroxide on the growth of microscopic mycelial fungi isolated from habitats with different levels of radioactive contamination

The effect of hydrogen peroxide ( 10(-9)-10(-1) M) on the mycelial growth of the fungi Alternaria alternata, Cladosporium cladosporioides, Mucor hiemalis, and Paecilomyces lilacinus has been studied. The growth of fungi isolated from habitats with a background level of radioactive contamination was stopped by H2O2 concentrations equal to 10(-3) and 10(-2) M, whereas the growth of fungi that were isolated from habitats with high levels of radioactive contamination was only arrested by 10(-1) M H2O2. The response of the different fungi to hydrogen peroxide was of three types: (1) a constant growth rate of fungal hyphae at H2O2 concentrations between 10(-9) and 10(-4) M and a decrease in this rate at 10(-3) M H2O2, (2) a gradual decrease in the growth rate as the H2O2 concentration was increased, and (3) an increase in the growth rate as the H2O2 concentration was increased from 10(-7) to 10(2)-5 M. The melanin-containing species A. alternata and C. cladosporioides exhibited all three types of growth response to hydrogen peroxide, whereas the light-pigmented species M. hiemalis and P. lilacinus showed only the first type of growth response. A concentration of hydrogen peroxide equal to 10(-1) M was found to be lethal to all of the fungi studied. The most resistant to hydrogen peroxide was found to be the strain A. alternata 56, isolated from the exclusion zone of the Chernobyl Nuclear Power Plant.     

Synthesis and Bioactive Studies of Complex 8-Hydroxyquinolinato-Bis-(Salicylato) Yttrium (III)

This paper reports the synthesis of a new bioactive complex, 8-hydroxyquinolinato-bis-(salicylato) yttrium (III) (HSAY), whose composition and structure were characterized by elemental analysis, IR spectra, thermogravimetric analysis, and X-ray diffraction. The power-time curves of the compounds HSAY, C(7)H(6)O(3), C(9)H(7)NO, and YCl(3)·6H(2)O on the growth metabolism of Schizosaccharomyces pombe (S. pombe) were determined at 32.00°C, respectively. The corresponding thermokinetics parameters, which include the microbial growth rate constant (κ), inhibition ratio (I), and half inhibition concentration (IC(50)), were also derived. The results showed that the generation time was 168.2 min, and all the compounds HSAY, C(7)H(6)O(3), C(9)H(7)NO, and YCl(3)·6H(2)O possessed good bioactivities on the growth metabolism of S. pombe, with the values of IC(50) being 0.055, 3.57, 0.057, and 1.35 mmol L(-1), respectively. The inhibition ability of these compounds above on the growth of the S. pombe has been observed to decrease in the order HSAY>C(9)H(7)NO>YCl(3)·6H(2)O>C(7)H(6)O(3).     

Fate of Escherichia coli O157:H7 as affected by pH or sodium chloride and in fermented, dry sausage.

The influence of pH adjusted with lactic acid or HCl or sodium chloride concentration on survival or growth of Escherichia coli O157:H7 in Trypticase soy broth (TSB) was determined. Studies also determined the fate of E. coli O157:H7 during the production and storage of fermented, dry sausage. The organism grew in TSB containing less than or equal to 6.5% NaCl or at a pH of 4.5 to 9.0, adjusted with HCl. When TSB was acidified with lactic acid, the organism grew at pH 4.6 but not at pH 4.5. A commercial sausage batter inoculated with 4.8 x 10(4) E. coli O157:H7 per g was fermented to pH 4.8 and dried until the moisture/protein ratio was less than or equal to 1.9:1. The sausage chubs were then vacuum packaged and stored at 4 degrees C for 2 months. The organism survived but did not grow during fermentation, drying, or subsequent storage at 4 degrees C and decreased by about 2 log10 CFU/g by the end of storage. These studies reveal the importance of using beef containing low populations or no E. coli O157:H7 in sausage batter, because when initially present at 10(4) CFU/g, this organism can survive fermentation, drying, and storage of fermented sausage regardless of whether an added starter culture was used.