The effect of fetal bovine serum on polyene macrolide antibiotic cytotoxicity and antifungal activity

Summary The relationships between fetal bovine serum (FBS) concentration and polyene macrolide antibiotic cytotoxicity to animal cells and to fungi were evaluated. The toxicity of amphotericin B (AB) and its derivative, amphotericin B methyl ester (AME), toward KB cells was found to be directly related to fetal bovine serum concentration. At higher FBS levels, increased concentrations of AB and AME were required to reduce 72-hr KB viable cell numbers to 50% of control values. Similarly, polyene macrolide antibiotic levels required to inhibit the growth ofSaccharomyces cerevisiae to 50% of controls, and for obtaining minimum fungicidal concentrations (MFC), were greater when higher levels of FBS were used. In addition, AME was less toxic than AB toward KB cells grown in media containing 2, 5, 10, 15 or 20% FBS, whereas the antifungal activities of AB and AME were similar. AME was also capable of eliminatingCandida albicans, Saccharomyces cerevisiae, Aspergillus niger orFusarium moniliforme from KB cultures at antibiotic levels which exhibited less cell toxicity than did the concentrations of AB required for a similar response. These findings indicate that AME may be a potentially useful antifungal antibiotic for tissue culture systems. Portions of this paper were presented at the 25th Annual Meeting of the Tissue Culture Association at Miami, Florida, 1974. This investigation was supported in part by contract NIH 69-2161, NIH grant no. AI-02095 and NIH training grant no. GM 507 from the National Institute of General Medical Sciences.     

Production of the Antibiotic Phenazine-1-Carboxylic Acid by Fluorescent Pseudomonas Species in the Rhizosphere of Wheat

Pseudomonas fluorescens 2-79 and P. aureofaciens 30-84 produce the antibiotic phenazine-1-carboxylic acid and suppress take-all, an important root disease of wheat caused by Gaeumannomyces graminis var. tritici. To determine whether the antibiotic is produced in situ, wheat seeds were treated with strain 2-79 or 30-84 or with phenazine-nonproducing mutants or were left untreated and then were sown in natural or steamed soil in the field or growth chamber. The antibiotic was isolated only from roots of wheat colonized by strain 2-79 or 30-84 in both growth chamber and field studies. No antibiotic was recovered from the roots of seedlings grown from seeds treated with phenazine-nonproducing mutants or left untreated. In natural soils, comparable amounts of antibiotic (27 to 43 ng/g of root with adhering soil) were recovered from roots colonized by strain 2-79 whether or not the pathogen was present. Roots of plants grown in steamed soil yielded larger bacterial populations and more antibiotic than roots from natural soils. In steamed and natural soils, roots from which the antibiotic was recovered had significantly less disease than roots with no antibiotic, indicating that suppression of take-all is related directly to the presence of the antibiotic in the rhizosphere.     

Streptomyces species producing the streptovaricin complex

Morphological, cultural and physiological-biochemical properties ofStreptomyces sp. strain 1000 and its antibiotic production were investigated. Antibiotics 1011 (identical with the streptovaricin complex) and 1012 (with antibacterial action) were isolated from the cultural broth of this strain. The overproducing natural variant 1011 was isolated from the population of a strain producing antibiotic 1011 at a concentration of 1000 mg/L (activity of the parent strain represents 41 mg/L only). Comparative taxonomical characteristic ofStreptomyces sp. strain 1000 with strains fromS. spectabilis showed that the strain 1000 differed in some properties and antibiotic production being considered as a new variant ofS. spectabilis. The strain shows an expressed antibiotic activity against G+ as well as G− bacterial and yeasts.     

二硫吡咯酮类抗生素的生物合成与代谢工程应用北大核心CSCD

二硫吡咯酮类抗生素是一类具有独特的吡咯酮二硫杂环戊二烯(4H-[1,2]二硫[4,3-b]吡咯-5-酮)骨架的化合物的总称。基于N-7位酰基侧链的不同以及N-4位是否含有甲基,可分为N-methyl-Nacylpyrrothine、N-acylpyrrothine和thiomarinols等类别。迄今为止,已有27种该类化合物被报道,重要代表包括全霉素(holomycin)、硫藤黄菌素(thiolutin)、金霉素(aureothricin)以及最近发现的thiomarinols。就生物活性而言,二硫吡咯酮类抗生素具有广谱的抗细菌活性,对多种微生物,包括革兰氏阴性菌、革兰氏阳性菌以及寄生虫都有较好的杀灭活性。甚至一些二硫吡咯酮衍生物表现出较强的抗肿瘤活性。近几年来,多个二硫吡咯酮类抗生素的生物合成基因簇相继被报道,其生物合成机理也逐步被阐明。本文将针对目前国内外二硫吡咯酮类抗生素的生物合成研究进展,以及在组合生物合成与代谢工程领域所取得的成果进行综述,旨在为通过合成生物学的方法创造结构新颖、高效低毒的"非天然"二硫吡咯酮类化合物提供理论借鉴。     

The paromomycin resistance mutation (parr-454) in the 15 S rRNA gene of the yeast Saccharomyces cerevisiae is involved in ribosomal frameshifting

Summary The leaky expression of the yeast mitochondrial geneoxi1, containing a frameshift mutation (+1), is caused by natural frameshift suppression, as shown previously (Fox and Weiss-Brummer 1980). A drastic decrease in the natural level of frameshifting is found in the presence of thepar ^r-454 mutation, localized at the 3′ end of the 15 S rRNA gene. This mutation causes resistance to the antibiotic paronomycin in the yeast strains D273-10B and KL14-4A (Li et al. 1982; Tabak et al. 1982). The results of this study imply that in the yeast strain 777-3A this mutation alone is sufficient for restriction of the level of natural frameshifting but is insufficient to confer resistance to paromomycin. A second mutation, arising spontaneously with a frequency of 10⁻⁴ leads, in combination with thepar ^r-454 mutation, to full paromomycin resistance in strain 777-3A.     

Studies on Antibiotics Produced by Psychrophilic Microorganisms

A screening for antibacterial antibiotics was carried out with psychrophilic microorganisms. The most active microorganism, a soil actinomycete, was selected and characterized to be a facultative psychrophile, Streptomyces sp. No. 81. This strain was found to produce antibiotic(s) in the culture fluid only at low temperature cultivation below 20°C but not at moderate temperature. Mycelial growth at low temperature seemed to be indispensable for the antibiotic production. The antibiotic produced by Streptomyces sp. No. 81 was isolated and characterized. It appeared that the antibiotic had the selective toxicity against several Gram-positive bacteria. From the comparative studies with several known antibiotics, the antibiotic appears to be a new compound derived from the new metabolic routes involving temperature-sensitive mechanisms.     

Interaction of nutrients and four antifungal antibiotics in their effects on Pythium species in vitro and in soil

Summary Griseofulvin, streptomycin, aureomycin, and actidione, with and without nutrients, were tested againstPythium ultimum Trow (two strains),P. irregulare Buis., andP. rostratum Butler. Streptomycin was tolerated in the highest concentration, and actidione and aureomycin in the lowest.P. rostratum, a saprophytic species, was more resistant to the antibiotics than the pathogenic species, which were inhibited at low concentrations. The two strains ofP. ultimum behaved differently, the oogonial strain being more tolerant than the sporangial strain. Yeast extract was usually superior to sucrose or asparagine in counteracting the toxicity of antibiotics.Germination of sporangia ofPythium irregulare was studiedin vitro and in a natural soil in the presence of antibiotic and antibiotic-nutrient solutions. Very meager germination of sporangia occurred in soil amended with antibiotics. Actidione severely restricted germination in soil. Nutrients nullified the toxicity to varying degrees. Usually higher germination of sporangia occurredin vitro than in soil. Sub-lethal concentrations of antibiotics induced morphological abnormalities in germ tubes. Aureomycin caused a dendroid type of branching; actidione caused distortion, vacuolation, and vesiculation; griseofulvin caused lysis and septation; and streptomycin caused distortion.Germ tubes were lysed in a natural soil and in soils amended with antibiotics, but nutrients, in general, prevented early lysis at low concentrations of antibiotics. No resistant bodies were formed prior to the initiation of lysis of germ tubes.     

A toxic metabolite of Nigrospora oryzae (Berk and Br.) petch

Nigrospora oryzae was isolated from dallisgrass (Paspalum dilatatum Poir.) collected in Auburn and from hay shipped under refrigeration to Florida. Some of these samples were eaten by cattle and horses that subsequently developed lameness. Metabolites of N. oryzae were separated by thin layer chromatography and tested for toxicity. Only one metabolite was toxic. Metabolite A showed toxicity to brine shrimp with an LD₅₀=500 g/ml in 8 h. It also had an antibiotic effect on Bacillus megaterium ATCC 14581 with a minimum inhibitory level of 10.1 g/disc. As little as 435 g of a crude methanolic extract of N. oryzae showed mild toxicity to chick embryos. The metabolite was not toxic to mice nor rats at the levels tested. Quantitative procedures developed for the determination of metabolite A showed that the maximum production occurred in yeast extract-sucrose liquid medium with an initial pH of 5–6, when incubated as a stationary culture for 28 days at 25 °C. It was concluded that metabolite A is a weak antibiotic rather than a mycotoxin, and was probably not associated with the symptoms of lameness observed in cattle and horses. The antibiotic is not one previously reported for N. oryzae.Alabama Agricultural Experiment Station Journal No. 6-84744     

Cloning of an endoglucanase gene fromPseudomonas fluorescens var.cellulosa intoEscherichia coli andPseudomonas fluorescens

Summary An endoglucanase chromosomal gene from the cellulolyticPseudomonas fluorescens var.cellulosa (NCIB 10462) was cloned inEscherichia coli. Chromosomal DNA was partially digested with the restriction enzymeEcoRI and ligated into the broad host-range, mobilizable plasmid pSUP104 that had been linearized with the same enzyme. After transformation ofEscherichia coli, and endoglucanase-positive clone was detected in situ by use of the Congo-red assay procedure. The endoglucanase gene on the recombinant plasmid pRUCL 100 was expressed in the non-cellulolyticPseudomonas fluorescens PF41. The DNA fragment carrying the gene was transferred to the plasmid pBR322, generating plasmids pRUCL150 and pRUCL151, and its restriction map was derived.Abbreviations CMC carboxymethylcellulose - EG endoglucanase - kb kilobase pairs - Mops 4-morpholinepropanesulfonic acid - Ap^r-s resistance-sensitivity to the antibiotic ampicillin - Cm^r-s resistance-sensitivity to the antibiotic chloramphenicol - Tc^r-s resistance-sensitivity to the antibiotic tetracycline - Sm^r-s resistance-sensitivity to the antibiotic streptomycin - Tp^r-s resistance-sensitivity to the antibiotic trimethoprim     

Progress of research on the toxicology of antibiotic pollution in aquatic organisms

Antibiotics are widely used to improve human and animal health and treat infections. Antibiotics are often used in livestock farms and fisheries to prevent diseases and promote growth. Recently, there has been increasing interest in the presence of antibiotics in aquatic environments. Low levels of antibiotic components are frequently detected in surface water, seawater, groundwater, and even drinking water. Antibiotics are consistently and continually discharged into the natural environment as parent molecules or metabolites, which are usually soluble and bioactive, and this results in a pseudo and persistent pollution. The effects of environmental antibiotic toxicity on non-target organisms, especially aquatic organisms, have become an increasing concern. Although antibiotics have been detected worldwide, their ecological and developmental effects have been poorly investigated, particularly in non-target organisms. This review describes the toxicity and underlying mechanism of antibiotic contamination in aquatic organisms, including the effects on vertebrate development. A considerable number of antibiotic effects on aquatic organisms have been investigated using acute toxicity assays, but only very little is known about the long-term effects. Aquatic photosynthetic autotrophs, such as Pseudokirchneriella subcapitata, Anabaena flos-aquae, and Lemna minor, were previously used for antibiotic toxicity tests because of low cost, simple operation, and high sensitivity. Certain antibiotics show a different degree of potency in algal toxicity tests on the basis of different test algae. Antibiotics inhibit protein synthesis, chloroplast development, and photosynthesis, ultimately leading to growth inhibition; some organisms exhibit growth stimulation at certain antibiotic concentrations. Daphnia magna and other aquatic invertebrates have also been used for checking the toxicity priority of antibiotics. When investigating the acute effect of antibiotics (e.g., growth inhibition), concentrations in standard laboratory organisms are usually about two or three orders of magnitude higher than the maximal concentrations in the aquatic environment, resulting in the underestimation of antibiotic hazards. Vertebrate organisms show a promising potential for chronic toxicity and potentially subtle effects of antibiotics, particularly on biochemical processes and molecular targets. The adverse developmental effects of macrolides, tetracyclines, sulfonamides, quinolones, and other antibiotic groups have been evaluated in aquatic vertebrates such as Danio rerio and Xenopus tropicalis. In acute toxicity tests, low levels of antibiotics have systematic teratogenic effects on fish. The effects of antibiotics on oxidative stress enzymes and cytochrome P450 have been investigated. Cytotoxicity, neurotoxicity, and genotoxicity have been observed for certain antibiotic amounts. However, there are no firm conclusions regarding the chronic toxicity of antibiotics at environmentally relevant levels because of the lack of long-term exposure studies. Herein, future perspectives and challenges of antibiotic toxicology were discussed. Researchers should pay more attention to the following points: chronic toxicity and potentially subtle effects of environmentally relevant antibiotics on vertebrates; effects of toxicity on biochemical processes and mode of action; combined toxicity of antibiotics and other antibiotics, metabolites, and heavy metals; and environmental factors such as temperature and pH.     

Modulation by Polymyxin B of the Effects of Interferon on Human Myelogenous Leukemia Cells

Natural and recombinant human interferon-α (IFN-α) and -γ (IFN-γ) exert differentiation-inducing and cytocidal effects in vitro on cells of the human myeloblastic leukemia cell line ML-2. These activities of IFNs are modulated by polymyxin B (PMB), a cyclic polycationic peptide antibiotic effective on Gram-negative bacilli. The modulating effect of PMB varies according to the species of IFN, namely, PMB enhances the activities of either natural IFN-γ or recombinant IFN-γ, while it inhibits the effects of either natural IFN-α or recombinant IFN-α. The cause of this variety in PMB effect on IFNs remains to be clarified.     

矿物油乳剂对烟蚜茧蜂的安全性评价

【目的】矿物油乳剂因其安全性好、杀虫谱广、不易产生抗性等优点,被广泛用于果蔬、农作物、园林害虫的防治,但有关其对害虫天敌烟蚜茧蜂的安全性尚不明确。因此,本文研究矿物油乳剂对烟蚜茧蜂不同发育阶段的安全性,为更好地协调蚜虫的化学防治和生物防治提供理论依据。【方法】在实验室条件下采用药膜法和浸渍法测定了不同浓度(150、250、350、450倍液)矿物油乳剂对烟蚜茧蜂各发育阶段的影响。【结果】矿物油乳剂对烟蚜茧蜂成虫的影响较小,无明显胃毒作用,但有一定的触杀作用,以最高浓度150倍液(4986.960 mg·L-1)处理24 h后的存活率依然高达92%;矿物油乳剂对烟蚜茧蜂寄生蚜有较高的致死率,LC50为859.541 mg·L-1,该浓度远远低于此次供试的最低浓度450倍液(1662.320 mg·L-1),说明矿物油乳剂对烟蚜茧蜂卵和幼虫的安全性较差;矿物油乳剂对烟蚜茧蜂蛹期羽化率的影响较显著,处理组的僵蚜与对照组的僵蚜相比,羽化高峰期均滞后1 d,且羽化率随着处理浓度的增大而下降(450倍液时羽化率为81.25%,150倍液时仅为47.75%)。【结论】当蚜虫发生严重时,可考虑在烟蚜茧蜂成虫期协调使用矿物油乳剂进行联合控制,但矿物油乳剂的使用浓度和施用时间还有待进一步确定。     

Helicobacter macacae MazF interplays with Escherichia coli homologs and enhances antibiotic tolerance

Background

Toxin-antitoxin systems are highly variable, even among strains of the same bacterial species. The MazEF toxin-antitoxin system is found in many bacteria and plays important roles in various biological processes such as antibiotic tolerance and phage defense. However, no interplay of MazEF systems between different species was reported.

Materials and Methods

MazEF toxin-antitoxin system of Helicobacter macacae was examined in three Escherichia coli strains with and without endogenous MazEF knockout. In vivo toxicity, antibiotic tolerance, and live/dead staining followed by flowcytometry analysis were performed to evaluate the functionality and interplay of the toxin-antitoxin system between the two species.

Results

Controlled ectopic expression of MazF of H. macacae (MazFhm) in E. coli did not affect its growth. However, in endogenous MazEF knockout E. coli strains, MazFhm expression caused a sharp growth arrest. The toxicity of MazFhm could be neutralized by both the antitoxin of MazE homolog of H.macacae and the antitoxin of MazE of E. coli, indicating interplay of MazEF toxin-antitoxin systems between the two species. Induced expression of MazFhm enhanced tolerance to a lethal dose of levofloxacin, suggesting enhanced persister formation, which was further confirmed by live/dead cell staining.

Conclusions

The MazEF toxin-antitoxin system of H. macace enhances persister formation and thus antibiotic tolerance in E. coli. Our findings reveal an interplay between the MazEF systems of H. macacae and E. coli, emphasizing the need to consider this interaction while evaluating the toxicity and functionality of MazF homologs from different species in future studies.     

The control of damping-off in Pisum sativum L. by cycioheximide

Experiments on the effect of cycioheximide (Acti-dione) in controlling damping-off disease of peas confirmed that phytotoxicity would preclude its use despite its high toxicity to Pythium spp. The antibiotic did not inhibit germination of peas, but retarded growth of the shoot; the tap root was apparently unaffected, but the lateral roots were stunted.     

TOXICITY OF COPPER TO THALASSIOSIRA PSEUDONANA IN UNENRICHED INSHORE SEAWATER1

Toxicity of copper to T. pseudonana (formerly Cyclotella nana, clone 13-1) wax examined in inshore seawater using a 96-hr bioassay method. Raw unenriched seawater wax filtered through a 0.22-μ membrane filter and then pasteurized, for 30 min at 60 C. Following this treatment, samples contained 0.68–1.14 μg Cu/liter. Copper was added as the chloride in 5-μg increments over the range of 5 to 30 μg/liter (about 0.1–0.5 μM). Population densities, mean cell, volume, and ¹⁴C bicarbonate uptake were measured. Population growth, and ¹⁴C uptake by T. pseudonana displayed inhibition over the entire range of added copper. Growth rate constant (k) of T. pseudonana decreased with increasing copper concentration and during the course of growth at each concentration. Correspondingly, mean cell volumes increased with copper concentration and time. Copper toxicity varied in different water samples. The presence of decomposed natural plankton and detritus decreased toxicity. In the absence of enrichment, bacteria had little effect on copper toxicity. H exults were influenced by glassware treatment, collection and storage of seawater, and absence of enrichments.     

Identification of a Potential Lead Structure for Designing New Antimicrobials to Treat Infections Caused by Staphylococcus epidermidis-Resistant Strains

Bacterial infections are a significant cause of morbidity and mortality among critically ill patients. The increase of antibiotic resistance in bacteria from human microbiota—such as Staphylococcus epidermidis, an important nosocomial pathogen that affects immunocompromised patients or those with indwelling devices—increased the desire for new antibiotics. In this study we designed, synthesized, and determined the antimicrobial activity of 27 thieno[2,3-b]pyridines (1, 2, 2a–2m, 3, 3a–3m) derivatives against a drug-resistant clinical S. epidermidis strain. In addition, we performed a structure-activity relationship analysis using a molecular modeling approach, and discuss the drug absorption, distribution, metabolism, excretion, and toxicity profile and Lipinski’s “rule of five,” which are tools to assess the relationship between structures and drug-like properties of active compounds. Our results showed that compound 3b (5-(1H-tetrazol-5-yl)-4-(3`-methylphenylamino)thieno[2,3-b]pyridine) was as active as oxacillin and chloramphenicol but with lower theoretical toxicity risks and a better drug likeness and drug score potential than chloramphenicol. All molecular modeling and biological results reinforced the promising profile of 3b for further experimental investigation and development of new antibacterial drugs. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synergism between fungal enzymes and bacterial antibiotics may enhance biocontrol

The interactions between biocontrol fungi and bacteria may play a key role in the natural process of biocontrol, although the molecular mechanisms involved are still largely unknown. Synergism can occur when different agents are applied together, and cell wall degrading enzymes (CWDEs) produced by fungi can increase the efficacy of bacteria. Pseudomonas spp. produce membrane-disrupting lipodepsipeptides (LDPs) syringotoxins (SP) and syringomycins (SR). SR are considered responsible for the antimicrobial activity, and SP for the phytotoxicity. CWDEs of Trichoderma spp. synergistically increased the toxicity of SP_25-A or SR_E purified from P. syringae against fungal pathogens. For instance, the fungal enzymes made Botrytis cinerea and other phytopathogenic fungi, normally resistant to SP_25-A alone, more susceptible to this antibiotic. Pseudomonas produced CWDEs in culture conditions that allow the synthesis of the LDPs. Purified bacterial enzymes and metabolites were also synergistic against fungal pathogens, although this mixture was less powerful than the combination with the Trichoderma CWDEs. The positive interaction between LDPs and CWDEs may be part of the biocontrol mechanism in some Pseudomonas strains, and co-induction of different antifungal compounds in both biocontrol bacteria and fungi may occur. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measuring the bioavailable/toxic concentration of copper in natural water by using anodic stripping voltammetry and Vibrio-qinghaiensis sp.Nov.-Q67 bioassay

Abstract

Bioassays were carried out in the culture media for Vibrio-qinghaiensis sp.Nov.-Q67 and the influences of alkalinity and different concentrations of chloride, ethylene diamine tetraacetic acid (EDTA) and natural derived fulvic acid (FA) on the labile concentration and toxicity of Cu were investigated. The labile concentration of Cu was obtained by differential pulse anodic stripping voltammetry with a double acidification method (DAM-DPASV). Changes in water alkalinity and chloride concentrations did not affect the labile concentration of Cu, but increases of alkalinity and concentrations of chloride reduced the toxicity on Q67. In the presence of EDTA and FA, both labile concentration of Cu and toxicity were reduced. By excluding Cu-carbonate complexes and Cu-chloride from labile concentration, a bioavailable concentration of Cu (or [Cu*]) was obtained and used to predict the acute toxicity of Cu on Q67. For natural waters, the labile concentration of Cu was measured by DAM-DPASV and [Cu*] was calculated by a MINTEQ A2 software based on composition of waters. This procedure was tested for Guanting Reservoir waters by spiking different concentration Cu. The results showed that [Cu*] was a good indicator for Cu toxicity and could be used in field conditions.     

Development of real time PCR assays for detection and quantification of transgene DNA of a <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> (Bt) corn hybrid in soil samples

Real time PCR assays were developed to detect and quantify the transgene DNA of a commercially released Bacillus thuringiensis (Bt) corn (Zea mays L.) hybrid (DKC42-23), which was derived from the event MON863 and also carried a neomycin phosphotransferase gene (the nptII gene). We applied the real time PCR assays to investigate the persistence of the transgene DNA in a field trial grown with DKC42-23 over 3 years, in combination with bacterial natural transformation. The results showed that under continuous cultivation of DKC42-23, its transgene DNA was detectable in the field plots all year around. Meanwhile, when soil DNA extracts from DKC42-23 plots were used as donor in bacterial natural transformation, successful recovery of kanamycin resistant (Km^R) transformants indicated that the nptII gene carried by DKC42-23 could be taken up and integrated into naturally competent Pseudomonas stutzeri pMR7 cells, leading to the restoration of the antibiotic resistance of P. stutzeri pMR7. However, after the cultivation of a soybean line in the same plots for the subsequent growing season, the presence of transgene DNA of DKC42-23 was reduced to undetectable levels at the end of that growing season. Therefore, existing corn-soybean crop rotation practices reduce the availability of transgene DNA in soil and thus minimize the risks that might be attributable to horizontal gene transfer. The real time PCR assays are useful for investigating the persistence of transgene DNA derived from the MON863 event in soil environments.     

Apparent Turnover Rate of Diaphragm Proteins in Rats

A new antibiotic, toromycin (antibiotic B-21085) was isolated as yellow crystals from the culture broth of Streptomyces collinus subsp. albescens subsp. nov. The antibiotic has the molecular formula C₂₇H₂₆O₉ and is the polycyclic aromatic hydrocarbon group of antibiotics. Toromycin is active against gram-positive bacteria, mycobacteria, mycoplasma, DNA viruses and some bacteriophages.