Pathway for uptake and degradation of X-prolyl tripeptides in Streptococcus mutans VA-29R and Streptococcus sanguis ATCC 10556

The growth of Streptococcus mutans and Streptococcus sanguis in the oral environment requires that these micro-organisms be able to degrade salivary proteins and to assimilate the resulting peptides as an amino nitrogen source. Our research is aimed at the definition of the proteolytic enzyme systems in these oral streptococci which allow them to utilize such substrates. In the present work, the nature of the hydrolytic activity expressed by S. mutans VA-29R and S. sanguis ATCC 10556 against X-Pro4-nitroanilide and X-Pro-Y tripeptide substrates was investigated. This activity was predominantly associated with a cytoplasmic dipeptidyl peptidase which preferentially catalyzes the release of an N-terminal dipeptide from substrates in which proline is the penultimate residue. These streptococci also possess a second cytoplasmic peptidase, pepD, which catalyzes the hydrolysis of X-Pro dipeptides. We found that Gly-Pro-Ala or Ala-Pro-Gly were transported into the bacterial cells only when an energy source such as glucose was present. Peptide uptake was time-dependent, and selective exodus of peptide-derived amino acids from the bacterial cells occurred during peptide uptake. Results from these studies provide evidence that S. mutans VA-29R and S. sanguis ATCC 10556 possess a pathway for the complete degradation of X-Pro tripeptides. Transport of the peptides into cells prior to hydrolysis provides an efficient way by which all amino acids of a peptide may be obtained at an energy expense equivalent to that associated with the transport of just one amino acid. In light of the abundance of proline in salivary polypeptides, this degradative pathway could be an important component in the proteolytic pathway for salivary polypeptide utilization in these oral streptococci.     

Synergist effect of sucrose fatty acid esters on nisin inhibition of gram-positive bacteria

Nisin in combination with the sucrose fatty acid esters, sucrose palmitate (P-1570 and P-1670) or sucrose stearate (S-1570 and S-1670) was tested against a range of Gram-negative and Gram-positive bacteria. Initial liquid culture investigation showed that the sugar ester P-1670 resulted in a synergist enhancement of the bacteriostatic activity of nisin against Gram-positive bacteria and not Gram-negative bacteria. Some enhancement of the bactericidal activity of nisin against Listeria monocytogenes was also observed. This increased nisin inhibitory effect was confirmed on solid media using plates with gradients of pH and NaCl. Synergism was observed with all four sucrose fatty acid esters, which enhanced the antimicrobial activity of nisin against several strains of L. monocytogenes, Bacillus cereus (both cells and spores), Lactobacillus plantarum and Staphylococcus aureus. The combination of nisin and the sucrose fatty acid esters showed no inhibition of Gram-negative bacteria (Salmonella enteritidis, Salm. typhimurium and Pseudomonas aeruginosa).     

What are archaebacteria: life's third domain or monoderm prokaryotes related to gram-positive bacteria? A new proposal for the classification of prokaryotic organisms

The evolutionary relationship within prokaryotes is examined based on signature sequences (defined as conserved inserts or deletions shared by specific taxa) and phylogenies derived from different proteins. Archaebacteria are indicated as being monophyletic by a number of proteins related to the information transfer processes. In contrast, for several other highly conserved proteins, common signature sequences are present in archaebacteria and Gram-positive bacteria, whereas Gram-negative bacteria are indicated as being distinct. For these proteins, archaebacteria do not form a phylogenetically distinct clade but show polyphyletic branching within Gram-positive bacteria. A closer relationship of archaebacteria to Gram-positive bacteria in comparison with Gram-negative bacteria is generally seen for the majority of the available gene/ protein sequences. To account for these results and the fact that both archaebacteria and Gram-positive bacteria are prokaryotes surrounded by a single cell membrane, I propose that the primary division within prokaryotes is between monoderm prokaryotes (surrounded by a single membrane) and diderm prokaryotes (i.e. all true Gram-negative bacteria containing both an inner cytoplasmic membrane and an outer membrane). This proposal is consistent with both cell morphology and signature sequences in different proteins. The monophyletic nature of archaebacteria for some genes, and their polyphyletic branching within Gram-positive bacteria as suggested by others, is critically examined, and several explanations, including derivation of archaebacteria from Gram-positive bacteria in response to antibiotic selection pressure, are proposed. Signature sequences in proteins also indicate that the low-G+C Gram-positive bacteria are phylogenetically distinct from the high-G+C Gram-positive group and that the diderm prokaryotes (i.e. Gram-negative bacteria) appear to have evolved from the latter group. Protein phylogenies and signature sequences also show that all eukaryotic cells have received significant gene contributions from both an archaebacterium and a Gram-negative eubacterium. Thus, the hypothesis that archaebacteria and eukaryotes shared a common ancestor exclusive of eubacteria is not supported. These observations provide evidence for an alternate view of the evolutionary relationship among living organisms that is different from the currently popular three-domain proposal.     

Killer toxins of certain yeast strains have potential growth inhibitory activity on gram-positive pathogenic bacteria

The killer yeast strains which are encountered most frequently among species in the genera Saccharomyces, Candida, Hansenula, Pichia and Kluyveromyces (ten killer strains in toto) were tested for the activity of their toxins on the growth of some pathogenic bacteria (four Gram-positive and six Gram-negative strains) in a test in which purified toxins were not required. Neither toxins of the killer Saccharomyces cerevisiae and Pichia membranefaciens strains were active against the bacterial strains. In contrast the killer toxins of Hansenula anamola, Hansenula mrakii, Candida tropicalis, Kluyveromyces drosphilarum and Kluyveromyces lactis showed potential growth inhibitory effects on Gram-positive pathogenic bacteria. Thus, yeast killer toxins were found to be active only on Gram-positive bacterial cell types.     

Synthesis and antimicrobial activity of some novel 2,5- and/or 6-substituted benzoxazole and benzimidazole derivatives

A new series of 2,5- and/or 6-substituted benzoxazoles (7a-f), benzimidazoles (8a-g) holding cyclohexyl or cyclopentyl moieties at position 2 and 5- or 6-substituted-2-cyclohexylaminomethylbenzoxazoles (9a, b) was synthesized in order to determine their antimicrobial activities and feasible structure-activity relationships. The synthesized compounds were tested in vitro against three Gram-positive, two Gram-negative bacteria and the yeast Candida albicans in comparison with several control drugs. Microbiological results showed that the synthesized compounds were possessing a broad spectrum of antibacterial activity against the tested microorganisms. 5-Chloro-2-(2-cyclohexylethyl)benzimidazole (8g) was found as the most active compound against the screened Gram-positive bacteria strains at a minimum inhibitory concentration (MIC) value of 12.5 microg/ml. However, it exhibited lower antibacterial potency than the compared control drugs. On the other side, compounds 7-9 indicated significant antibacterial activity against the Gram-negative enterobacter Pseudomonas aeruginosa having MIC values of 50 microg/ml, providing either the same effect as tetracycline or higher activity than streptomycin, but showing less potency than the compared control drug gentamycin. Moreover, the synthesized compounds also possessed antimycotic activity against the yeast C. albicans showing MIC values between 25-50 microg/ml.     

Antibacterial and antifungal activity of aromatic constituents of essential oils

Five aromatic constituents of essential oils (cineole, citral, geraniol, linalool and menthol) were tested for antimicrobial activity against eighteen bacteria (including Gram-positive cocci and rods, and Gram-negative rods) and twelve fungi (three yeast-like and nine filamentous). In terms of antibacterial activity linalool was the most effective and inhibited seventeen bacteria, followed by cineole, geraniol (each of which inhibited sixteen bacteria), menthol and citral aromatic compounds, which inhibited fifteen and fourteen bacteria, respectively. Against fungi the citral and geraniol oils were the most effective (inhibiting all twelve fungi), followed by linalool (inhibiting ten fungi), cineole and menthol (each of which inhibited seven fungi) compounds.     

Anesthesia information management systems as a cost containment tool

A systematic evaluation of the ability of different bacterial genera to transform 2,4,6-trinitrotoluene (TNT), and grow in its presence, was conducted. Aerobic Gram-negative organisms degraded TNT and evidenced net consumption of reduced metabolites when cultured in molasses medium. Some Gram-negative isolates transformed all the initial TNT to undetectable metabolites, with no adsorption of TNT or metabolites to cells. Growth and TNT transformation capacity of Gram-positive bacteria both exhibited 50% reductions in the presence of approximately 10 microg TNT ml-1. Most non-sporeforming Gram-positive organisms incubated in molasses media amended with 80 microg TNT ml-1 became unculturable, whereas all strains tested remained culturable when incubated in mineral media amended with 98 microg TNT ml-1, indicating that TNT sensitivity is linked to metabolic activity. These results indicate that the microbial ecology of soil may be severely impacted by TNT contamination.     

Ascorbate recycling in human neutrophils: induction by bacteria

Ascorbate (vitamin C) recycling occurs when extracellular ascorbate is oxidized, transported as dehydroascorbic acid, and reduced intracellularly to ascorbate. We investigated microorganism induction of ascorbate recycling in human neutrophils and in microorganisms themselves. Ascorbate recycling was determined by measuring intracellular ascorbate accumulation. Ascorbate recycling in neutrophils was induced by both Gram-positive and Gram-negative pathogenic bacteria, and the fungal pathogen Candida albicans. Induction of recycling resulted in as high as a 30-fold increase in intracellular ascorbate compared with neutrophils not exposed to microorganisms. Recycling occurred at physiologic concentrations of extracellular ascorbate within 20 min, occurred over a 100-fold range of effector/target ratios, and depended on oxidation of extracellular ascorbate to dehydroascorbic acid. Ascorbate recycling did not occur in bacteria nor in C. albicans. Ascorbate did not enter microorganisms, and dehydroascorbic acid entry was less than could be accounted for by diffusion. Because microorganism lysates reduced dehydroascorbic acid to ascorbate, ascorbate recycling was absent because of negligible entry of the substrate dehydroascorbic acid. Because ascorbate recycling occurs in human neutrophils but not in microorganisms, it may represent a eukaryotic defense mechanism against oxidants with possible clinical implications.     

The oxidation of dithiothreitol by peroxidases and oxygen

Horseradish peroxidase (1.11.1.7), lactoperoxidase (1.11.1.7), and the fragment of cytochrome c known as microperoxidase have been shown to catalyze the oxidation of reduced dithiothreitol in an oxygen-consuming reaction. Evidence for horseradish peroxidase intermediates compound III and compound II has been observed, although ferroperoxidase was not identified during the course of the reaction. The stoichiometry has been extablished as 1 : 1 for oxygen consumed to dithiothreitol oxidized. Cysteine and glutathione have also been shown to be substrates for horseradish peroxidase oxidase reaction.     

A new antibiotic XK-90 I. Taxonomy of the producing organism, fermentation, isolation and physicochemical and biological properties

A new antibiotic XK-90 is produced by Streptomyces sp. MK-90 and is active against Gram-positive and Gram-negative bacteria. The taxonomy of the organism, fermentation, isolation and physiochemical and biological properties are described.     

Liquid Sodium Ferrate and Fenton’s Reagent for Treatment of Mature Landfill Leachate

As landfills mature, biodegradable matter in leachate is consumed and remaining compounds are increasingly recalcitrant. In this work, ferrate was compared to Fenton’s reagent for the purpose of removing nonbiodegradable organic compounds from mature leachate. Oxidation conditions (time, pH, and dose) were optimized to yield maximum organic removal using two leachate samples from 20- and 12-year-old solid waste cells. Results from this study demonstrated that Ferrate and Fenton’s reagent had similar optimum pH ranges (3–5), but different organic removal capacities, ranging from 54 to 79% of initial leachate organic contents. An advantage of ferrate was that it was effective over a wide pH range. Advantages associated with Fenton’s reagent include that it had higher organic removal capacity, produced more oxidized organic compounds (measured as chemical oxygen demand/dissolved organic carbon), and produced more biodegradable byproducts (measured as chemical oxygen demand/5-day biochemical oxygen demand). Finally, both treatments were found to attack larger molecules (>1,000?Dalton), as indicated by an increase in smaller molecule contribution to organic carbon.     

Sensitivity of bacteria to therapeutic drugs (Zurich 1996)

This paper describes the frequency of susceptibility of Gram-negative and Gram-positive bacteria against antibacterial agents. The data are based on all susceptibility tests performed in 1996 at the Department of Medical Microbiology of the University of Zurich and at the private medical laboratory "medica" in Zurich. The evaluation of the results from 1975 to 1996 shows that susceptibilities against the antimicrobial agents tested have not changed markedly in this period with few exceptions. The tables may be a help for the physician in his decision for a "calculated chemotherapy" of bacterial infections.     

Evaluation of a rapid technique for antibiotic sensitivity testing using an MS-2 automate and blood culture medium

The authors propose a rapid method for studying antibiotic sensitivity of bacteria isolated from blood cultures. An MS-2 automate is used directly with bacteria collected after centrifugation. With the exception of the sensitivity of Gram-positive cocci to the combination of sulfamethoxazole-trimethoprime and to Penicillin G and of Gram-negative bacillus to beta lactamines, the results were comparable to those obtained after isolation of bacteria on gel medium. Various causes for error are discussed.     

简述降低废水COD方法

COD即化学需氧量,它是表征水体中还原性物质的综合指标,除特殊水样外,还原性物质主要是有机物。在自然界的循环中,这些还原性物质,特别是有机化合物在生物氧化降解过程中消耗溶解氧而造成水体氧的缺损,溶解氧的缺损会破坏环境和生物群落的生态平衡,引起水质恶化,甚至发生溶氧消耗殆尽,厌氧菌滋生,造成水体变黑发臭。使水质严重污染,如何有效去除废水中的有机物已经成为废水处理中的主要课题。     

The mosaic nature of the eukaryotic nucleus

The phylogenies for each of the protein-coding genes from the Methanococcus jannaschii genome were surveyed to determine the history of the major groups of life. For each gene, homologous sequences from other archaea, eucarya, and Gram-positive and Gram-negative bacteria were collected and aligned, and a phylogeny was reconstructed with a maximum-likelihood algorithm. The majority of significant phylogenies favor the eucarya and the archaca as sister groups. A smaller, but still substantial, portion of these significant phylogenies favor an eucarya/Gram-negative clade. These results indicate that support for the early history of life is not unequivocal. A chimeric origin of eukaryotes or an ancient, massive horizontal transfer of genes from Gram-negative bacteria to eucarya can explain many of the observed phylogenies.     

The effect of dietary fatty acids on lactic acid bacteria associated with the epithelial mucosa and from faecalia of Arctic charr, Salvelinus alpinus (L.)

Arctic charr, Salvelinus alpinus (L.), held in fresh water, were fed four experimental diets containing different polyunsaturated fatty acids (PUFA). In addition, one group fed a diet containing only coconut oil as sole lipid source served as control. The population of aerobic heterotrophic bacteria associated with the epithelial mucosa and the faecalia was estimated using the dilution plate technique. Generally, the population level of adherent bacteria increased along the digestive tract (stomach, small intestine and large intestine). Adherent Gram-negative and Gram-positive bacteria seemed to be present at equal levels in all parts of the alimentary tract. Lactic acid bacteria dominated among the Gram-positive bacteria, and they were detected in all regions of fish fed the PUFA supplemented diets. The frequency of lactic acid bacteria was highest in the digestive tract of fish fed diets with added 7.0% linolenic acid (18:3 n-3) or 4% of a PUFA mix. A lower frequency of lactic acid bacteria was found in fish fed dietary linoleic acid (18:2 n-6), and they were absent or present in low numbers in fish fed the coconut oil diet. It is suggested that dietary fatty acids affect the attachment sites for the gastrointestinal microbiota, possibly by modifying the fatty acid composition of the intestine wall. Numerical taxonomy procedures showed that the lactic acid bacteria Carnobacterium spp. and a Carnobacterium piscicola-like strain were predominant, with smaller numbers of Lactobacillus plantarum, Streptococcus spp. and Leuconostoc mesenteroides present. Seven strains of Carnobacterium spp. were further identified on the basis of 16S rDNA sequence analysis, and all these strains were identified as Carnobacterium piscicola.     

Effect of three months' frequent use of sugar-free chewing gum with and without urea on calculus formation

Studies on the relationship between gum-chewing and calculus formation have produced contradictory results, and it is not clear whether frequent use of chewing gum promotes or inhibits calculus formation. Also, little is known about whether the addition of a small amount of urea to the chewing gum influences calculus formation. The aim of this investigation was to study the effect of sugar-free chewing gum--with and without urea--on calculus formation and some associated clinical variables. Three three-month periods were studied in a double-blind, crossover design, during which the subjects: (1) chewed 5 pieces/day of a sugar-free, urea-containing chewing gum (20 mg urea/piece); (2) chewed 5 pieces/day of a sugar-free, non-urea-containing gum; or (3) performed no gum-chewing. Twenty-nine persons, all calculus-formers, participated. They were scored for calculus at mesio-lingual, lingual, and disto-lingual sites on the 6 anterior mandibular teeth according to the Volpe-Manhold index. Plaque and gingival bleeding index, stimulated salivary secretion rate and buffer capacity, resting plaque pH, mutans streptococci in saliva and plaque, and lactobacilli in saliva were also determined. No differences in calculus formation were found among the 3 periods. The resting plaque pH was higher after the period with urea-containing gum than after the period with non-urea-containing gum and the no-gum period (p < 0.05). A slight increase in stimulated salivary secretion rate was found after the 2 gum periods (p < 0.05). The plaque and gingival bleeding indices decreased, while resting plaque pH and salivary buffer capacity increased throughout the entire study (p < 0.05). No significant differences in prevalence of the acidogenic micro-organisms were found among the test periods. The main conclusion from this study is that three months' frequent use of sugar-free chewing gum--with or without urea--neither promotes nor inhibits calculus formation.     

DNA ploidy analysis in breast carcinoma. Comparison of unfixed and fixed tissue analyzed by image and flow cytometry

We present here the isolation and characterization of four antimicrobial peptides produced by a European bumblebee Bombus pascuorum. A 51-residue insect defensin was characterized which, like the Apis mellifera defensins, had a highly conserved 12-residue extension to its C-terminal compared to defensins from other insects. Monoisotopic mass analysis of the C-terminal of B. pascuorum defensin confirmed that this molecule was C-terminally amidated. This defensin showed strong anti-Gram-positive activity and some anti-fungal activity; also, in contrast to other insect defensins, it showed anti-Gram-negative activity. A 17-residue apidaecin was characterized, showing anti-Gram-negative activity, and differing by a single amino acid substitution from the A. mellifera apidaecin. A 39-residue abaecin was isolated, the largest proline-rich antimicrobial peptide characterized to date, which showed activity against both Gram-negative and Gram-positive bacteria. Finally, we isolated an N-terminally blocked molecule, with a molecular mass of 10,122 Da, which showed activity against Gram-negative bacteria only. These characteristics are reminiscent of hymenoptaecin from the honeybee A. mellifera, but a definitive characterization of this molecule awaits further work. No evidence of lysozyme activity was found in the haemolymph of challenged or naive B. pascuorum.     

2-Substituted penems with amino acid-related side chains: synthesis and antibacterial activity of a new series of beta-lactam antibiotics

A new series of 6-(hydroxyethyl)penems 2-substituted with amino acid-related side chains was synthesized. The nature of the amino acyl derivative proved to be crucial both from a synthetic point of view, as beta-lactam ring opening can compete with C-2 nucleophilic substitution, and for antibacterial activity. Primary amino acid amides emerged as the most suitable side chains for enhancing permeability through a Gram-negative outer membrane. In vitro activity of the new 2-[(aminoamido)methyl]penems 3a-u was influenced by the nature and position of the amide moiety, the ring size for cyclic amides, and the configuration of the amino acid. Compounds bearing amides derived from small N-methyl amino acids (such as 3a) or from cyclic amino acids (such as prolinamide 3p and 4-hydroxyprolinamide 3r) showed broad spectrum in vitro activity against both Gram-positive and Gram-negative microorganisms.