Abiotrophia balaenopterae sp. nov., isolated from the minke whale (Balaenoptera acutorostrata).
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Phenotypic and phylogenetic studies were performed on a hitherto undescribed micro-organism isolated from a minke whale (Balaenoptera acutorostrata). Comparative 16S rRNA gene sequencing studies demonstrated that the unknown strain constituted a new subline close to, but distinct from, Abiotrophia adiacens and Abiotrophia elegans. The unknown bacterium was readily distinguished from these two Abiotrophia species by biochemical tests and electrophoretic analysis of whole-cell proteins. On the basis of phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as Abiotrophia balaenopterae sp. nov., the type strain of which is M1975/96/1T (= CCUG 37380T). (+info)
Development of bacterial contamination during production of yeast extracts.
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Baker's yeast suspensions having bacterial populations of 10(6) and 10(8) CFU/ml were subjected to autolysis processes designed to obtain yeast extracts (YE). The bacterial contaminants added to the yeast cell suspensions were produced with spent broths obtained from a commercial yeast production plant and contained 59% cocci (Leuconostoc, Aerococcus, Lactococcus) as well as 41% bacilli (Bacillus). Autolyses were conducted at four different pH levels (4.0, 5.5, 7.0, and 8.5) and with two autolysis-promoting agents (ethyl acetate and chitosan). Processing parameters were more important than the initial bacterial population in the development of contaminating bacteria during manufacture of YE. Drops in the viable bacterial population after a 24-h autolysis were observed when pH was adjusted to 4.0 or when ethyl acetate was added. A significant interaction was found between the effects of pH and autolysis promoters on the bacterial population in YE, indicating that the activity of ethyl acetate, as opposed to that of chitosan, was not influenced by pH. (+info)
Abiotrophia elegans strains comprise 8% of the nutritionally variant streptococci isolated from the human mouth.
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Ninety-one isolates of nutritionally variant streptococci (NVS) that were previously isolated from the human mouth were regarded as consisting of 7 Streptococcus defectivus isolates, 78 Streptococcus adjacens isolates, and 6 Gemella morbillorum isolates. However, recent references to the taxonomic reclassification of NVS, from S. defectivus to Abiotrophia defectiva and from S. adjacens to Abiotrophia adiacens, and the newly introduced species Abiotrophia elegans as a third Abiotrophia species, emphasize the need for genetic analyses for identification of NVS. When PCR-restriction fragment length polymorphism (RFLP) and phylogenetic distances were examined based on 16S rRNA gene sequences, the results indicated that 7 of the 91 NVS isolates were closely related to A. elegans. These seven isolates consisted of four isolates previously identified as G. morbillorum and three isolates previously identified as S. adjacens. Two isolates previously identified as G. morbillorum were related to A. adiacens. In biochemical tests, A. elegans and the seven isolates related to it possessed arginine dihydrolase (ADH) activity but the other Abiotrophia species did not. As a result, A. elegans strains comprised 8% of the 91 NVS isolates. Our findings suggest that A. elegans, A. adiacens, and A. defectiva exist in the human mouth in proportions of about 1:11:1 and that A. elegans can be genetically distinguished from the other two Abiotrophia species by PCR-RFLP analysis of 16S rRNA gene sequences and can be biochemically distinguished by ADH activity. (+info)
Helcococcus ovis sp. nov., a gram-positive organism from sheep.
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Two strains of a hitherto undescribed Gram-positive, catalase-negative, facultatively anaerobic coccus isolated from sheep were characterized by phenotypic and molecular taxonomic methods. Comparative 16S rRNA gene sequencing studies demonstrated that the unknown strains were genealogically highly related and constitute a new line close to, but distinct from, Helcococcus kunzii. The unknown bacterium was readily distinguished from H. kunzii by biochemical tests and electrophoretic analysis of whole-cell proteins. Based on phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as Helcococcus ovis sp. nov. The type strain of Helcococcus ovis is CCUG 37441T. (+info)
Penaeidins, antimicrobial peptides with chitin-binding activity, are produced and stored in shrimp granulocytes and released after microbial challenge.
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Penaeidins are members of a new family of antimicrobial peptides isolated from a crustacean, which present both Gram-positive antibacterial and antifungal activities. We have studied the localization of synthesis and storage of penaeidins in the shrimp Penaeus vannamei. The distribution of penaeidin transcripts and peptides in various tissues reveals that penaeidins are constitutively synthesized and stored in the shrimp haemocytes. It was shown by immunocytochemistry, at both optical and ultrastructural levels, that the peptides are localized in granulocyte cytoplasmic granules. The expression and localization of penaeidins were further analysed in shrimp subjected to microbial challenge. We found that (1) penaeidin mRNA levels decrease in circulating haemocytes in the first 3 hours following stimulation and (2) an increase in plasma penaeidin concentration occurs after microbial challenge, together with (3) a penaeidin immunoreactivity in cuticular tissue, which can be related to the chitin-binding activity we demonstrate here for penaeidins. (+info)
Genetic heterogeneities and phenotypic characteristics of strains of the genus Abiotrophia and proposal of Abiotrophia para-adiacens sp. nov.
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The genus Abiotrophia represents a heterogeneous group of fastidious cocci that show a dependence on pyridoxal hydrochloride analogs for growth. The genetic heterogeneity in the genus Abiotrophia was examined by DNA-DNA hybridization, PCR assay of genomic DNA sequences, and restriction fragment length polymorphism and sequence homology analyses of the PCR-amplified 16S rRNA gene. Nine type or reference strains of Abiotrophia defectiva, Abiotrophia adiacens, and Abiotrophia elegans and 36 oral Abiotrophia isolates including the ones presumptively identified as Gemella morbillorum by the rapid ID32 STREP system were divided into four groups: A. defectiva (genotype 1), A. adiacens (genotype 2), A. elegans (genotype 4), and a fourth species (genotype 3) which we propose be named Abiotrophia para-adiacens sp. nov. A PCR assay specific for detection and identification of the novel Abiotrophia species was developed. A. para-adiacens generally produced beta-glucosidase but did not produce alpha- or beta-galactosidase or arginine dihydrolase, did not ferment, trehalose, pullulan, or tagatose, and was serotype IV, V, or VI. Thus, it was distinguished phenotypically from A. adiacens, A. elegans, and A. defectiva as well as, apparently, from the recently described species Abiotrophia balaenopterae sp. nov., which produces arginine dihydrolase and which ferments pullulan but not sucrose (P. A. Lawson et al., Int. J. Syst. Bacteriol. 49:503-506, 1999). Strain ATCC 27527, currently listed as G. morbillorum, was a member of the species A. para-adiacens. (+info)
On the interpretation of quantitative structure-function activity relationship data for lactate oxidase.
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The native flavin, FMN, has been removed from the l-lactate oxidase of Aerococcus viridans, and the apoprotein reconstituted with 12 FMN derivatives with various substituents at the flavin 6- and 8-positions. Impressive linear relationships are exhibited between the sum of the Hammett final sigma(para) and final sigma(ortho) parameters and the redox potentials of the free flavins, and between the redox potentials of the free and enzyme-bound flavins. Rapid reaction kinetics studies of the reconstituted enzymes with the substrates l-lactate and l-mandelate show an increase in the reduction rate constant with increasing redox potential, except that, with lactate, a limiting rate constant of approximately 700 s(-1) is obtained with flavins of high potential. Similar breakpoints are found in plots of the rate constants for flavin N5-sulfite adduct formation and for the reaction of the reduced enzymes with molecular oxygen. These results are interpreted in terms of a two-step equilibrium preceding the chemical reaction step, in which the second equilibrium step provides an upper limit to the rate with which the particular substrate or ligand is positioned with the flavin in the correct fashion for the observed chemical reaction to occur. The relationship of rate constants for flavin reduction and N5-sulfite adduct formation with flavin redox potential below the observed breakpoint indicate development of significant negative charge in the transition states of the reactions. In the case of reduction by substrate, the results are consistent either with a hydride transfer mechanism or with the so called "carbanion" mechanism, in which the substrate alpha-proton is abstracted by an enzyme base protected from exchange with solvent. These conclusions are supported by substrate alpha-deuterium isotope effects and by solvent viscosity effects on sulfite binding. (+info)
Heterologous inducible expression of Enterococcus faecalis pCF10 aggregation substance asc10 in Lactococcus lactis and Streptococcus gordonii contributes to cell hydrophobicity and adhesion to fibrin.
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Aggregation substance proteins encoded by the sex pheromone plasmid family of Enterococcus faecalis have been shown previously to contribute to the formation of a stable mating complex between donor and recipient cells and have been implicated in the virulence of this increasingly important nosocomial pathogen. In an effort to characterize the protein further, prgB, the gene encoding the aggregation substance Asc10 on pCF10, was cloned in a vector containing the nisin-inducible nisA promoter and its two-component regulatory system. Expression of aggregation substance after nisin addition to cultures of E. faecalis and the heterologous bacteria Lactococcus lactis and Streptococcus gordonii was demonstrated. Electron microscopy revealed that Asc10 was presented on the cell surfaces of E. faecalis and L. lactis but not on that of S. gordonii. The protein was also found in the cell culture supernatants of all three species. Characterization of Asc10 on the cell surfaces of E. faecalis and L. lactis revealed a significant increase in cell surface hydrophobicity upon expression of the protein. Heterologous expression of Asc10 on L. lactis also allowed the recognition of its binding ligand (EBS) on the enterococcal cell surface, as indicated by increased transfer of a conjugative transposon. We also found that adhesion of Asc10-expressing bacterial cells to fibrin was elevated, consistent with a role for the protein in the pathogenesis of enterococcal endocarditis. The data demonstrate that Asc10 expressed under the control of the nisA promoter in heterologous species will be an useful tool in the detailed characterization of this important enterococcal conjugation protein and virulence factor. (+info)