Enzymatical properties of psychrophilic phosphatase I.
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Phosphatase I purified from a psychrophile (Shewanella sp.) [Tsuruta et al. (1998) J. Biochem. 123, 219-225] dephosphorylated O-phospho-L-tyrosine and phospho-tyrosyl residues in phosphorylated poly(Glu4,Tyr1) random polymer (polyEY) and phosphorylated myelin basic protein (MBP) but not phosphoseryl and/or phosphothreonyl residues in phosphorylated histone H1, casein and phosphorylase a, indicating that the enzyme showed protein-tyrosine-phosphatase (PTPase, EC 3.1.3.48)-like activity in vitro. The enzyme was remarkably inhibited by diethylpyrocarbonate (DEPC), monoiodoacetic acid (MIAA), and monoiodoacetamide (MIAM). Binding of 1 mol of DEPC to 1 mol of the enzyme caused complete inhibition of the enzyme; and 0.88 mol of 1-carboxymethylated histidine per mole of the enzyme was found when 90% of enzyme activity was lost by modification with 14C-MIAA. These results indicated that this psychrophilic enzyme was a PTPase-like enzyme with histidine as its catalytic residue. (+info)
Primary Shewanella alga septicemia in a patient on hemodialysis.
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We report the first Japanese case of primary septicemia with Shewanella alga and also describe the bacteriological characteristics of and results of antibiotic susceptibility tests of the isolate. S. alga was repeatedly isolated, at times simultaneously with Escherichia coli, from the blood of a 64-year-old female undergoing hemodialysis. The isolated organism was determined to be S. alga based on recently published identification criteria, such as hemolysis on sheep blood agar, no acid production from carbohydrates, and growth on agar containing 6. 5% NaCl. Results of antibiotic susceptibility tests demonstrated that the isolate was sensitive to levofloxacin and cefpirome (MICs, 128, 64, and 8 microg/ml, respectively). Although the role of S. alga as a human pathogen has not been fully determined, accumulating data suggest that this organism may be a potential pathogen, especially in compromised hosts. (+info)
Iron isotope biosignatures.
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The (56)Fe/(54)Fe of Fe-bearing phases precipitated in sedimentary environments varies by 2.5 per mil (delta(56)Fe values of +0.9 to -1. 6 per mil). In contrast, the (56)Fe/(54)Fe of Fe-bearing phases in igneous rocks from Earth and the moon does not vary measurably (delta(56)Fe = 0.0 +/- 0.3 per mil). Experiments with dissimilatory Fe-reducing bacteria of the genus Shewanella algae grown on a ferrihydrite substrate indicate that the delta(56)Fe of ferrous Fe in solution is isotopically lighter than the ferrihydrite substrate by 1.3 per mil. Therefore, the range in delta(56)Fe values of sedimentary rocks may reflect biogenic fractionation, and the isotopic composition of Fe may be used to trace the distribution of microorganisms in modern and ancient Earth. (+info)
A study of deep-sea natural microbial populations and barophilic pure cultures using a high-pressure chemostat.
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Continuous cultures in which a high-pressure chemostat was used were employed to study the growth responses of (i) deep-sea microbial populations with the naturally occurring carbon available in seawater and with limiting concentrations of supplemental organic substrates and (ii) pure cultures of copiotrophic barophilic and barotolerant deep-sea isolates in the presence of limiting carbon concentrations at various pressures, dilution rates, and temperatures. We found that the growth rates of natural populations could not be measured or were extremely low (e.g., a doubling time of 629 h), as determined from the difference between the dilution rate and the washout rate. A low concentration of supplemental carbon (0.33 mg/liter) resulted in positive growth responses in the natural population, which resulted in an increase in the number of cells and eventually a steady population of cells. We found that the growth responses to imposed growth pressure by barophilic and barotolerant pure-culture isolates that were previously isolated and characterized under high-nutrient-concentration conditions were maintained under the low-nutrient-concentration limiting conditions (0.33 to 3.33 mg of C per liter) characteristic of the deep-sea environment. Our results indicate that deep-sea microbes can respond to small changes in substrate availability. Also, barophilic microbes that are copiotrophic as determined by their isolation in the presence of high carbon concentrations and their preference for high carbon concentrations are versatile and are able to compete and grow as barophiles in the low-carbon-concentration oligotrophic deep-sea environment in which they normally exist. (+info)
Infective endocarditis complicated with progressive heart failure due to beta-lactamase-producing Cardiobacterium hominis.
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We describe a 66-year-old woman with infective endocarditis due to Cardiobacterium hominis whose condition, complicated by severe aortic regurgitation and congestive heart failure, necessitated aortic valve replacement despite treatment with ceftriaxone followed by ciprofloxacin. The blood isolate of C. hominis produced beta-lactamase and exhibited high-level resistance to penicillin (MIC, >==256 microgram/ml) and reduced susceptibility to vancomycin (MIC, 8 microgram/ml). (+info)
Muricauda ruestringensis gen. nov., sp. nov., a facultatively anaerobic, appendaged bacterium from German North Sea intertidal sediment.
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A gram-negative, facultatively anaerobic bacterium with appendages was isolated from continuous cultures with a seawater-sediment suspension containing hexadecane as the sole carbon source. Although this organism was isolated from a hexadecane-degrading bacterial community, it was not able to degrade hexadecane. However, this bacterium was able to use different sugars and amino acids for growth, indicating that it probably profits from the lysis or from products like surfactants of other cells in the community. 16S rDNA analysis demonstrated that the isolated strain is phylogenetically related to the family Flavobacteriaceae of the phylum 'Cytophaga-Flavobacterium-Bacteroides'. Evidence based on phenotypic characteristics and 16S rDNA analysis supports the conclusion that this bacterium is distinct from its nearest relative, Zobellia uliginosa (90.72% similarity in 16S rRNA gene sequence), and from the other genera of the Flavobacteriaceae. It is therefore proposed that the isolated marine bacterium represents a novel taxon, designated Muricauda ruestringensis gen. nov., sp. nov. The type strain is strain B1T (= DSM 13258T = LMG 19739T). (+info)
Paenibacillus koleovorans sp. nov., able to grow on the sheath of Sphaerotilus natans.
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Two bacterial strains that are able to grow specifically on the sheath of a sheathed filamentous bacterium, Sphaerotilus natans, were isolated from soil samples. The sheath-degrading organisms, designated strains TB(T) and TK, are facultatively anaerobic and form endospores. The Gram reaction was negative at all stages of cultivation. The optimum growth temperature and pH were 30 degrees C and pH 7. The DNA G+C content was 54.0-55.8 mol%. MK-7 was the predominant menaquinone and anteiso-C15:0 was the major fatty acid. Phylogenetic analysis based on the 16S rDNA sequences revealed that the isolates were closely related to Paenibacillus chondroitinus, Paenibacillus alginolyticus, Paenibacillus koreensis, Paenibacillus validus, Paenibacillus larvae subsp. larvae and P. larvae subsp. pulvifaciens. The sequences were found to contain consensus sequences characteristic of all Paenibacillus species. The isolates were able to lyse and utilize the purified sheath of S. natans as the sole carbon and energy source. Acid was not produced from common carbon sources, allowing easy distinction from other members of Paenibacillus. It is concluded that the two strains represent a novel Paenibacillus species, for which the name Paenibacillus koleovorans sp. nov. is proposed. The type strain is strain TB(T) (= JCM 11186T = IAM 14926T = KCTC 13912T). (+info)
Cloning, sequencing, and expression of the Zymomonas mobilis fructokinase gene and structural comparison of the enzyme with other hexose kinases.
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The frk gene encoding the enzyme fructokinase (fructose 6-phosphotransferase [EC 2.7.1.4]) from Zymomonas mobilis has been isolated on a partial TaqI digest fragment of the genome and sequenced. An open reading frame of 906 bp corresponding to 302 amino acids was identified on a 3-kbp TaqI fragment. The deduced amino acid sequence corresponds to the first 20 amino acids (including an N-terminal methionine) determined by amino acid sequencing of the purified protein. The 118 bp preceding the methionine codon on this fragment does not appear to contain a promoter sequence. There was weak expression of the active enzyme in the recombinant Escherichia coli clone under control of the lac promoter on the pUC plasmid. Comparison of the amino acid sequence with that of the glucokinase enzyme (EC 2.7.1.2) from Z. mobilis reveals relatively little homology, despite the fact that fructokinase also binds glucose and has kinetic and structural properties similar to those of glucokinase. Also, there is little homology with hexose kinases that have been sequenced from other organisms. Northern (RNA) blot analysis showed that the frk transcript is 1.2 kb long. Fructokinase activity is elevated up to twofold when Z. mobilis was grown on fructose instead of glucose, and there was a parallel increase in frk mRNA levels. Differential mRNA stability was not a factor, since the half-lives of the frk transcript were 6.2 min for glucose-grown cells and 6.6 min for fructose-grown cells. (+info)