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Applied and Environmental Microbiology Jan 2007The gut bacteria of the North American medicinal leech, Macrobdella decora, were characterized. Biochemical tests and DNA sequences indicated that Aeromonas jandaei is...
The gut bacteria of the North American medicinal leech, Macrobdella decora, were characterized. Biochemical tests and DNA sequences indicated that Aeromonas jandaei is the dominant culturable symbiont in leeches from a broad geographic area. In this work we identified a new habitat for A. jandaei, and here we suggest that there is unexpected specificity between leeches and Aeromonas species.
Topics: Aeromonas; Animals; Bacterial Typing Techniques; Gastrointestinal Tract; Leeches; North America; Phenotype; Phylogeny; Sequence Analysis, DNA; Symbiosis
PubMed: 17114316
DOI: 10.1128/AEM.01282-06 -
FEBS Open Bio Jun 2018Understanding the role of specific amino acid residues in the molecular mechanism of a protein's function is one of the most challenging problems in modern biology. A...
Understanding the role of specific amino acid residues in the molecular mechanism of a protein's function is one of the most challenging problems in modern biology. A systematic bioinformatic analysis of protein families and superfamilies can help in the study of structure-function relationships and in the design of improved variants of enzymes/proteins, but represents a methodological challenge. The pyridoxal-5'-phosphate (PLP)-dependent enzymes are catalytically diverse and include the aspartate aminotransferase superfamily which implements a common structural framework known as type fold I. In this work, the recently developed bioinformatic online methods Mustguseal and Zebra were used to collect and study a large representative set of the aspartate aminotransferase superfamily with high structural, but low sequence similarity to l-threonine aldolase from (LTAaj), in order to identify conserved positions that provide general properties in the superfamily, and to reveal family-specific positions (FSPs) responsible for functional diversity. The roles of the identified residues in the catalytic mechanism and reaction specificity of LTAaj were then studied by experimental site-directed mutagenesis and molecular modelling. It was shown that FSPs determine reaction specificity by coordinating the PLP cofactor in the enzyme's active centre, thus influencing its activation and the tautomeric equilibrium of the intermediates, which can be used as hotspots to modulate the protein's functional properties. Mutagenesis at the selected FSPs in LTAaj led to a reduction in a native catalytic activity and increased the rate of promiscuous reactions. The results provide insight into the structural basis of catalytic promiscuity of the PLP-dependent enzymes and demonstrate the potential of bioinformatic analysis in studying structure-function relationship in protein superfamilies.
PubMed: 29928580
DOI: 10.1002/2211-5463.12441 -
Revista Da Sociedade Brasileira de... 2008Aeromonas spp is recognized as pathogenic to humans after consumption of contaminated water and food. In the present investigation, 2,323 rectal swab samples from...
Aeromonas spp is recognized as pathogenic to humans after consumption of contaminated water and food. In the present investigation, 2,323 rectal swab samples from newborns hospitalized in Rio de Janeiro were evaluated with a view to isolating Aeromonas. The samples were collected and sent to the national reference laboratory for cholera and other bacterial intestinal infections, at the Oswaldo Cruz Institute of the Oswaldo Cruz Foundation. The swabs were subjected to enrichment in alkaline peptonated water with the addition of 1% sodium chloride (NaCl) and alkaline peptonated water plus 3% NaCl (37 degrees C/18-24h) and were streaked onto agar that was selective for Pseudomonas-Aeromonas (GSP Agar). Fifty-six Aeromonas strains were isolated, distributed as follows: Aeromonas caviae (42.8%), Aeromonas media (25%), Aeromonas veronii biogroup sobria (10.7%), Aeromonas hydrophila (9%), Aeromonas veronii biogroup veronii (5.3%), Aeromonas sobria (1.8%), Aeromonas jandaei (1.8%), Aeromonas schubertii (1.8%) and Aeromonas sp (1.8%). Resistance to one or more antimicrobial drugs was observed in 26.8% of the strains. Considering the importance of Aeromonas, there is an urgent need to warn about this in relation to nosocomial infection control.
Topics: Aeromonas; Anti-Bacterial Agents; Drug Resistance, Microbial; Humans; Infant, Newborn; Microbial Sensitivity Tests; Rectum
PubMed: 18545840
DOI: 10.1590/s0037-86822008000200009 -
Frontiers in Bioengineering and... 2019Most of biochemical and mutagenesis studies performed with L-threonine aldolases were done with respect to natural activity, the cleavage of L-threonine and sometimes...
Most of biochemical and mutagenesis studies performed with L-threonine aldolases were done with respect to natural activity, the cleavage of L-threonine and sometimes L-β-phenylserine. However, the properties of variants and the impact of mutations on the product synthesis are more interesting from an applications point of view. Here we performed site-directed mutagenesis of active site residues of L-threonine aldolase from to analyze their impact on the retro-aldol activity and on the aldol synthesis of L-β-phenylserine and L-α-alkyl-β-phenylserines. Consequently, reduced retro-aldol activity upon mutation of catalytically important residues led to increased conversions and diastereoselectivities in the synthetic direction. Thus, L-β-phenylserine can be produced with conversions up to 60% and .'s up to 80% () under kinetic control. Furthermorem, the donor specificity of L-threonine aldolase was increased upon mutation of active site residues, which enlarged the pocket size for an efficient binding and stabilization of donor molecules in the active site. This study broadens the knowledge about L-threonine aldolase catalyzed reactions and improves the synthetic protocols for the biocatalytic asymmetric synthesis of unnatural amino acids.
PubMed: 31192202
DOI: 10.3389/fbioe.2019.00119 -
Applied and Environmental Microbiology Dec 1999The hemolytic activity and siderophore production of several strains of motile aeromonads were determined. The hemolytic activity of Aeromonas caviae and Aeromonas...
The hemolytic activity and siderophore production of several strains of motile aeromonads were determined. The hemolytic activity of Aeromonas caviae and Aeromonas eucrenophila was enhanced after trypsinization of the samples. The enhancement of hemolysis was observed in strains that carried an aerolysin-like gene, detected by a PCR procedure. Siderophore production was demonstrated in all but one strain of Aeromonas jandaei. No apparent relationship was observed between the presence of plasmid DNA and hemolysis or siderophore production.
Topics: Aeromonas; Animals; Bacterial Toxins; Esocidae; Hemolysin Proteins; Hemolysis; Oncorhynchus mykiss; Plasmids; Polymerase Chain Reaction; Pore Forming Cytotoxic Proteins; Rabbits; Sheep; Siderophores; Trout
PubMed: 10584028
DOI: 10.1128/AEM.65.12.5612-5614.1999 -
Applied and Environmental Microbiology Nov 1995Aeromonas isolates were obtained from fish intestines, water, and sediments from an urban river and identified by the DNA-DNA microplate hybridization method. The...
Aeromonas isolates were obtained from fish intestines, water, and sediments from an urban river and identified by the DNA-DNA microplate hybridization method. The isolates were Aeromonas veronii (22%), Aeromonas caviae (18%), Aeromonas hydrophila (13%), Aeromonas sobria (8%), Aeromonas jandaei (7%), and other Aeromonas spp. (33%). Aeromonas species occurred at high densities with high incidences, regardless of season. The results strongly suggest that aeromonads are indigenous in fish intestines, water, and sediments of rivers and have the potential to be predominant in aquatic environments.
PubMed: 16535171
DOI: 10.1128/aem.61.11.4128-4130.1995 -
Revista Chilena de Infectologia :... Jun 2007Extraintestinal infections caused by the genera Aeromonas, Vibrio and Plesiomonas have high morbidity and mortality rates in different areas of world. From January 2002...
Extraintestinal infections caused by the genera Aeromonas, Vibrio and Plesiomonas have high morbidity and mortality rates in different areas of world. From January 2002 to December 2003, the National Reference Laboratory for Acute Diarrhoeal Diseases of the Pedro Kourí Tropical Medicine Institute received 95 gram-negative, facultative anaerobic, oxidase positive bacilli strains from different extraintestinal specimen (blood, ear exudates, infected wounds, conjunctive exudates, urine, and catheters, among others) sent by different provincial laboratories along the country. Aeromonas caviae, Aeromonas veronii bv sobria, Aeromonas jandaei, Vibrio cholerae no-O1, Vibrio vulnificus, Vibrio fluvialis and Plesiomonas shigelloides were the species most frequently found in the sample analysed.
Topics: Aeromonas; Bacterial Typing Techniques; Cuba; Humans; Plesiomonas; Vibrio cholerae
PubMed: 17554439
DOI: 10.4067/s0716-10182007000300005 -
Applied and Environmental Microbiology Aug 1994Aeromonas isolates were obtained from the intestinal tracts of six species of cultured freshwater fish and identified on the basis of their genotypic and phenotypic...
Aeromonas isolates were obtained from the intestinal tracts of six species of cultured freshwater fish and identified on the basis of their genotypic and phenotypic characters. The microplate hybridization method could differentiate type strains of Aeromonas species and related bacteria. DNA-DNA hybridization analysis showed that 65 aeromonad isolates were 72 to 100% related with either Aeromonas caviae, Aeromonas hydrophila, Aeromonas jandaei, Aeromonas sobria, or Aeromonas veronii. As many as 48% of the genotypically identified A. caviae, A. hydrophila, and A. sobria isolates differed from the type strains of corresponding species in one to three phenotypic characters. These results strongly suggest that not all aeromonad isolates from freshwater fish could be identified correctly on the basis of only the phenotypic characters, indicating the usefulness of the microplate hybridization method for the identification of aeromonads.
PubMed: 16349363
DOI: 10.1128/aem.60.8.3036-3038.1994 -
Applied and Environmental Microbiology Feb 1998A low-specificity L-threonine aldolase (L-TA) gene from Pseudomonas sp. strain NCIMB 10558 was cloned and sequenced. The gene contains an open reading frame consisting...
A low-specificity L-threonine aldolase (L-TA) gene from Pseudomonas sp. strain NCIMB 10558 was cloned and sequenced. The gene contains an open reading frame consisting of 1,041 nucleotides corresponding to 346 amino acid residues. The gene was overexpressed in Escherichia coli cells, and the recombinant enzyme was purified and characterized. The enzyme, requiring pyridoxal 5'-phosphate as a coenzyme, is strictly L specific at the alpha position, whereas it cannot distinguish between threo and erythro forms at the beta position. In addition to threonine, the enzyme also acts on various other L-beta-hydroxy-alpha-amino acids, including L-beta-3,4-dihydroxyphenylserine, L-beta-3,4-methylenedioxyphenylserine, and L-beta-phenylserine. The predicted amino acid sequence displayed less than 20% identity with those of low-specificity L-TA from Saccharomyces cerevisiae, L-allo-threonine aldolase from Aeromonas jandaei, and four relevant hypothetical proteins from other microorganisms. However, lysine 207 of low-specificity L-TA from Pseudomonas sp. strain NCIMB 10558 was found to be completely conserved in these proteins. Site-directed mutagenesis experiments showed that substitution of Lys207 with Ala or Arg resulted in a significant loss of enzyme activity, with the corresponding disappearance of the absorption maximum at 420 nm. Thus, Lys207 of the L-TA probably functions as an essential catalytic residue, forming an internal Schiff base with the pyridoxal 5'-phosphate of the enzyme to catalyze the reversible aldol reaction.
Topics: Amino Acid Sequence; Binding Sites; Cloning, Molecular; Escherichia coli; Glycine Hydroxymethyltransferase; Hydrogen-Ion Concentration; Molecular Sequence Data; Molecular Weight; Pseudomonas; Substrate Specificity; Temperature
PubMed: 9464392
DOI: 10.1128/AEM.64.2.549-554.1998