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PubMed2000

An ACC deaminase minus mutant of Enterobacter cloacae UW4 no longer promotes root elongation.

The ACC deaminase gene (acdS) from Enterobacter cloacae UW4 was replaced by homologous recombination with the acdS gene with a tetracycline resistance gene inserted within the coding region. Upon characterization of this AcdS minus mutant, it was determined that both ACC deaminase activity and the ability to promote the elongation of canola roots under gnotobiotic conditions were greatly diminished. This result is consistent with a previously postulated model that suggests that a major mechanism utilized by plant growth-promoting bacteria involves the lowering of plant ethylene levels, and hence ethylene inhibition of root elongation, by bacterial ACC deaminase.

Anti-Bacterial Agents↗
PubMed2001

Recombinant Enterobacter amnigenus highly toxic to Anopheles dirus mosquito larvae.

The mosquito-larvicidal binary toxin of Bacillus sphaericus 2297 was expressed in Enterobacter amnigenus, a Gram-negative bacterium isolated from Anopheles dirus larvae gut. The toxin was placed under the regulation of various promoters in order to improve the expression level of the toxin. Amongst the recombinants obtained, E. amnigenus harboring pBS373, a plasmid which contains the toxin genes under the control of the native B. sphaericus promoter, expressed a significant amount of protein, comparable to that found in B. sphaericus 2297. In addition, this recombinant provided approximately twenty times higher toxicity against second-instar Anopheles dirus larvae when compared to B. sphaericus 2297. The procedure of obtaining this environmentally isolated bacterium from larvae gut and introducing the system for mosquito-larvicidal toxin synthesis is noteworthy. The promising result presented here provides a substantial degree of confidence for further field studies.

Animals↗
PubMed1998

Plasmid-mediated gene transfer between insect-resident bacteria, Enterobacter cloacae, and plant-epiphytic bacteria, Erwinia herbicola, in guts of silkworm larvae.

Five strains of Enterobacter cloacae isolated from several species of plants and insects were able to grow in the guts of silkworm larvae. A much larger population of Ent. cloacae strains was detected in the insect guts and feces collected 3 and 6 days than in samples collected 1 day after feeding artificial diets contaminating these bacteria. Furthermore, insect-origin strains of Ent. cloacae were mated with a donor strain, epiphytic Erwinia herbicola, harboring RSF1010 and pBPW1::Tn7 plasmids in the insect guts by introducing these bacteria through separate artificial diets administered at different times. A number of transconjugants, Ent. cloacae strains which had acquired RSF1010 plasmid, were detected from guts and fecal samples at transfer frequencies of 10(-2) to 10(-3) per recipient. Thus, gene transfer between epiphytic Er. herbicola and insect-resident Ent. cloacae strains in the insect guts was confirmed. These findings may provide significant information about the role of "in insecta mating" in the evolution of these bacteria.

Animals↗
PubMed1998

The gene for indole-3-acetyl-L-aspartic acid hydrolase from Enterobacter agglomerans: molecular cloning, nucleotide sequence, and expression in Escherichia coli.

A 5.5-kb DNA fragment containing the indole-3-acetyl-aspartic acid (IAA-asp) hydrolase gene (iaaspH) was isolated from Enterobacter agglomerans strain GK12 using a hybridization probe based on the N-terminal amino acid sequence of the protein. The DNA sequence of a 2.4-kb region of this fragment was determined and revealed a 1311-nucleotide ORF large enough to encode the 45-kDa IAA-asp hydrolase. A 1.5-kb DNA fragment containing iaaspH was subcloned into the Escherichia coli expression plasmid pTTQ8 to yield plasmid pJCC2. Extracts of IPTG-induced E. coli cultures containing the pJCC2 recombinant plasmid showed IAA-asp hydrolase levels 5 to 10-fold higher than those in E. agglomerans extracts. Homology searches revealed that the IAA-asp hydrolase was similar to a variety of amidohydrolases. In addition, IAA-asp hydrolase showed 70% sequence identity to a putative thermostable carboxypeptidase of E. coli.

Amidohydrolases↗
PubMed2004

Enhanced production of acetoin and butanediol in recombinant Enterobacter aerogenes carrying Vitreoscilla hemoglobin gene.

Microbial production of butanediol and acetoin has received increasing interest because of their diverse potential practical uses. Although both products are fermentative in nature, their optimal production requires a low level of oxygen. In this study, the use of a recombinant oxygen uptake system on production of these metabolites was investigated. Enterobacter aerogenes was transformed with a pUC8-based plasmid carrying the gene (vgb) encoding Vitreoscilla (bacterial)hemoglobin (VHb). The presence of vgb and production of VHb by this strain resulted in an increase in viability from 72 to 96 h in culture, but no overall increase in cell mass. Accumulation of the fermentation products acetoin and butanediol were enhanced (up to 83%) by the presence of vgb/VHb. This vgb/VHb related effect appears to be due to an increase of flux through the acetoin/butanediol pathway, but not at the expense of acid production.

Acetoin↗
PubMed2005

Cells of Pseudomonas putida and Enterobacter sp. adapt to toxic organic compounds by increasing their size.

The phenol-degrading solvent-tolerant bacterium Pseudomonas putida P8 changed its cell shape when grown in the presence of aromatic compounds such as phenol and 4-chlorophenol. The sizes of cells that had been growing after addition of different concentrations of the toxic compounds were measured using a coulter counter that calculates the sizes of the rod-shaped bacteria to diameters of virtual spheres. The cells showed an increase in the diameter depending on the toxic effects of the applied concentrations of both solvents. The same effect was measured for an alkanol degrading bacterium, Enterobacter sp. VKGH12, in the presence of n-butanol. The reaction of the cells to different concentrations of n-butanol was examined by scanning electron microscopy. With this technique it could be shown that the size of the bacteria increased with increasing concentrations of n-butanol. These changes in cell size were dependent on the cellular activity and occurred only after addition of non-lethal concentrations. In the presence of lethal concentrations that completely inhibited cell growth, the cell sizes were similar to those of cells without intoxication. Taking into account the mathematical formula for spherical and cylindrical diameter and surface, respectively, the cells reacted to the presence of organic solvents by decreasing the ratio between surface and volume of the cells and therefore reducing their relative surfaces. As the cell surface and especially the cytoplasmic membrane are the major targets for the toxic effects of membrane-active compounds, this reduction of the relative surface represents an adaptive response to the presence of such compounds.

1-Butanol↗
PubMed2005

Effects of formate on fermentative hydrogen production by Enterobacter aerogenes.

This paper describes the effects of formate on fermentative hydrogen production by Enterobacter aerogenes by way of batch culture. When 20 mM formate was added to pH 6.3 and pH 5.8 E. aerogenes glucose cultures (formate culture) at the beginning of cultivation, hydrogen evolution through both glucose consumption and decomposition of the extrinsic formate occurred together, while hydrogen evolution occurred only through glucose consumption in the control cultures. The hydrogen evolution rates in the formate cultures were faster than in the control cultures, although cell growth and glucose consumption rates in the formate cultures were slower than the control cultures'. The decomposition rate of the extrinsic formate in the pH 5.8 formate culture was faster than in the pH 6.3 formate culture. The hydrogen yield from glucose in the pH 6.3 formate culture increased due to the increasing amount of the nicotinamide adenine dinucleotide for hydrogen production.

Bioreactors↗
PubMed2004

Antifungal and sprout regulatory bioactivities of phenylacetic acid, indole-3-acetic acid, and tyrosol isolated from the potato dry rot suppressive bacterium Enterobacter cloacae S11:T:07.

Enterobacter cloacae S11: T:07 (NRRL B-21050) is a promising biological control agent that has significantly reduced both fungal dry rot disease and sprouting in laboratory and pilot potato storages. The metabolites phenylacetic acid (PAA), indole-3-acetic acid (IAA), and tyrosol (TSL) were isolated from S11:T:07 liquid cultures provided with three different growth media. The bioactivities of these metabolites were investigated via thin-layer chromatography bioautography of antifungal activity, wounded potato assays of dry rot suppressiveness, and cored potato eye assays of sprout inhibition. Relative accumulations of PAA, IAA, and TSL in cultures were nutrient dependent. For the first time, IAA, TSL, and PAA were shown to have antifungal activity against the dry rot causative pathogen Gibberella pulicaris, and to suppress dry rot infection of wounded potatoes. Disease suppression was optimal when all three metabolites were applied in combination. Dosages of IAA that resulted in disease suppression also resulted in sprout inhibition. These results suggest the potential for designing culture production and formulation conditions to achieve a dual purpose biological control agent able to suppress both dry rot and sprouting of stored potatoes.

Antibiosis↗
PubMed2006

Improvement of biohydrogen production under decreased partial pressure of H2 by Enterobacter cloacae.

When the partial pressure of H(2) was decreased by lowering the total pressure in the headspace of the reactor in a batch fermentation process from 760 mm Hg to 380 mm Hg containing Enterobacter cloacae, the molar yield of H(2) increased from 1.9 mol to 3.9 mol H(2)/mol glucose. The maximum production rate was 0.017 mmol H(2)/h l at 380 mm Hg. The lag period as well as total batch time of H(2) production decreased using a decreased partial pressure.

Air Pressure↗
PubMed2006

Conversion of sucrose into isomaltulose by Enterobacter sp. FMB1, an isomaltulose-producing microorganism isolated from traditional Korean food.

Over 500 microorganisms isolated from Korean traditional foods, Maeju (source of soybean paste) and Nuruk (Korean koji), were screened to obtain an isomaltulose-producing microorganism. It was identified as Enterobacter sp. FMB-1 by 16S rRNA sequencing and the API 20E system. It had a greater than 90% conversion of sucrose (as 4 g/l) to isomaltulose in 2 days. Small amounts of trehalulose, glucose, and fructose were produced as byproducts, implying that this strain could be possibly employed in the production of isomaltulose in industry.

Enterobacter↗
PubMed2004

Vitreoscilla hemoglobin renders Enterobacter aerogenes highly susceptible to heavy metals.

When expressed in heterologous microorganisms Vitreoscilla hemoglobin (VHb) acts as oxygen storage and causes a higher oxygen uptake. In this study, the effect of this protein on growth, sensitivity and antioxidant properties of Enterobacter aerogenes exposed to metal stress was investigated. The strain expressing VHb was more sensitive to mercury and cadmium as the minimal inhibitory concentration (MIC) for these metals was up to 2-fold lower in this strain than the host and the recombinant strain carrying a comparable plasmid. At lower concentrations than MIC, the metals partially limited growth and caused an inhibition proportional to metal concentration applied. The growth pattern of VHb expressing strain was also distinctly different from other two non-hemoglobin strains. The hemoglobin containing strain showed substantially higher superoxide dismuates (SOD) activity than the non-hemoglobin strains, while catalase levels were similar in all strains. All strains exposed to copper, however, showed similar MIC values, growth patterns, and SOD and catalase levels.

Animals↗
PubMed1979

Clinical isolation and characterization of aminoglycoside-resistant small colony variants of Enterobacter aerogenes.

Small colony variants of Enterobacter aerogenes, as well as the parental large colony type, grew in blood drawn for cultures on three separate days from a patient who had received suboptimal gentamicin therapy. Minimum inhibitory concentrations of four aminoglycoside antibiotics were eight to more than 16 times higher for small colony variants than for the normal large colony type. Small colony variants had defective catalase activity, which may have interfered with oxidative metabolism and aminoglycoside uptake. Small colony variants reverted readily to the parental type in vitro in the absence of aminoglycosides. Clinically isolated small colony variants appeared similar to those selected in the presence of gentamicin in vitro, with respect to colony morphology, aminoglycoside resistance and catalase deficiency. The isolation of small colony variants during gentamicin therapy in vivo suggests that such variants may be a cause of treatment failure in patients receiving aminoglycosides.

Aminoglycosides↗
PubMed1989

Origin of p-aminobenzoic acid from chorismic rather than iso-chorismic acid in Enterobacter aerogenes and Streptomyces species.

Enzyme extracts from Enterobacter aerogenes (62-1), Streptomyces aminophilus, and Streptomyces coelicolor were used to investigate the biosynthesis of p-aminobenzoic acid. The enzyme preparations from E. aerogenes and S. aminophilus contained both p-aminobenzoate synthase and iso-chorismate synthase activity, and were able to convert both chorismic and iso-chorismic acid to p-aminobenzoic acid. The apparent KM for chorismic acid was, however, significantly lower than that for iso-chorismic acid, while the Vmax was identical for both substrates in both enzyme systems. The enzyme preparations from S. coelicolor did not contain iso-chorismate synthase activity and p-aminobenzoic acid synthesis took place in this system from chorismic acid only. It is concluded that iso-chorismic acid is not an obligatory intermediate in p-aminobenzoic acid biosynthesis in these organisms.

4-Aminobenzoic Acid↗
PubMed1986

Structure of the extracellular gelling polysaccharide produced by Enterobacter (NCIB 11870) species.

The gelling polysaccharide produced by a species of Enterobacter (NCIB 11870) contains L-fucose, D-glucose, and D-glucuronic acid in the ratios 1:2:1. Analysis of the methylated and methylated, carboxyl-reduced polysaccharide revealed terminal non-reducing glucose, (1----3)-linked fucose, (1----3,1----4)-linked glucose, and (1----4)-linked glucuronic acid in the ratios 1:1:1.2:0.8. From the results of Smith degradation of the polysaccharide and spectroscopic studies of the acidic tetra- and octa-saccharides produced by bacteriophage-induced enzymic depolymerization of the polysaccharide, the following tetrasaccharide repeating-unit is proposed. (Formula: see text). This repeating-unit is identical to that of the capsular polysaccharide produced by Klebsiella aerogenes serotype K54 except for the absence of O-acetyl groups. The effects of the O-acetyl groups on the secondary structure and rheological properties of these polysaccharides are discussed.

Carbohydrate Conformation↗
PubMed1989

Structure of the O-specific polysaccharide from Enterobacter cloacae strain N.C.T.C. 11579 (serogroup O10).

The O-specific polysaccharide from the reference strain (N.C.T.C. 11579) for Enterobacter cloacae serogroup O10 has been isolated and characterised. By means of n.m.r. spectroscopy and methylation analysis, and by studies of the products obtained by Smith degradation or by N-deacetylation-deamination, the repeating unit of the polysaccharide could be allocated the structure shown. The polysaccharides from two cross-reacting serogroups (O9 and O11) have the same monosaccharide composition. (Formula: see text)

Antigens, Bacterial↗
PubMed1983

EaeI: a restriction endonuclease from Enterobacter aerogenes.

We describe the isolation and characterization of a type II restriction endonuclease from Enterobacter aerogenes. This recognises and cleaves the family of related sequences: 5'-Py-G-G-C-C-Pu-3' to generate DNA fragments with 5'-tetranucleotide extensions. EaeI may be useful in molecular cloning experiments, especially in conjunction with other enzymes which generate the same terminal extensions. Potential problems in the methods used to determine the cleavage specificity are discussed.

Bacteriophage lambda↗
PubMed1987

Effect of lipid fluidity upon the activity and structure of the 39 kDa porin from Enterobacter cloacae 908S.

The 39 kDa porin from Enterobacter cloacae 908S was isolated in a lipopolysaccharide-free form using the non-ionic detergent, octylpentaoxyethylene, and reconstituted into vesicles of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC), respectively. Porin activity, measured by the rate of hydrolysis of the lipid-impermeant beta-lactam cephazoline by entrapped lactamase, could be demonstrated for porin-DMPC but not for porin-DOPC vesicles, and for the former was significantly lower in the gel than in the liquid-crystalline phase. The fluorescence changes are thought to arise from lipid phase-induced structural/dynamic changes of the porin structure.

Bacterial Outer Membrane Proteins↗
PubMed1992

The UDP-N-acetylglucosamine 1-carboxyvinyl-transferase of Enterobacter cloacae. Molecular cloning, sequencing of the gene and overexpression of the enzyme.

The UDP-N-acetylglucosamine 1-carboxyvinyltransferase (enolpyruvyltransferase, EC 2.5.1.7) which catalyses the first committed step in the biosynthesis of the bacterial cell-wall peptidoglycan was purified to near homogeneity from Enterobacter cloacae and the NH2-terminal amino-acid sequence determined. Using the polymerase chain reaction a 53-bp DNA fragment was synthesized; this fragment encodes the NH2-terminal sequence of the enzyme. A clone was then isolated which contained an open reading frame of 1257 bp coding for a protein of 419 amino acids. This protein was overexpressed 100-fold in transformed Escherichia coli cells and shown to possess the enolpyruvyltransferase activity. The overall amino-acid sequence of the enolpyruvyltransferase is significantly similar to that of the 5-enolpyruvylshikimate 3-phosphate synthase, the only other enzyme known to catalyse the transfer of the enolpyruvate moiety of phosphoenolpyruvate to a substrate.

Alkyl and Aryl Transferases↗