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PubMed2004

Biodegradation of chlorpyrifos by enterobacter strain B-14 and its use in bioremediation of contaminated soils.

Six chlorpyrifos-degrading bacteria were isolated from an Australian soil and compared by biochemical and molecular methods. The isolates were indistinguishable, and one (strain B-14) was selected for further analysis. This strain showed greatest similarity to members of the order Enterobacteriales and was closest to members of the Enterobacter asburiae group. The ability of the strain to mineralize chlorpyrifos was investigated under different culture conditions, and the strain utilized chlorpyrifos as the sole source of carbon and phosphorus. Studies with ring or uniformly labeled [(14)C]chlorpyrifos in liquid culture demonstrated that the isolate hydrolyzed chlorpyrifos to diethylthiophospshate (DETP) and 3, 5, 6-trichloro-2-pyridinol, and utilized DETP for growth and energy. The isolate was found to possess mono- and diphosphatase activities along with a phosphotriesterase activity. Addition of other sources of carbon (glucose and succinate) resulted in slowing down of the initial rate of degradation of chlorpyrifos. The isolate degraded the DETP-containing organophosphates parathion, diazinon, coumaphos, and isazofos when provided as the sole source of carbon and phosphorus, but not fenamiphos, fonofos, ethoprop, and cadusafos, which have different side chains. Studies of the molecular basis of degradation suggested that the degrading ability could be polygenic and chromosome based. Further studies revealed that the strain possessed a novel phosphotriesterase enzyme system, as the gene coding for this enzyme had a different sequence from the widely studied organophosphate-degrading gene (opd). The addition of strain B-14 (10(6) cells g(-1)) to soil with a low indigenous population of chlorpyrifos-degrading bacteria treated with 35 mg of chlorpyrifos kg(-1) resulted in a higher degradation rate than was observed in noninoculated soils. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.

Biodegradation, Environmental↗
PubMed1968

Nitrogen-deficient medium in the differential isolation of Klebsiella and Enterobacter from feces.

On a nitrogen-deficient agar medium, the tribe Klebsielleae formed large, glistening, mucoid colonies which were easily distinguished from other colony types. Of 113 Klebsielleae isolates from human feces which were characterized, Klebsiella accounted for 88% of the total; 75% were K. pneumoniae; K. ozaenae (13%) was isolated from one individual only. The remaining strains (12%) were identified as Enterobacter cloacae. Counts (for the tribe) ranged from 10(2) to 10(6), with a median of 10(4); 9 of 53 stool specimens were negative. K. pneumoniae was also isolated from 6 of 41 frozen foil-pack foods. Anaerobic studies at room temperature and 37 C revealed no appreciable differences from aerobic plates. The nitrogen-deficient medium appeared better than E M B for isolation of Klebsielleae when they were present in low numbers relative to other coliforms; slime production by Klebsielleae concomitant with minimal growth of other bacteria is involved.

Culture Media↗
PubMed1972

Comparison of the substrate specificities of the -lactamases from Klebsiella aerogenes 1082E and Enterobacter cloacae P99.

A potent beta-lactamase (EC 3.5.2.6) produced by a strain of Klebsiella aerogenes (K. pneumoniae), 1082E, isolated from a hospital patient, has been examined. Its properties were different from those of most gram-negative beta-lactamases previously reported. The enzyme has been partly purified, and its activity against a range of substrates has been compared with that of the enzyme from Enterobacter cloacae (Aerobacter cloacae) P99. The K. aerogenes enzyme, although predominantly a penicillinase, had a wide range of specificity. In addition to hydrolyzing the cephalosporins, it attacked the normally beta-lactamaseresistant compounds methicillin and cloxacillin as well as cephalosporin analogues with the same acyl substituents. The results obtained with the E. cloacae enzyme confirmed its cephalosporinase activity and showed that, unlike the enzyme from K. aerogenes, it was relatively inactive against the penicillins.

Ampicillin↗
PubMed1994

Invasion of rabbit ileal tissue by Enterobacter cloacae varies with the concentration of OmpX in the outer membrane.

The outer membrane protein OmpX of Enterobacter cloacae shows high amino acid homology with virulence proteins PagC and Rck from Salmonella typhimurium and with Ail from Yersinia enterocolitica. Here we demonstrate a role for OmpX in the invasion of rabbit ileal tissue by E. cloacae. An organ culture system was used for maintenance of rabbit gut tissue during the experiments. The invasiveness of three E. cloacae strains, which differed in OmpX content, were compared with each other and with that of Salmonella typhimurium TML (a highly invasive strain) and S. typhimurium LT7 (a noninvasive strain). There was no significant difference between the invasiveness of the wild type and that of an ompX deletion mutant strain of E. cloacae; they were equally as invasive or less invasive than S. typhimurium LT7. The invasiveness of an OmpX overproducer strain of E. cloacae was 10-fold higher than that of its immediate parent carrying only the multicopy plasmid, higher than that of S. typhimurium LT7, but lower than that of S. typhimurium TML. The invasiveness of E. cloacae thus varied directly with the level of OmpX in the outer membrane in rabbit ileal enterocytes challenged in situ.

Animals↗
PubMed1997

Specificity of the high-mannose recognition site between Enterobacter cloacae pili adhesin and HT-29 cell membranes.

Enterobacter cloacae has been implicated as one of the causative agents in neonatal infection and causes a septicemia thought to be initiated via the gastrointestinal tract. The adhesion of radiolabeled E. cloacae to HT-29 cells was concentration and temperature dependent and was effectively blocked by unlabeled bacteria or by millimolar concentrations of alpha-mannosides and micromolar concentrations of high-mannose oligosaccharides. A variety of well-characterized mannose oligosaccharides were tested as inhibitors of adhesion. The best inhibitor was the Man9(GlcNAc)2-tyrosinamide, which was considerably better than other tyrosinamide-linked oligosaccharides such as Man7(GlcNAc)2, Man6(GlcNAc)2 or Man5(GlcNAc)2. Further evidence that the bacteria preferred Man9(GlcNAc)2 structures was obtained by growing HT-29 cells in the presence of glycoprotein processing inhibitors that block mannosidase I and increase the amount of protein-bound Man9(GlcNAc)2 at the cell surface. Such cells bound 1.5- to 2-fold more bacteria than did control cells. The adhesin involved in binding to high-mannose structures was purified from isolated pili. On sodium dodecyl sulfate-gels, a 35-kDa protein was identified by its specific binding to a mannose-containing biotinylated albumin. The amino acid sequences of several peptides from the 35-kDa subunit showed over 85% identity to FimH, the mannose-specific adhesin of Salmonella typhimurium. Pili were labeled with 125I and examined for the ability to bind to HT-29 cells. Binding showed saturation kinetics and was inhibited by the addition of Man9(GlcNAc)2-tyrosinamide but not by oligosaccharides with fewer mannose residues. Polyclonal antibody against this 35-kDa protein also effectively blocked adhesion of pili or E. cloacae, but no effect was observed with nonspecific antibody. These studies demonstrate that the 35-kDa pilus subunit is a lectin whose specificity is directed toward Man, (GlcNAc)2 oligosaccharides.

1-Deoxynojirimycin↗
PubMed1998

Occurrence of virulence-associated properties in Enterobacter cloacae.

Enterobacter cloacae is not a primary human pathogen but has been considered to be an important cause of nosocomial infections. Even so, there are almost no reports on its ability to produce recognized virulence-associated properties. In this study, we show that most of the E. cloacae strains examined were resistant to serum bactericidal activity and were able to produce aerobactin and mannose-sensitive hemagglutinin, and all of them could adhere to and invade HEp-2 cells. Since E. cloacae is part of the normal intestinal floras of many individuals, we believe that infectious disease due to endogenous E. cloacae might be a result of both host predisposing factors and the bacterial virulence determinants that we have detected in this survey.

Bacterial Adhesion↗
PubMed1974

Effect of sodium on the transport and utilization of citric acid by Aerobacter (Enterobacter) aerogenes.

Sodium inhibited citrate uptake by two of the four strains of Aerobacter (Enterobacter) aerogenes used in these studies, had no effect on one strain, and stimulated citrate uptake by one strain. Two of the four strains grew well anaerobically on citrate in the presence of Na(+), one grew poorly, and one grew not at all either in the presence or absence of Na(+). Na(+) stimulated the aerobic growth of one strain on citrate, increased the total growth but not the rate of growth of one strain, and prolonged the lag phase but not the rate of growth or total growth of two strains. The experimental data reported herein, therefore, indicate that there are appreciable physiological differences among strains of A. aerogenes.

Aerobiosis↗
PubMed1975

Physiological and biochemical role of the butanediol pathway in Aerobacter (Enterobacter) aerogenes.

Aerobacter (Enterobacter) aerogenes wild type and three mutants deficient in the formation of acetoin and 2,3-butanediol were grown in a glucose minimal medium. Culture densities, pH, and diacetyl, acetoin, and 2,3-butanediol levels were recorded. The pH in wild-type cultures dropped from 7.0 to 5.8, remained constant while acetoin and 2,3-butanediol were formed, and increased to pH 6.5 after exhaustion of the carbon source. More 2,3-butanediol than acetoin was formed initially, but after glucose exhaustion reoxidation to acetoin occurred. The three mutants differed from the wild type in yielding acid cultures (pH below 4.5). The wild type and one of the mutants were grown exponentially under aerobic and anaerobic conditions with the pH fixed at 7.0, 5.8, and 5.0, respectively. Growth rates decreased with decreasing pH values. Aerobically, this effect was weak, and the two strains were affected to the same degree. Under anaerobic conditions, the growth rates were markedly inhibited at a low pH, and the mutant was slightly more affected than the wild type. Levels of alcohol dehydrogenase were low under all conditions, indicating that the enzyme plays no role during exponential growth. The levels of diacetyl (acetoin) reductase, lactate dehydrogenase, and phosphotransacetylase were independent of the pH during aerobic growth of the two strains. Under anaerobic conditions, the formation of diacetyl (acetoin) reductase was pH dependent, with much higher levels of the enzyme at pH 5.0 than at pH 7.0. Lactate dehydrogenase and phosphotransacetylase revealed the same pattern of pH-dependent formation in the mutant, but not in the wild type.

Acetates↗
PubMed1975

Induction of citrate lyase in Enterobacter cloacae grown under aerated conditions and its effect on citrate metabolism.

Growth of Enterobacter cloacae on K+ citrate under aerated conditions (no detectable oxygen tension in the medium even though it was aerated) was slower (mean generation time, 130 min) than under aerobic conditions (mean generation time, 72 min), but with a faster utilization of citrate, resulting in a molar growth yield of 10.6 g (dry weight) of cells per mol of citrate utilized versus 40 g (dry weight) of cells per mol of citrate utilized for aerobic growth. The rapid utilization of citrate under aerated conditions was apparently due to the induction of citrate lyase and was supported by the finding that cells excreted acetate and a small amount of oxalacetate under aerated conditions, but not under aerobic conditions when the cells were devoid of citrate lyase activity. The activity of oxalacetate decarboxylase in aerated cells was slightly lower than in aerobic cells, indicating that little of the oxalacetate produced by the citrate lyase was metabolized by the decarboxylase. Oxalacetate was probably metabolized by malate dehydrogenase, previously shown to be present in anaerobic and aerobic cells. Thus, about 70% of the citrate was cleaved by the citrate lyase, resulting in little or no production of energy for growth. The remaining citrate was metabolized via the citric acid cycle under aerated conditions, since the cells contained alpha-ketoglutarate dehydrogenase at the same level as in aerobically grown cells. The presence of the other enzymes of the cycle was shown in earlier studies.

Acetates↗
PubMed1977

Energy-dependent inactivation of citrate lyase in Enterobacter aerogenes.

Enterobacter aerogenes was grown in continous culture with ammonia as the growth-limiting substrate, and changes in citrate lyase and citrate synthase activities were monitored after growth shifts from anaerobic growth on citrate to aerobic growth on citrate, aerobic growth on glucose, anaerobic growth on glucose, and anaerobic growth on glucose plus nitrate. Citrate lyase was inactivated during aerobic growth on glucose and during anaerobic growth with glucose plus nitrate. Inactivation did not occur during anaerobic growth on glucose, and as a result of the simultaneous presence of citrate lyase and citrate synthase, growth difficulties were observed. Citrate lyase inactivation consisted of deacetylation of the enzyme. The corresponding deacetylase could not be demonstrated in cell extracts, and it is concluded that, as in a number of other inactivations, electron transport to oxygen or nitrate was required for inactivation.

Aerobiosis↗
PubMed1977

Host-dependent, thermosensitive replication of an R plasmid, pJY5, isolated from Enterobacter cloacae.

The thermosensitive replication of an R plasmid, pJY5, isolated from Enterobacter cloacae, was studied. pJY5 consisted of 61 million daltons of covalently closed circular (CCC) deoxyribonucleic acid (DNA) with a buoyant density of 1.714 g/cm3 (55 mol % guanine plus cytosine). In Escherichia coli, this plasmid replicated stringently at 32 degrees C, but ceased its CCC DNA replication after a short incubation at 42 degrees C, resulting in production of R- segregants. The thermosensitive replication of pJY5 was not overcome by the coexistence of non-thermosensitive R plasmids. The plasmid manifested an inhibitory effect on host bacterial cell growth at 42 degrees C, although the effect was less prominent than that of R plasmids belonging to the T-incompatibility group, Rts1, R401, and R402. When the pJY5 plasmid was transferred into E. cloacae, however, no R- segregants were detected at any culture temperature, even 42 degrees C. Alkaline sucrose gradient analysis revealed that a significant amount of pJY5 CCC DNA was synthesized in E. cloacae at the high temperature but not in E. coli. Furthermore, the growth-inhibitory effect of pJY5 on hosts at 42 degrees C was not observed in E. cloacae. On the other hand, Rts1 and R401 were found to be thermosensitive in E. cloacae as well as in E. coli.

DNA, Bacterial↗
PubMed1979

Purification and characterization of cloacin DF13 receptor from Enterobacter cloacae and its interaction with cloacin DF13 in vitro.

Extraction of the crude cell envelope fraction of cloacin DF13-susceptible Enterobacter cloacae strain 02 with Triton X-100 and ethylenediaminetetraacetate solubilized an outer membrane fraction which neutralized the lethal activity of cloacin DF13. A similar fraction could not be isolated from strains known to be lacking functional cloacin DF13 receptors. On this basis the isolated outer membrane fraction was assumed to contain the specific cloacin DF13 receptor. The receptor was purified to homogeneity by acetone precipitation and affinity chromatography, using cloacin DF13 as a ligand. The purified receptor was identified as a protein which consisted of a single polypeptide chain with an apparent molecular weight of 90,000 and a preponderance of acidic amino acids (pI = 5.0). The interaction of equimolar amounts of purified receptor and cloacin DF13 in vitro resulted in a complete, irreversible neutralization of the lethal activity of the bacteriocin. This interaction showed a temperature optimum at 43 degrees C but was only slightly affected by variation of the pH between 5.0 and 8.5 or by increasing the ionic strength of the incubation buffer. The receptor had no neutralizing activity towards other bacteriocins, such as colicin E1 or colicin E3.

Bacterial Proteins↗
PubMed1982

Cloning and expression in Escherichia coli K-12 of the genes for major outer membrane protein OmpA from Shigella dysenteriae, Enterobacter aerogenes, and Serratia marcescens.

The outer membranes of many gram-negative bacteria contain a major heat-modifiable protein which shows serological cross-reactivity with the OmpA protein of Escherichia coli K-12. Using the cloned gene for the E. coli K12 protein as a DNA-DNA hybridization probe, we were able to identify the corresponding genes from Shigella dysenteriae. Enterobacter aerogenes, and Serratia marcescens. These were cloned in a phage lambda vector, and their expression in E. coli K-12 was studied. All three OmpA proteins were fully produced and correctly exported to the outer membrane. In several cases, complete or partial restoration of known function of the E. coli K-12 protein was observed.

Bacterial Outer Membrane Proteins↗
PubMed1982

Siderophore production by Enterobacter cloacae and a common receptor protein for the uptake of aerobactin and cloacin DF13.

Iron-starved cultures of Enterobacter cloacae produced two siderophores, identified as enterochelin and aerobactin. The aerobactin was excreted in larger amounts than was enterochelin, and it was synthesized preferentially in the late logarithmic and stationary growth phases under iron-deficient conditions. Enterochelin was synthesized by cultures in the logarithmic phase of growth and preferentially in medium with 1 microM ferric chloride. Both siderophores appeared to be excreted immediately after their synthesis, since no intracellular aerobactin or enterochelin could be detected. The killing activity of the bacteriocin cloacin DF13 was inhibited by aerobactin. It was shown that aerobactin and cloacin DF13 bound to the same receptor sites located in the outer membrane. The synthesis of these receptor sites was induced by iron limitation. We conclude that the receptor for the uptake of aerobactin also functions as receptor for cloacin DF13.

Adsorption↗
PubMed1982

Primary structure of the chromosomal origins (oriC) of Enterobacter aerogenes and Klebsiella pneumoniae: comparisons and evolutionary relationships.

The nucleotide sequences of the Enterobacter aerogenes and Klebsiella pneumoniae DNA replication origins (oriC) were determined and compared with those of Escherichia coli and Salmonella typhimurium. Four interrelated, 9-base-pair repeats were identified from the conserved regions within the minimal origin. Evolutionary rates calculated from the minimal origin sequences yielded a quantitative phylogenic tree which agreed with the taxonomic classification of these genera.

Base Sequence↗
PubMed1982

Chromosomal replication origins (oriC) of Enterobacter aerogenes and Klebsiella pneumoniae are functional in Escherichia coli.

The chromosomal DNA replication origins (oriC) from two members of the family Enterobacteriaceae, Enterobacter aerogenes and Klebsiella pneumoniae, have been isolated as functional replication origins in Escherichia coli. The origins in the SalI restriction fragments of 17.5 and 10.2 kilobase pairs, cloned from E. aerogenes and K. pneumoniae, respectively, were found to be between the asnA and uncB genes, as are the origins of the E. coli and Salmonella typhimurium chromosomes. Plasmids containing oriC from E aerogenes, K. pneumoniae, and S. typhimurium replicate in the E. coli cell-free enzyme system (Fuller, et al., Proc. Natl. Acad. Sci. U.S.A. 78:7370--7374, 1981), and this replication is dependent on dnaA protein activity. These SalI fragments from E. aerogenes and K. pneumoniae carry a region which is lethal to E. coli when many copies are present. We show that this region is also carried on the E. coli 9.0-kilobase-pair EcoRI restriction fragment containing oriC. The F0 genes of the atp or unc operon, when linked to the unc operon promoter, are apparently responsible for the lethality.

Bacterial Proteins↗
PubMed1984

Transfer of the chromosomal bla gene from Enterobacter cloacae to Escherichia coli by RP4::mini-Mu.

The resistance gene for beta-lactamase-stable cephalosporins from Enterobacter cloacae was transferred to Escherichia coli by the aid of RP4::mini-Mu. The R-prime plasmids generated carried 60 to 80 kilobases (kb) of E. cloacae DNA and coded for the chromosomal E. cloacae beta-lactamase. The gene was fully expressed in the recipient. Restriction endonuclease EcoRI fragments of the R-prime plasmid pBP100 were cloned into the vector pBP328, yielding the plasmid pBP102 with a size of 14 kb. A restriction map of this plasmid was constructed. By digesting pBP102 into seven PstI fragments, ligating the fragments, and looking for the smallest plasmid generated, pBP103 was isolated. It consisted of three PstI fragments, two of them (together 4.2 kb) necessary for resistance. During the experiment (performed in a recA+ background) the largest PstI fragment had undergone a substitution of a 0.3-kb segment of pBP102 by a 0.7-kb segment in pBP103 (as deduced by heteroduplex analysis). The bla gene of resistant E. cloacae strains was dominant over the gene of susceptible organisms.

Cephalosporins↗