Showing papers on "Escherichia coli published in 1977"
TL;DR: A cytotoxin was found in culture filtrates of a number of Escherichia coli strains that differed from the known heat-stable and heat-labile enterotoxins of E. coli.
Abstract: A cytotoxin was found in culture filtrates of a number of Escherichia coli strains that differed from the known heat-stable and heat-labile enterotoxins of E. coli. It was cytotoxic for Vero but not for Y-1 or CHO cells, and its effect on Vero was distinctly different from that of heat-labile enterotoxin. It was labile to heat and antigenically different from heat-labile enterotoxin, and membrane filtration indicated a molecular weight of 10,000 to 30,000.
1,149 citations
TL;DR: This work has reported the first synthesis of a functional polypeptide product from a gene of chemically synthesized origin, including the sequence of amino acids corresponding to somatostatin, in vitro.
Abstract: A gene for somatostatin, a mammalian peptide (14 amino acid residues) hormone, was synthesized by chemical methods. This gene was fused to the Escherichia coli beta-galactosidase gene on the plasmid pBR322. Transformation of E. coli with the chimeric plasmid DNA led to the synthesis of a polypeptide including the sequence of amino acids corresponding to somatostatin. In vitro, active somatostatin was specifically cleaved from the large chimeric protein by treatment with cyanogen bromide. This represents the first synthesis of a functional polypeptide product from a gene of chemically synthesized origin.
928 citations
870 citations
TL;DR: A novel β-lactamase inhibitor has been isolated from Streptomyces clavuligerus ATCC 27064 and given the nameClavulanic acid, which resembles the nucleus of a penicillin but differs in having no acylamino side chain, having oxygen instead of sulfur, and containing a β-hydroxyethylidine substituent in the oxazolidine ring.
Abstract: A novel beta-lactamase inhibitor has been isolated from Streptomyces clavuligerus ATCC 27064 and given the name clavulanic acid. Conditions for the cultivation of the organism and detection and isolation of clavulanic acid are described. This compound resembles the nucleus of a penicillin but differs in having no acylamino side chain, having oxygen instead of sulfur, and containing a beta-hydroxyethylidine substituent in the oxazolidine ring. Clavulanic acid is a potent inhibitor of many beta-lactamases, including those found in Escherichia coli (plasmid mediated), Klebsiella aerogenes, Proteus mirabilis, and Staphylococcus aureus, the inhibition being of a progressive type. The cephalosporinase type of beta-lactamase found in Pseudomonas aeruginosa and Enterobacter cloacae P99 and the chromosomally mediated beta-lactamase of E. coli are less well inhibited. The minimum inhibitory concentrations of ampicillin and cephaloridine against beta-lactamase-producing, penicillin-resistant strains of S. aureus, K. aerogenes, P. mirabilis, and E. coli have been shown to be considerably reduced by the addition of low concentrations of clavulanic acid.
673 citations
TL;DR: The relationship between ambient concentration of various mutagens and resulting mutation rate was determined and the first mutagen studied was MNNG and the results were totally unexpected.
Abstract: MOST studies on mutagenesis involve exposing a growing population of cells to a large dose of mutagen for a short period. In a natural environment, however, cells are probably exposed more often to a low concentration of mutagens for long periods. We therefore measured the accumulation of mutants in Escherichia coli cells growing continuously in the presence of very low concentrations of mutagens. Because many mutagens are highly unstable, it was necessary to devise a system in which cells could be continuously exposed to fresh mutagen. To do this we took advantage of the fact that certain bacteria can grow and divide while attached to the underside of a Millipore filter. This system was originally developed by Helmstetter and Cummings1 as a means of producing synchronous cells, because as growth medium is passed through the filter it carries away with it the unattached daughter from each pair of newly divided cells. The mutagen to be studied can therefore be stored in stable conditions and only mixed with the growth medium immediately before being passed through the filter; for example the mutagen N-methyl-N′-nitro-nitro-soguanidine (MNNG) can be stored in citrate buffer at pH 5.0 in which it has a half life of 40 h compared with 2.3 h in synthetic minimal media2,3. We had intended to determine the relationship between ambient concentration of various mutagens and resulting mutation rate. The first mutagen studied was MNNG and the results were totally unexpected.
666 citations
TL;DR: Data indicate that Uracil-DNA glycosidase functions in the repair of DNA containing accidentally introduced uracil residues, and has no cofactor dependence and apparently acts by hydrolytic cleavage of the base-sugar bonds in dUMP residues.
478 citations
391 citations
TL;DR: Although Pta- and Ack- mutants are greatly impaired in their growth on acetate, they incorporate [2-14C]acetate added to cultures growing on glycerol, but not on glucose; an inducible acetyl-CoA synthetase effects this uptake of acetate.
Abstract: Summary: Mutants of Escherichia coli
k12 have been isolated that grow on media containing pyruvate or proline as sole carbon sources despite the presence of 10 or 50 mm-sodium fluoroacetate. Such mutants lack either acetate kinase [ATP:acetate phosphotransferase; EC 2.7.2.1] or phosphotransacetylase [acetyl-CoA:orthophosphate acetyltransferase; EC 2.3.1.8] activity. Unlike wild-type E. coli, phosphotransacetylase mutants do not excrete acetate when growing aerobically or anaerobically on glucose; their anaerobic growth on this sugar is slow. The genes that specify acetate kinase (ack) and phosphotransacetylase (pta) activities are cotransducible with each other and with purF and are thus located at about min 50 on the E. coli linkage map. Although Pta- and Ack- mutants are greatly impaired in their growth on acetate, they incorporate [2-14C]acetate added to cultures growing on glycerol, but not on glucose. An inducible acetyl-CoA synthetase [acetate:CoA ligase (AMP-forming); EC 6.2.1.1] effects this uptake of acetate.
373 citations
328 citations
TL;DR: Evidence is presented that three Escherichia coli phages use the major outer membrane proteins Ia, Ib, and II, respectively, as receptors, and that lipopolysaccharide may thus cause the specific localization of these proteins.
Abstract: Three Escherichia coli phages, TuIa, TuIb, and TuII, were isolated from local sewage. We present evidence that they use the major outer membrane proteins Ia, Ib, and II, respectively, as receptors. In all cases the proteins, under the experimental conditions used, required lipopolysaccharide to exhibit their receptor activity. For proteins Ia and II, an approximately two- to eightfold molar excess of lipopolysaccharide (based on one diglucosamine unit) was necessary to reach maximal receptor activity. Lipopolysaccharide did not appear to possess phage-binding sites. It seemed that the lipopolysaccharide requirement reflected a protein-lipopolysaccharide interaction in vivo, and lipopolysaccharide may thus cause the specific localization of these proteins. Inactivation of phage TuII by a protein II-lipopolysaccharide complex was reversible as long as the complex was in solution. Precipitation of the complex with Mg2+ led to irreversible phage inactivation with an inactivation constant (37 degrees C)K = 7 X 10-2 ml/min per microgram. With phages TuIa and TuIb and their respective protein-lipopolysaccharide complexes, only irreversible inactivation was found at 37 degrees C. The activity of the three proteins as phage receptors shows that part of them must be located at the cells surface. In addition, the association of proteins Ia and Ib with the murein layer of the cell envelope makes this pair trans-membrane proteins.
295 citations
TL;DR: In mutants of the generally nonchemotactic cheR class of Salmonella typhimurium, the methylase is not required for tumbling but appears to be essential for maintaining the appropriate rate constants and levels of the regulator of the chemotactic response.
Abstract: Methylation of membrane-bound proteins with apparent molecular weights around 65,000 does not occur in mutants of the generally nonchemotactic cheR class of Salmonella typhimurium. This was shown to be due to the lack of a protein methyltransferase in these mutants by means of an in vitro assay using soluble proteins, membranes, and S-adenosylmethionine as the methyl donor. The methylase from the wild type was purified, characterized, and shown to be of molecular weight 38,000. It is specific for proteins in S. typhimurium and Escherichia coli membranes. The methylase is not required for tumbling but appears to be essential for maintaining the appropriate rate constants and levels of the regulator of the chemotactic response.
TL;DR: Using this vector and in vitro packaging, several E. coli and phage P1 endo R. Eco RI fragments were cloned and the use of a D am mutation to facilitate recognition of size classes of inserted fragments is described.
TL;DR: The messenger RNA for the lipoprotein of the E. coli outer membrane was found to code for a putative precursor, prolipoprotein, which has 20 additional amino acid residues extending from the amino terminus of the lipiprotein, and the complete amino acid sequence of the amino-terminal precursor region was determined to be as follows.
Abstract: The messenger RNA for the lipoprotein of the E coli outer membrane was found to code for a putative precursor, prolipoprotein, which has 20 additional amino acid residues extending from the amino terminus of the lipoprotein Using the prolipoprotein synthesized in an E coli cell-free system directed by purified messenger RNA for the lipoprotein, the complete amino acid sequence of the amino-terminal precursor region was determined to be as follows: (formula: see text) It was also found that the prolipoprotein that accumulates in toluene-treated cells has the same sequence The significance of the amino acid sequence is discussed in terms of the mechanism of biosynthesis and assembly of the lipoprotein in the E coli outer membrane
TL;DR: The behavioral defects are shown to correlate with alterations in the properties of a methylation reaction involved in chemotaxis, and the relationship between the genetic loci (tsr and tar) and the methyl-accepting proteins is discussed.
Abstract: The properties of two classes of behavioral mutants of Escherichia coli (called tsr and tar) are described. The mutations in these strains define two complementary pathways of information flow in bacterial chemotaxis: behavioral responses to one set of stimuli are defective in tsr mutants, while responses to a complementary set of stimuli are defective in tar mutants. A double mutant containing both genetic lesions is defective in responses to all stimuli tested. The behavioral defects are shown to correlate with alterations in the properties of a methylation reaction involved in chemotaxis. Two independent sets of methyl-accepting proteins are demonstrated in the wild type, each set functioning in one of the two pathways mentioned above. Methylation of one set of proteins is defective in tsr mutants, while methylation of the complementary set is defective in tar mutants. The double mutant shows no methylation of either set. The relationship between the genetic loci (tsr and tar) and the methyl-accepting proteins is discussed.
TL;DR: It is concluded that purified pili alone cause HA of erythrocytes by binding to mannose-like molecules on the ery Throthrocyte surface by bindingto mannosed-like molecule on the surface of the cell membranes.
Abstract: Many enterobacteria can cause agglutination of erythrocytes, but previous investigations have not proven which components of the bacteria are responsible. We used a strain of Escherichia coli K12 which causes mannose-sensitive hemagglutination (HA) of guinea pig cells. Common pili were purified from these bacteria by shearing them from the bacteria followed by selective precipitation in acid and ammonium sulfate. Isopycnic centrifugation in cesium chloride removed the remaining outer membrane protein contaminants. These pili are pure by electron microscopy and gel electrophoresis. By amino acid analysis, they have a mol wt of 17,099 and consist of 45% nonpolar residues. These purified pili agglutinate guinea pig erythrocytes, a reaction that is inhibited by anti-pili antibodies and by saccharides related in structure to D-mannose. Proteolytic treatment of erythrocytes does not diminish HA but rather increases the pili-induced HA of human cells. Neuraminidase enhances HA and mannosidase slightly diminishes it. It is concluded that purified pili alone cause HA of erythrocytes by binding to mannose-like molecules on the erythrocyte surface. Thus HA by bacterial pili serves as a useful model system for the mechanism of bacterial pili attachment ot cell membranes.
TL;DR: It is proposed that subsequent association of the membrane-bound aminoglycoside with higher-affinity binding sites on membrane-associated ribosomes carrying out a normal ribosomal cycle and protein synthesis results in a more rapid transport rate (termed energy-dependent phase II).
Abstract: Several mutants of Escherichia coli affecting aerobic energy generation and energization of the bacterial membrane have been examined for their effect on streptomycin and gentamicin accumulation and susceptibility. A heme-deficient mutant (K207) and two mutants (CJ-8 [colicin K insensitive] and NR-70) associated with defective aerobic active transport were associated with decreased transport of streptomycin and gentamicin and increased resistance to those antibiotics. These mutants also exhibited increased resistance to several other aminoglycoside antibiotics, but not the aminocyclitol spectinomycin. The same observations were made with a ubiquinone-deficient mutant, but a strA derivative of this mutant was shown additionally to be saturable for streptomycin accumulation at a concentration four or more times lower than that required for saturation of the parent. A mutant uncoupled for adenosine 5′-triphosphate synthesis from electron transport and membrane Mg-adenosine 5′-triphosphatase deficient was hypersensitive to those aminoglycosides tested and spectinomycin, and showed enhanced transport of streptomycin and gentamicin. A variety of compounds structurally related to streptomycin were examined at high concentrations for inhibition of streptomycin uptake in a strA mutant of E. coli K-12 SA 1306, but no evidence for competition was detected, suggesting the absence of a common transport carrier. Four different divalent cations were shown to inhibit streptomycin and gentamicin accumulation in E. coli K-12 SA 1306. Divalent cations were shown to inhibit uptake of these two drugs in two bacterial species with distinct cell wall structures, Pseudomonas aeruginosa and Staphylococcus aureus , and to inhibit streptomycin uptake in spheroplasts of streptomycin-susceptible and -resistant E. coli . However, calcium had almost no inhibitory effect on streptomycin uptake by the ubiquinone-deficient mutant E. coli AN66. These and previous findings have been used to formulate a model for aminoglycoside entry into bacteria using a low-affinity membranous complex involved in membrane energization that includes respiratory quinones, which probably act to bind and transport aminoglycosides across the cell membrane. This phase of transport is associated with the lowest accumulation rate (termed energy-dependent phase I) that is rate limiting for susceptibility. It is further proposed that subsequent association of the membrane-bound aminoglycoside with higher-affinity binding sites on membrane-associated ribosomes carrying out a normal ribosomal cycle and protein synthesis results in a more rapid transport rate (termed energy-dependent phase II). The increased rate could result from a state of membrane energization analogous to that causing enhanced aminoglycoside transport rates seen in the uncoupled mutant, AN120. How this model explains the mechanism by which enzymatically modified aminoglycosides render cells resistant to unmodified aminoglycosides is also discussed.
TL;DR: Escherichia coli cells prepared for transformation by treatment with cold 0.1 M CaCl2 remained viable and competent after storage at -82 degrees C in 15% glycerol; thawed-cell samples yielded up to 10(6) transformants per microgram of plasmid deoxyribonucleic acid.
Abstract: Escherichia coli cells prepared for transformation by treatment with cold 0.1 M CaCl2 remained viable and competent after storage at -82 degrees C in 15% glycerol; thawed-cell samples yielded up to 10(6) transformants per microgram of plasmid deoxyribonucleic acid.
TL;DR: Complementation of bacterial mutations by yeast DNA segments does not appear to be a rare phenomenon.
Abstract: A collection of hybrid circular DNAs was constructed in vitro using the poly(dA-dT) "connector" method: each hybrid circle contained one molecule of poly(dT)-tailed DNA of plasmid ColE1 (made linear by digestion with EcoRI endonuclease) annealed to a poly(dA)-tailed fragment of yeast (Saccharomyces cerevisiae) DNA, produced originally by shearing total yeast DNA to an average size of 8 X 10(6) daltons. This DNA preparation was used to transform E. coli cells, selecting colicin-E1-resistant clones that contain hybrid ColE1-yeast DNA plasmids. Sufficient numbers of transformant clones were obtained to ensure that the hybrid plasmid population was representative of the entire yeast genome. Various hybrid ColE1-yeast DNA plasmids capable of complementing E. coli auxotrophic mutations were selected from this population. Plasmid pYeleu 10 complements several different point or deletion mutations in the E. coli or S. typhimurium leuB gene (beta-isopropylmalate dehydrogenase); plasmids pYeleu11, pYeleu12, and pYeleu17 are specific suppressors of the leuB6 mutation in E. coli C600. Plasmid pYehis2 complements a deletion in the E. coli hisB gene (imidazole glycerol phosphate dehydratase). Complementation of bacterial mutations by yeast DNA segments does not appear to be a rare phenomenon.
TL;DR: It is evident that E. coli can produce diarrhea without being able to invade the mucosa or synthesize enterotoxin.
Abstract: A strain of Escherichia coli O15 (RDEC-1) isolated from several rabbits with diarrhea was examined to determine (1) whether the strain could produce diarrhea when administered by the orogastric route to other rabbits and (2) whether this strain was invasive or enterotoxigenic. Strain RDEC-1 produced diarrhea in 48 of 62 rabbits when given by the orogastric route in doses that ranged from 1.5 X 10(2) to 4 X 10(10) bacteria. The organism did not give a positive result in the 18-hr ileal loop or Sereny tests and did not invade HeLa cells. Culture supernatants of strain RDEC-1 did not give positive results in the 6- or 18-hr rabbit ileal loop, suckling mouse, Y-1 adrenal cell, or Chinese hamster ovary cell assays. Fluorescent antibody staining of sections of intestine prepared in a cryostat revealed great numbers of E. coli strain RDEC-1 that adhered to the epithelial surface. It is evident that E. coli can produce diarrhea without being able to invade the mucosa or synthesize enterotoxin. Strains of E. coli similar to RDEC-1 may account for some of the E. coli-associated diarrhea that occurs in humans.
TL;DR: A mutant of E. coli lacking a specific outer membrane lipoprotein was found in this article, which is referred to as lpo, and the mutation occurred during the production of an F'.
Abstract: A mutant of E. coli lacking a specific outer membrane lipoprotein was found. Both the free and the bound form have been lost in this mutant. No material that cross-reacted with antiserum against lipoprotein was detected by the Ouchterlony test. The mutant was defective in producing mRNA active for lipoprotein synthesis. The mutation leading to the loss of lipoprotein synthesis, referred to as lpo, seems to have arisen during production of an F'. The map position of lpo was at 36.5 min on the E. coli K12 map, in the order man, uidA, lpo, aroD, pps. The lpo mutant grew and divided normally and remained susceptible to bacteriophages lambda, phi80, P1, P2, the T series, and f1, f2, and MS2 in its male derivatives. The mutant was hypersensitive to EDTA and cationic dves and somewhat sensitive to detergents. There was considerable leakage of periplasmic enzymes but passive transport of beta-galactoside was unchanged. These physiological characteristics of the mutant suggest that lipoprotein is involved in maintaining the integrity of the outer envelope structure, by bridging the outer membrane and murein, but not in the vital processes of growth and division.
TL;DR: Adhesion was found to vary, between individuals and epithelial cell types, with epithelialcell viability, bacterial cultivation medium and growth phase, number of bacteria added to the epithelial cells, and incubation time and temperature, and influenced by variations in pH and osmolarity.
Abstract: Optimal conditions for in vitro adherence of Escherichia coli to uroepithelial cells, previously shown to more efficient for strains causing acute symptomatic than that for strains causing "asymptomatic" urinary tract infections, were investigated. Uroepithelial cells from fresh morning urine of healthy individuals and E. coli bacteria from patients with various forms of urinary tract infeciton were used. Adhesion was found to vary, between individuals and epithelial cell types, with epithelial cell viability, bacterial cultivation medium and growth phase, number of bacteria added to the epithelial cells, and incubation time and temperature. Adhesion was also influenced by variations in pH and osmolarity. Optimal test conditions were obtained with post-log-phase bacterial cultures grown on nutrient broth when 10(8) bacteria were added to 10(5) epithelial cells and incubated for 60 min. Considerable variation was found between experiments done on different days, whereas the variation between duplicates was small. The method described may provide a useful tool in the study of the host-parasite relationship in urinary tract infections.
TL;DR: The properties of this and related strains provide additional evidence that induction of phage and induction of error-prone DNA repair occur by a similar mechanism, and further suggest a model for the regulation of these pathways.
Abstract: A mutant of E. coli (designated the STS mutant) has been isolated in which the phage induction and error-prone DNA repair pathways appear to be expressed constitutively without the cells having received an inducing signal. Phage lambda was not able to lysogenize this mutant, whereas a noninducible mutant of lambda, lambdacIind-, known to synthesize a repressor that is insensitive to the induction mechanism, lysogenized it normally. This result suggested that normal phage repressor was synthesized in the STS mutant but was then inactivated by the induction mechanism. The STS strain also had mutator characteristics, and showed spontaneous, error-prone repair of UV-damaged phage lambda. Derived from a lexA tif sfiA parent strain, the STS mutant carried an additional mutation spr at the lexA locus that resulted in a high level of expression of the induction pathways. The properties of this and related strains provide additional evidence that induction of phage and induction of error-prone DNA repair occur by a similar mechanism, and further suggest a model for the regulation of these pathways.
TL;DR: Bacterial binding can occur via pili which act like lectins and presumably bind to mannose-containing glycoproteins on mammalian cell surfaces, as demonstrated by binding of purified pili from Escherichia coli to Vero cell monolayers.
Abstract: We have demonstrated binding of purified pili from a strain of Escherichia coli to Vero cell monolayers as a model of prokaryotic-eukaryotic cell adherence. Pili bound to the tissue culture in a rapid reaction that did not require enzymatic activation. Attachment occurred optimally at pH 4-5 and could be inhibited by analogues of D-mannose, anti-pili antibodies, or by preincubation of tissue cells with mannose-specific plant lectins. Binding remained after treatment of the monolayer with glycosidases, trypsin, or a protease mixture but was enhanced after neuraminidase treatment. These results indicate that bacterial binding can occur via pili which act like lectins and presumably bind to mannose-containing glycoproteins on mammalian cell surfaces.
TL;DR: The development of an enzyme-linked immunosorbent assay (ELISA) for the detection of heat-labile Escherichia coli enterotoxin is described, which is similar in design to a radioimmunoassay but utilizes enzyme-labeled rather than radioactive isotope-labeling reagents.
Abstract: The development of an enzyme-linked immunosorbent assay (ELISA) for the detection of heat-labile Escherichia coli enterotoxin is described. The assay, which is based on the immunological similarity between Vibrio cholerae toxin and heat-labile E. coli enterotoxin, is similar in design to a radioimmunoassay but utilizes enzyme-labeled rather than radioactive isotope-labeled reagents. The ELISA system is as sensitive as both radioimmunoassay and the y-1 adrenal cell assay for the detection of heat-labile E. coli enterotoxin but requires neither radioactive reagents nor tissue culture techniques. The ELISA is easy to perform and is adaptable for use in small laboratories.
TL;DR: Examination of temperature-sensitive cell division mutants of Escherichia coli provides extremely strong evidence that the inactivation of PBP3 at 42 degrees C in the mutants is the cause of the inhibition of cell division at this temperature and identifies P BP3 as an essential component of the process of celldivision in E. coli.
Abstract: The thermostability of the penicillin-binding proteins (PBPs) of 31 temperature-sensitive cell division mutants of Escherichia coli has been examined. Two independent cell division mutants have been found that have highly thermolabile PBP3. Binding of [14C]benzylpenicillin to PBP3 (measured in envelopes prepared from cells grown at the permissive temperature) was about 30% of the normal level at 30°C, and the ability to bind [14C]benzylpenicillin was rapidly lost on incubation at 42°C. The other PBPs were normal in both mutants. At 30°C both mutants were slightly longer than their parents and on shifting to 42°C they ceased dividing, but cell mass and deoxyribonucleic acid synthesis continued and long filaments were formed. At 42°C division slowly recommenced, but at 44°C this did not occur. The inhibition of division at 42°C was suppressed by 0.35 M sucrose, and in one of the mutants it was partially suppressed by 10 mM MgCl2. PBP3 was not stabilized in vitro at 42°C by these concentrations of sucrose or MgCl2. Revertants that grew as normal rods at 42°C regained both the normal level and the normal thermostability of PBP3. The results provide extremely strong evidence that the inactivation of PBP3 at 42°C in the mutants is the cause of the inhibition of cell division at this temperature and identify PBP3 as an essential component of the process of cell division in E. coli. It is the inactivation of this protein by penicillins and cephalosporins that results in the inhibition of division characteristic of low concentrations of many of these antibiotics.
TL;DR: A new DNA endonuclease has been purified 3000-fold from Escherichia coli and seems to be active in DNA repair, presumably at apurinic and apyrimidinic sites introduced by the radiation treatment.
Journal Article•
TL;DR: The K99 antigen of Escherichia coli can be detected more readily in cultures grown on Minca medium at 37 degrees C for 6 to 8 h or grown onMinca plus 1% Iso VitaleX for 20 to 24 h.
Abstract: The K99 antigen of Escherichia coli can be detected more readily in cultures grown on Minca medium at 37 degrees C for 6 to 8 h or grown on Minca plus 1% Iso VitaleX for 20 to 24 h.
TL;DR: The results suggest that the surface of phagocytes, like that of epithelial cells, contains D-mannose residues which serve for the attachment of certain Gram negative bacteria.
TL;DR: Mutants of Escherichia coli B/r lacking a major outer membrane protein, protein b, were obtained by selecting for resistance to copper and showed a decreased ability to utilize a variety of metabolites when the metabolites were present at low concentrations.
Abstract: Mutants of Escherichia coli B/r lacking a major outer membrane protein, protein b, were obtained by selecting for resistance to copper. These mutants showed a decreased ability to utilize a variety of metabolites when the metabolites were present at low concentrations. Also, mutants of E. coli K-12 lacking proteins b and c from the outer membrane were shown to have an identical defect in the uptake of various metabolites. These results are discussed with regard to their implications as to the role of these proteins in permeability of the outer membrane,
TL;DR: The K99 antigen of Escherichia coli can be detected more readily in cultures grown on Minca medium at 37 degrees C for 6 to 8 h or grown on MINCA plus 1% Iso VitaleX for 20 to 24 h as mentioned in this paper.
Abstract: The K99 antigen of Escherichia coli can be detected more readily in cultures grown on Minca medium at 37 degrees C for 6 to 8 h or grown on Minca plus 1% Iso VitaleX for 20 to 24 h.