Showing papers in "Fems Microbiology Letters in 1988"
TL;DR: Transfer of plasmid RP4 between introduced pseudomonads was studied in rhizosphere and non-rhizosphere soil of wheat, in soil chambers and in culture tubes, indicating an influence of the experimental set-up.
Abstract: Transfer of plasmid RP4 between introduced pseudomonads was studied in rhizosphere and non-rhizosphere soil of wheat, in soil chambers and in culture tubes. In both experiments, the presence of growing wheat roots stimulated the occurrence of plasmid transfers in the soil. The plasmid transfer frequencies in rhizosphere soil in the soil chambers were consistently higher than those in rhizosphere soil in the culture tubes, indicating an influence of the experimental set-up. In the soil chambers, both the survival of introduced donor and recipient strains and the plasmid transfer frequencies decreased drastically at increasing distances from the roots. In addition, plasmid transfer frequencies were influenced by the inoculum densities of both donor and recipient strains; higher frequencies were observed in soil that was initially inoculated with higher cell numbers.
226 citations
TL;DR: Two constitutive acetyl-CoA acetyltransferases (3-ketothiolases A and B) were purified from Alcaligenes eutrophus and the condensation reaction was potently inhibited by CoA in both cases.
Abstract: Two constitutive acetyl-CoA acetyltransferases (3-ketothiolases A and B) were purified from Alcaligenes eutrophus. Enzyme A was active with only acetoacetyl-CoA and 3-ketopentanoyl-CoA, whereas enzyme B was active with all the 3-ketoacyl-CoAs (C4−C10) tested. Enzyme A appeared to be a tetramer (Mr 70 000) with identical subunits (Mr 44 000) and enzyme B had a similar Mr of 168 000 (containing Mr 46 000 subunits). Enzymes A and B had isoelectric points of 5.0 and 6.4, respectively. The stoichiometry of the reactions catalysed by each enzyme was confirmed. Km values of 44 μM and 394 μM for acetoacetyl-CoA, and 16 μM and 93 μM for CoA, were determined with enzymes A and B, respectively. Enzymes A and B gave Km values of 1.1 mM and 230 μM, respectively, for acetyl-CoA. The condensation reaction was potently inhibited by CoA in both cases.
206 citations
TL;DR: It appears that, for the methanogens, changes in the intracellular ion concentration are the basis of thermoadaptation.
Abstract: An inter- and intra-species correlation was found between the intracellular potassium concentration and growth temperature within the Methanobacteriales, comprising mesophiles as well as moderate (Methanobacterium thermoautotrophicum) and extreme thermophiles (Methanothermus fervidus, Mt. sociabilis). Potassium concentrations in different species were determined at optimal growth temperatures and for the same species cultured at different temperatures. The main anionic component was found to be the unusual trianionic cyclic 2,3-diphosphiglycerate. In vitro experiments with the thermolabile enzymes glyceraldehyde-3-phosphate dehydrogenase and malate dehydrogenase from Mt. fervidus indicated that the potassium salt of the cyclic diphosphoglycerate acts as potent thermostabilizer. Thus it appears that, for the methanogens, changes in the intracellular ion concentration are the basis of thermoadaptation.
201 citations
TL;DR: In this paper, two constitutive AcAc-CoA reductases were purified from Alcaligenes eutrophus, and the NADH-and NADPH-linked enzymes were determined for the coenzymes, respectively.
Abstract: Two constitutive acetoacetyl-CoA (AcAc-CoA) reductases were purified from Alcaligenes eutrophus. Incorporation of [1-14C]-acetyl-CoA into poly-3-hydroxybutyrate (PHB) by systems reconstituted from purified preparations of either 3-ketothiolase, AcAc-CoA reductase and PHB synthase, occurred only when NADPH-AcAc-CoA reductase was present. The NADH reductase was active with all of the D (−)- and L (+)-3-hydroxyacyl-CoA substrates tested (C4-C10), whereas the NADPH reductase was only active with D (−)-3-hydroxyacyl-CoAs (C4-C6). The products of AcAc-CoA reduction by the NADH- and NADPH-linked enzymes were L (+)-3-hydroxybutyryl-CoA and D (−)-3-hydroxybutyryl-CoA, respectively. The NADH-linked enzyme had an Mr of 150,000 (containing identical Mr 30,000 sub-units) and the NADPH-linked enzyme appeared to be a tetramer (Mr 84,000) with identical sub-units (Mr 23,000). Kmapp values of 22 μM and 5 μM for AcAc-CoA and 13 μM (NADH) and 19 μM (NADPH) for the coenzymes were determined for the NADH- and NADPH-linked enzymes, respectively.
192 citations
TL;DR: Verocytotoxin 2 (VT2) was purified from Escherichia coli strain E32511 using cells harvested from a Penassay broth culture incubated for 6 h at 37°C in the presence of mitomycin C.
Abstract: Verocytotoxin 2 (VT2) was purified from Escherichia coli strain E32511 using, as starting material, cells harvested from a Penassay broth culture incubated for 6 h at 37°C in the presence of mitomycin C (0.2 μg/ml). A crude extract of VT2, obtained by polymyxin B treatment of cell pellets, was purified using differential ammonium sulphate precipitation, and sequential column chromatography. The purified toxin was estimated to have a pI of 6.5 by chromatofocusing and a molecular weight of 42 000 by gel filtration; it had a specific activity of 1.39 × 106 CD50 units/mg protein in Vero cells, and resolved as a major band of Mr 35 000 and another band of
167 citations
TL;DR: Further experiments with molecular genetic techniques are required to define the relative roles of the thioredoxin and glutaredoxin systems in intracellular redox reactions.
Abstract: Thioredoxin is a small (Mr 12,000) ubiquitous redox protein with the conserved active site structure: -Trp-Cys-Gly-Pro-Cys-. The oxidized form (Trx-S2) contains a disulfide bridge which is reduced by NADPH and thioredoxin reductase; the reduced form [Trx(SH)2] is a powerful protein disulfide oxidoreductase. Thioredoxins have been characterized in a wide variety of prokaryotic cells, and generally show about 50% amino acid homology to Escherichia coli thioredoxin with a known three-dimensional structure. In vitro Trx-(SH)2 serves as a hydrogen donor for ribonucleotide reductase, an essential enzyme in DNA synthesis, and for enzymes reducing sulfate or methionine sulfoxide. E. coli Trx-(SH)2 is essential for phage T7 DNA replication as a subunit of T7 DNA polymerase and also for assembly of the filamentous phages f1 and M13 perhaps through its localization at the cellular plasma membrane. Some photosynthetic organisms reduce Trx-S2 by light and ferrodoxin; Trx-(SH)2 is used as a disulfide reductase to regulate the activity of enzymes by thiol redox control.
Thioredoxin-negative mutants (trxA) of E. coli are viable making the precise cellular physiological functions of thioredoxin unknown. Another small E. coli protein, glutaredoxin, enables GSH to be hydrogen donor for ribonucleotide reductase or PAPS reductase. Further experiments with molecular genetic techniques are required to define the relative roles of the thioredoxin and glutaredoxin systems in intracellular redox reactions.
164 citations
TL;DR: Strains of Lactobacillus plantarum and Leuconostoc mesenteroides were tested for bacteriocin production against each other and a range of closely related bacteria and an inhibitory substance was found that is a potential bacteriOCin and has been named plantacin B.
Abstract: Strains of Lactobacillus plantarum and Leuconostoc mesenteroides were tested for bacteriocin production against each other and a range of closely related bacteria. L. plantarum 1193 was found to produce an inhibitory substance active against L. plantarum 340 and 1752, L. mesenteroides 8015 and Pediococcus damnosus 1832. This substance is a potential bacteriocin and has been named plantacin B.
159 citations
TL;DR: Plasmid DNA indistinguishable from that introduced, on the basis of agarose gel electrophoresis, was observed in transformants containing either plasmid in a method for the introduction of plasmids into Clostridium acetobutylicum ATCC 8052 by electroporation.
Abstract: A method is presented for the introduction of plasmids into Clostridium acetobutylicum ATCC 8052 by electroporation. A plasmid shuttle vector, pMTL500E, which contains the erythromycin resistance gene and replication machinery of plasmid pAMβ1, was constructed and introduced into C. acetobutylicum by electroporation. The vector was then used to introduce a 2.2 kb ClaI/SphI chromosomal fragment from C. pasteurianum into a leucine requiring mutant of C. acetobutylicum, SBA9, where complementation of auxotrophy was observed. Plasmid DNA indistinguishable from that introduced, on the basis of agarose gel electrophoresis, was observed in transformants containing either plasmid.
131 citations
TL;DR: It appears that methanogens/methanogenesis play an important role in the anaerobic dechlorination of chlorinated aliphatics such as PCE.
Abstract: Perchloroethylene (PCE) was reductively dechlorinated to trichloroethylene in a 10% anaerobic sewage sludge. About 80% of the initially added PCE (300 nmol) was dechlorinated within three weeks. The calculated rates were 250 nM and 445 nM · day −1 during the first and second weeks of incubation, respectively. The depletion of PCE varied in sludges obtained from different sources. The role of methanogenesis in the dechlorination of PCE was evaluated by inhibiting the methanogens by addition of bromoethane sulfonic acid, a potent methanogenic inhibitor. Dechlorination of PCE was significantly inhibited in sludges amended with the inhibitor. Almost 41–48% less PCE was dechlorinated in sludges containing 5 mM BESA, indicating a relation between the two processes (methanogenesis and dechlorination). Direct proof that methanogens can transform chlorinated aliphatic compounds was obtained using axenic cultures of acetate-cleaving methanogens. Methanosarcina sp , originally isolated from a chlorophenol degrading consortium, showed significantly higher dechlorinating activity as compared to Ms. mazei . Based on these studies and other recently reported observations, it appears that methanogens/methanogenesis play an important role in the anaerobic dechlorination of chlorinated aliphatics such as PCE.
114 citations
TL;DR: In this paper, Dimethyl sulfide (DMS) was found to be readily metabolized by microbes in marsh sediments and that this metabolism may be responsible for reducing the emission of DMS from the marsh surface.
Abstract: Anoxic sediment slurries prepared from Spartina salt marsh soils contained dimethyl sulfide (DMS) at concentrations ranging from 1 to 10 μM. DMS was produced in slurries over the initial 1–24 h incubation. After the initial period of production, DMS decreased to undetectable levels and methane thiol (MSH) was produced. Inhibition of methanogenesis caused a 20% decrease in the rate of DMS consumption, while inhibition of sulfate reduction caused a 80% decrease in DMS consumption. When sulfate reduction and methanogenesis were simultaneously inhibited, DMS did not decrease. DMS contributed about 28% to the methane production rate, while DMS probably contributed only 1% or less to the sulfate reduction rate. Incubation of the sediment slurries under an atmosphere of air resulted in similar DMS consumption compared to anaerobic incubations, but MSH and CH 4 were not evolved. Sediments from the marsh released significant quantities of DMS when treated with cold alkali, indicating that potentially significant sources of DMS existed in the sediments. Values of base-hydrolyzable DMS as high as 190 μmol per liter of sediment were observed near the sediment surface, and values always decreased with depth in the sediment. Simple flux experiments with small intact sediment cores, showed that DMS was emitted from the marsh surface when cores were injected with glutaraldehyde or molybdate and 2-bromoethanesulfonate (BES), but nit when cores were left uninhibited. These results showed that DMS was readily metabolized by microbes in marsh sediments and that this metabolism may be responsible for reducing the emission of DMS from the marsh surface.
110 citations
TL;DR: Rhizobium strains nodulating Galega species were characterized by metabolic tests, maximum growth temperature determinations in a temperature gradient incubator and phage typing, and compared with other fast-growing rhizobia, and suggest that Rhizobum sp.
Abstract: Rhizobium strains nodulating Galega species were characterized by metabolic tests, maximum growth temperature determinations in a temperature gradient incubator and phage typing, and compared with other fast-growing rhizobia By numerical taxonomy it was shown that the Galega Rhizobium strains are closely related to each other and unrelated to the recognized species of Rhizobium The maximum growth temperature of rhizobia nodulating G orientalis was 330–340°C and of rhizobia nodulating G officinalis 350–370°C The Galega rhizobia were only lysed by their own phages, and not by typing phages for other Rhizobium species The G + C% of Rhizobium sp (Galega) strainswas 63%44 previously unclassified fast-growing rhizobia from tropical plants, which were included in the experiments, were shown to form a heterogenous group with diverse properties The results confirm and extend previous findings, and suggest that Rhizobum sp (Galega) should be considered a new species of Rhizobium
TL;DR: Results indicate that the cutaneous strains represent a new mycolic acid-less Corynebacterium species for which the name CoryneBacterium amycolatum sp.
Abstract: Chemotaxonomic studies were performed on some gram-positive coryneform bacteria of uncertain taxonomic position isolated from human skin. The results indicate that the cutaneous strains represent a new mycolic acid-less Corynebacterium species for which the name Corynebacterium amycolatum sp. nov. is proposed.
TL;DR: In this paper, all three isomers of trichlorobenzene were reductively dechlorinated to monochlorobensene via dichlorobenzenes in anaerobic sediment columns.
Abstract: All three isomers of trichlorobenzene were reductively dechlorinated to monochlorobenzene via dichlorobenzenes in anaerobic sediment columns The dechlorination was specific: 1,2,3- and 1,3,5-trichlorobenzene were solely transformed to 1,3-dichlorobenzene, while 1,4-dichlorobenzene was the only product of 1,2,4-trichlorobenzene transformation Microorganisms were responsible for the observed transformations Since monochlorobenzene and dichlorobenzene are mineralized by bacteria in the presence of oxygen, the process of reductive dechlorination may be an important initial step to obtain complete mineralization of otherwise recalcitrant trichlorobenzenes This is especially true for the 1,3,5-isomer, which seems to resist biodegradation in oxic environments
TL;DR: On the basis of chemical characteristics it is suggested that Arthrobacter radiotolerans be reclassified in a new genus Rubrobacter, as Rubrobacteria radiotoleranceans comb.
Abstract: The chemotaxonomic characteristics of Arthrobacter radiotolerans were investigated. The species possesses a peptidoglycan based on l-lysine (variation A3α) and a DNA base composition of 67.9 mol% G + C. The cellular fatty acids were primarily of the methyl branched types with 12-methyl-hexadecanoic acid as the predominant component. The major isoprenoid quinone was menaquinone with eight isoprene units and the polar lipids consisted of four phospholipids, one phosphoglycolipid and one glycolipid. On the basis of chemical characteristics it is suggested that Arthrobacter radiotolerans be reclassified in a new genus Rubrobacter, as Rubrobacter radiotolerans comb. nov.
TL;DR: When grown for 15 h in rice culture, 13 out of 15 Bacillus cereus strains associated with emetic-syndrome food poisoning (87%) caused vacuoles to appear in HEp-2 cells, compared with 5 out of 11 B. Cereus strains from other sources (45%).
Abstract: When grown for 15 h in rice culture, 13 out of 15 Bacillus cereus strains associated with emetic-syndrome food poisoning (87%) caused vacuoles to appear in HEp-2 cells, compared with 5 out of 11 B. cereus strains from other sources (45%). No other Bacillus species tested gave rise to this response under these conditions. Six out of eight rice samples involved in incidents of B. cereus emetic illness produced vacuoles in HEp-2 cells, whereas control rice samples and foods from vomiting episodes caused by other Bacillus spp. failed to do so. This vacuole response may have application as a simple in vitro assay for organisms and foods implicated in B. cereus emetic-syndrome food poisoning.
TL;DR: This is the first demonstration of a light-dependent ethane formation and of the occurrence of the alternative nitrogenase in any phototroph.
Abstract: Anabaena variabilis can be grown with dependence on either molybdenum (Mo) or vanadium (V) in the medium with essentially the same growth rates. Vanadium cultures reduce C2H2 to C2H4 and partly (to 2–3%) to C2H6. These C2H4 and C2H6 formations can be shown to be strictly light dependent, proving that the gases are formed by the cyanobacterium. C2H4 and C2H6 productions are accompanied by a H2 formation which is much higher than in Mo cultures. Maximal C2H2-formation rates are 2/3 lower in V-grown cells compared to Mo control cultures. This is the first demonstration of a light-dependent ethane formation and of the occurrence of the alternative nitrogenase in any phototroph.
TL;DR: Two independent collections of clones containing Clostridium thermocellum genes involved in cellulose have been previously obtained at IAPGR, Cambridge, and at the Pasteur Institute, Paris and compared for cross-hybridization, restriction maps and enzyme phenotypes.
Abstract: Two independent collections of clones containing Clostridium thermocellum genes involved in cellulose have been previously obtained at IAPGR, Cambridge, and at the Pasteur Institute, Paris. The two collections were compared for cross-hybridization, restriction maps and enzyme phenotypes. Truly distinct genes were one β-glucosidase gene, two xylanase genes, and fifteen endogluconase genes. Two of the cloned fragments contained extraneous DNA which was absent from their respective counterparts isolated in the other collection. The dicrepancies resulted from in vivo rearrangements which had occurred in either of the C. thermocellum NCIB 10682 stocks used to generate the two gene banks.
TL;DR: Analysis, by in vitro recombination, indicated that each mutation contributes to the extented substrate range of the enzyme, compared to that of the TEM-type penicillinase, and that the strength of the promoter of blaT-3 is responsible for high-level resistance towards broad-spectrum cephalosporins of strains producing T EM-3.
Abstract: We have determined the nucleotide sequence of the blaT-3 gene of plasmid pCF04 which confers resistance to penicillins and most cephalosporins by mediating the production of TEM-3 β-lactamase. The deduced amino acid sequence of TEM-3 differed in two positions from that of the TEM-2 penicillinase: Lys (TEM-3) for Glu (TEM-2) at position 102, and Ser (TEM-3) for Gly (TEM-2) at position 236 of the unprocessed protein. Examination of the location of the two modified amino acids of TEM-3 in the tertiary structure of class A β-lactamases suggested that they both are part of the substrate binding site. Analysis, by in vitro recombination, indicated that each mutation contributes to the extented substrate range of the enzyme, compared to that of the TEM-type penicillinase, and that the strength of the promoter of blaT-3 is responsible for high-level resistance towards broad-spectrum cephalosporins of strains producing TEM-3.
TL;DR: There was no change in hydrophobicity following re-isolation of the bacteria from experimentally infected rainbow trout, Salmo gairdneri, and strains could not be distinguished using biochemical tests.
Abstract: The cell surface hydrophobicity of Renibacterium salmoninarum strains was examined using a salt aggregation method. Those strains which were virulent in the test animal were sticky, auto-agglutinating and possessed a hydrophobic cell surface. Those strains with a low virulence were non-sticky, non-agglutinating and failed to aggregate in a high molar salt. Strains could not be distinguished using biochemical tests. There was no change in hydrophobicity following re-isolation of the bacteria from experimentally infected rainbow trout, Salmo gairdneri.
TL;DR: An Fe(II)-oxidizing enzyme was purified from Thiobacillus ferrooxidans to an electrophoretically homogeneous state and showed absorption peaks at 282 and 382 nm and contained 18–20 atoms of non-haem iron and 6 atoms of inorganic sulphide in the molecule.
Abstract: An Fe(II)-oxidizing enzyme was purified from Thiobacillus ferrooxidans to an electrophoretically homogeneous state. The enzyme showed absorption peaks at 282 and 382 nm and contained 18–20 atoms of non-haem iron and 6 atoms of inorganic sulphide in the molecule. Its molecular weight was determined to be 63 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The enzyme rapidly reduced T. ferrooxidans ferricytochrome c-552 with Fe2+ ions at pH 3.5. Rusticyanin was not reduced by the enzyme with Fe2+ ions, while it was reduced rapidly by the enzyme with the ions in the presence of a small amount of cytochrome c-552.
TL;DR: Pure cultures of Methanobacterium- and Methanosarcina-like organisms were isolated from H2CO2 and methanol enrichment cultures, respectively, and were characterized for various nutritional and growth conditions.
Abstract: Enrichment cultures for H2CO2, methanol- or acetate-utilizing methanogens were prepared from two rice field soil samples. All the cultures except one acetate enrichment showed significant methane production. Pure cultures of Methanobacterium- and Methanosarcina-like organisms were isolated from H2CO2 and methanol enrichment cultures, respectively, and were characterized for various nutritional and growth conditions. The organisms had an optimal pH range of 6.4–6.6 and a temperature optimum of 37°C. The Methanobacterium isolates were able to utilize H2CO2 but no other substrates as sole energy source, while the Methanosarcina isolates were able to utilize methanol, methylamines or H2CO2 as sole energy sources. Both Methanobacterium isolates and one isolate of Methanosarcina were able to use dinitrogen as the sole source of nitrogen for growth. The isolates used several sulfur compounds as sole sources of sulfur.
TL;DR: Ruthenium red was shown to penetrate beneath the surface layers of the gel, in the regions surrounding a fungal colony where degradation of polygalacturonate had occurred, and did not penetrate the medium, was restricted to binding to thesurface layers and was easily washed off.
Abstract: A method for the detection of polygalacturonase activity has been developed using ruthenium red staining of fungal colonies on polygalacturonate- agarose plates. Ruthenium red was shown to penetrate beneath the surface layers of the gel, in the regions surrounding a fungal colony where degradation of polygalacturonate had occurred. Without degradation of polygalacturonate ruthenium red did not penetrate the medium, was restricted to binding to the surface layers and was easily washed off. The medium containing undegraded polygalacturonate was a colourless clear background and areas of polygalacturonate degradation around the colonies were visualised as an intense purple-red halo. The method has been used to screen yeasts and filamentous fungi for polygalacturonase secretion.
TL;DR: The N-terminal of the mature amylase has been determined and shown to be in accordance with signal peptidase processing after a typical Gram-positive signal sequence of 33 amino acids.
Abstract: We have cloned and expressed a novel maltogenic alpha-amylase from B. stearothermophilus on plasmid in B. subtilis. Originally the plasmid was very unstable in the absence of selection, but was stabilized due to a spontaneous, copy number reducing mutation. The promoter region and the extension of the gene have been analysed, and a provisional DNA sequence has been determined. The N-terminal of the mature amylase has been determined and shown to be in accordance with signal peptidase processing after a typical Gram-positive signal sequence of 33 amino acids.
TL;DR: Soil type, but not inoculum density between 10 4 and 10 8 cells per gram of soil, significantly influenced the recovery percentage of the immunofluorescence technique, and recovery percentages determined using selective plating were independent of either soil type or inoculumdensity.
Abstract: After the introduction of Rhizobium leguminosarum biovar trifolii into a loamy sand and a silt loam, high recovery percentages were determined using quantitative immunofluorescence. Soil type, but not inoculum density between 10 4 and 10 8 cells per gram of soil, significantly influenced the recovery percentage of the immunofluorescence technique. Recovery percentages determined using selective plating were independent of either soil type or inoculum density and exceeded those determined by immunofluorescence. The serological and genetic markers used for detection were stable during 55 days of incubation in phosphate-buffered saline and soil extract solution. After the introduction of R. leguminosarum biovar trifolii into both sterilized soil types, the population increased to 0.5–1×10 9 cells per gram of soil, but a decline was demonstrated in non-sterile loamy sand and silt loam during incubation of 90 days at 15°C. Starvation of rhizobial cells in the phosphate-buffered saline and soil extract solution, as well as incubation in both soil types, resulted in a significant decrease in mean cell size.
TL;DR: Results support earlier evidence for the functioning of this pathway on the basis of enzyme assays and support a randomizing route such as the methylmalonyl-CoA pathway for propionate degradation.
Abstract: The degradation of [1-14C]- and [2-14C] propionate to acetate and bicarbonate by the sulfate- reducing bacterium Desulfobulbus propionicus was studied. When [1-14C]propionate was used, more than 95% of the label was recovered in the HCO3− fraction. [2-14C]Propionate was quantitatively converted into labeled acetate of which the methyl and carboxyl group were equally labeled. These results are in accordance with a randomizing route such as the methylmalonyl-CoA pathway for propionate degradation and support earlier evidence for the functioning of this pathway on the basis of enzyme assays.
TL;DR: The orientation of the green flagellate, Euglena gracilis, in a vertical column immersed in a pond was studied using automatic cell counting based on computerized image analysis, and it is suggested that this behavior provides an opportunity for the organisms to escape from detrimental bright light.
Abstract: The orientation of the green flagellate, Euglena gracilis, in a vertical column immersed in a pond was studied using automatic cell counting based on computerized image analysis. When exposed to solar radiation, the population moved downward in the column, probably guided by negative phototaxis, and formed a dense layer at the bottom. It is suggested that this behavior provides an opportunity for the organisms to escape from detrimental bright light. The downward movement is faster than the swimming speed of the cells allows and could be accelerated by a fluid mechanic effect. The upward movement observed at night may be due to the precise negative gravitaxis observed in the organisms. These antagonistic types of behavior allow the organisms to actively search for and to stay in areas with suitable conditions.
TL;DR: Protection of vaccinees against challenge with the living homologous ETEC (strain H-10407) was demonstrated, demonstrating that colicin E2-treated CFA-positive E. coli cells are an efficient vehicle in terms of delivery of antigens to the gut immune system.
Abstract: An oral killed (non-replicating) whole-cell anti-ETEC vaccine was prepared by treating enterotoxigenic Escherichia coli strain H-10407 (ST + LT +; 078: H11: CFA/I) with a 100%-lethal amount of colicin E2. Colicin E2 is a potent DNA endonuclease which enters the target bacterial cells without disrupting cellular integrity. Thus the vaccine consists of intact cells lacking chromosomal and plasmid DNA but possessing a normal complement of antigens, including CFA/I and enterotoxin(s), unaltered by chemical- or heat-treatment. Young healthy volunteers were administered two oral doses, one month apart, of approximately 3×1010 vaccine cells. Of 22 vaccinees, 17 (77.3%) showed an intestinal anti-CFA/I IgA response and 19 (86.4%) showed an increase in intestinal anti-LT IgA. Twenty of 22 (90.9%) vaccinees had antibody responses to either CFA/I, LT, or both antigens, demonstrating that colicin E2-treated CFA-positive E. coli cells are an efficient vehicle in terms of delivery of antigens to the gut immune system. We previously demonstrated protection of vaccinees against challenge with the living homologous ETEC (strain H-10407). In this study, two groups of 8 vaccinees were challenged with a diarrheagenic dose of virulent ST+LT+ETEC of heterologous serotype; one group was challenged with a CFA/I-positive 063 : H- strain and the other group was challenged with a CFA/II-positive 06 : H16 strain. Approximately 75% efficacy was achieved in both challenge groups. None of the 16 vaccinees who had responded to both CFA/I and LT became ill upon challenge while both of the vaccinees who had not responded to either antigen did. That protection against challenge with heterologous ETEC was due to non-specific immunostimulation proved to be unlikely since only 1 of the remaining 6 vaccinees showed mild symptoms when challenged with strain H-10407 6 months after vaccination. These results indicate that ETEC heterologous with respect to O, H, and CFA may share other antigens which contribute to a protective intestinal immune response.