Toxin Gene Contents and Activity of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Strains Against Two Sugarcane Borer Species, <Emphasis Type="Italic">Diatraea saccharalis</Emphasis> (F.) and <Emphasis Type="Italic">D. flavipennella</Emphasis> (Box)

Bacillus thuringiensis (Berliner) bears essential characteristics in the control of insect pests, such as its unique mode of action, which confers specificity and selectivity. This study assessed cry gene contents from Bt strains and their entomotoxicity against Diatraea saccharalis (F.) and Diatraea flavipennella (Box) (Lepidoptera: Crambidae). Bioassays with Bt strains were performed against neonates to evaluate their lethal and sublethal activities and were further analyzed by PCR, using primers to identify toxin genes. For D. saccharalis and D. flavipennella, 16 and 18 strains showed over 30% larval mortality in the 7th day, respectively. The LC₅₀ values of strains for D. saccharalis varied from 0.08 × 10⁵ (LIIT-0105) to 4104 × 10⁵ (LIIT-2707) spores + crystals mL^?1. For D. flavipennella, the LC₅₀ values of strains varied from 0.40 × 10⁵ (LIIT-2707) to 542 × 10⁵ (LIIT-2109) spores + crystals mL^?1. For the LIIT-0105 strain, which was the most toxic to D. saccharalis, the genes cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1F, cry1I, cry2Aa, cry2Ab, cry8, and cry9C were detected, whereas for the strain LIIT-2707, which was the most toxic to D. flavipennella, detected genes were cry1Aa, cry1Ab, cry1Ac, cry1B, cry1D, cry1F, cry1I, cry2Aa, cry2Ab, and cry9. The toxicity data and toxin gene content in these strains of Bt suggest a great variability of activity with potential to be used in the development of novel biopesticides or as source of resistance genes that can be expressed in plants to control pests.     

<Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Cry11Ba works synergistically with Cry4Aa but not with Cry11Aa for toxicity against mosquito <Emphasis Type="Italic">Culex pipiens</Emphasis> (Diptera: Culicidae) larvae

A 2,175-bp modified gene (cry11Ba-S1) encoding Cry11Ba from Bacillus thuringiensis subsp. jegathesan was designed and the recombinant protein was expressed as a fusion protein with glutathione S-transferase in Escherichia coli. The recombinant Cry11Ba was highly toxic against Culex pipiens mosquito larvae, being nine and 17 times more toxic than mosquitocidal Cry4Aa and Cry11Aa from Bacillus thuringiensis subsp. israelensis, respectively. Interestingly, a further increase in the toxicity of the recombinant Cry11Ba was achieved by mixing with Cry4Aa, but not with Cry11Aa. These findings suggested that Cry11Ba worked synergistically with Cry4Aa, but not with Cry11Aa, in exhibiting toxicity against C. pipiens larvae. On the other hand, the amount of Cry toxin bound to brush border membrane vesicles (BBMVs) did not significantly change between individual toxins and the toxin mixtures, suggesting that the increase in toxins binding to BBMVs was not a reason for the observed synergistic effect. It is generally accepted that synergism of toxins is a potentially powerful tool for enhancing insecticidal activity and managing Cry toxin resistance in mosquitoes. The mixture of Cry4Aa and Cry11Ba in order to increase toxicity would be very valuable in terms of mosquito control.     

Development of leaffolder resistant transgenic rice expressing <Emphasis Type="Italic">cry2AX1</Emphasis> gene driven by green tissue-specific <Emphasis Type="Italic">rbcS</Emphasis> promoter

The insecticidal cry genes of Bacillus thuringiensis (Bt) have been successfully used for development of insect resistant transgenic rice plants. In this study, a novel cry2AX1 gene consisting a sequence of cry2Aa and cry2Ac gene driven by rice rbcS promoter was introduced into a rice cultivar, ASD16. Among 27 putative rice transformants, 20 plants were found to be positive for cry2AX1 gene. The expression of Cry2AX1 protein in transgenic rice plants ranged from 5.95 to 122.40 ng/g of fresh leaf tissue. Stable integration of the transgene was confirmed in putative transformants of rice by Southern blot hybridization analysis. Insect bioassay on T₀ transgenic rice plants against rice leaffolder (Cnaphalocrosis medinalis) recorded larval mortality up to 83.33 %. Stable inheritance and expression of cry2AX1 gene in T₁ progenies was demonstrated using Southern and ELISA. The detached leaf bit bioassay with selected T₁ plants showed 83.33–90.00 % mortality against C. medinalis. The whole plant bioassay for T₁ plants with rice leaffolder showed significant level of resistance even at a lower level of Cry2AX1 expression varying from 131 to 158 ng/g fresh leaf tissue during tillering stage.     

Conjugative plasmid transfer from <Emphasis Type="Italic">Escherichia coli</Emphasis> is a versatile approach for genetic transformation of thermophilic <Emphasis Type="Italic">Bacillus</Emphasis> and <Emphasis Type="Italic">Geobacillus</Emphasis> species

We previously demonstrated efficient transformation of the thermophile Geobacillus kaustophilus HTA426 using conjugative plasmid transfer from Escherichia coli BR408. To evaluate the versatility of this approach to thermophile transformation, this study examined genetic transformation of various thermophilic Bacillus and Geobacillus spp. using conjugative plasmid transfer from E. coli strains. E. coli BR408 successfully transferred the E. coli–Geobacillus shuttle plasmid pUCG18T to 16 of 18 thermophiles with transformation efficiencies between 4.1 × 10^?7 and 3.8 × 10^?2/recipient. Other E. coli strains that are different from E. coli BR408 in intracellular DNA methylation also generated transformants from 9 to 15 of the 18 thermophiles, including one that E. coli BR408 could not transform, although the transformation efficiencies of these strains were generally lower than those of E. coli BR408. The conjugation was performed by simple incubation of an E. coli donor and a thermophile recipient without optimization of experimental conditions. Moreover, thermophile transformants were distinguished from abundant E. coli donor only by high temperature incubation. These observations suggest that conjugative plasmid transfer, particularly using E. coli BR408, is a facile and versatile approach for plasmid introduction into thermophilic Bacillus and Geobacillus spp., and potentially a variety of other thermophiles.     

Clinical strains of <Emphasis Type="Italic">Lactobacillus</Emphasis> reduce the filamentation of <Emphasis Type="Italic">Candida albicans</Emphasis> and protect <Emphasis Type="Italic">Galleria mellonella</Emphasis> against experimental candidiasis

Candida albicans is the most common human fungal pathogen and can grow as yeast or filaments, depending on the environmental conditions. The filamentous form is of particular interest because it can play a direct role in adherence and pathogenicity. Therefore, the purpose of this study was to evaluate the effects of three clinical strains of Lactobacillus on C. albicans filamentation as well as their probiotic potential in pathogen-host interactions via an experimental candidiasis model study in Galleria mellonella. We used the reference strain Candida albicans ATCC 18804 and three clinical strains of Lactobacillus: L. rhamnosus strain 5.2, L. paracasei strain 20.3, and L. fermentum strain 20.4. First, the capacity of C. albicans to form hyphae was tested in vitro through association with the Lactobacillus strains. After that, we verified the ability of these strains to attenuate experimental candidiasis in a Galleria mellonella model through a survival curve assay. Regarding the filamentation assay, a significant reduction in hyphae formation of up to 57% was observed when C. albicans was incubated in the presence of the Lactobacillus strains, compared to a control group composed of only C. albicans. In addition, when the larvae were pretreated with Lactobacillus spp. prior to C. albicans infection, the survival rate of G. mellonela increased in all experimental groups. We concluded that Lactobacillus influences the growth and expression C. albicans virulence factors, which may interfere with the pathogenicity of these microorganisms.     

The diversity of rhizobia nodulating the <Emphasis Type="Italic">Medicago</Emphasis>, <Emphasis Type="Italic">Melilotus</Emphasis> and <Emphasis Type="Italic">Trigonella</Emphasis> inoculation group in Egypt is marked by the dominance of two genetic types

Twenty four rhizobial strains were isolated from root nodules of Melilotus, Medicago and Trigonella plants growing wild in soils throughout Egypt. The nearly complete 16S rRNA gene sequence from each strain showed that 12 strains (50 %) were closely related to the Ensifer meliloti LMG6133^T type strain with identity values higher than 99.0 %, that 9 (37.5 %) strains were more than 99 % identical to the E. medicae WSM419^T type strain, and that 3 (12.5 %) strains showed 100 % identity with the type strain of N. huautlense S02^T. Accordingly, the diversity of rhizobial strains nodulating wild Melilotus, Medicago and Trigonella species in Egypt is marked by predominance of two genetic types, E. meliloti and E. medicae, although the frequency of isolation was slightly higher in E. meliloti. Sequencing of the symbiotic nodC gene from selected Medicago and Melilotus strains revealed that they were all similar to those of the E. meliloti LMG6133^T and E. medicae WSM419^T type strains, respectively. Similarly, nodC sequences of strains identified as members of the genus Neorhizobium were more than 99 % identical to that of N. galegae symbiovar officinalis HAMBI 114.     

Different response of an elite <Emphasis Type="Italic">Bt</Emphasis> restorer line of hybrid rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) in adaptation to nitrogen deficiency

Transgenic Bacillus thuringiensis (Bt) rice have been reported to acquire effective resistance against the target pests; however, the insertion and expression of alien Bt genes may have some unintended effects on the growth characteristics of rice. A screen-house experiment was conducted and repeated twice to investigate the growth characteristics and Bt protein expressions in two Bt rice lines [MH63 (Cry2A*) and MH63 (Cry1Ab/Ac)], which had different Bt protein expression levels in leaves, under zero nitrogen (N0) and recommended nitrogen (NR) fertilizer applications. Compared to the counterpart MH63, MH63 (Cry2A*) under N0 experienced accelerated leaf senescence and a lower internal N use efficiency (IE_N), resulting in a 23.2% decrease in grain yield and a lower accumulated biomass. These variations were revealed to be correlated to the higher ratio of the Bt protein content to the soluble protein content (BTC/SPC) with a maximum value of 4.3‰ in MH63 (Cry2A*) leaves in the late growth stage. Under NR, no differences in growth characteristics between MH63 (Cry2A*) and MH63 were found. The growth characteristics of MH63 (Cry1Ab/Ac), with a lower BTC/SPC in the late growth stage compared to MH63 (Cry2A*), were identical to those of MH63 under the two N applications. Results show that the transgenic Bt rice MH63 (Cry2A*), with a relatively higher Bt protein expression in the late growth stage, had an inferior adaptation to nitrogen deficiency compared to its non-Bt counterpart. And this inferior adaptation was found to be correlated with the higher BTC/SPC in MH63 (Cry2A*) leaves in the late growth stage.     

Stability,oviposition attraction,and larvicidal activity of binary toxin from <Emphasis Type="Italic">Bacillus sphaericus</Emphasis> expressed in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Bacillus sphaericus produces a two-chain binary toxin composed of BinA (42 kDa) and BinB (51 kDa), which are deposited as parasporal crystals during sporulation. The toxin is highly active against Culex larvae and Aedes and Anopheles mosquitoes, which are the principal vectors for the transmission of malaria, yellow fever, encephalitis, and dengue. The use of B. sphaericus and Bacillus thuringiensis in mosquito control programs is limited by their sedimentation in still water. In this study, the binA and binB genes were cloned and the recombinant BinAB protein was expressed in three strains of Escherichia coli. These recombinant strains were used in a toxicity assay against Culex quinquefasciatus larvae. The highest expression level was achieved when both proteins were expressed in a single operon construct. The BinAB protein expressed in the E. coli Arctic strain showed higher larvicidal activity than either of the recombinant proteins from the E. coli Ril or pLysS strains. Furthermore, it had the highest oviposition attraction (49.1%, P?相似文献   

Genome-wide identification and evolution of <Emphasis Type="Italic">TC1</Emphasis>/<Emphasis Type="Italic">Mariner</Emphasis> in the silkworm (<Emphasis Type="Italic">Bombyx mori</Emphasis>) genome

TC1/Mariner transposons belong to class II transposable elements (TEs) that use DNA-mediated “cut and paste” mechanism to transpose, and they have been identified in almost all organisms. Although silkworm (Bombyx mori) has a large amount of TC1/Mariner elements, the genome wide information of this superfamily in the silkworm is unknown. In this study, we have identified 2670 TC1/Mariner (Bmmar) elements in the silkworm genome. All the TEs were classified into 22 families by means of fgclust, a tool of repetitive sequence classification, seven of which was first reported in this study. Phylogenetic and structure analyses based on the catalytic domain (DDxD/E) of transposase sequences indicated that all members of TC1/Mariner were grouped into five subgroups: Mariner, Tc1, maT, DD40D and DD41D/E. Of these five subgroups, maT rather than Mariner possessed most members of TC1/Mariner (51.23%) in the silkworm genome. In particular, phylogenetic analysis and structure analysis revealed that Bmmar15 (DD40D) formed a new basal subgroup of TC1/Mariner element in insects, which was referred to as bmori. Furthermore, we concluded that DD40D appeared to intermediate between mariner and Tc1. Finally, we estimated the insertion time for each copy of TC1/Mariner in the silkworm and found that most of members were dramatically amplified during a period from 0 to 1 mya. Moreover, the detailed functional data analysis showed that Bmmar1, Bmmar6 and Bmmar9 had EST evidence and intact transposases. These implied that TC1/Mariner might have potential transpositional activity. In conclusion, this study provides some new insights into the landscape, origin and evolution of TC1/Mariner in the insect genomes.     

Cyclohexanone-induced stress metabolism of <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Solvent stress occurs during whole-cell biocatalysis of organic chemicals. Organic substrates and/or products may accumulate in the cellular membranes of whole cells, causing structural destabilization of the membranes, which leads to disturbances in cellular carbon and energy metabolism. Here, we investigate the effect of cyclohexanone on carbon metabolism in Escherichia coli BL21 and Corynebacterium glutamicum ATCC13032. Adding cyclohexanone to the culture medium (i.e., glucose mineral medium) resulted in a decreased specific growth rate and increased cellular maintenance energy in both strains of bacteria. Notably, carbon metabolism, which is mainly involved to increase cellular maintenance energy, was very different between the bacteria. Carbon flux into the acetic acid fermentation pathway was dominantly enhanced in E. coli, whereas the TCA cycle appeared to be activated in C. glutamicum. In fact, carbon flux into the TCA cycle in E. coli appeared to be reduced with increasing amounts of cyclohexanone in the culture medium. Metabolic engineering of E. coli cells to maintain or improve TCA cycle activity and, presumably, that of the electron transport chain, which are involved in regeneration of cofactors (e.g., NAD(P)H and ATP) and formation of toxic metabolites (e.g., acetic acid), may be useful in increasing solvent tolerance and biotransformation of organic chemicals (e.g., cyclohexanone).     

Potency of the mosquitocidal Cry46Ab toxin produced using a 4AaCter-tag,which facilitates formation of protein inclusion bodies in <Emphasis Type="Italic">Escherichia coli</Emphasis>

A Cry46Ab toxin derived from Bacillus thuringiensis strain TK-E6 shows mosquitocidal activity against Culex pipiens pallens Coquillett (Diptera: Culicidae) larvae as well as preferential cytotoxicity against human cancer cells. In B. thuringiensis cells, Cry46Ab is produced and accumulates as a protein crystal that is processed into the active 29-kDa toxin upon solubilization in the alkaline environment of the insect midgut. The Cry46Ab protoxin is 30 kDa, and is therefore thought to require an accessory protein such as P20 and/or ORF2 for efficient crystal formation. In the present study, the potency of the 4AaCter-tag was investigated for the production of alkali-soluble inclusion bodies of recombinant Cry46Ab in Escherichia coli. The 4AaCter-tag is a polypeptide derived from the C-terminal region of the B. thuringiensis Cry4Aa toxin and facilitates the formation of alkali-soluble protein inclusion bodies in E. coli. Fusion with the 4AaCter-tag enhanced both Cry46Ab production and the formation of Cry46Ab inclusion bodies. In addition, upon optimization of protein expression procedures, the Cry46Ab–4AaCter inclusion bodies showed mosquitocidal activity and stability in aqueous environments comparable to Cry46Ab without the 4AaCter-tag. Our study suggests that use of the 4AaCter-tag is a straightforward approach for preparing formulations of smaller-sized Cry toxins such as Cry46Ab in E. coli.     

Discovery of a Highly Virulent Strain of <Emphasis Type="Italic">Photorhabdus luminescens</Emphasis> ssp<Emphasis Type="Italic">. akhurstii</Emphasis> from Meghalaya,India

Photorhabdus is an insect-pathogenic Gram negative enterobacterium found in the gut of Heterorhabditis nematodes. Photorhabdus is highly virulent to insects, and can kill insects rapidly upon injection at very low concentrations of one to few cells. We characterized the virulence of Photorhabdus symbionts isolated from the Heterorhabditis nematodes collected from various parts of India by injecting different concentrations of bacterial cells into fourth instar larval stage of insect Galleria mellonella. Photorhabdus luminescens ssp. akhurstii strain IARI-SGMG3 from Meghalaya was identified as the most virulent of all the tested strains on the basis of LT₅₀ and LC₅₀ values. This study forms a basis for further investigations on the genetic basis of virulence in Photorhabdus bacteria.     

<Emphasis Type="Italic">Candida krusei</Emphasis> and <Emphasis Type="Italic">Candida glabrata</Emphasis> reduce the filamentation of <Emphasis Type="Italic">Candida albicans</Emphasis> by downregulating expression of <Emphasis Type="Italic">HWP1</Emphasis> gene

Pathogenicity of Candida albicans is associated with its capacity switch from yeast-like to hyphal growth. The hyphal form is capable to penetrate the epithelial surfaces and to damage the host tissues. Therefore, many investigations have focused on mechanisms that control the morphological transitions of C. albicans. Recently, certain studies have showed that non-albicans Candida species can reduce the capacity of C. albicans to form biofilms and to develop candidiasis in animal models. Then, the objective of this study was to evaluate the effects of Candida krusei and Candida glabrata on the morphogenesis of C. albicans. Firstly, the capacity of reference and clinical strains of C. albicans in forming hyphae was tested in vitro. After that, the expression of HWP1 (hyphal wall protein 1) gene was determined by quantitative real-time PCR (polymerase chain reaction) assay. For both reference and clinical strains, a significant inhibition of the hyphae formation was observed when C. albicans was incubated in the presence of C. krusei or C. glabrata compared to the control group composed only by C. albicans. In addition, the culture mixed of C. albicans-C. krusei or C. albicans-C. glabrata reduced significantly the expression of HWP1 gene of C. albicans in relation to single cultures of this specie. In both filamentation and gene expression assays, C. krusei showed the higher inhibitory activity on the morphogenesis of C. albicans compared to C. glabrata. C. krusei and C. glabrata are capable to reduce the filamentation of C. albicans and consequently decrease the expression of the HWP1 gene.     

Deletion of <Emphasis Type="Italic">ldh</Emphasis>A and <Emphasis Type="Italic">ald</Emphasis>H genes in <Emphasis Type="Italic">Klebsiella</Emphasis><Emphasis Type="Italic">pneumoniae</Emphasis> to enhance 1,3-propanediol production

Objectives

To improve 1,3-propanediol (1,3-PD) production and reduce byproduct concentration during the fermentation of Klebsiella pneumonia.

Results

Klebsiella. pneumonia 2-1ΔldhA, K. pneumonia 2-1ΔaldH and K. pneumonia 2-1ΔldhAΔaldH mutant strains were obtained through deletion of the ldhA gene encoding lactate dehydrogenase required for lactate synthesis and the aldH gene encoding acetaldehyde dehydrogenase involved in the synthesis of ethanol. After fed-batch fermentation, the production of 1,3-PD from glycerol was enhanced and the concentrations of byproducts were reduced compared with the original strain K. pneumonia 2-1. The maximum yields of 1,3-PD were 85.7, 82.5 and 87.5 g/l in the respective mutant strains.

Conclusion

Deletion of either aldH or ldhA promoted 1,3-PD production in K. pneumonia.

     

Interaction between toxin crystals and vegetative insecticidal proteins of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> in lepidopteran larvae

Insecticides based on crystalline toxins of Bacillus thuringiensis are very good biological plant protection products. However, the spectrum of activity of some toxins is narrow or resistance among insects has been developed. We tested the insecticidal activity of crystals of the B. thuringiensis MPU B9 strain alone and supplemented with Vip3Aa proteins against important pests: Spodoptera exigua Hübner (Lepidoptera: Noctuidae), Cydia pomonella L. (Lepidoptera: Tortricidae) and Dendrolimus pini L. (Lepidoptera: Lasiocampidae). The Cry toxins were more active for D. pini but less active against S. exigua and C. pomonella than Vip3Aa. Supplementation of Cry toxins by small amounts of vegetative insecticidal proteins demonstrated synergistic effect and significantly enhanced the toxicity of the insecticide. The results indicate the utility of Cry and Vip3Aa toxins mixtures to control populations of crops and forests insect pests.     

<Emphasis Type="Italic">Aeromonas</Emphasis> and <Emphasis Type="Italic">Plesiomonas</Emphasis> species from scarlet ibis (<Emphasis Type="Italic">Eudocimus ruber</Emphasis>) and their environment: monitoring antimicrobial susceptibility and virulence

The present study aimed at evaluating the role of captive scarlet ibises (Eudocimus ruber) and their environment as reservoirs of Aeromonas spp. and Plesiomonas spp., and analyzing the in vitro antimicrobial susceptibility and virulence of the recovered bacterial isolates. Thus, non-lactose and weak-lactose fermenting, oxidase positive Gram-negative bacilli were recovered from cloacal samples (n = 30) of scarlet ibises kept in a conservational facility and from water samples (n = 30) from their environment. Then, the antimicrobial susceptibility, hemolytic activity and biofilm production of the recovered Aeromonas spp. and Plesiomonas shigelloides strains were assessed. In addition, the virulence-associated genes of Aeromonas spp. were detected. Ten Aeromonas veronii bv. sobria, 2 Aeromonas hydrophila complex and 10 P. shigelloides were recovered. Intermediate susceptibility to piperacillin-tazobactam and cefepime was observed in 2 Aeromonas spp. and 1 P. shigelloides, respectively, and resistance to gentamicin was observed in 4 P. shigelloides. The automated susceptibility analysis revealed resistance to piperacillin-tazobactam and meropenem among Aeromonas spp. and intermediate susceptibility to gentamicin among P. shigelloides. All Aeromonas isolates presented hemolytic activity, while 3 P. shigelloides were non-hemolytic. All Aeromonas spp. and 3/10 P. shigelloides were biofilm-producers, at 28 °C, while 10 Aeromonas spp. and 6/10 P. shigelloides produced biofilms, at 37 °C. The most prevalent virulence genes of Aeromonas spp. were asa1 and ascV. Scarlet ibises and their environment harbour potentially pathogenic bacteria, thus requiring monitoring and measures to prevent contamination of humans and other animals.     

<Emphasis Type="Italic">In vivo</Emphasis> fluorescence observation of parasporal inclusion formation in <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>

A recombinant gene expressing a Cry1Ac-GFP fusion protein with a molecular mass of approximately 160 kD was constructed to investigate the expression of cry1Ac, the localization of its gene product Cry1Ac, and its role in crystal development in Bacillus thuringiensis. The cry1Ac-gfp fusion gene under the control of the cry1Ac promoter was cloned into the plasmid pHT304, and this construct was designated pHTcry1Ac-gfp. pHTcry1Ac-gfp was transformed into the crystal-negative strain, HD-73 cry⁻, and the resulting strain was named HD-73⁻(pHTcry1Ac-gfp). The gfp gene was then inserted into the large HD-73 endogenous plasmid pHT73 and fused with the 3′ terminal of the cry1Ac gene by homologous recombination, yielding HD-73Φ(cry1Ac-gfp)3534. Laser confocal microscopy and Western blot analyses showed for the first time that the Cry1Ac-GFP fusion proteins in both HD-73⁻(pHTcry1Ac-gfp) and HD-73Φ(cry1Ac-gfp)3534 were produced during asymmetric septum formation. Surprisingly, the Cry1Ac-GFP fusion protein showed polarity and was located near the septa in both strains. There was no significant difference between Cry1Ac-GFP and Cry1Ac in their toxicity to Plutella xylostella larvae.     

Characterization of the lipopolysaccharide of <Emphasis Type="Italic">Escherichia coli</Emphasis> 126

The lipopolysaccharide (LPS) of Escherichia coli 126 was isolated and studied. The lipid A fatty acid composition of the investigated LPS was similar to that of other members of the family Enterobacteriaceae. The E. coli 126 LPS was more toxic than the LPSs of previously studied E. coli strains and of other members of the Enterobacteriaceae (Budvicia aquatica and Pragia fontium), and was less pyrogenic than pyrogenal. SDS-PAG electrophoresis showed a bimodal distribution typical of S-form LPSs. The LPS of E. coli 126 decreased the adhesive index indicating a possible competition between LPS molecules of E. coli 126 and adhesins of E. coli F-50 on rabbit erythrocytes. The LPS of E. coli 126 in a homologous system showed antigenic activity in the reactions of double immunodiffusion in agar by Ouchterlony. No serological cross-reaction of the LPS of other E. coli strains, as well as of that of the B. aquatica type strain, with the antiserum to E. coli 126 was observed. The structural components of the lipopolysaccharide obtained by mild acid hydrolysis were lipid A, the core oligosaccharide, and the O-specific polysaccharide. Based on the data of monosaccharide analysis and ¹H and ¹³C NMR spectroscopy it was found that the O-specific polysaccharide had the structure characteristic of the representatives of E. coli serogroup O15.