Bacillus thuringiensis: a common member of microflora in activated sludges of a sewage treatment plant

Bacillus thuringiensis was recovered at a high frequency from activated-sludge system environments in an urban sewage-digestive plant. All of the test materials, sampled at several digesting steps, contained the organism. Of 515 colonies belonging to the B. cereus/B. thuringiensis group, 45 (8.7%) were assigned to B. thuringiensis. The highest density of this bacterium was 1.6 x 103 cfu/ml in a scum sample of the first aeration basin. Among the 45 isolates, 7 were assigned to the known H serovars. Two isolates of the serovar kenyae isolates exhibited Lepidoptera-specific toxicity. Diptera-specific toxicity was shown by an isolate of serovar israelensis and a serologically undefined isolate. Lectin activity was associated with 12 isolates.

Protein kinase Cdelta-mediated phosphorylation of alpha6beta4 is associated with reduced integrin localization to the hemidesmosome and decreased keratinocyte attachment

In mammalian epidermis, expression of the alpha6beta4 integrin is restricted to the hemidesmosome complexes, which connect the proliferative basal cell layer with the underlying basement membrane. Keratinocyte differentiation is associated with down-regulation of alpha6beta4 expression and detachment of keratinocytes from the basement membrane. Neoplastic keratinocytes delay maturation, proliferate suprabasally, and retain the expression of the alpha6beta4 integrin in suprabasal cells disassociated from the hemidesmosomes. We now show that the alpha6beta4 integrin is a substrate for serine phosphorylation by protein kinase C in keratinocytes. Furthermore, protein kinase C-mediated phosphorylation of alpha6beta4 is associated with redistribution of this integrin from the hemidesmosome to the cytosol. Specifically, in vitro kinase assays identified the protein kinase Cdelta as the primary isoform phosphorylating alpha6 and beta4 integrin subunits. Using recombinant protein kinase C adenoviruses, overexpression of protein kinase Cdelta but not protein kinase Calpha in primary keratinocytes increased beta4 serine phosphorylation, decreased alpha6beta4 localization to the hemidesmosome complexes, and reduced keratinocyte attachment. Taken together, these results establish a link between protein kinase Cdelta-mediated serine phosphorylation of alpha6beta4 integrin and its effects on alpha6beta4 subcellular localization and keratinocyte attachment to the laminin underlying matrix.

A 28 kDa protein of the Bacillus thuringiensis serovar shandongiensis isolate 89-T-34-22 induces a human leukemic cell-specific cytotoxicity

A 28 kDa protein that exhibits cytocidal activity specific for human leukemic T (MOLT-4) cells was purified from proteinase K-digested parasporal inclusion of a Bacillus thuringiensis serovar shandongiensis isolate. The N-terminal sequence of the protein was identical with that of the 32 kDa protein, regarded as a protoxin, of the inclusion proteins. The median effective concentration of this protein was 0.23 microg/ml against MOLT-4 cells and its specific activity was 7.9 times greater than that of the whole inclusion proteins. The 28 kDa protein induced necrosis-like cytotoxicity against MOLT-4 cells and the cytopathic effect with the passage of time was characterized by cell swelling, nuclear membrane isolation and chromatin condensation.

Defibrinogenating effect of batroxobin (Defibrase®) in rats and inhibition of migration of human vascular smooth muscle cells by the plasma of batroxobin-treated rats in vitro

The defibrinogenating effect of batroxobin (Defibrase) in male Wistar rats and the inhibitory effects of the plasma of batroxobin-treated rats on the migration of human vascular smooth muscle cells (SMCs) were investigated in vitro. At 1 h after a single intravenous injection of 3.0, 10.0 or 30.0 BU/kg batroxobin (ten rats in each group), the fibrinogen levels in the plasma of the rats decreased to 88.3, 66.2 and 16.5%, respectively, of that in the plasma of control saline-treated rats (261.0+/-26.7 mg/dl). When the plasma from the batroxobin-treated rats was added to Dulbecco's modified Eagle's medium at a concentration of 0.2% for a vascular SMC migration assay and incubated in a modified Boyden's chamber system at 37 degrees C for 24 h, significant inhibitory effects on vascular SMC migration were observed in the 10.0 (P<0.05) and 30.0 BU/kg (P<0.01) batroxobin-treated rats. The plasma of batroxobin-treated rats as well as standard rat fibrinogen induced vascular SMC migration in a fibrinogen content-dependent manner except the plasma of the 30.0 BU/kg batroxobin-treated rats. Moreover, the rat serum (0.1 approximately 5.0%) did not show any activity on vascular SMC migration in the present experimental system. These results indicate that the plasma fibrinogen significantly influences vascular SMC migration, and that the inhibitory effect of the plasma of batroxobin-treated rats on vascular SMC migration is related to the defibrinogenating action of batroxobin in vivo.

Insulin stimulates PKCzeta -mediated phosphorylation of insulin receptor substrate-1 (IRS-1). A self-attenuated mechanism to negatively regulate the function of IRS proteins

Incubation of rat hepatoma Fao cells with insulin leads to a transient rise in Tyr phosphorylation of insulin receptor substrate (IRS) proteins. This is followed by elevation in their P-Ser/Thr content, and their dissociation from the insulin receptor (IR). Wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor, abolished the increase in the P-Ser/Thr content of IRS-1, its dissociation from the IR, and the decrease in its P-Tyr content following 60 min of insulin treatment, indicating that the Ser kinases that negatively regulate IRS-1 function are downstream effectors of PI3K. PKCzeta fulfills this criterion, being an insulin-activated downstream effector of PI3K. Overexpression of PKCzeta in Fao cells, by infection of the cells with adenovirus-based PKCzeta construct, had no effect on its own, but it accelerated the rate of insulin-stimulated dissociation of IR.IRS-1 complexes and the rate of Tyr dephosphorylation of IRS-1. The insulin-stimulated negative regulatory role of PKCzeta was specific and could not be mimic by infecting Fao cells with adenoviral constructs encoding for PKC alpha, delta, or eta. Because the reduction in P-Tyr content of IRS-1 was accompanied by a reduced association of IRS-1 with p85, the regulatory subunit of PI3K, it suggests that this negative regulatory process induced by PKCzeta, has a built-in attenuation signal. Hence, insulin triggers a sequential cascade in which PI3K-mediated activation of PKCzeta inhibits IRS-1 functions, reduces complex formation between IRS-1 and PI3K, and inhibits further activation of PKCzeta itself. These findings implicate PKCzeta as a key element in a multistep negative feedback control mechanism of IRS-1 functions.

Inhibition of insulin-induced activation of Akt by a kinase-deficient mutant of the epsilon isozyme of protein kinase C

Akt, also known as protein kinase B, is a protein-serine/threonine kinase that is activated by growth factors in a phosphoinositide (PI) 3-kinase-dependent manner. Although Akt mediates a variety of biological activities, the mechanisms by which its activity is regulated remain unclear. The potential role of the epsilon isozyme of protein kinase C (PKC) in the activation of Akt induced by insulin has now been examined. Expression of a kinase-deficient mutant of PKCepsilon (epsilonKD), but not that of wild-type PKCepsilon or of kinase-deficient mutants of PKCalpha or PKClambda, with the use of adenovirus-mediated gene transfer inhibited the phosphorylation and activation of Akt induced by insulin in Chinese hamster ovary cells or L6 myotubes. Whereas the epsilonKD mutant did not affect insulin stimulation of PI 3-kinase activity, the phosphorylation and activation of Akt induced by a constitutively active mutant of PI 3-kinase were inhibited by epsilonKD, suggesting that epsilonKD affects insulin signaling downstream of PI 3-kinase. PDK1 (3'-phosphoinositide-dependent kinase 1) is thought to participate in Akt activation. Overexpression of PDK1 with the use of an adenovirus vector induced the phosphorylation and activation of Akt; epsilonKD inhibited, whereas wild-type PKCepsilon had no effect on, these actions of PDK1. These results suggest that epsilonKD inhibits the insulin-induced phosphorylation and activation of Akt by interfering with the ability of PDK1 to phosphorylate Akt.

Long-term graft acceptance in rat heart transplantation by CTLA4Ig gene transfection combined with FTY720 treatment

CTLA4Ig strongly adheres to B7 molecules on antigen-presenting cells to block intracellular signal transduction via CD28 on helper T cells, which eventually inhibits immune responses. We have demonstrated that the administration to recipient animals of adenoviral vectors containing CTLA4Ig gene (adCTLA4Ig) prolonged graft survival, although the gene expression diminished in a time-dependent manner and the grafts were finally rejected. In addition, recipient animals treated with FTY720, a new immunosuppressant, exhibited a decrease in the number of peripheral lymphocytes due to apoptosis. In this study, we performed adCTLA4Ig transfection combined with FTY720 treatment in heart-grafted rats to determine if the combination could induce a mutual effect on graft survival. The recipient animals were given injections of 1 x 10(9) plaque-forming units of adCTLA4Ig via the tail vein immediately after grafting. On the day before transplantation we administered FTY720 orally to some of these animals at a dosage of 5 mg/kg and again on the day of transplantation. The median graft survival period in the adCTLA4Ig-only group was 27 days, whereas that in the combination group was markedly prolonged to 56 days. Of 15 grafts, 5 survived indefinitely. In these groups we observed detectable levels of CTLA4Ig in the sera 49 days after grafting; the levels were always higher in the combination group than in the adCTLA4Ig-only group. As a result, this study revealed that FTY720 and adCTLA4Ig have a potent mutual effect on graft survival during rat heart transplantation. Furthermore, it is highly possible that FTY720 enhances gene expression of adCTLA4Ig, which may be related to the long-term acceptance of grafts.

Insulin induces specific interaction between insulin receptor and protein kinase C delta in primary cultured skeletal muscle

Certain protein kinase C (PKC) isoforms, in particular PKCs beta II, delta, and zeta, are activated by insulin stimulation. In primary cultures of skeletal muscle, PKCs beta II and zeta, but not PKC delta, are activated via a phosphatidylinositol 3-kinase (PI3K)-dependent pathway. The purpose of this study was to investigate the possibility that PKC delta may be activated upstream of PI3K by direct interaction with insulin receptor (IR). Experiments were done on primary cultures of newborn rat skeletal muscle, age 5--6 days in vitro. The time course of insulin-induced activation of PKC delta closely paralleled that of IR. Insulin stimulation caused a selective coprecipitation of PKC delta with IR, and these IR immunoprecipitates from insulin-stimulated cells displayed a striking induction of PKC activity due specifically to PKC delta. To examine the involvement of PKC delta in the IR signaling cascade, we used recombinant adenovirus constructs of wild-type (W.T.) or dominant negative (D.N.) PKC delta. Overexpression of W.T.PKC delta induced PKC delta activity and coassociation of PKC delta and IR without addition of insulin. Overexpression of D.N.PKC delta abrogated insulin- induced coassociation of PKC delta and IR. Insulin-induced tyrosine phosphorylation of IR was greatly attenuated in cells overexpressing W.T.PKC delta, whereas in myotubes overexpressing D.N.PKC delta, tyrosine phosphorylation occurred without addition of insulin and was sustained longer than that in control myotubes. In control myotubes IR displayed a low level of serine phosphorylation, which was increased by insulin stimulation. In cells overexpressing W.T.PKC delta, serine phosphorylation was strikingly high under basal conditions and did not increase after insulin stimulation. In contrast, in cells overexpressing D.N.PKC delta, the level of serine phosphorylation was lower than that in nonoverexpressing cells and did not change notably after addition of insulin. Overexpression of W.T.PKC delta caused IR to localize mainly in the internal membrane fractions, and blockade of PKC delta abrogated insulin-induced IR internalization. We conclude that PKC delta is involved in regulation of IR activity and routing, and this regulation may be important in subsequent steps in the IR signaling cascade.

Screening of the Bacillus thuringiensis Cry1Ac delta-endotoxin on the artificial phospholipid monolayer incorporated with brush border membrane vesicles of Plutella xylostella by optical biosensor technology

The binding of Cry1Ac, an insecticidal protein of Bacillus thuringiensis, to a brush border membrane (BBM) isolated from midguts of the diamondback moth Plutella xylostella was examined by surface plasmon resonance (SPR)-based biosensor. BBM was mixed with 1,3-ditetradecylglycero-2-phosphocholine (PC14), a neutral charged artificial lipid, and was reconstructed to a monolayer on a hydrophobic chip for the biosensor. The binding of Cry1Ac to the reconstructed monolayer was analyzed by a two-state binding model, and it was shown that Cry1Ac bound to the monolayer in the first step with an affinity constant (K(1)) of 508 nM, followed by the second uni-molecular step with an equilibrium constant (K(2)) of 0.472. The overall affinity constant K(d) was determined to be 240 nM. The binding was markedly inhibited by N-acetyl-D-galactosamine (K(i)=8 mM). The monolayer was shown to retain a high affinity to Cry1Ac, providing an insect-free system for rapid and large-scale screening of B. thuringiensis insecticidal proteins by the SPR-based biosensor technology.

PKC delta mediates ionizing radiation-induced activation of c-Jun NH(2)-terminal kinase through MKK7 in human thyroid cells

The thyroid gland is one of the most sensitive organs in ionizing radiation (IR)-induced carcinogenesis. To determine, therefore, the specific cascade of IR-induced signal transduction in human thyroid cells, we investigated the functional role of protein kinase C (PKC), especially its interlocking activation of c-Jun NH(2)-terminal kinase (JNK) pathway. In the present study, using adenovirus expression vectors for diverse dominant-negative (DN) types of PKC isoforms (alpha, beta2, delta, epsilon and zeta) expressed in primary cultured human thyroid cells, only DN/PKC delta suppressed IR-induced JNK activation. In addition, Rottlerin, a PKC delta specific inhibitor, inhibited IR-induced JNK activation. IR-induced activation of transcription factor AP-1, downstream target of JNK, was also attenuated by DN/PKC delta. To examine the involvement of upstream kinases of JNK, we performed immune-complex kinase assays of mitogen-activated protein kinase kinase 4 (MKK4) and MKK7. IR activated MKK7 but not MKK4, and this activation was inhibited by Rottlerin. Furthermore, IR-induced JNK activation was suppressed by overexpression of kinase-deficient MKK7. Our results indicate that IR selectively activates the cascade of PKC delta-MKK7-JNK-AP-1 in human thyroid cells, suggesting a not apoptotic but radio-resistant role of PKC delta in human thyroid cells following IR.

Two delta-endotoxin genes, cry9Da and a novel related gene, commonly occurring in Lepidoptera-specific Bacillus thuringiensis Japanese isolates that produce spherical parasporal inclusions

Six Lepidoptera-specific Bacillus thuringiensis isolates, which belong to the four H serovars (sotto, fukuokaensis, canadensis, and galleriae) and produce spherical parasporal inclusions, were examined for assignment of the classes of the delta-endotoxin genes. Gene analysis was conducted by PCR technique with primers designed to probe the genes cry9Ca and cry9Da. The data revealed that the delta-endotoxin of a serovar canadensis isolate is encoded by the gene cry9Da, while those of the five other strains are encoded by an undescribed delta-endotoxin gene. DNA fragments from five strains had an identical 1917-bp nucleotide sequence, covering the four conserved regions and a partial sequence of the block 5 region. The deduced amino acid sequence exhibited a 70.6% homology to that of the corresponding region of the Cry9Ea delta-endotoxin protein which is active on the order Lepidoptera, and a 63.1% homology to the Cry9Ca protein highly toxic to the noctuid lepidopterans. The results showed that Japanese isolates of B. thuringiensis producing spherical parasporal inclusions with Lepidoptera-specific activity are categorized into two groups: one produces the class Cry9Da protein and the other a novel delta-endotoxin allied to the class Cry9. It also appeared that heterogeneous multiple H serovars are involved in each group.

PKCdelta activation: a divergence point in the signaling of insulin and IGF-1-induced proliferation of skin keratinocytes

Insulin and insulin-like growth factor-1 (IGF-1) are members of the family of the insulin family of growth factors, which activate similar cellular downstream pathways. In this study, we analyzed the effects of insulin and IGF-1 on the proliferation of murine skin keratinocytes in an attempt to determine whether these hormones trigger the same signaling pathways. Increasing doses of insulin and IGF-1 promote keratinocyte proliferation in an additive manner. We identified downstream pathways specifically involved in insulin signaling that are known to play a role in skin physiology; these include activation of the Na+/K+ pump and protein kinase C (PKC). Insulin, but not IGF-1, stimulated Na+/K+ pump activity. Furthermore, ouabain, a specific Na+/K+ pump inhibitor, abolished the proliferative effect of insulin but not that of IGF-1. Insulin and IGF-1 also differentially regulated PKC activation. Insulin, but not IGF-1, specifically activated and translocated the PKCB isoform to the membrane fraction. There was no effect on PKC isoforms alpha, eta, epsilon, and zeta, which are expressed in skin. PKC8 overexpression increased keratinocyte proliferation and Na+/K+ pump activity to a degree similar to that induced by insulin but had no affect on IGF-1-induced proliferation. Furthermore, a dominant negative form of PKCdelta abolished the effects of insulin on both proliferation and Na+/K+ pump activity but did not abrogate induction of keratinocyte proliferation induced by other growth factors. These data indicate that though insulin or IGF-1 stimulation induce keratinocyte proliferation, only insulin action is specifically mediated via PKC8 and involves activation of the Na+/K+ pump.

PKCeta associates with cyclin E/cdk2/p21 complex, phosphorylates p21 and inhibits cdk2 kinase in keratinocytes

PKC is activated on the cell membrane by phospholipids, thereby transducing signals to intracellular pathways. We provide here another function of PKC, namely, regulating cell cycle by interaction with the cyclin E/cdk2/p21 complex. Among the 10 isoforms of PKC, PKCeta is predominantly expressed in squamous cell epithelia and induces terminal differentiation of keratinocytes. PKCeta that is endogenously expressed or overexpressed was found to associate with the cyclin E/cdk2/p21 complex in keratinocytes of mice and humans. Requirement of a possible adaptor protein to the binding was suggested by the reconstitution of PKCeta and the cyclin E/cdk2/p21 complex which were prepared from human keratinocytes or Sf9 insect cells. Colocalization of PKCeta with cdk2 and cyclin E was observed in the cytoplasm, particularly in the perinuclear region. p21 was phosphorylated in the complex in a PKC-activator dependent manner. Association of PKCeta with cdk2 resulted in marked inhibition of cdk2-kinase activity when measured by phosphorylation of Rb. Dominant negative PKCeta associated with the cyclin E/cdk2/p21 complex, but caused a little inhibition of cdk2 kinase activity. Among the known regulatory mechanisms of cdk2 activity, dephosphorylation of Thr160 was demonstrated. Oncogene (2000) 19, 6334 - 6341.

Characterization of the anti-cancer-cell parasporal proteins of a Bacillus thuringiensis isolate

An unusual activity, associated with non-insecticidal and non-haemolytic parasporal inclusion proteins of a Bacillus thuringiensis soil isolate, designated 89-T-26-17, was characterized. The parasporal inclusion of this isolate was bipyramidal, rounded at both ends, containing proteins of 180, 150, 120, 100, and 88 kDa. No homologies with the Cry and Cyt proteins of B. thuringiensis were detected based on N-terminal sequences. Proteolytic processing of the inclusion proteins by proteinase K, trypsin, and chymotrypsin produced a major protein of 64 kDa exhibiting cytocidal activity against human leukaemic T cells and uterus cervix cancer (HeLa) cells. The protease-activated proteins showed no cytotoxicity to normal T cells.

Treatment for "A" and "V" exotropia by slanting muscle insertions

PURPOSE

The purpose of the present study is to evaluate the therapeutic effects of slanting muscle insertions for "A" and "V" exotropia.

METHODS

We performed slanting recession and resection of medial or lateral rectus muscles. A slanting surgical incision creating a 3-4 mm difference between the upper and lower margins of the muscles was performed in 28 patients with "A" or "V" exotropia ( "V" exotropia, 16 patients; "A" exotropia, 12 patients). Cases of "V" exotropia with moderate or marked overaction of the inferior oblique muscle were excluded.

RESULTS

"V" exotropia: The average "V" pattern was 17.9 prism diopters (Delta) before and 7.6 delta after the operation. Slanting surgery reduced the "V" pattern in 15 of the 16 "V" patients. The mean reduction was 10.3 Delta in the "V" pattern and 29.8 Delta in the upward gaze deviation. "A" exotropia: The average "A" pattern was 26.6 Delta before and 6.3 Delta after the operation. Slanting surgery reduced the "A" pattern in 8 of the 12 "A" patients. The mean reduction was 20.3 Delta in the "A" pattern and 36.4 Delta in the downward gaze deviation.

CONCLUSION

We conclude that the surgical technique of slanting muscle insertions for correcting exotropia of "A" pattern with superior oblique muscle overaction and "V" pattern without moderate or marked inferior oblique muscle overaction is suitable for reducing "A" and "V" patterns.

Parasporin, a human leukemic cell-recognizing parasporal protein of Bacillus thuringiensis

An unusual property, human leukemic cell-recognizing activity, associated with parasporal inclusions of a noninsecticidal Bacillus thuringiensis soil isolate was investigated, and a protein (named parasporin in this study) responsible for the activity was cloned. The parasporin, encoded by a gene 2,169 bp long, was a polypeptide of 723 amino acid residues with a predicted molecular weight of 81, 045. The sequence of parasporin contained the five conserved blocks commonly found in B. thuringiensis Cry proteins; however, only very low homologies (<25%) between parasporin and the existing classes of Cry and Cyt proteins were detected. Parasporin exhibited cytocidal activity only when degraded by proteases into smaller molecules of 40 to 60 kDa. Trypsin and proteinase K activated parasporin, while chymotrypsin did not. The activated parasporin showed strong cytocidal activity against human leukemic T cells (MOLT-4) and human uterus cervix cancer cells (HeLa) but not against normal T cells.

In vitro cytotoxicity of non-cyt inclusion proteins of a Bacillus thuringiensis isolate against human cells, including cancer cells

A soil isolate designated 90-F-45-14, belonging to Bacillus thuringiensis serovar dakota (H15), was examined for characterization of in vitro cytotoxicity, associated with parasporal inclusion proteins, against human cells. When activated with proteolytic processing, inclusion proteins of the isolate 90-F-45-14 exhibited a moderate cytotoxicity against the human uterus cervix cancer cells (HeLa) with an EC(50) value of 60.8 microg ml(-1), while showing extremely high activities on the human leukaemic T cells (MOLT-4) and the normal T cells with EC(50) values of 0.27 and 0.20 microg ml(-1), respectively. Anti-leukaemic cell activity of the 90-F-45-14 proteins was eight to nine times greater than that of the B. thuringiensis serovar israelensis proteins containing the Cyt1 protein, a broad-spectrum cytolysin. The cytopathy by the 90-F-45-14 proteins was characterized by marked cell-ballooning, while the israelensis proteins induced early breakdown of the cells due to cytolysis. Inclusions of the isolate consisted of five major polypeptides of 170, 103, 73, 40 and 32 kDa. A 100% homology was observed in the sequence of 15 N-terminal amino acids between the proteins of 170 and 103 kDa. There was no N-terminal sequence homology between 90-F-45-14 proteins and the existing Cry/Cyt proteins of B. thuringiensis. Proteolytic processing by proteinase K yielded several proteins with molecular masses ranging from 40 to 28 kDa.

Unique appendages associated with spores of Bacillus cereus isolates

Electron microscopic observations revealed the presence of a new type of large appendage on the spores of two Bacillus cereus strains isolated from phylloplanes. The appendages were thin and sword-like in shape, having the sizes of 1.5 to 2.8 microns in length and 0.03 to 0.6 micron in width. There were no core or sheath structures in these appendages. The number of appendages on a spore ranged from three to more than twenty, radiating from the swelling on one end of the exosporium. These appendages gave a unique octopus- or jellyfish-like feature to the spores.

Recovery of Bacillus thuringiensis from marine sediments of Japan

Marine sediments from a Japanese bay were examined for the occurrence of Bacillus thuringiensis. Of 1313 colonies belonging to the Bacillus cereus/B. thuringiensis group, 22 (1.7%) were allocated to B. thuringiensis. Marine isolates of B. thuringiensis consisted of heterogeneous multiple H serogroups; 10 isolates were assigned to the eight serovars (kurstaki, sumiyoshiensis, sotto, aizawai, darmstadiensis, thompsoni, neoleonensis, and higo); two motile isolates failed to react with the reference antisera; and the others were serologically untestable. Insecticidal activities were associated with two kurstaki isolates (toxic to both Lepidoptera and Diptera) and a higo isolate (Diptera-specific). None of the parasporal inclusion proteins of the 22 isolates exhibited in vitro cytotoxic activity against two vertebrate cells, sheep erythrocytes and HeLa cells. All B. thuringiensis isolates had no halophilism, although seawater-based medium supported their growth, sporulation, and formation of parasporal inclusions.

Noninsecticidal parasporal proteins of a Bacillus thuringiensis serovar shandongiensis isolate exhibit a preferential cytotoxicity against human leukemic T cells

A Bacillus thuringiensis isolate, 89-T-34-22, belonging to the serovar shandongiensis (H22) produced noninsecticidal and nonhemolytic proteins crystallizing into irregular-shaped parasporal inclusions. The proteins showed in vitro cytotoxicity to human cells, including cancer cells, only when activated by protease treatment. The human leukemic T (MOLT-4) cells were > 100 times more susceptible than HeLa and normal T cells to the proteins of 89-T-34-22. The cytotoxicity was dose dependent and the median effective concentration for the MOLT-4 was 3.5 microg/ml. The cytopathy induced by the 89-T-34-22 proteins was characterized by remarkable condensation of the nucleus and cell-ballooning. Five major parasporal proteins of 89-T-34-22, with molecular masses in the range of 16-160 kDa, shared no similarity with the previously reported proteins in terms of the N-terminal sequence.

Cloning and characterization of a Bacillus thuringiensis serovar higo gene encoding a novel class of the delta-endotoxin protein, Cry27A, specifically active on the Anopheles mosquito

A novel gene encoding a 98-kDa mosquitocidal delta-endotoxin protein, designated Cry27A, was cloned from a Bacillus thuringiensis serovar higo strain. The Cry27A protein contained the five sequence blocks of amino acids commonly conserved in most B. thuringiensis Cry proteins. Relatively high homologies, ranging from 43.0% to 84.4%, existed between the Cry27A protein and several established classes of mosquitocidal Cry proteins (Cry4A, Cry10A, Cry19A, Cry19B, and Cry20A) in the sequence of 51 N-terminal amino acids. The complete sequence of this protein, however, showed low levels (<40%) of amino acid identity to those of the known Cry proteins. Although the expression level of the cry27A gene was low in the transformants under the control of its own promoter, the use of the cyt1A promoter resulted in high-level expression of the gene, leading to the formation of inclusions. The expressed Cry27A protein showed larvicidal activity highly specific for Anopheles stephensi, but lacked the toxicity against Culex pipiens molestus and Aedes aegypti. The results suggest that the Cry27A protein is responsible for the Anopheles-preferential toxicity of the B. thuringiensis serovar higo strain.

Bacillus thuringiensis soil populations naturally occurring in the Ryukyus, a subtropic region of Japan

Of 809 soil samples collected from the seven islands of the Ryukyus, Japan, 107 samples (13.2%) contained Bacillus thuringiensis. The frequency of B. thuringiensis among the B. cereus group was 1.1% (235/21842) on the average. The B. thuringiensis soil populations of the Ryukyus consisted of more than 22 H serogroups. The predominant H serotype was the H5ac/21 (serovar canadensis/colmeri), followed by the H3ad (serovar sumiyoshiensis) and H16 (serovar indiana). Geographically, most widely distributed H serogroups were the H16 and H10ac (serovar londrina); the former was recovered from five islands and the latter from three islands. Parasporal inclusions of the isolates were morphologically heterogeneous, roughly grouped into four categories: bipyramidal/cuboidal, spherical/ovoid, irregularly-pointed, and irregular-shaped. About 53% of the isolates formed spherical to ovoid parasporal inclusions. None of the isolates exhibited larvicidal activity against the silkworm, Bombyx mori. Only four isolates belonging to four different serotypes killed larvae of the mosquito, Aedes aegypti. These mosquito-specific isolates all produced spherical parasporal inclusions.