Biological treatment of clogged emitters in a drip irrigation system

This study was conducted to investigate microbial organisms that can be used for preventing clogging in drip irrigation systems caused by biological factors. A total of 25 fungi isolate and 121 bacterial strains were isolated from water samples collected from drip irrigation systems in tomato greenhouses in the eastern Anatolia region of Turkey in the spring season of 2001. Biological clogging of emitters in a model drip irrigation system was experimentally caused by application of the microorganisms (fungi and bacteria) isolated in the study. Three antagonistic bacterial strains in the genus Bacillus spp (ERZ, OSU-142) and Burkholdria spp (OSU-7) were used for treatment of biological clogging of the emitters. The results showed that the antagonistic bacterial strains tested have the potential to be used as anti-clogging agents for treatment of emitters in drip irrigation system. This is the first study that demonstrated that antagonistic microorganisms can be utilized for treatment of clogging in drip irrigation systems.

Fluorescent nanometer microspheres as a reporter for sensitive detection of simulants of biological threats using multiplexed suspension arrays

We succeeded in using 40 nm FRET (fluorescence resonance energy transfer) microspheres conjugated to antibodies as the fluorescent reporters to perform the multiplexing suspension array measurements on two simulants of biological threats, ricin (A chain) and a crude spore preparation of Bacillus globigii (Bg). The microspheres were impregnated with two types of fluorophores in equal number (approximately 140 fluorophores in total per microsphere) and displayed bright PE-like fluorescence via a fluorescence resonance energy transfer mechanism. Activated microspheres (aldehyde groups) were directly coupled to antibodies and used to form sandwich-type immunoassays in a suspension array. For the crude preparations of Bg, the assay sensitivity using antibody-conjugated microspheres is an order of magnitude higher than that using the conventional fluorescent reporter, R-phycoerythrin (PE). Using the microspheres, Bg at the concentration of 5 ng/mL can be easily detected. For ricin, the assay sensitivity was similar to that obtained using PE as the reporter, but washing the reaction mixtures resulted in the fluorescence signals that were 2-3 times higher compared to those using PE. Ricin at a concentration of 1 ng/mL can be readily identified. Importantly, the two simulants do not interfere with each other in the multiplexing experiments. The 40 nm FRET microspheres are a new sensitive alternative as fluorescent reporters for detection in suspension arrays.

Bacillus sp. B16 kills nematodes with a serine protease identified as a pathogenic factor

An endospore-forming bacterium, strain B16, was isolated from a soil sample and identified as a Bacillus sp. The strain presented remarkable nematotoxic activity against nematode Panagrellus redivivus. The crude extracellular protein extract from culture supernatant of the bacteria killed about 80% of the tested nematodes within 24 h, suggesting the involvement of extracellular proteases. A homogeneous extracellular protease was purified by chromatography, and the hypothesis of proteinaceous pathogeny in the infection of B16 strain was confirmed by the experiments of killing living nematodes and by the degradation of purified nematode cuticle when treated with the homogenous protease. The gene for the virulence protease was cloned, and the nucleotide sequence was determined. The deduced amino acid sequence showed significant similarity with subtilisin BPN' but low homology with the other cuticle-degrading proteases previously reported in fungi. Characterization of the purified protease revealed the molecular mass of 28 kDa and the optimum activity at pH 10, 50 degrees C. The purified protease can hydrolyze several native proteinaceous substrates, including collagen and nematode cuticle. To our knowledge, this is the first report of a serine protease from a Bacillus genus of bacteria that serves as a pathogenic factor against nematodes, an important step in understanding the relationship between bacterial pathogen and host and in improving the nematocidal activity in biological control.

Recombinant larvicidal bacteria with markedly improved efficacy against culex vectors of west nile virus

An urgent need exists for new agents to control mosquito vectors of disease. Mosquito larvicides based on the bacteria Bacillus thuringiensis subsp. israelensis (Bti) or B. sphaericus (Bs) are effective in many habitats, but use is limited by their high cost. Moreover, mosquito resistance evolves rapidly to Bs where it is used intensively. The efficacy of these bacteria is due to a binary protein (BsB) in Bs and four proteins (Cry4A, Cry4B, Cry11A, and Cyt1A) in Bti. Here we report the use of cyt1A promoters and a 5' mRNA stabilizing sequence to synthesize high levels of Bs2362 binary toxin in Bti strains. The recombinant BtiIPS-82/BsB showed high potency against fourth instars of Culex quinquefasciatus, a vector of West Nile virus, being 21-fold as potent as BtiIPS-82, and 32-fold as potent as Bs2362. Similar improved efficacy was obtained against larvae of Cx. tarsalis. Moreover, BtiIPS-82/BsB suppressed resistance to Bs2362 in Cx. quinquefasciatus.

The effect of different initial densities of nematode (Meloidogyne javanica) on the build-up of Pasteuria penetrans population

Pasteuria penetrans will build-up faster where there is a high initial nematode density and can suppress root-knot nematode populations in the roots of tomato plants. The effect of different initial densities of nematode (Meloidogyne javanica) (150, 750, 1500, 3000) and P. penetrans infected females (F1, F3) densities (F0=control and AC=absolute control without nematode or P. penetrans inoculum) on the build-up of Pasteuria population was investigated over four crop cycles. Two major points of interest were highlighted. First, that within a confined soil volume, densities of P. penetrans can increase >100 times within 2 or 3 crop cycles. Second, from a relatively small amount of spore inoculum, infection of the host is very high. There were more infected females in the higher P. penetrans doses. The root growth data confirms the greater number of females in the controls particularly at the higher inoculum densities in the third and fourth crops. P. penetrans generally caused the fresh root weights to be higher than those in the control. P. penetrans has shown greater reduction of egg masses per plant at most densities. The effects of different initial densities of M. javanica and P. penetrans on the development of the pest and parasite populations were monitored. And no attempt was made to return the P. penetrans spores to the pots after each crop so the build-up in actual numbers of infected females and spores under natural conditions may be underestimated.

Evolution of resistance toward Bacillus sphaericus or a mixture of B. sphaericus+Cyt1A from Bacillus thuringiensis, in the mosquito, Culex quinquefasciatus (Diptera: Culicidae)

The 2362 strain of Bacillus sphaericus (Bs) Neide is a highly mosquitocidal bacterium used in commercial bacterial larvicides primarily to control mosquitoes of the genus Culex. Unfortunately, Bs is at high risk for selecting resistance in mosquito populations, because its binary toxin apparently only binds to a single receptor type on midgut microvilli. A potential key strategy for delaying resistance to insecticidal proteins is to use mixtures of toxins that act at different targets within the insect, especially mixtures that interact synergistically. We tested this hypothesis for delaying the phenotypic expression of resistance by exposing Culex quinquefasciatus Say larvae to Bs alone or in combination with Cyt1A from Bacillus thuringiensis subsp. israelensis. Two laboratory lines of Cx. quinquefasciatus, one sensitive to Bs and the other containing Bs resistance alleles, were subjected to intensive selection pressure for 20 generations with either Bs 2362 or a 3:1 mixture of Bs 2362+Cyt1A. At the end of the study, the sensitive line had evolved >1000-fold resistance when selected with Bs alone, whereas the parallel line selected with Bs+Cyt1A exhibited only low resistance toward this mixture (RR95, 1.4). Similar results were observed in the lines containing Bs resistance alleles. Both lines selected with Bs+Cyt1A exhibited substantial resistance to Bs in the absence of Cyt1A. Although selection with Bs+Cyt1A did not prevent the underlying evolution of resistance to Bs, these results suggest that a mixture of Bs with other endotoxins, particularly one like Bs+Cyt1A in which the components interact synergistically, will provide longer lasting and more effective mosquito control than Bs alone.

Bacterial inactivation in open air by the afterglow plume emitted from a grounded hollow slot electrode

Escherichia coli, Bacillus atrophaeus, and Bacillus atrophaeus spores were exposed to a downstream plasma afterglow plume emitted from a slotted plasma device operating in open air at atmospheric pressure. The reactor electrodes were RF powered at 13.56 MHz to excite a mixture of argon and oxygen gases by a capacitive discharge as it flowed past the electrodes into open air. Bacterial inactivation experiments on surfaces exposed to the plasma afterglow were conducted with varying plasma exposure times. Experimental results demonstrated a colony forming unit (CFU) reduction of almost 5 log10 of E. coli with only 1 s of exposure per unit area. One log CFU reduction was observed in B. atrophaeus with the same treatment time of 1 s per unit area. B. atrophaeus spores showed a reduction of 3 log10 with exposure time of 10 min. Comparison on various growth media suggests that cells are killed rather than sublethally injured, while the mechanistic action of the plasma appears to affect both nucleic acids as well as the cell wall structure. These results present a promising means of inactivation of harmful microbes in a practical environment with an electrically grounded device that is handheld, much like a wand applicator. Results are applicable to the development of plasma sterilization tools for various environmental purposes.

Host-parasite and genotype-by-environment interactions: temperature modifies potential for selection by a sterilizing pathogen

Parasite-mediated selection is potentially of great importance in modulating genetic diversity. Genetic variation for resistance, the fuel for natural selection, appears to be common in host-parasite interactions, but responses to selection are rarely observed. In the present study, we tested whether environmental variation could mediate infection and determine evolutionary outcomes. Temperature was shown to dramatically alter the potential for parasite-mediated selection in two independent laboratory infection experiments at four temperatures. The bacterial parasite, Pasteuria ramosa, was extremely virulent at 20 degrees C and 25 degrees C, sterilizing its host, Daphnia magna, so that females often never produced a single brood. However, at 10 degrees C and 15 degrees C, the host-parasite interaction was much more benign, as nearly all females produced broods before becoming sterile. This association between virulence and temperature alone could stabilize coexistence and lead to the maintenance of diversity, because it would weaken parasite-mediated selection during parts of the season. Additionally, highly significant genotype-by-environment interactions were found, with changes in clone rank order for infection rates at different temperatures. Our results clearly show that the outcome of parasite-mediated selection in this system is strongly context dependent.

Degradation characteristics of two Bacillus strains on the Microcystis aeruginosa

The degradation kinetics of strains P05 and P07 and the degradation effects of mixed strain on Microcystis aeruginosa were studied. The results showed that: (1) The degradation processes of strains P05 and P07 on Microcystis aeruginosa accorded with the first-order reaction model when the range of Chl-a concentration was from 0 to 1500 microg/L. (2) The initial bacterium densities had a strong influence on the degradation velocity. The greater the initial bacterium density was, the faster the degradation was. The degradation velocity constants of P05 were 0.1913, 0.2175 and 0.3092 respectively, when bacterium densities were 4.8 x 10(5), 4.8 x 10(6), 2.4 x 10(7) cells/ml. For strain P07, they were 0.1509, 0.1647 and 0.2708. The degradation velocity constant of strain P05 was higher than that of P07 when the bacterium density was under 4.8 x 10(5) cells/ml, but the constant increasing of P07 was quicker than that of P05. (3) The degradation effects of P05 and P07 strains did not antagonize. When the concentration of Chl-a was high, the degradation effects of mixed strain excelled that of any single strains. But with the decrease of the Chl-a concentration, this advantage was not clear. When the concentration was less than 180 microg/L, the degradation effects of mixed were consistent with that of strain P07.

TwoBacillus sphaericusbinary toxins share the midgut receptor binding site: implications for resistance ofCulex pipienscomplex (Diptera: Culicidae) larvae

This work demonstrates that Bin1 and Bin2 toxins, produced by Bacillus sphaericus strains IAB59 and 2362, respectively, share a binding site in midgut brush border membranes (BBMF) from Culex pipiens complex larvae. However, a colony selected with strain IAB59, displaying a resistance ratio of only 42-fold to IAB59, but a 162,000-fold resistance to strain 2362, was found to miss receptors for Bin2 in the BBMF. This correlates with results showing that Bin1, produced in strain IAB59, failed to bind specifically to BBMF from other colony highly resistant to strain 2362. Data indicate the loss of the BBMF bound receptor as a general mechanism of resistance to binary toxins in mosquito.

Binary bacterial toxins: biochemistry, biology, and applications of common Clostridium and Bacillus proteins

Certain pathogenic species of Bacillus and Clostridium have developed unique methods for intoxicating cells that employ the classic enzymatic "A-B" paradigm for protein toxins. The binary toxins produced by B. anthracis, B. cereus, C. botulinum, C. difficile, C. perfringens, and C. spiroforme consist of components not physically associated in solution that are linked to various diseases in humans, animals, or insects. The "B" components are synthesized as precursors that are subsequently activated by serine-type proteases on the targeted cell surface and/or in solution. Following release of a 20-kDa N-terminal peptide, the activated "B" components form homoheptameric rings that subsequently dock with an "A" component(s) on the cell surface. By following an acidified endosomal route and translocation into the cytosol, "A" molecules disable a cell (and host organism) via disruption of the actin cytoskeleton, increasing intracellular levels of cyclic AMP, or inactivation of signaling pathways linked to mitogen-activated protein kinase kinases. Recently, B. anthracis has gleaned much notoriety as a biowarfare/bioterrorism agent, and of primary interest has been the edema and lethal toxins, their role in anthrax, as well as the development of efficacious vaccines and therapeutics targeting these virulence factors and ultimately B. anthracis. This review comprehensively surveys the literature and discusses the similarities, as well as distinct differences, between each Clostridium and Bacillus binary toxin in terms of their biochemistry, biology, genetics, structure, and applications in science and medicine. The information may foster future studies that aid novel vaccine and drug development, as well as a better understanding of a conserved intoxication process utilized by various gram-positive, spore-forming bacteria.

Rotational application of bioinsecticide with deltamethrin-An antilarval measure for the control of filarial vector, Culex quinquefasciatus (Culicidae: Diptera)

A laboratory investigation was undertaken to study the cyclic usage of field recommended doses of Bacillus thuringiensis israelensis (Bti), Bacillus sphaericus (Bsp) and combination of Bti and Bsp (half the recommended dose of each) with deltamethrin 2.8 EC to attain better control of mosquito larvae. To understand the susceptibility status of the Culex quinquefasciatus larvae in the field, early fourth instar field collected larvae were exposed to the above treatments of biopesticides and were monitored for their persistency till 50% mortality was obtained. The larvae those survived in each treatment were transferred to the concentration of deltamethrin that gave 50% mortality. Observations on larval mortality after the treatment with deltamethrin were recorded after 24 h. The results revealed that Bti excels Bsp, as it recorded 54% mortality only on 17th day after application. The other salient finding of this study is LC50 of deltamethrin is sufficient to follow the biopesticides application for an effective control of Culex larvae.

Genotyping and toxigenic potential of Bacillus subtilis and Bacillus pumilus strains occurring in industrial and artisanal cured sausages

Artisanal and industrial sausages were analyzed for their aerobic, heat-resistant microflora to assess whether new emerging pathogens could be present among Bacillus strains naturally contaminating cured meat products. Sixty-four isolates were characterized by randomly amplified polymorphic DNA (RAPD)-PCR and fluorescent amplified fragment length polymorphism (fAFLP). The biotypes, identified by partial 16S rRNA gene sequence analysis, belonged to Bacillus subtilis, Bacillus pumilus, and Bacillus amyloliquefaciens species. Both RAPD-PCR and fAFLP analyses demonstrated that a high genetic heterogeneity is present in the B. subtilis group even in strains harvested from the same source, making it possible to isolate 56 different biotypes. Moreover, fAFLP analysis made it possible to distinguish B. subtilis from B. pumilus strains. The strains were characterized for their toxigenic potential by molecular, physiological, and immunological techniques. Specific PCR analyses revealed the absence of DNA sequences related to HBL, BcET, NHE, and entFM Bacillus cereus enterotoxins and the enzymes sphingomyelinase Sph and phospholipase PI-PLC in all strains; also, the immunological analyses showed that Bacillus strains did not react with NHE- and HBL-specific antibodies. However, some isolates were found to be positive for hemolytic and lecithinase activity. The absence of toxigenic potential in Bacillus strains from the sausages analyzed indicates that these products can be considered safe under the processing conditions they were produced; however, great care should be taken when the ripening time is shortened, particularly in the case of traditional sausages, which could contain high amounts of Bacillus strains and possibly some B. cereus cells.

Factors affecting the toxicity of Bacillus thuringiensis var. israelensis and Bacillus sphaericus to fourth instar larvae of Chironomus tepperi (Diptera: Chironomidae)

Laboratory bioassays (48h duration, 25+/-1 degrees C) were used to determine the toxicity of Bacillus thuringiensis var. israelensis (B.t.i.) and Bacillus sphaericus to fourth instar larvae of Chironomus tepperi, a major pest of rice in southern Australia. Bioassays were conducted using different combinations of larval ages and densities to determine if these factors affected toxicity. The effects of temperature and substrate type on B.t.i. toxicity were also investigated. Tests were conducted using a commercial B.t.i. formulation (VectoBac WDG, 3000ITU/mg), a spore/crystal mixture derived from the VectoBac WDG strain, and VectoLex WDG, a commercial B. sphaericus formulation (650ITU/mg). VectoBac WDG was highly toxic to fourth instar C. tepperi in bioassays using a sand substrate (LC(50) 0.46mg/L, older larvae); younger fourth instar larvae were more susceptible (LC(50) 0.20mg/L). Increasing larval densities (from 10 to 30 per bioassay cup) increased LC(50) values for both age groups, significantly so in the case of older larvae (higher density LC(50) 0.80mg/L). Use of a soil substrate increased the LC(50) value (older larvae, 10 per cup) to 0.99mg/L. Similar differences in toxicity relative to larval age and substrate type were found in bioassays using the B.t.i. spore/crystal mixture. VectoBac WDG and the spore/crystal mixture both showed similar (approximately 6-fold) declines in activity between 30 and 17.5 degrees C. At lower temperatures (between 17.5 and 15 degrees C), activity of the spore/crystal mixture declined much more rapidly than that of VectoBac WDG. VectoLex WDG showed very low toxicity to C. tepperi larvae, and the overall impact of larval age and density was relatively minor (LC(50) values 1062-1340mg/L). Autoclaving VectoLex WDG did not substantially reduce its toxicity (LC(50) 1426mg/L), suggesting that formulation additives (i.e., surfactants and other adjuvants) are responsible for much of the toxicity occurring at the high product concentrations required to cause C. tepperi mortality. Whilst VectoLex WDG was ineffective against C. tepperi, VectoBac WDG has the potential to provide selective control of this rice pest at economically viable application rates.

Cytotoxic Bacillus spp. belonging to the B. cereus and B. subtilis groups in Norwegian surface waters

AIMS

To investigate the presence and numbers of Bacillus spp. spores in surface waters and examine isolates belonging to the B. cereus and B. subtilis groups for cytotoxicity, and to discuss the presence of cytotoxic Bacillus spp. in surface water as hazard identification in a risk assessment approach in the food industry.

METHODS AND RESULTS

Samples from eight different rivers with variable degree of faecal pollution, and two drinking water sources, were heat shocked and examined for the presence of Bacillus spp. spores using membrane filtration followed by cultivation on bovine blood agar plates. Bacillus spp. was present in all samples. The numbers varied from 15 to 1400 CFU 100 ml(-1). Pure cultures of 86 Bacillus spp. isolates representing all sampling sites were characterized using colony morphology, atmospheric requirements, spore and sporangium morphology, and API 50 CHB and API 20E. Bacillus spp. representing the B. cereus and B. subtilis groups were isolated from all samples. Twenty-one isolates belonging to the B. cereus and B. subtilis groups, representing eight samples, were screened for cytotoxicity. Nine strains of B. cereus and five strains belonging to the B. subtilis group were cytotoxic.

CONCLUSIONS

The presence of cytotoxic Bacillus spp. in surface water represents a possible source for food contamination. Filtration and chlorination of surface water, the most common drinking water treatment in Norway, do not remove Bacillus spores efficiently. This was confirmed by isolation of spores from tap water samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

Contamination of food with water containing low numbers of Bacillus spores implies a risk for bacterial growth in foods. Consequently, high numbers of Bacillus spp. may occur after growth in some products. High numbers of cytotoxic Bacillus spp. in foods may represent a risk for food poisoning.

gyrB as a phylogenetic discriminator for members of the Bacillus anthracis-cereus-thuringiensis group

Bacillus anthracis, the causative agent of the human disease anthrax, Bacillus cereus, a food-borne pathogen capable of causing human illness, and Bacillus thuringiensis, a well-characterized insecticidal toxin producer, all cluster together within a very tight clade (B. cereus group) phylogenetically and are indistinguishable from one another via 16S rDNA sequence analysis. As new pathogens are continually emerging, it is imperative to devise a system capable of rapidly and accurately differentiating closely related, yet phenotypically distinct species. Although the gyrB gene has proven useful in discriminating closely related species, its sequence analysis has not yet been validated by DNA:DNA hybridization, the taxonomically accepted "gold standard". We phylogenetically characterized the gyrB sequences of various species and serotypes encompassed in the "B. cereus group," including lab strains and environmental isolates. Results were compared to those obtained from analyses of phenotypic characteristics, 16S rDNA sequence, DNA:DNA hybridization, and virulence factors. The gyrB gene proved more highly differential than 16S, while, at the same time, as analytical as costly and laborious DNA:DNA hybridization techniques in differentiating species within the B. cereus group.

Characterization of Bacillus probiotics available for human use

Bacillus species (Bacillus cereus, Bacillus clausii, Bacillus pumilus) carried in five commercial probiotic products consisting of bacterial spores were characterized for potential attributes (colonization, immunostimulation, and antimicrobial activity) that could account for their claimed probiotic properties. Three B. cereus strains were shown to persist in the mouse gastrointestinal tract for up to 18 days postadministration, demonstrating that these organisms have some ability to colonize. Spores of one B. cereus strain were extremely sensitive to simulated gastric conditions and simulated intestinal fluids. Spores of all strains were immunogenic when they were given orally to mice, but the B. pumilus strain was found to generate particularly high anti-spore immunoglobulin G titers. Spores of B. pumilus and of a laboratory strain of B. subtilis were found to induce the proinflammatory cytokine interleukin-6 in a cultured macrophage cell line, and in vivo, spores of B. pumilus and B. subtilis induced the proinflammatory cytokine tumor necrosis factor alpha and the Th1 cytokine gamma interferon. The B. pumilus strain and one B. cereus strain (B. cereus var. vietnami) were found to produce a bacteriocin-like activity against other Bacillus species. The results that provided evidence of colonization, immunostimulation, and antimicrobial activity support the hypothesis that the organisms have a potential probiotic effect. However, the three B. cereus strains were also found to produce the Hbl and Nhe enterotoxins, which makes them unsafe for human use.

Newly isolated bacterial strains belonging to Bacillaceae (Bacillus sp.) and Micrococcaceae accelerate death of the honey bee mite, Varroa destructor (V. jacobsoni), in laboratory assays

Newly isolated bacterial strains belonging to Bacillaceae (Bacillus sp.), Micrococcaceae and three unidentified strains were tested for their pathogenicity against the mite, Varroa destructor. The Bacillus sp. strain and two of the strains belonging to the Micrococcaceae family significantly decreased the time for 50% mortality of the mite population (up to 57%) and hence may be potential control agents. In in vitro bioassay whole cells, extracellular broth and cellular extract of the Bacillus sp. strain effectively killed the mites, suggesting that both endotoxins and exotoxins contributed to the killing.

Inheritance and mechanism of resistance to Bacillus sphaericus in Culex quinquefasciatus (Diptera: Culicidae) from China and Brazil

Investigations on the inheritance and mechanism of resistance to Bacillus sphaericus Neide in Culex quinquefasciatus Say colonies, selected with strains C3-41 (RLCq1/C3-41) and 2362 (CqRL1/2362), were performed in China and Brazil, respectively. The progeny of reciprocal F1 crosses (susceptible female x resistant male and vice versa) from both resistant colonies responded alike in bioassays, indicating recessive inheritance. Data on larvae susceptibility from the backcross offspring between F1 and their respective susceptible and resistant parental colonies are consistent with a monofactorial and autosomal mode of inheritance. In vitro binding assays between 125I binary (Bin2) toxin and the brush border membrane fractions (BBMF) from CqRL1/2362 and RLCq1/C3-41 larvae showed that resistance, in both colonies, is caused by a failure in the binding step of the B. sphaericus Bin2 toxin to its specific midgut receptor. The specific and saturable binding of Bin2 toxin to BBMF from F1 larvae (CqRL1/2362 X susceptible counterpart) confirms the recessive inheritance of the resistance gene. Further studies are needed to advance understanding of B. sphaericus resistance.

16S rDNA targeted PCR for the detection of Paenibacillus macerans

AIMS

To develop a PCR detection method, which could be used for the detection of Paenibacillus macerans in environmental samples or to help the identification of strains suspected to belong to this species.

METHODS AND RESULTS

Primers specific for P. macerans were developed based on the 16S rRNA gene sequence and were evaluated by PCR performed with genomic DNA from other Paenibacillus, other bacteria and DNA from soil as templates. The primers were shown to be specific for P. macerans strains and to amplify a 981-bp amplicon. Vegetative cells of P. macerans LMD 24.10T were tracked in Cerrado soil in 24-h experiments and PCR allowed the detection of 103 introduced cells per gram of dry soil.

CONCLUSIONS

This PCR detection method was adequate to assess the presence of P. macerans in Cerrado soil.

SIGNIFICANCE AND IMPACT OF THE STUDY

It can also be used after culturing to rapid confirm the identity of isolates suspected to belong to P. macerans.

Antimicrobial activity of Paenibacillus peoriae strain NRRL BD-62 against a broad spectrum of phytopathogenic bacteria and fungi

AIMS

To investigate the potential antagonistic activity of Paenibacillus peoriae strain NRRL BD-62 against phytopathogenic micro-organisms and to determine the physiological and biochemical characteristics of the antimicrobial compound produced by this strain.

METHODS AND RESULTS

Strain NRRL BD-62 showed a broad inhibition spectrum with activity against various phytopathogenic bacteria and fungi. Physico-chemical characterization of the antimicrobial activity showed that it was stable during heat treatment and was retained even after autoclave at 121 degrees C for 10 min. The compound was also stable after the treatment with organic solvents, hydrolytic enzymes and its activity was preserved at a wide range of pH. The partial purification carried out by Sephadex G25 gel filtration showed two profiles of inhibition against the indicator strains tested, suggesting at least two different substances with distinct molecular weight.

CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on the production of antimicrobial substances in P. peoriae. Besides the antimicrobial inhibition capability, the strain NRRL BD-62 is also able to effectively fix molecular nitrogen, and produce chitinases and proteases as well, suggesting that further studies should be addressed to use P. peoriae strain NRRL BD-62 as a plant growth promoter and/or as a biocontrol agent in field experiments.

Susceptibility profile of Culex quinquefasciatus (Diptera: Culicidae) to Bacillus sphaericus on selection with rotation and mixture of B. sphaericus and B. thuringiensis israelensis

Several strains of Bacillus sphaericus (Neide) (Bsph), a spore-forming bacterium that produces potent mosquitocidal toxins, have been widely used against mosquito larvae globally. In some locations in the field and in the laboratory, moderate to high levels of resistance in Culex pipiens complex mosquito larvae to Bsph have been reported. Practical strategies for dealing with the resistance problem and more importantly to delay or possibly prevent development of resistance to Bsph in the first place are urgently needed. From published reports, we deduced that Bsph-resistant mosquito larvae are completely susceptible to Bacillus thuringiensis ssp. isreaelensis (Bti) and that there is no appearance of cross-resistance to Bti. On the basis of this information, we hypothesized that Bti offers a good potential for the management of resistance to Bsph, especially when it comes to delaying or preventing emergence of resistance. We conducted laboratory studies to see whether rotation of Bsph and Bti or mixture of both delays or prevents resistance development in Bsph-susceptible California Cx. quinquefasciatus. Development of resistance using Bsph alone increased after F15 and fluctuated slightly on further selections. Rotation of Bsph and Bti resulted in much higher level and rapid emergence of resistance to Bsph. However, selection with mixtures of Bti and Bsph for 36 generations showed no emergence of resistance. On the basis of this information, we believe mixtures have a good potential in delaying or preventing Bsph resistance.

Bacteriocin diversity in Bacillus sphaericus

Nondenaturing polyacrylamide gel electrophoresis revealed the presence of diversity among bacteriocins produced by strains of Bacillus sphaericus. Bacteriocin bands of six strains (pathogenic and non pathogenic) were found to be located just below the stacking gel. However, in two other strains (1 pathogenic and 1 collection strain) more than one protein band with bacteriocin activity were seen in the middle of resolving gel. In bacteriocin-treated cultures, electron-microscopy studies revealed the growth of lysedswollen ghost cells, and loss of viability among sensitive strains.

Relationship of plcR-regulated factors to Bacillus endophthalmitis virulence

The explosive, destructive course of Bacillus endophthalmitis has been attributed to the production of toxins during infection. In this study we analyzed the contribution of toxins controlled by the global regulator plcR to the pathogenesis of experimental Bacillus endophthalmitis. Isogenic plcR-deficient mutants of Bacillus cereus and Bacillus thuringiensis were constructed by insertional inactivation of plcR by the kanamycin resistance cassette, aphA3. Rabbit eyes were injected intravitreally with approximately 100 CFU of wild-type B. cereus or B. thuringiensis or a plcR-deficient mutant. The evolution of endophthalmitis resulting from each plcR-deficient mutant was considerably slower than that caused by each wild-type strain. Retinal function was not eliminated until 42 h postinfection in rabbits with endophthalmitis caused by the plcR-deficient mutants, whereas wild-type infections resulted in a complete loss of retinal function within 18 h. The intraocular inflammatory cell influx and retinal destruction in plcR-deficient endophthalmitis approached the severity observed in wild-ype infections, but not until 36 h postinfection. Gross and histological examinations of eyes infected with plcR mutants demonstrated that the anterior and posterior segment changes were muted compared to the changes observed in eyes infected with the wild types. The loss of plcR-regulated factors significantly attenuated the severity of Bacillus endophthalmitis. The results therefore suggest that plcR may represent a target for which adjunct therapies could be designed for the prevention of blindness during Bacillus endophthalmitis.

Bacteremia due to three Bacillus species in a case of Munchausen's syndrome

We report on a case of recurrent bacteremia due to three Bacillus spp. in an immunocompetent patient with no history of intravenous drug use. The source of the organisms was postulated to be a self-injected compound containing Bacillus spores, given the patient's past history of psychiatric illness and self-destructive behavior.

Production of diarrheal enterotoxins and other potential virulence factors by veterinary isolates of bacillus species associated with nongastrointestinal infections

With the exceptions of Bacillus cereus and Bacillus anthracis, Bacillus species are generally perceived to be inconsequential. However, the relevance of other Bacillus species as food poisoning organisms and etiological agents in nongastrointestinal infections is being increasingly recognized. Eleven Bacillus species isolated from veterinary samples associated with severe nongastrointestinal infections were assessed for the presence and expression of diarrheagenic enterotoxins and other potential virulence factors. PCR studies revealed the presence of DNA sequences encoding hemolysin BL (HBL) enterotoxin complex and B. cereus enterotoxin T (BceT) in five B. cereus strains and in Bacillus coagulans NB11. Enterotoxin HBL was also harbored by Bacillus polymyxa NB6. After 18 h of growth in brain heart infusion broth, all seven Bacillus isolates carrying genes encoding enterotoxin HBL produced this toxin. Cell-free supernatant fluids from all 11 Bacillus isolates demonstrated cytotoxicity toward human HEp-2 cells; only one Bacillus licheniformis strain adhered to this test cell line, and none of the Bacillus isolates were invasive. This study constitutes the first demonstration that Bacillus spp. associated with serious nongastrointestinal infections in animals may harbor and express diarrheagenic enterotoxins traditionally linked to toxigenic B. cereus.

Rapid detection of Paenibacillus larvae from honey and hive samples with a novel nested PCR protocol

The bacterial pathogen Paenibacillus larvae is the causative agent of American foulbrood disease in honeybees (Apis mellifera). A touchdown nested PCR protocol was developed to detect the presence of P. larvae spores directly in honey and hive samples. This approach allows early discovery of the bacteria even at concentrations below pathogenic levels, opening the door to new prophylactic approaches against American foulbrood and real-time epidemiological studies.

Novel cost-effective method of screening soils for the presence of mosquito-pathogenic bacilli

AIMS

The aim was to simplify the cumbersome conventional process of isolating virulent bacilli, which involves isolating all bacilli strains from a source followed by screening for strains that are effective for bio-control of mosquito vectors.

METHODS

A new simplified technique involving eight steps was devised for screening soil samples for the presence of mosquito-pathogenic bacilli before isolating individual strains.

RESULTS

Using the new technique, we obtained eight bacilli strains (KSD1-8) showing pathogenic activity against mosquito larvae from three out of 10 soil samples screened. These strains were characterized, identified and the main bioassay tests were performed with three most promising strains (KSD-4, KSD-7 and KSD-8), and their pathogenic activity against Anopheles stephensi Liston, Culex quinquefasciatus, Say and Aedes aegypti Linnaeus compared well with commercial reference strains of B. thuringiensis israelensis and B. sphaericus.

SIGNIFICANCE AND IMPACT OF THE STUDY

The new technique of screening soil samples for the presence of virulent pathogenic strains of bacilli against mosquito larvae proved quick, efficient and cost effective.

Is this the historical 'cancer germ'?

A highly pleomorphic bacterium, isolated from a canine mammary tumour was found to share many characteristics with recently described cancer-related bacteria and with the Glover organism, a historically important 'cancer germ'. We suggest that both the Glover organism, and possibly other cancer-related bacteria, are likely to be a strain of the highly pleomorphic bacterium, Bacillus licheniformis.

Experiences and perspectives for the use of a Paenibacillus strain as a plant protectant

A study on the microbial ecology in an active slow sand filter, used for disinfecting the circulating plant nutrient solutions, showed that spore-forming plant-associated bacteria belonging to the Bacillus-Paenibacillus complex are well adapted for transmission in the solutions and passage through the filter. Therefore, strains from this bacterial group were suitable candidates for biological control in irrigated and closed plant growth systems. The spore-forming Paenibacillus polymyxa strain PpDGB was selected in in vitro tests as a potent pathogen-antagonist and was tested as a prophylactic protection agent in the plant rhizosphere, especially for cultures stages that are highly susceptible to stress and disease. Plant cuttings, in vitro plants and seeds of different plant types were bacterized and planted in their typical disease-conducive environment where nutrient solutions or water irrigation was applied and further plant development was monitored. Observed plant parameters were plant survival, weight, chlorophyll concentration in the leaf mesophyl, root health and root hair formation. The PpDGB treatment initially induced stress in the plants, which was observed as a transient stop in plant transpiration. This effect caused some necrosis in the most stress-sensitive in vitro plant species. In the other plants this stress period was followed by a significant enhancement in plant growth. In case of seed treatment, more seeds germinated and seedling growth was faster. In the tested formulation, PpDGB enhanced growth but not disease resistance, probably due to simultaneous activation of the residual plant pathogens. Therefore variant formulations have to be tested. The influence of PpDGB on the composition of the bacterial communities in the rhizosphere was assessed by DGGE profiling. In soilless plant cultures, PpDGB-driven profile changes could be observed from the 5th day after the initial treatment. P. polymyxa bacteria were shown to be widely present in association with plants and specific PpDGB detection in plant and rhizosphere was only possible with newly developed strain-specific PCR primers based on Nif H gene sequences. Quantitative PCR based on SYBR Green fluorescence enabled detection of low PpDGB concentrations in the plant rhizosphere.

Serious infections caused by enteric gram-negative bacilli--mechanisms of antibiotic resistance and implications for therapy of gram-negative sepsis in the transplanted patient

The Enterobacteriaceae (eg, Escherichia coli, Klebsiella spp., Enterobacter spp.) are common causes of intraabdominal, respiratory tract, and bloodstream infections in transplant recipients. Antibiotic resistance in these organisms is increasing. The major mechanism of resistance to cephalosporins is beta-lactamase production. The most important beta-lactamases are the inducible group 1 cephalosporinases, which are resistant to beta-lactamase inhibitors, and the plasmid-mediated extended-spectrum beta-lactamases (ESBLs). Organisms producing these beta-lactamases also may be resistant to quinolones and aminoglycosides by different mechanisms. A worrying recent development has been the detection of plasmid-mediated carbapenemases, which can inactivate antibiotics such as imipenem and meropenem. In general, third-generation cephalosporins should be avoided in the therapy of serious infections in transplant recipients because of the common occurrence of cephalospo-rinases in the Enterobacteriaceae. Antibiotic options are becoming more limited as the prevalence of resistance mechanisms in gram-negative bacilli increases.

Toxicity of Bacillus thuringiensis and B. sphaericus to laboratory populations of Drosophila melanogaster (Diptera: Drosophilidae)

A total of 65 samples, consisting of 8 sample types, collected from the Jordan Valley, were examined for the presence of Bacillus thuringiensis and B. sphaericus and for their toxicity against the larvae of the fruit fly Drosophila melanogaster. The frequency of samples containing toxic aerobic spore-forming bacilli was 12%; of which 21.7% belonged to B. thuringiensis and 17.4% to B. sphaericus. The B. thuringiensis populations consisted of 5 serogroups: thuringiensis (H1), entomocidus (H6), pakistani (H13), autoagglunated, in addition to a new serotype. The B. sphaericus population consisted of 3 serogroups, and belonged to serovars H5, H9, and H13. All B. thuringiensis and B. sphaericus local isolates, in addition to the reference strains B. thuringiensis kuristaki, and B. thuringiensis israelensis, showed high toxicity towards 3(rd) instar larvae of D. melanogaster. The toxic concentrations ranged between 2.0 x 10(6) and 4.4 x 10(7) viable spores ml(-1).

Molecular mechanisms of Bacillus endophthalmitis pathogenesis

Bacillus endophthalmitis is one of the most devastating intraocular infections, frequently resulting in significant vision loss, if not loss of the eye itself, in only a few days. This review summarizes recent research focused on characterizing the interactions between Bacillus and the host response during endophthalmitis. Analyses of the contribution of Bacillus toxins and cell wall components, and the behavior of the organism during progressive disease are discussed. A better understanding of the host/pathogen interactions occurring during endophthalmitis is critical for the development of novel therapeutic agents designed to impede the progression of infection and protect vision.

Rhizobacteria-induced resistance perturbs viral disease progress and triggers defense-related gene expression

Selected strain of nonpathogenic rhizobacterium EXTN-1 from the Bacillus amyloliquefaciens is capable of eliciting broad-spectrum induced systemic resistance (ISR) in several crops that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). In tobacco (Nicotiana tabacum cv. Samsun-nn), EXTN-1 treatment also perturbs the disease progress by Pepper mild mottle virus (PMMoV), a member of Tobamovirus group. To investigate the defense mechanisms induced by this rhizobacterium, expression patterns of defense-related genes were analyzed. The EXTN-1-treated tobacco plants showed augmented, rapid transcript accumulation of defense-related genes including PR-1a, phenylalanine ammonia-lyase (PAL), and 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) following inoculation with PMMoV. This was the typical phenomenon of potentiation. Accelerated expression of all these genes was subsequently detected in the noninoculated, upper leaves; thus, their expression is associated with the development of both local and systemic resistance. Coordinated reduction of viral genome accumulation was clearly detected in the leaves of tobacco pretreated with EXTN-1. EXTN-1 treatment on Arabidopsis wild type Col-0 resulted in the activation of PR-1 and PDF1.2 at the same time. All these results may indicated that EXTN-1 induces systemic resistance via salicylic acid- and jasmonic acid-dependent pathways and timely recognition followed by rapid counter attack against the viral invasion is the key differences between incompatible interaction and compatible one.

[Viability and virulence of Francisella tularensis subsp. Holarctica in water ecosystems (experimental study)]

Under conditions of artificial water biocenosis a virulent strain of F. tularensis could be detected in fresh water shrimps and mollusks for about a month, in Conepoda for up to 20 days and in Chydorus sphaericus for up to 7 days from the moment of the aquaria water contamination. In silt F. tularensis could be detected for a longer period (up to 2 months). Daphnia, Oligochaeta and C. sphaericus appeared to be unfavorable environment for this microorganism. The virulence level of F. tularensis microbial cells decreased in paralell with prolongation of their stay in water biocenosis. The presence of water biota favours F. tularensis preservation in water reservoirs for a longer time.

Roles of Bacillus endospores in the environment

The occurrence and diverse roles of Bacillus spp. and their endospores in the environment is reviewed, with particular emphasis on soil ecology, host-symbiont and host-parasite interactions, and human exploitation of spores as biological control agents and probiotics.

An isolate of Bacillus circulans toxic to mosquito larvae

A new strain of Bacillus circulans isolated from a larva of Culex quinquefasciatus showed larvicidal activity on 3 mosquitoes of medical importance. Compared to Bacillus sphaericus strain 2362, this B. circulans isolate proved less toxic to Cx. quinquefasciatus and Anopheles gambiae but was 107 times more toxic to Aedes aegypti. Moreover, in comparison to other studies, B. circulans was at least as pathogenic as B. thuringiensis var. israelensis in Ae. aegypti. The tests have showed that the toxicity of the bacterial culture of B. circulans resulted from its spores and not from the insecticidal effect of chitinases or exotoxins.

Mosquito larval control with Bacillus sphaericus: reduction in adult populations in low-income communities in Nonthaburi Province, Thailand

During 1999 and 2000 several larvicidal treatments of Bacillus sphaericus strain 2362 water dispersible granular (WDG) formulations were made at 50 to 200 mg/m2 in mosquito developmental sites in low-income communities in Nonthaburi Province, Thailand to determine whether larviciding dense populations would results in a noticeable reduction of adult mosquitoes in small treated areas. In the treated area in 1999 (Soi Jumpa), immature populations were suppressed to extremely low levels for extended periods, especially at the higher dosages. This decline in immature populations was followed by a substantial decline in adult mosquitoes. There was a lag of 7 to 14 days post-larval treatments before maximum decline in adults was noted. Adults that emerged prior to treatments survived for 7-14 days or longer, thus no drastic reduction was noted soon after treatments. Despite a slight resurgence in adult mosquitoes during the middle of the experimental period, adult female mosquitoes (over 98% Cx quinquefasciatus), remained low during the 5-month period of trials. During the last 2 weeks (17 days post last treatment) of the experimental period, female populations reached the pre-treatment level. During the 2000 tests at Wat Pikul reduction in larvae was 87-98% for 7 weeks after first treatment at 200 mg/m2, resulting in a reduction of 24 to 73% (2 and 7 days post-treatment respectively) and 87 to 98 (2-6 weeks) in the adults. In the second and third treatments at 50 mg/m2, larval control and subsequent adult reduction were lower and shorter-lived than at the high dosage, and the fourth treatment at 100 mg/m2 did not yield a high level of reduction in the larvae (18 to 33%), but reduction of adults was still 80%. The final fifth treatment at 200 mg/m2 yielded only 18% control of larvae, suggesting tolerance to B. sphaericus at this site. It was shown that at both treated sites repeated treatments with a larvicide such as B. sphaericus could result in substantial reduction in adult mosquitoes. Vigilance for detection of resistance development should be practiced, as resistance could emerge in certain populations following a few treatments.

Putative virulence factor expression by clinical and food isolates of Bacillus spp. after growth in reconstituted infant milk formulae

Forty-seven strains representing 14 different Bacillus species isolated from clinical and food samples were grown in reconstituted infant milk formulae (IMF) and subsequently assessed for adherence to, invasion of, and cytotoxicity toward HEp-2 and Caco-2 cells. Cell-free supernatant fluids from 38 strains (81%) were shown to be cytotoxic, 43 strains (91%) adhered to the test cell lines, and 23 strains (49%) demonstrated various levels of invasion. Of the 21 Bacillus cereus strains examined, 5 (24%) were invasive. A larger percentage of clinically derived Bacillus species (20%) than of similar species tested from the food environment were invasive. Increased invasion occurred after growth of selected Bacillus species in reconstituted IMF containing glucose. While PCR primer studies revealed that many different Bacillus species contained DNA sequences encoding the hemolysin BL (HBL) enterotoxin complex and B. cereus enterotoxin T, not all of these isolates expressed these diarrheagenic genes after growth in reconstituted IMF. Of the 47 Bacillus isolates examined, 3 isolates of B. cereus and 1 isolate of B. subtilis produced the HBL enterotoxin after 18 h of growth in brain heart infusion broth. However, eight isolates belonging to the species B. cereus, B. licheniformis, B. circulans, and B. megaterium were found to produce this enterotoxin after growth in reconstituted IMF when assessed with the B. cereus enterotoxin (diarrheal type) reversed passive latex agglutination (RPLA) kit. It is concluded that several Bacillus species occurring occasionally in clinical specimens and food samples are of potential medical significance due to the expression of putative virulence factors.

Toxic Bacillus pumilus from indoor air, recycled paper pulp, Norway spruce, food poisoning outbreaks and clinical samples

Forty-four B. pumilus isolates of food poisoning, clinical, environmental and industrial origins were investigated for toxin production using the boar spermatozoan motility assay, previously shown to be a sensitive method for detecting non-protein toxins from B. cereus and B. licheniformis. The three toxic isolates originated from live tree, indoor air and recycled paper pulp and were more toxic than the previously described food poisoning isolates of B. licheniformis, whereas the B. pumilus food poisoning and clinical isolates were lower in toxicity. The type strain also produced inhibitory substances. The toxic substances were insensitive to heat (100 degrees C, 20 min), to pH 2 or pH 10 and to digestion with pronase. The substances were readily soluble in methanol and chloroform, but less soluble in toluene. Exposure of boar spermatozoa to 1-10 microg ml(-1) (EC50) of methanol soluble substance from the four strains disrupted the plasma membrane permeability barrier, induced abnormalities in the postacrosomal sheath, collapsed the mitochondrial and suppressed cytoplasmic NAD reduction. No change was observed in human peripheral blood lymphocytes exposed to concentrations of B. pumilus extract that affected spermatozoa. The toxin producing isolates were 99.4 to 99.6% similar in 16SrDNA (500 bp) to the type strain and could not be distinguished from the 41 non-toxic isolates by biochemical properties or whole cell fatty acid composition.

Biocidal activity of Bacillus species for Anopheles larvae

It is generally accepted that Bacillus thuringiensis (B.t.) is specifically toxic to some insects but does not pose any threat to the environment, operators, or consumers. There are several other Bacillus species which can be used as effective bioinsecticides. In this study four different species of Bacillus, i.e., B. coagulans, B. megaterium, B. brevis, and B. sphaericus were isolated from soil samples collected from Kala Shah Kakoo and Kasur areas, in the suburbs of Lahore. Isolated Bacillus species were administered to mosquito larvae to evaluate their biocidal activity. B. coagulans I from Kala Shah Kakoo showed 93% mortality, while B. coagulans III from Kasur showed 70% mortality. Bacterial isolates most toxic to Anopheles larvae showed optimum growth at 37 degrees C and pH 7. These isolates have a great potency to controlling anopheline population.

Pathogen evolution: How good bacteria go bad

Recent findings suggest that dysentery-causing Shigella strains have arisen several times from Escherichia coli via plasmid acquisition and phenotypic convergence. Similarly, three Bacillus strains with distinct pathogenic properties are derivatives of a single species whose behavior is profoundly altered by acquired plasmids.

Pathogens associated with southwestern corn borers and southern corn stalk borers (Lepidoptera: Crambidae)

A study was undertaken to isolate entomopathogens of southwestern corn borer, Diatraea grandiosella Dyer, and southern corn stalk borer, Diatraea crambidoides (Grote). Field-collected diapausing larvae of southwestern corn borer (three sites in Mississippi) and southern corn stalk borer (one site in North Carolina), and a laboratory strain of D. grandiosella in the diapause state were maintained in a simulated winter followed by a simulated spring environnent. Few larvae (< or = 6%) collected from any of the field sites died in the winter environment, and most insect mortality (11-25%) occurred after transfer of the larvae to the simulated spring environment. Mortality during the simulated spring period differed among the collection sites, and the highest mortality was recorded for southwestern corn borers from Washington County (25%), followed by Marshall (16%) and Oktibbeha (11%) Counties. A high level of mortality was also observed in southern corn stalk borers during the simulated spring period (27%). No viruses were observed, but a number of bacteria, microsporidia, and fungi were isolated from both southwestern corn borer and southern corn stalk borer larvae and pupae. In most instances, numerous bacterial taxa were isolated from cadavers, but on some occasions a single taxon predominated. The most prevalent bacterial taxon from larval and pupal cadavers was Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilppel-Balz, but Bacillus spp., Pseudomonas aeruginosa (Schroeter) Migula, and Serratia marcescens Bizio were frequently isolated as well. Few fungi (1-7%) were recovered from southwestern corn borer and southern corn stalk borer larvae and pupae. The most common entomopathogenic taxon isolated was Beauveria bassiana (Balsamo) Vuillemin from southern corn stalk borer larvae. Microsporidia were not isolated from southern corn stalk borers. However, Nosema spp. were isolated from southwestern corn borer cadavers from Washington (15%), Marshall (1%), and Oktibbeha (3%) Counties in Mississippi. In addition, we observed parasitism of southern corn stalk borer larvae by Macrocentrus cingulum Reinhard (Hymenoptera: Braconidae). No parasitism of southwestern corn borers was observed. Isolates of Bacillus, Beauveria, Entercoccus, Nosema, Pseudomonas and Serratia were all pathogenic to southwestern corn borer larvae under controlled environmental conditions, and with the exception of B. bassiana, these are novel pathogens of Diatraea corn borers.

Number of triplets in 16S rRNA gene related with pathogenicity of Bacillus spp. and Clostridium spp

The relation between the number of some trinucleotides in the sequence of 16S rRNA gene and pathogenicity of bacterial species from the genera of Bacillus and Clostridium was revealed. The species of genus Bacillus, which are pathogenic for humans, mammals and insects, have an increased number of AAA and TAT triplets in 16S rRNA gene. Theoretically, these species, B. anthracis and B. cereus for example, may be detected in the specimen by the higher ratio of AAA plus TAT triplets to the number of GGG triplet. Species of genus Clostridium, which are pathogenic for humans and mammals, have a maximum ratio of AAA and TAT triplet numbers. This ratio was higher than 2.6 for pathogenic species and lower than 2.2 for saprophytic ones. These theoretical data may open a new way for detecting pathogenic bacteria through the determination of triplet numbers in the sequences of 16S rRNA or rRNA. However, the mechanism of evolutionary relation between the number of AAA and TAT triplets in the sequence of 16S rRNA gene and the pathogenicity of bacterial species is not known.

Histochemical characterization of cell death in honeybee larvae midgut after treatment with Paenibacillus larvae, Amitraz and Oxytetracycline

A number of techniques were employed to assess cell death induced in honeybee larvae midgut after per os inoculation of bacterium Paenibacillus larvae var. larvae, the causative agent of American foulbrood disease, and separately with acaricide Amitraz and antibiotic Oxytetracycline. In honeybee larvae exposed to Amitraz, which demonstrates both necrosis and apoptosis, cell death was found in 82% of midgut columnar and in 50% of regenerative epithelial cells, 24 h after treatment. Cell death reduced to 36% in the epithelial cells, 48 h after treatment. In Oxytetracycline-treated larvae, cell death was identified in 40% of midgut epithelial cells, 24 h after inoculation and increased to 55% over the next 24 h. In Paenibacillus -infected larvae, all midgut epithelial cells died. Using ApopTag (Oncor) to label the multiple DNA ends generated by DNA fragmentation showed programmed cell death in 49% of columnar midgut cells 24 h after Amitraz application. Cell death was reduced to 9% over the next 24 h. Our data indicate that cell death could be identified and quantified in situ, using TUNEL techniques. This study also shows that the acaricide Amitraz is a trigger for programmed cell death in the midgut epithelial cells of honeybee larvae, unlike Paenibacillus which induces necrosis only. The data show that immunohistochemical methods are useful for studying in situ tissue pathology, and indicate possibilities for monitoring the effects of infective and chemical environmental stressors on cell death in honeybee larvae tissue.

Toxic lactonic lipopeptide from food poisoning isolates of Bacillus licheniformis

Toxins from three Bacillus licheniformis strains connected to a fatal food poisoning were isolated and their structures elucidated. Toxins were purified from methanol extracts of the B. licheniformis biomass using boar sperm cells as the toxicity indicator. The HPLC purified toxins showed protonated masses m/z 1007, 1021 and 1035 in MALDI-TOF-MS. The toxins isolated from the strains of different origins contained the same three components of which and each had a same amino-acid residues L-Gln, L-Leu, D-Leu, L-Val, L-Asp, D-Leu and L-Ile in that order. Toxins were identified as lichenysin A, a cyclic lactonic heptalipopeptide in which the main 3-hydroxy fatty acids are 13-15 carbons in length. We showed that the toxins from food and food poisoning isolates of B. licheniformis were identical to lichenysin A both in the structure and in the toxic symptoms induced to boar spermatozoa. Confocal laser scanning microscopy showed that the acrosome and the plasma membrane of boar spermatozoa were the targets of lichenysin A toxicity.

Clinical and microbiological profile of Bacillus keratitis

PURPOSE

To examine the clinical and microbiological profile of Bacillus keratitis.

METHODS

A retrospective review was done of all medical and laboratory records of patients with infectious keratitis in an urban tertiary level eye-care center in South India between January 1991 and June 1997.

RESULTS

Nineteen eyes of 17 patients having microbiologically proven Bacillus keratitis were reviewed. The mean age of the patients was 32.64 years (range, 3-70). The duration of symptoms ranged from 1 day to 3 months, with 11 eyes seen within a week of onset of symptoms. Trauma (five eyes), lagophthalmos (two eyes), topical corticosteroid therapy (one eye), bullous keratopathy (two eyes), previous corneal scars (two eyes), and diabetes (one eye) were identified as predisposing factors. Severe corneal features, disproportionate to the duration of symptoms, were present in most of the eyes. Gram stain of corneal scrapings showed variably stained bacilli in eight (42.1%) cases. Polymicrobial infection was present in six eyes (two fungal, four bacterial). Of the 16 isolates tested for in vitro antibiotic susceptibility, 100% were sensitive to gentamicin, 15 (93.75%) were sensitive to ciprofloxacin and norfloxacin, 14 (87.5%) were sensitive to chloramphenicol, and 10 (62.5%) were sensitive to cefazolin. Whereas 12 (63.1%) eyes required only medical therapy, adjunctive procedures were required in seven (36.8%) eyes. The ulcers healed (mean time to healing, 37.4+/-28.6 days) in 16 eyes (lost to follow-up, three). Visual acuity had improved after treatment in 10 (71.4%) of 14 eyes in whom vision could be recorded.

CONCLUSION

Bacillus is an unusual pathogen in the clinical setting of infectious keratitis. The infection is mostly amenable to treatment with commonly used antibiotics, and the final outcome is often satisfactory.