Novel Genetic Dysregulations and Oxidative Damage in Fusarium graminearum Induced by Plant Defense Eliciting Psychrophilic Bacillus atrophaeus TS1

This study elaborates inter-kingdom signaling mechanisms, presenting a sustainable and eco-friendly approach to combat biotic as well as abiotic stress in wheat. Fusarium graminearum is a devastating pathogen causing head and seedling blight in wheat, leading to huge yield and economic losses. Psychrophilic Bacillus atrophaeus strain TS1 was found as a potential biocontrol agent for suppression of F. graminearum under low temperature by carrying out extensive biochemical and molecular studies in comparison with a temperate biocontrol model strain Bacillus amyloliquefaciens FZB42 at 15 and 25 °C. TS1 was able to produce hydrolytic extracellular enzymes as well as antimicrobial lipopeptides, i.e., surfactin, bacillomycin, and fengycin, efficiently at low temperatures. The Bacillus strain-induced oxidative cellular damage, ultrastructural deformities, and novel genetic dysregulations in the fungal pathogen as the bacterial treatment at low temperature were able to downregulate the expression of newly predicted novel fungal genes potentially belonging to necrosis inducing protein families (fgHCE and fgNPP1). The wheat pot experiments conducted at 15 and 25 °C revealed the potential of TS1 to elicit sudden induction of plant defense, namely, H₂O₂ and callose enhanced activity of plant defense-related enzymes and induced over-expression of defense-related genes which accumulatively lead to the suppression of F. graminearum and decreased diseased leaf area.

Prevalence of toxigenic fungi and mycotoxins in Arabic coffee (Coffea arabica): Protective role of traditional coffee roasting, brewing and bacterial volatiles

Fungal infection and synthesis of mycotoxins in coffee leads to significant economic losses. This study aimed to investigate the prevalence of toxigenic fungi, their metabolites, and the effect of traditional roasting and brewing on ochratoxin A (OTA) and aflatoxins (AFs) contents of naturally contaminated coffee samples. In addition, in vivo biocontrol assays were performed to explore the antagonistic activities of Bacillus simplex 350–3 (BS350-3) on the growth and mycotoxins synthesis of Aspergillus ochraceus and A. flavus. The relative density of A. niger, A. flavus, Penicillium verrucosum and A. carbonarius on green coffee bean was 60.82%, 7.21%, 3.09% and 1.03%, respectively. OTA contents were lowest in green coffee beans (2.15 μg/kg), followed by roasted (2.76 μg/kg) and soluble coffee (8.95 μg/kg). Likewise, AFs levels were highest in soluble coffee (90.58 μg/kg) followed by roasted (33.61 μg/kg) and green coffee (9.07 μg/kg). Roasting naturally contaminated coffee beans at three traditional methods; low, medium and high, followed by brewing resulted in reduction of 58.74% (3.50 μg/kg), 60.88% (3.72 μg/kg) and 64.70% (4.11 μg/kg) in OTA and 40.18% (34.65 μg/kg), 47.86% (41.17 μg/kg) and 62.38% (53.73 μg/kg) AFs contents, respectively. Significant inhibitions of AFs and OTA synthesis by A. flavus and A. carbonarius, respectively, on infected coffee beans were observed in presence of Bacillus simplex BS350-3 volatiles. Gas chromatography mass spectrochemistry (GC-MS/MS) analysis of head-space BS350-3 volatiles showed quinoline, benzenemethanamine and 1-Octadecene as bioactive antifungal molecules. These findings suggest that marketed coffee samples are generally contaminated with OTA and AFs, with a significant level of roasted and soluble coffee contaminated above EU permissible limits for OTA. Further, along with coffee roasting and brewing; microbial volatiles can be optimized to minimize the dietary exposure to mycotoxins.

Genomic and pathogenicity of a Bacillus paranthracis isolated from book page surface

I report here the genome sequences of a Bacillus paranthracis strain isolated from book page surface. The presented data show a new study field for this species, which is frequently encountered in several environment, including soil, rhizosphere and notably human samples. I provide some insights about genomic content of Bacillus paranthracis, for example the presence of multiple antibiotic resistance genes, genes for polyhydroxybutyrate metabolism, 120 genes related to stress resistance and pathogenicity-related genes such as phospholipase C, metalloprotease and a cluster for non-hemolytic enterotoxin. In vitro tests showed that this isolate has motility, ability to produce biofilm, cytotoxic and enterotoxic ability, which makes this isolate a potential pathogen.

Bacillus simplex treatment promotes soybean defence against soybean cyst nematodes: A metabolomics study using GC-MS

We aimed to profile the metabolism of soybean roots that were infected with soybean cyst nematodes and treated with Bacillus simplex to identify metabolic differences that may explain nematode resistance. Compared with control soybean roots, B. simplex-treated soybean roots contained lower levels of glucose, fructose, sucrose, and trehalose, which reduced the nematodes' food source. Furthermore, treatment with B. simplex led to higher levels of melibiose, gluconic acid, lactic acid, phytosphingosine, and noradrenaline in soybean roots, which promoted nematocidal activity. The levels of oxoproline, maltose, and galactose were lowered after B. simplex treatment, which improved disease resistance. Collectively, this study provides insight into the metabolic alterations induced by B. simplex treatment, which affects the interactions with soybean cyst nematodes.

Clinical Significance of Isolates Known to Be Blood Culture Contaminants in Pediatric Patients

Background and objectives: The objective of this study was to investigate the clinical significance of isolates from blood stream infection known to be blood culture contaminants in pediatric patients. Materials and Methods: Microbiological reports and medical records of all blood culture tests issued from 2002 to 2012 (n = 76,331) were retrospectively reviewed. Evaluation for potential contaminants were done by reviewing medical records of patients with the following isolates: coagulase-negative Staphylococcus, viridans group Streptococcus, Bacillus, Corynebacterium, Micrococcus, Aerococcus, and Proprionibacterium species. Repeated cultures with same isolates were considered as a single case. Cases were evaluated for their status as a pathogen. Results: Coagulase-negative Staphylococcus had clinical significance in 23.8% of all cases. Its rate of being a true pathogen was particularly high in patients with malignancy (43.7%). Viridans group Streptococcus showed clinical significance in 46.2% of all cases. Its rate of being a true pathogen was similar regardless of the underlying morbidity of the patient. The rate of being a true pathogens for remaining isolates was 27.7% for Bacillus and 19.0% for Corynebacterium species. Conclusions: Coagulase-negative Staphylococcus and viridans group Streptococcus isolates showed high probability of being true pathogens in the pediatric population, especially in patients with underlying malignancy.

Targeted interplay between bacterial pathogens and host autophagy

Due to the critical role played by autophagy in pathogen clearance, pathogens have developed diverse strategies to subvert it. Despite previous key findings of bacteria-autophagy interplay, asystems-level insight into selective targeting by the host and autophagy modulation by the pathogens is lacking. We predicted potential interactions between human autophagy proteins and effector proteins from 56 pathogenic bacterial species by identifying bacterial proteins predicted to have recognition motifs for selective autophagy receptors SQSTM1/p62, CALCOCO2/NDP52 and MAP1LC3/LC3. Using structure-based interaction prediction, we identified bacterial proteins capable to modify core autophagy components. Our analysis revealed that autophagy receptors in general potentially target mostly genus-specific proteins, and not those present in multiple genera. The complementarity between the predicted SQSTM1/p62 and CALCOCO2/NDP52 targets, which has been shown for Salmonella, Listeria and Shigella, could be observed across other pathogens. This complementarity potentially leaves the host more susceptible to chronic infections upon the mutation of autophagy receptors. Proteins derived from enterotoxigenic and non-toxigenic Bacillus outer membrane vesicles indicated that autophagy targets pathogenic proteins rather than non-pathogenic ones. We also observed apathogen-specific pattern as to which autophagy phase could be modulated by specific genera. We found intriguing examples of bacterial proteins that could modulate autophagy, and in turn being targeted by autophagy as ahost defense mechanism. We confirmed experimentally an interplay between a Salmonella protease, YhjJ and autophagy. Our comparative meta-analysis points out key commonalities and differences in how pathogens could affect autophagy and how autophagy potentially recognizes these pathogenic effectors. Abbreviations: ATG5: autophagy related 5; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; GST: glutathione S-transferase; LIR: MAP1LC3/LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3 alpha; OMV: outer membrane vesicles; SQSTM1/p62: sequestosome 1; SCV: Salmonella containing vesicle; TECPR1: tectonin beta-propeller repeat containing 1; YhjJ: hypothetical zinc-protease.

Bacterial-derived Neutrophilic Inflammation Drives Lung Remodeling in a Mouse Model of Chronic Obstructive Pulmonary Disease

Loss of secretory IgA is common in the small airways of patients with chronic obstructive pulmonary disease and may contribute to disease pathogenesis. Using mice that lack secretory IgA in the airways due to genetic deficiency of polymeric Ig receptor (pIgR-/- mice), we investigated the role of neutrophils in driving the fibrotic small airway wall remodeling and emphysema that develops spontaneously in these mice. By flow cytometry, we found an increase in the percentage of neutrophils among CD45+ cells in the lungs, as well as an increase in total neutrophils, in pIgR-/- mice compared with wild-type controls. This increase in neutrophils in pIgR-/- mice was associated with elastin degradation in the alveolar compartment and around small airways, along with increased collagen deposition in small airway walls. Neutrophil depletion using anti-Ly6G antibodies or treatment with broad-spectrum antibiotics inhibited development of both emphysema and small airway remodeling, suggesting that airway bacteria provide the stimulus for deleterious neutrophilic inflammation in this model. Exogenous bacterial challenge using lysates prepared from pathogenic and nonpathogenic bacteria worsened neutrophilic inflammation and lung remodeling in pIgR-/- mice. This phenotype was abrogated by antiinflammatory therapy with roflumilast. Together, these studies support the concept that disruption of the mucosal immune barrier in small airways contributes to chronic obstructive pulmonary disease progression by allowing bacteria to stimulate chronic neutrophilic inflammation, which, in turn, drives progressive airway wall fibrosis and emphysematous changes in the lung parenchyma.

Intraclade Variability in Toxin Production and Cytotoxicity of Bacillus cereus Group Type Strains and Dairy-Associated Isolates

While some species in the Bacillus cereus group are well-characterized human pathogens (e.g., B. anthracis and B. cereus sensu stricto), the pathogenicity of other species (e.g., B. pseudomycoides) either has not been characterized or is presently not well understood. To provide an updated characterization of the pathogenic potential of species in the B. cereus group, we classified a set of 52 isolates, including 8 type strains and 44 isolates from dairy-associated sources, into 7 phylogenetic clades and characterized them for (i) the presence of toxin genes, (ii) phenotypic characteristics used for identification, and (iii) cytotoxicity to human epithelial cells. Overall, we found that B. cereus toxin genes are broadly distributed but are not consistently present within individual species and/or clades. After growth at 37°C, isolates within a clade did not typically show a consistent cytotoxicity phenotype, except for isolates in clade VI (B. weihenstephanensis/B. mycoides), where none of the isolates were cytotoxic, and isolates in clade I (B. pseudomycoides), which consistently displayed cytotoxic activity. Importantly, our study highlights that B. pseudomycoides is cytotoxic toward human cells. Our results indicate that the detection of toxin genes does not provide a reliable approach to predict the pathogenic potential of B. cereus group isolates, as the presence of toxin genes is not always consistent with cytotoxicity phenotype. Overall, our results suggest that isolates from multiple B. cereus group clades have the potential to cause foodborne illness, although cytotoxicity is not always consistently found among isolates within each clade.IMPORTANCE Despite the importance of the Bacillus cereus group as a foodborne pathogen, characterizations of the pathogenic potential of all B. cereus group species were lacking. We show here that B. pseudomycoides (clade I), which has been considered a harmless environmental microorganism, produces toxins and exhibits a phenotype consistent with the production of pore-forming toxins. Furthermore, B. mycoides/B. weihenstephanensis isolates (clade VI) did not show cytotoxicity when grown at 37°C, despite carrying multiple toxin genes. Overall, we show that the current standard methods to characterize B. cereus group isolates and to detect the presence of toxin genes are not reliable indicators of species, phylogenetic clades, or an isolate's cytotoxic capacity, suggesting that novel methods are still needed for differentiating pathogenic from nonpathogenic species within the B. cereus group. Our results also contribute data that are necessary to facilitate risk assessments and a better understanding as to which B. cereus group species are likely to cause foodborne illness.

[The mass-spectrometric analysis of MALDI-TOF in identification and typing of strains of comma bacillus]

The data base “Protein profiles of mass-specters of representatives of species of Vibrio cholerae for program MALDI Biotyper” was used to implement typing of strains of comma bacillus isolated at the territory of the Russian Federation in 2010-2012. Also, analysis of degree of similarity and differences among constant ribosomal proteins was implemented. According the results of MALDI-TOF mass-spectrometry strains of V.cholerae were grouped in two distinct clusters. The first cluster included all epidemically dangerous strains isolated from people arrived in Moscow from India 2010-2012. The second cluster included atoxigenic vibrio with no relation to serogroups O1/O139 isolated from residents of Taganrog in 2011. The analysis of main specters of all collection permitted to identify taxon - specific components distinguishing strains of non-O1/non-O139 from strains of V.cholerae El Tor. Hence, the developed data base of proteom portraits of V.cholerae permits identifying, studying and to typing of agents of cholera and other representatives of V.cholerae species detecting their phylogenetic affinity that is ultimately useful for establishing origin of strains isolated from objects of environment and epidemiological decoding of episodes of disease.

[BACILLUS STRAINS'S SCREENING--ACTIVE ANTAGONISTS OF BACTERIAL AND FUNGAL PHYTOPATHOGENS]

Antagonistic activity 100 strains of Bacillus bacteria towards to museum and actual strains of phytopathogenic bacteria and fungy was defined. Relation between level of antagonistic activity to phytopathogenic bacteria and genus accessory of the last was shown. The medium level of antagonism to fungal phytopathogens at 30% of the studied strains of Bacillus bacteria was shown. 5 strains of Bacillus sp. with high and medium levels of antagonism to phytopathogens bacterial and fungy nature was selected and considered as perspective for creation of biological preparations for plant protection.

Microbiological Analysis of Necrosols Collected from Urban Cemeteries in Poland

Decomposition of organic matter is the primary function in the soil ecosystem, which involves bacteria and fungi. Soil microbial content depends on many factors, and secondary biological and chemical contaminations change and affect environmental feedback. Little work has been done to estimate the microbiological risk for cemetery employees and visitors. The potential risk of infection for people in the cemetery is primarily associated with injury and wound contamination during performing the work. The aim of this study was to analyze the microbiota of cemetery soil obtained from cemeteries and bacterial composition in selected soil layers encountered by gravediggers and cemetery caretakers. The most common bacterial pathogens were Enterococcus spp. (80.6%), Bacillus spp. (77.4%), and E. coli (45.1%). The fungi Penicillium spp. and Aspergillus spp. were isolated from 51% and 6.4% of samples, respectively. Other bacterial species were in the ground cemetery relatively sparse. Sampling depth was not correlated with bacterial growth (p > 0.05), but it was correlated with several differences in microbiota composition (superficial versus deep layer).

Knockout of the adp gene related with colonization in Bacillus nematocida B16 using customized transcription activator-like effectors nucleases

Bacillus nematocida B16 is able to dominate in the intestines of the worm Caenorhabditis elegans in 'Trojan horse' pathogenic mechanism. The adp is one candidate gene which potentially play a vital role in the colonization from our previous random mutagenesis screening results. To analyse the functional role of this gene, we constructed the adp knockout mutant through customized transcription activator-like effectors nucleases (TALEN), which has been successfully used in yeasts, nematodes, zebrafish and human pluripotent cells. Here, we first time report this knockout method in bacteria on this paper. Bioassay experiments demonstrated that the adp knockout mutant of B16 showed considerably lower colonization activity, reduced numbers of intestines and less than 80% nematocidal activity compared with the wild-type strain when infected for 48 h. However, no obvious change on proteolytic activity was observed in the mutant. Conversely, the complementation of adp gene restored most of the above deficient phenotypes. These results indicated that the adp gene was involved in surface adhesion and played a comparatively important role in colonizing host nematodes. Moreover, TALENs successfully disrupt target genes in bacteria.

Antibacterial metabolites and bacteriolytic enzymes produced by Bacillus pumilus during bacteriolysis of Arthrobacter citreus

The marine isolate Bacillus pumilus SBUG 1800 is able to lyse living cells of Arthrobacter citreus on solid media as well as pasteurized A. citreus cells in liquid mineral salt medium. The cultivation of B. pumilus in the presence of pasteurized A. citreus is accompanied by an enhanced production of 2,5-diketopiperazines (DKPs). DKPs inhibit bacterial growth, but do not seem to cause bacteriolysis. This study shows that B. pumilus also lyses living cells of A. citreus in co-culture experiments as an intraguild predator, even if the inoculum of B. pumilus is low. In order to characterize the bacteriolytic process, more precisely changes in the extracellular metabolome and proteome have been analyzed under different culture conditions. Besides the known DKPs, a number of different pumilacidins and bacteriolytic enzymes are produced. Two lipopeptides with [M + H](+) = 1008 and [M + H](+) = 1022 were detected and are proposed to be pumilacidin H and I. While the lipopeptides lyse living bacterial cells in lysis test assays, a set of extracellular enzymes degrades the dead cell material. Two of the cell wall hydrolases involved have been identified as N-acetylmuramoyl-L-alanine amidase and beta-N-acetylglucosaminidase. These findings together with electron microscopic and cell growth monitoring during co-culture experiments give a detailed view on the bacteriolytic process.

Genomic analysis of a ginger pathogen Bacillus pumilus providing the understanding to the pathogenesis and the novel control strategy

Bacillus pumilus has been widely identified as a pathogen of plant and human, while the genetic information is rarely available for pathogenic B. pumilus strains. B. pumilus GR8 is a pathogen that causes ginger rhizome rot disease by invading ginger rhizome parenchymatous tissues, growing in the extracellular space, and producing plant cell wall-degrading enzymes to destroy ginger cells. In this study, the genome of GR8 was sequenced and characterized. This genome was the third completely sequenced genome of the B. pumilus species, and it exhibited high similarity to the genome of the B. pumilus strain B6033. The genome of GR8 was 3.67 Mb in length and encoded 3,713 putative ORFs. Among these predicted proteins, numerous plant cell wall-degrading enzymes and several proteins associated with invading and adapting to the environment in the extracellular space of the ginger rhizome parenchymatous tissue were found. The GR8 genome contained only one restriction-modification system and no CRISPR/Cas system. The lack of phage-resistant system suggested that phages might be potential agents for the control of GR8. The genomic analysis of GR8 provided the understanding to the pathogenesis and the phage-control strategy of pathogenic B. pumilus strains.

Clostridium and bacillus binary enterotoxins: bad for the bowels, and eukaryotic being

Some pathogenic spore-forming bacilli employ a binary protein mechanism for intoxicating the intestinal tracts of insects, animals, and humans. These Gram-positive bacteria and their toxins include Clostridium botulinum (C2 toxin), Clostridium difficile (C. difficile toxin or CDT), Clostridium perfringens (ι-toxin and binary enterotoxin, or BEC), Clostridium spiroforme (C. spiroforme toxin or CST), as well as Bacillus cereus (vegetative insecticidal protein or VIP). These gut-acting proteins form an AB complex composed of ADP-ribosyl transferase (A) and cell-binding (B) components that intoxicate cells via receptor-mediated endocytosis and endosomal trafficking. Once inside the cytosol, the A components inhibit normal cell functions by mono-ADP-ribosylation of globular actin, which induces cytoskeletal disarray and death. Important aspects of each bacterium and binary enterotoxin will be highlighted in this review, with particular focus upon the disease process involving the biochemistry and modes of action for each toxin.

[Establishment and application of efficient nematicidal screening model in Bacillus amyloliquefaciens]

OBJECTIVE

The mechanisms of nematophagous bacteria against nematodes remain unclear, limiting the use of biocontrol bacteria in the agriculture. Therefore, we constructed a rapid and efficient screening model to quickly identify new candidate genes involved in nematode infection.

METHODS

The wild-type Bacillus amyloliquefaciens FZB42 as well as more than 400 random mutants were inoculated into 5 mL liquid bioassay medium. After growth at 37 degrees C for 24 h, 200 microL bacterial culture and 50-60 Level 4 age nematodes were added to 24-well plates, and then the survival rates of nematodes were determined at different time points. Through several rescreening, we selected the mutant strains whose nematicidal activities significantly decreased compared with the wild-type strain. Meanwhile, the conventional bioassay of solid plate was used as control.

RESULTS

Two mutants (F1 and F2) with obvious decreased nematicidal activities were selected from the random mutation library by liquid bioassay, consistent with the result of conventional solid plate bioassay. By comparing to 168 h-screening in each round of the solid plate bioassay, the method of liquid bioassay required only 24 h. The result indicated that the liquid bioassay greatly reduced the experimental time.

CONCLUSION

Our current study has successfully constructed a rapid and efficient method to bioassay the nematicidal activity, which could also lay the foundation for further cloning the candidate genes involved in the microbial infection against nematodes.

Mass spectrometry identification of antifungal lipopeptides from Bacillus sp. BCLRB2 against Rhizoctonia solani and Sclerotinia sclerotiorum

This work aims to characterize the bioactive molecules produced by an antagonistic Bacillus sp. strain BCLRB2 isolated from healthy leaves of olive tree against Rhizoctonia solani and Sclerotinia sclerotiorum. The bacterial strain isolated showed a high and persistent antifungal activity against the two pathogens. The free-cell supernatant showed also a high antifungal activity against R. solani and at a lower extent against S. sclerotiorum. The partial purification of the antifungal substances with methanol gradient applied to C18 column binding the Bacillus BCLRB2 culture supernatant showed that the 20% and 60% methanol fractions had a high and specific activity against S. sclerotiorum and R. solani, respectively. The mass spectrometry identification of the compounds in the fraction specifically active against S. sclerotiorum revealed the presence of bacillomycin D C16 as a major lipopeptide. The fraction specifically active against R. solani contained bacillomycin D C15 and 2 unknown lipopeptides. The 80% methanol fraction had a moderate and a broad spectrum activity against the two pathogens and consisted from two iturin D (C13 and C14) as a major lipopeptides.

Use of silkworms to evaluate the pathogenicity of bacteria attached to cedar pollen

Injection of a Japanese cedar pollen suspension into silkworm hemolymph kills the silkworms. A certain species of bacteria proliferated in the hemolymph of the dead silkworms. A 16S rDNA analysis demonstrated that the proliferating bacteria were Bacillus cereus, Bacillus thuringiensis, Bacillus weihenstephanensis, and Bacillus amyloliquefaciens. Among them, B. cereus, B. thuringiensis, and B. weihenstephanensis exhibited hemolysis against sheep red blood cells and were lethal to mice. A culture filtrate of B. amyloliquefaciens showed enzyme activity toward the pectic membrane of cedar pollen. These results suggest that silkworms as an animal model are useful for evaluating the pathogenicity of bacteria attached to cedar pollen.

Disruption of microbial biofilms by an extracellular protein isolated from epibiotic tropical marine strain of Bacillus licheniformis

BACKGROUND

Marine epibiotic bacteria produce bioactive compounds effective against microbial biofilms. The study examines antibiofilm ability of a protein obtained from a tropical marine strain of Bacillus licheniformis D1.

METHODOLOGY/PRINCIPAL FINDINGS

B. licheniformis strain D1 isolated from the surface of green mussel, Perna viridis showed antimicrobial activity against pathogenic Candida albicans BH, Pseudomonas aeruginosa PAO1 and biofouling Bacillus pumilus TiO1 cultures. The antimicrobial activity was lost after treatment with trypsin and proteinase K. The protein was purified by ultrafiltration and size-exclusion chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis revealed the antimicrobial agent to be a 14 kDa protein designated as BL-DZ1. The protein was stable at 75°C for 30 min and over a pH range of 3.0 to 11.0. The sequence alignment of the MALDI-fingerprint showed homology with the NCBI entry for a hypothetical protein (BL00275) derived from B. licheniformis ATCC 14580 with the accession number gi52082584. The protein showed minimum inhibitory concentration (MIC) value of 1.6 µg/ml against C. albicans. Against both P. aeruginosa and B. pumilus the MIC was 3.12 µg/ml. The protein inhibited microbial growth, decreased biofilm formation and dispersed pre-formed biofilms of the representative cultures in polystyrene microtiter plates and on glass surfaces.

CONCLUSION/SIGNIFICANCE

We isolated a protein from a tropical marine strain of B. licheniformis, assigned a function to the hypothetical protein entry in the NCBI database and described its application as a potential antibiofilm agent.

[Influence of bacteria of Bacillus genus on the causative agent of bacterial cancer of tomatoes]

It has been shown that bacteria of the genus Bacillus inhibited the development of infection caused by Clavibacter michiganensis subsp. michiganensis, in tomatoes. Pre-sowing seed treatment with suspensions of Bacillus subtilis IMV B-7023 and Bacillus pumilus 3 enhanced resistance of plants to bacterial disease of cancer, probably due to the synthesis of biologically active substances with antimicrobial properties by these bacteria. Of the two strains of bacillus, differing by antagonist properties to C. michiganensis subsp. michiganensis, a significant stimulating effect on the growth and development of tomatoes was provided by the strain B. subtilis IMV B-7023, which is part of the bacterial preparations for crop production.

Distinct antimicrobial activities in aphid galls on Pistacia atlantica

Gall-formers are parasitic organisms that manipulate plant traits for their own benefit. Galls have been shown to protect their inhabitants from natural enemies such as predators and parasitoids by various chemical and mechanical means. Much less attention, however, has been given to the possibility of defense against microbial pathogens in the humid and nutrient-rich gall environment. We found that the large, cauliflower-shaped, galls induced by the aphid Slavum wertheimae on buds of Pistacia atlantica trees express antibacterial and antifungal activities distinct from those found in leaves. Antibacterial activity was especially profound against Bacillus spp (a genus of many known insect pathogen) and against Pseudomonas aeruginosa (a known plant pathogen). Antifungal activity was also demonstrated against multiple filamentous fungi. Our results provide evidence for the protective antimicrobial role of galls. This remarkable antibacterial and antifungal activity in the galls of S. wertheimae may be of agricultural and pharmaceutical value.

Properties of bacteria that trigger hemocytopenia in the Atlantic blue crab, Callinectes sapidus

In the blue crab Callinectes sapidus, injection with the bacterial pathogen Vibrio campbellii causes a decrease in oxygen consumption. Histological and physiological evidence suggests that the physical obstruction of hemolymph flow through the gill vasculature, caused by aggregations of bacteria and hemocytes, underlies the decrease in aerobic function associated with bacterial infection. We sought to elucidate the bacterial properties sufficient to induce a decrease in circulating hemocytes (hemocytopenia) as an indicator for the initiation of hemocyte aggregation and subsequent impairment of respiration. Lipopolysaccharide (LPS), the primary component of the gram-negative bacterial cell wall, is known to interact with crustacean hemocytes. Purified LPS was covalently bound to the surfaces of polystyrene beads resembling bacteria in size. Injection of these "LPS beads" caused a decrease in circulating hemocytes comparable to that seen with V. campbellii injection, while beads alone failed to do so. These data suggest that in general, gram-negative bacteria could stimulate hemocytopenia. To test this hypothesis, crabs were injected with different bacteria--seven gram-negative and one gram-positive species--and their effects on circulating hemocytes were assessed. With one exception, all gram-negative strains caused decreases in circulating hemocytes, suggesting an important role for LPS in the induction of this response. However, LPS is not necessary to provoke the immune response given that Bacillus coral, a gram-positive species that lacks LPS, caused a decrease in circulating hemocytes. These results suggest that a wide range of bacteria could impair metabolism in C. sapidus.

Synergism between wild-type Bacillus thuringiensis subsp. israelensis and B. sphaericus strains: a study based on isobolographic analysis and histopathology

Prevention is the best resistance management strategy in integrated vector control programs. Combined use of insecticides of different classes that interact synergistically and show multi-site actions within the insect is recognized as a potential key strategy to be implemented even before the onset of resistance. The present study is aimed at harvesting the benefits of synergism between the wild-type Bacillus thuringiensis subsp. israelensis-H14 (Bti) and Bacillus sphaericus-2362 (Bs) strains by evaluating six different combinations of mixtures toxic to Aedes and Culex mosquito larvae. Isobolographic analysis was performed to distinguish the synergistic combinations of Bti and Bs, followed by determination of the degree of synergism through synergy and improvement factors. Furthermore, the speed of activity of Bs when combined with Bti is studied by histopathological investigations on the fate of midgut muscles of mosquito larvae upon exposure to individual wild-type strains as well as their mixtures.

Selection of a Bacillus pumilus strain highly active against Ceratitis capitata (Wiedemann) larvae

Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), the Mediterranean fruit fly (medfly), is one of the most important fruit pests worldwide. The medfly is a polyphagous species that causes losses in many crops, which leads to huge economic losses. Entomopathogenic bacteria belonging to the genus Bacillus have been proven to be safe, environmentally friendly, and cost-effective tools to control pest populations. As no control method for C. capitata based on these bacteria has been developed, isolation of novel strains is needed. Here, we report the isolation of 115 bacterial strains and the results of toxicity screening with adults and larvae of C. capitata. As a result of this analysis, we obtained a novel Bacillus pumilus strain, strain 15.1, that is highly toxic to C. capitata larvae. The toxicity of this strain for C. capitata was related to the sporulation process and was observed only when cultures were incubated at low temperatures before they were used in a bioassay. The mortality rate for C. capitata larvae ranged from 68 to 94% depending on the conditions under which the culture was kept before the bioassay. Toxicity was proven to be a special characteristic of the newly isolated strain, since other B. pumilus strains did not have a toxic effect on C. capitata larvae. The results of the present study suggest that B. pumilus 15.1 could be considered a strong candidate for developing strategies for biological control of C. capitata.

Toxicity assessment and clearance of Brazilian microbial pest control agents in mice

The environmental toxicology of chemical pesticides have increased interest in the development and use of microbial pest control agents. In the present study four new Brazilian strains of Bacillus and one fungus were tested to evaluate the acute oral toxicity and clearance of these microbials in C57BL6 mice. No mortality was observed after exposure for any of the microorganisms tested. Clearance was significant after 30 days but for one strain of B. thuringiensis and one of B. sphaericus this time was not enough to completely eliminate the spores.

Enhancement of tolerance to soft rot disease in the transgenic Chinese cabbage (Brassica rapa L. ssp. pekinensis) inbred line, Kenshin

We developed a transgenic Chinese cabbage (Brassica rapa L. ssp. pekinensis) inbred line, Kenshin, with high tolerance to soft rot disease. Tolerance was conferred by expression of N-acyl-homoserine lactonase (AHL-lactonase) in Chinese cabbage through an efficient Agrobacterium-mediated transformation method. To synthesize and express the AHL-lactonase in Chinese cabbage, the plant was transformed with the aii gene (AHL-lactonase gene from Bacillus sp. GH02) fused to the PinII signal peptide (protease inhibitor II from potato). Five transgenic lines were selected by growth on hygromycin-containing medium (3.7% transformation efficiency). Southern blot analysis showed that the transgene was stably integrated into the genome. Among these five transgenic lines, single copy number integrations were observed in four lines and a double copy number integration was observed in one transgenic line. Northern blot analysis confirmed that pinIISP-aii fusion gene was expressed in all the transgenic lines. Soft rot disease tolerance was evaluated at tissue and seedling stage. Transgenic plants showed a significantly enhanced tolerance (2-3-fold) to soft rot disease compared to wild-type plants. Thus, expression of the fusion gene pinIISP-aii reduces susceptibility to soft rot disease in Chinese cabbage. We conclude that the recombinant AHL-lactonase, encoded by aii, can effectively quench bacterial quorum-sensing and prevent bacterial population density-dependent infections. To the best of our knowledge, the present study is the first to demonstrate the transformation of Chinese cabbage inbred line Kenshin, and the first to describe the effect of the fusion gene pinIISP-aii on enhancement of soft rot disease tolerance.

Screening of Pseudomonas and Bacillus isolates for potential biocontrol of the damping-off of bean (Phaseolus coccineus)

In this study fifteen isolates of identified Pseudomonas fluorescens and Bacillus subtilis were investigated for control of bean damping-off disease caused by Rhizoctonia solani. In vitro, P. fluorescens P-6 and B. subtilis B-3 showed the most inhibitory zone in dual culture assay against R. solani. The growth of P-6 (4.5 x 10(8) cfu/ml) was significantly higher than in the other treatments. In greenhouse condition, all of the isolates effectively controlled damping-off on bean. P. fluorescens P-5 and P-6 showed the considerable results against R. solani and could reduce the damping-off disease from 100% to less than 30%. P-5, P-6 (P. fluorescens) and 8-16 (8. subtilis) strains had the highest effect on fresh weight of bean.

The occurrence of Bacillus cereus, B. thuringiensis and B. mycoides in Chinese pasteurized full fat milk

In 2006, a total of 54 samples of pasteurized full fat milk packaged in cartons were collected in spring and in autumn from chain supermarkets in Wuhan, China. The samples were examined and enumerated by MPN methods strictly according to guidelines laid out in US FDA/CFSAN BAM Chapter 14. Among 102 isolated B. cereus-like bacteria, 92 isolates were identified to be B. cereus, 9 B. thuringiensis and 1 B. mycoides. It was found that the occurrences of B. cereus were 71.4% and 33.3% in spring and in autumn samples respectively and the average count among the positive samples was 11.7 MPN/ml. The PCR detection results revealed that the enterotoxin genes hblA, hblC, hblD, nheA, nheB and nheC occurred in B. cereus isolates with frequencies of 37.0%, 66.3%, 71.7%, 71.7%, 62.0% and 71.7% respectively. Nine B. thuringiensis isolates were also identified from six pasteurized milk samples, and most of them harbored six enterotoxic genes and the insecticidal toxin cry1A gene. The single B. mycoides isolate harbored nheA and nheC genes. The data provides information for further evaluating the effect of B. cereus-like bacteria on food safety of Chinese milk products.

Proteases from Bacillus: a new insight into the mechanism of action for rhizobacterial suppression of nematode populations

AIMS

The aim of this study was to investigate the role of proteases in Bacillus spp. of rhizobacteria in suppressing nematode populations and to understand their mechanism of action.

METHODS AND RESULTS

Rhizobacteria with nematicidal activity were isolated from soil samples of five root knot nematode-infested farms. Among these strains, nematotoxicities of Bacillus strains were intensively analysed. Further assays of nematicidal toxins from Bacillus sp. strain RH219 indicated an extracellular cuticle-degrading protease Apr219 was an important pathogenic factor. The Apr219 shared high similarity with previously reported cuticle-degrading proteases from Brevibacillus laterosporus strain G4 and Bacillus sp. B16 (Bacillus nematocida). The cuticle-degrading protease genes were also amplified from four other nematicidal Bacillus strains isolated from the rhizosphere. In addition to Apr219, a neutral protease Npr219 from Bacillus sp. RH219 was also investigated for activity against nematodes.

CONCLUSIONS

The wide distribution of cuticle-degrading proteases in Bacillus strains with nematicidal activity suggested that these enzymes likely play an important role in bacteria-nematode-plant-environment interactions and that they may serve as important nematicidal factors in balancing nematode populations in the soil.

SIGNIFICANCE AND IMPACT OF THE STUDY

Increased understanding of the mechanism of action of Bacillus spp. against nematodes could potentially enhance the value of these species as effective nematicidal agents and develop new biological control strategies.

Central venous catheter infection with Bacillus pumilus in an immunocompetent child: a case report

BACKGROUND

Bacillus organisms are common laboratory contaminants. The majority of Bacillus bacteraemias are transient and not clinically significant. Clinically significant infection due to Bacillus species is rare and mostly due to Bacillus cereus infections in immuno-compromised hosts.

CASE PRESENTATION

We report a case of central venous catheter infection with Bacillus pumilus in an immunocompetent child with tufting enteropathy on long-term parenteral nutrition (PN). There were three episodes of central venous catheter infection with Bacillus pumilus in three months. Despite adequate and appropriate use of intravenous antibiotics, the infection failed to clear resulting in the need for removal of the catheter for complete cure.

CONCLUSION

Bacillus species can cause clinically significant central venous catheter infection, even in an immunocompetent host. Despite adequate antibiotic treatment, the central venous catheter may need removal for complete cure.

Mtx toxins synergize Bacillus sphaericus and Cry11Aa against susceptible and insecticide-resistant Culex quinquefasciatus larvae

Two mosquitocidal toxins (Mtx) of Bacillus sphaericus, which are produced during vegetative growth, were investigated for their potential to increase toxicity and reduce the expression of insecticide resistance through their interactions with other mosquitocidal proteins. Mtx-1 and Mtx-2 were fused with glutathione S-transferase and produced in Escherichia coli, after which lyophilized powders of these fusions were assayed against Culex quinquefasciatus larvae. Both Mtx proteins showed a high level of activity against susceptible C. quinquefasciatus mosquitoes, with 50% lethal concentrations (LC(50)) of Mtx-1 and Mtx-2 of 0.246 and 4.13 microg/ml, respectively. The LC(50)s were 0.406 to 0.430 microg/ml when Mtx-1 or Mtx-2 was mixed with B. sphaericus, and synergy improved activity and reduced resistance levels. When the proteins were combined with a recombinant Bacillus thuringiensis strain that produces Cry11Aa, the mixtures were highly active against Cry11A-resistant larvae and resistance was also reduced. The mixture of two Mtx toxins and B. sphaericus was 10 times more active against susceptible mosquitoes than B. sphaericus alone, demonstrating the influence of relatively low concentrations of these toxins. These results show that, similar to Cyt toxins from B. thuringiensis subsp. israelensis, Mtx toxins can increase the toxicity of other mosquitocidal proteins and may be useful for both increasing the activity of commercial bacterial larvicides and managing potential resistance to these substances among mosquito populations.

A new Cry toxin with a unique two-component dependency from Bacillus sphaericus

Highly pathogenic strains of Bacillus sphaericus produce the mosquitocidal Bin proteins, but resistance to this toxin can be produced under laboratory and field conditions. Analysis of strains able to overcome this resistance revealed the presence of a previously undescribed type of two-component toxin. One subunit, Cry48Aa1, is related to the 3-domain crystal toxins of Bacillus thuringiensis. Uniquely for this type of protein, insect toxicity is only achieved in the presence of a second, accessory protein, Cry49Aa1. This protein is itself related to both the binary toxin of B. sphaericus and to Cry35 and Cry36 of B. thuringiensis, none of which require interaction with Cry48Aa1-like proteins for their activity. The necessity for both Cry48Aa1 and Cry49Aa1 components for pathogenicity, therefore, indicates an unprecedented interaction to generate toxicity. Despite high potency for purified Cry48Aa1/Cry49Aa1 proteins (LC50 for third instar Culex quinquefasciatus larvae: 15.9 ng/ml and 6.3 ng/ml respectively), bacteria producing them show suboptimal mosquitocidal activity due to low-level Cry48Aa1 production. This new toxin combination may indicate a fortuitous combination of members of the gene families that encode 3-domain Cry toxins and Binary-like toxins, permitting the "mix-and-match" evolution of a new component in the mosquitocidal armoury.

[Detection of some toxin genes related to pathogenicity in Bacillus cereus group strains]

Bacillus thuringiensis is a member of the B. cereus group, which also contains B. cereus, B. mycoides, B. pseudomycoides , B. anthracis and B. weihenstephanensis. Among them, B. thuringiensis and B. cereus share a high level chromosomal similarity and are phenotypically similar except that B. thuringiensis has insecticidal plasmid encoding crystal proteins. Twenty-six B. cereus group strains were surveyed in this study for the presence of enterotoxin genes and other toxin genes related to pathogenicity. PCR results showed that the pleiotropic virulence regulator plcR was presented in 17 B. cereus group strains. About 73% of the B. cereus group strains and 83% of the B. thuringiensis strains contained at least one of the three hbl genes and one of the three nhe genes, indicating that B. thuringiensis, including strains used commercially, had enterotoxin encoding genes. Additionally, B. cereus DBt248 was proved to be devoid of all three hbl genes, three nhe genes or plcR. Thus this strain might be a potential candidate as a host strain for expressing B. thuringiensis crystal toxins to construct safety insecticidal engineering strains without enterotoxic activity.

Toxinogenic Bacillus pumilus and Bacillus licheniformis from mastitic milk

To elucidate the occurrence of heat-stable toxin-producing strains among mastitic Bacillus isolates, 100 milk samples of mastitic cows from different parts of Finland were screened. Bacillus was identified as the major organism in 23 samples. Toxinogenic Bacillus isolates identified by sperm cell motility inhibition assay were isolated from six samples. Four isolates belonged to the species Bacillus pumilus and two to Bacillus licheniformis. The toxic substances were heat-stable and soluble to methanol thus being of non-protein nature. The methanol extracted substances disrupted the sperm cell plasma membrane permeability barrier at exposure concentrations of 1-15 microg ml(-1) (B. pumilus) or 20-30 microg ml(-1) (B. licheniformis). The toxic properties of the two mastitic B. licheniformis strains were similar to those of B. licheniformis strains known to produce the lipopeptide lichenysin A and the synthetase genes lchAA, lchAB and lchAC for lichenysin were found in the mastitic strains by PCR. Toxin synthetase genes for the syntheses of lichenysin or surfactin were searched but not found in the toxic B. pumilus strains. The ribopatterns of the mastitic B. pumilus and B. licheniformis isolates were similar to those of the toxinogenic strains described earlier from food poisoning incidents and contaminated indoor air. B. licheniformis and B. pumilus survive pasteurization and other heat treatments as spores. Toxin-producing strains of these species in the dairy production chain may thus be of food safety concern.

Plant biological warfare: thorns inject pathogenic bacteria into herbivores

Thorns, spines and prickles are among the rich arsenal of antiherbivore defence mechanisms that plants have evolved. Many of these thorns are aposematic, that is, marked by various types of warning coloration. This coloration was recently proposed to deter large herbivores. Yet, the mechanical defence provided by thorns against large herbivores might be only the tip of the iceberg in a much more complicated story. Here we present evidence that thorns harbour an array of pathogenic bacteria that are much more dangerous to herbivores than the painful mechanical wounding by the thorns. Pathogenic bacteria like Clostridium perfringens, the causative agent of the life-threatening gas gangrene, and others, were isolated and identified from date palm (with green-yellow-black aposematic spines) and common hawthorn (with red aposematic thorns). These thorn-inhabiting bacteria have a considerable potential role in antiherbivory, and may have uniquely contributed to the common evolution of aposematism (warning coloration) in thorny plants.

Analysis of pMA67, a predicted rolling-circle replicating, mobilizable, tetracycline-resistance plasmid from the honey bee pathogen, Paenibacillus larvae

This work characterizes a recently discovered natural tetracycline-resistance plasmid called pMA67 from Paenibacillus larvae--a Gram-positive bacterial pathogen of honey bees. We provide evidence that pMA67 replicates by the rolling-circle mechanism, and sequence comparisons place it in the pMV158 family of rolling-circle replicons. The plasmid contains predicted rep, cop, and rnaII genes for control of replication initiating at a predicted double-strand origin. The plasmid has an ssoT single-strand origin, which is efficient enough to allow only very small amounts of the single-stranded DNA intermediate to accumulate. The overall efficiency of replication is sufficient to render the plasmid segregationally stable without selection in P. larvae and in Bacillus megaterium, but not in Escherichia coli. The plasmid is expected to be mobilizable due to the presence of a mob gene and an oriT site. The plasmid contains a tetL gene, whose predicted amino acid sequence implies a relatively ancient divergence from all previously known plasmid-encoded tetL genes. We confirm that the tetL gene alone is sufficient for conferring resistance to tetracyclines. Sequence comparisons, mostly with the well-characterized pMV158, allow us to predict promoters, DNA and RNA secondary structures, DNA and protein motifs, and other elements.

Functional identification of the gene bace16 from nematophagous bacterium Bacillus nematocida

Bacillus nematocida is a Gram-positive bacterium capable of killing nematodes. Our recent studies identified an extracellular serine protease Bace16 in B. nematocida as a candidate of pathogenic factor in the infection against nematodes, which displayed a high similarity with the serine protease family subtilisin BPN', and the MEROPS ID is S08.034. To further confirm the roles that bace16 played in the mechanism of nematocidal pathogenesis, recombinant mature Bace16 (rm-Bace16) was expressed in Escherichia coli strain BL21 using pET-30 vector system. Bioassay experiments demonstrated that the purified recombinant protease had the ability to degrade nematode cuticles and kill nematodes. In addition, a bace16 knockout mutant of B. nematocida constructed by homologous recombination showed considerably lower proteolytic activity and less than 50% nematocidal activity than the wild-type strain. These results confirmed that Bace16 could serve as an important virulence factor during the infectious process.

Empirical support for optimal virulence in a castrating parasite

The trade-off hypothesis for the evolution of virulence predicts that parasite transmission stage production and host exploitation are balanced such that lifetime transmission success (LTS) is maximised. However, the experimental evidence for this prediction is weak, mainly because LTS, which indicates parasite fitness, has been difficult to measure. For castrating parasites, this simple model has been modified to take into account that parasites convert host reproductive resources into transmission stages. Parasites that kill the host too early will hardly benefit from these resources, while postponing the killing of the host results in diminished returns. As predicted from optimality models, a parasite inducing castration should therefore castrate early, but show intermediate levels of virulence, where virulence is measured as time to host killing. We studied virulence in an experimental system where a bacterial parasite castrates its host and produces spores that are not released until after host death. This permits estimating the LTS of the parasite, which can then be related to its virulence. We exposed replicate individual Daphnia magna (Crustacea) of one host clone to the same amount of bacterial spores and followed individuals until their death. We found that the parasite shows strong variation in the time to kill its host and that transmission stage production peaks at an intermediate level of virulence. A further experiment tested for the genetic basis of variation in virulence by comparing survival curves of daphniids infected with parasite spores obtained from early killing versus late killing infections. Hosts infected with early killer spores had a significantly higher death rate as compared to those infected with late killers, indicating that variation in time to death was at least in part caused by genetic differences among parasites. We speculate that the clear peak in lifetime reproductive success at intermediate killing times may be caused by the exceptionally strong physiological trade-off between host and parasite reproduction. This is the first experimental study to demonstrate that the production of propagules is highest at intermediate levels of virulence and that parasite genetic variability is available to drive the evolution of virulence in this system.

A field evaluation of four larval mosquito control methods in urban catch basins

Effective control of mosquitoes in rural Midwestern communities that lack organized mosquito control districts would be aided by baseline data on optimal breeding sites, interannual effects of climate on population emergence and abundance, and efficacy of various control options under field conditions. During 19 surveillance weeks in the summer of 2005, we sampled 100 catch basins each week that were distributed among 10 study zones. Catch basins within each study zone were subjected to 1 of 4 different mosquito control methods or were left untreated. Of the 10 study zones, 5 were in high-intensity urban areas and 5 in low-intensity urban areas. During the study period, treatment of urban catch basins with Altosid XR extended residual briquets resulted in a 69.5% reduction in mosquito larvae numbers. However, the product did not provide sustained treatment for the 120-150 days suggested by the manufacturer. Vectolex WSP, when applied according to manufacturer's suggestions, resulted in a 73.4% reduction in mosquito larvae. VectolexWSP effectiveness was impacted by heavy rainfalls early in the surveillance period. Cleaning catch basins once or twice during the surveillance period resulted in a 40.1% and a 39.9% reduction in mosquito larvae, respectively. Catch basins in high-intensity urban areas comprised 27.7% of the total collection compared to 72.3% from low-intensity urban areas. The AltosidXR extended residual briquets and the VectolexWSP products both impacted the number of mosquito larvae collected. However, a single treatment to control mosquitoes in this study area may not be sufficient. We suggest that treatment of urban catch basins is optimized when accompanied by a comprehensive surveillance plan, and that a combination of treatments or multiple treatments during the season may be necessary to mitigate risks of vector-borne infectious diseases in areas with similar climate and precipitation trends.

Growth characteristics of virulent Bacillus anthracis and potential surrogate strains

The objectives of this study were to compare generation and lag times of virulent Bacillus anthracis strains with those of other Bacillus strains, to identify possible surrogates for growth studies, and to determine if the B. cereus module of the U.S. Department of Agriculture Pathogen Modeling Program (PMP) had predictive value for B. anthracis. Growth characteristics of B. anthracis, B. cereus, B. mycoides, and B. subtilis strains in brain heart infusion broth at pH 6.5, 6.0, and 5.5 were determined by absorbance measurements. Growth curves of B. anthracis Sterne and B. cereus strains appeared similar, and the generation times for strain Sterne fell within the PMP's 95% confidence interval for B. cereus. However, the virulent B. anthracis strains Vollum and Pasteur had shorter generation times than the avirulent Sterne strain and most other surrogates and were lower than the PMP's 95% confidence interval for B. cereus. Growth curves of B. cereus ATCC 9818 and B. subtilis ATCC 6633 were more similar to those of virulent B. anthracis strains, but all potential surrogates had significantly different generation times and lag times under some conditions.

A loop network within the anthrax toxin pore positions the phenylalanine clamp in an active conformation

Heptameric pores formed in the endosomal membrane by the protective antigen moiety of anthrax toxin serve as portals for entry of the enzymatic moieties of the toxin into the cytosol. In the aqueous lumen of each pore is a "Phe clamp," a heptad of narrowly apposed Phe residues (Phe-427), that catalyzes the unfolding and translocation of the enzymatic moieties across the membrane. Here, we provide evidence for a "loop swap" between neighboring protective antigen subunits, which is required for efficient translocation and is mediated by a salt bridge formed between the side chains of Lys-397 and Asp-426. We propose that the interaction between residues 397 and 426 creates a structural framework that positions Phe-427 within the pore lumen, forming a functional Phe clamp and, hence, a translocation-competent pore.

A neutral protease from Bacillus nematocida, another potential virulence factor in the infection against nematodes

A neutral protease (npr) (designated Bae16) toxic to nematodes was purified to homogeneity from the strain Bacillus nematocida. The purified protease showed a molecular mass of approximately 40 kDa and displayed optimal activity at 55 degrees C, pH 6.5. Bioassay experiments demonstrated that this purified protease could destroy the nematode cuticle and its hydrolytic substrates included gelatin and collagen. The gene encoding Bae16 was cloned, and the deduced amino acid sequence showed 94% sequence identity with npr gene from B. amyloliquefaciens, but had low similarity (13-43%) with the previously reported virulence serine proteases from fungi or bacteria, which reflected their differences. Recombinant mature Bae16 (rm-Bae16) was expressed in Escherichia coli BL21 using pET30 vector system, and its nematicidal activity confirmed that Bae16 could be involved in the infection process. Our present study revealed that the npr besides the known alkaline serine protease could serve as a potential virulence factor in the infection against nematodes, furthermore, the two proteases with different characteristics produced by the same strain co-ordinated efforts to kill nematodes. These data helped to understand the interaction between this bacterial pathogen and its host.

Colony-level impacts of immune responsiveness in honey bees, Apis mellifera

Social insects have evolved both communal and individual traits that reduce the impacts of their numerous parasites and pathogens. Among the individual traits, innate-immune responses have the potential to reduce both individual mortality and the spread of pathogens among colony members. An understanding of the costs and benefits of such responses can provide a more complete understanding of a primary risk of social life, horizontal disease transmission among colony members. Here we assess the impacts of individual immunity on colony-level disease in honey bee (Apis mellifera) colonies following exposure to an important bacterial pathogen (Paenibacillus larvae subsp. larvae, cause of the disease American foulbrood). Colony-level disease rates were negatively correlated with the immune responsiveness of colony members, as assessed by larval transcript levels for the gene encoding the antibacterial peptide abaecin. Concomitantly, colonies whose members mounted a stronger abaecin response showed significantly lower productivity, indicating a colony-level cost to this immune response. The results show considerable variation across colonies in an immune trait important for survival, and point toward a significant trade-off between this trait and colony productivity.

[A study of the safety of probiotic bacilli]

The aim of the study was to evaluate the biological safety of a range of probiotic bacilli, ingredients of the commercial preparations biosporin, bactisubtil, and irilis; their biological effects were scrutinized in an animal experiment. The study demonstrated that the strains B. subtilis 3, 07, and B. licheniformis 31, 09, ingredients of biosporin and irilis, unlike B. cereus IP 5832, an ingredient of bactisubtil, were not toxic, toxigenic, or virulent, and did not impair the antitoxic hepatic function, which allows considering them to be safe.

Rapid Ped-2E9 cell-based cytotoxicity analysis and genotyping of Bacillus species

Bacillus species causing food-borne disease produce multiple toxins eliciting gastroenteritis. Toxin assays with mammalian cell cultures are reliable but may take 24 to 72 h to complete and also lack sensitivity. Here, a sensitive and rapid assay was developed using a murine hybridoma Ped-2E9 cell model. Bacillus culture supernatants containing toxins were added to a Ped-2E9 cell line and analyzed for cytotoxicity with an alkaline phosphatase release assay. Most Bacillus cereus strains produced positive cytotoxicity results within 1 h, and data were comparable to those obtained with the standard Chinese hamster ovary (CHO)-based cytotoxicity assay, which took about 72 h to complete. Moreover, the Ped-2E9 cell assay had 25- to 58-fold-higher sensitivity than the CHO assay. Enterotoxin-producing Bacillus thuringiensis also gave positive results with Ped-2E9 cells, while several other Bacillus species were negative. Eight isolates from food suspected of Bacillus contamination were also tested, and only one strain, which was later confirmed as B. cereus, gave a positive result. In comparison with two commercial diarrheal toxin assay kits (BDE-VIA and BCET-RPLA), the Ped-2E9 assay performed more reliably. Toxin fractions of >30 kDa showed the highest degree of cytotoxicity effects, and heat treatment significantly reduced the toxin activity, indicating the involvement of a heat-labile high-molecular-weight component in Ped-2E9 cytotoxicity. PCR results, in most cases, were in agreement with the cytotoxic potential of each strain. Ribotyping was used to identify cultures and indicated differences for several previously reported isolates. This Ped-2E9 cell assay could be used as a rapid (approximately 1-h) alternative to current methods for sensitive detection of enterotoxins from Bacillus species.

Effect of recombinant murine granulocyte colony-stimulating factor with or without fluoroquinolone therapy on mixed-infection abscesses in mice

The aim of the study was to determine if immunomodulation of host defense with recombinant murine granulocyte colony-stimulating factor (G-CSF) improves the efficacy of trovafloxacin or moxifloxacin in abscesses containing Bacillus fragilis ATCC 23745 and different Escherichia coli strains varying in virulence. Treatment of mice inoculated with 10(7) CFU B. fragilis and 10(5) CFU low-virulence E. coli with either trovafloxacin (150 mg/kg/day every 24 hours, days 3 to 7) or moxifloxacin (96 mg/kg/day every 12 hours, days 3 to 7), significantly reduced the number of B. fragilis to 6.9 +/- 0.35 and 5.8 +/- 0.10 and that of E. coli to 4.9 +/- 0.09 and 4.2 +/- 0.07 log CFU/abscess for trovafloxacin and moxifloxacin, respectively, compared to controls (B. fragilis 8.7 and E. coli 7.4 log CFU/abscess) on day 8. Also, moxifloxacin was more potent than trovafloxacin. Addition of G-CSF prophylaxis (1 mug once on day -1) or therapy (1 mug/day on days 3 to 7) to fluoroquinolone treatment did not improve the efficacy of fluoroquinolone therapy alone. The effect of moxifloxacin with or without G-CSF prophylaxis on abscesses with a virulent hemolytic E. coli strain was also studied. In moxifloxacin-treated mice, 75% survived infection compared to 10% of controls. Combining moxifloxacin with G-CSF prophylaxis significantly decreased survival (30%) compared to moxifloxacin alone. In addition, G-CSF prophylaxis resulted in a threefold (E. coli) to 100-fold (B. fragilis) increased outgrowth in the abscesses of surviving mice. In conclusion, the addition of G-CSF to a fluoroquinolone is not advisable since, depending on the virulence of the E. coli strains, this might detrimentally influence the outcome of therapy.

Crystal protein synthesis is dependent on early sporulation gene expression inBacillus sphaericus

Insertional mutations in the spo0A and spoIIAC genes of Bacillus sphaericus 2362 were prepared by conjugation with Escherichia coli using a suicide plasmid containing cloned portions of the target genes. The mutants resembled their Bacillus subtilis counterparts phenotypically and were devoid of crystal proteins as determined by electron microscopy, SDS-PAGE and Western blots. The mutants had greatly reduced toxicity to anopheline mosquito larvae compared to the parental strain. We conclude that crystal protein synthesis in this bacterium is dependent on expression of early sporulation genes.