A comparative study ofBacillus cereus,Bacillus thuringiensis andBacillus anthracis extracellular proteomes

Characterization of diverse lysine acylations in Bacillus thuringiensis: Substrate profiling and functional exploration

Lysine acylation has been extensively investigated due to its regulatory role in a diverse range of biological functions across prokaryotic and eukaryotic species. In-depth acylomic profiles have the potential to enhance comprehension of the biological implications of organisms. However, the extent of research on global acylation profiles in microorganisms is limited. Here, four lysine acylomes were conducted in Bacillus thuringiensis by using the LC-MS/MS based proteomics combined with antibody-enrichment strategies, and a total of 3438 acetylated sites, 5797 propionylated sites, 1705 succinylated sites, and 925 malonylated sites were identified. The motif analysis of these modified proteins revealed a high conservation of glutamate in acetylation and propionylation, whereas such conservation was not observed in succinylation and malonylation modifications. Besides, conservation analysis showed that homologous acylated proteins in Bacillus subtilis and Escherichia coli were connected with ribosome and aminoacyl-tRNA biosynthesis. Further biological experiments showed that lysine acylation lowered the RNA binding ability of CodY and impaired the in vivo protein activity of MetK. In conclusion, our study expanded the current understanding of the global acylation in Bacillus, and the comparative analysis demonstrated that shared acylation proteins could play important roles in regulating both metabolism and RNA transcription progression.

Ectopical expression of bacterial collagen-like protein supports its role as adhesin in host-parasite coevolution

For a profound understanding of antagonistic coevolution, it is necessary to identify the coevolving genes. The bacterium Pasteuria and its host, the microcrustacean Daphnia, are a well-characterized paradigm for co-evolution, but the underlying genes remain largely unknown. A genome-wide association study suggested a Pasteuria collagen-like protein 7 (Pcl7) as a candidate mediating parasite attachment and driving its coevolution with the host. Since Pasteuria ramosa cannot currently be genetically manipulated, we used Bacillus thuringiensis to express a fusion protein of a Pcl7 carboxy-terminus from P. ramosa and the amino-terminal domain of a B. thuringiensis collagen-like protein (CLP). Mutant B. thuringiensis (Pcl7-Bt) spores but not wild-type B. thuringiensis (WT-Bt) spores attached to the same site of susceptible hosts as P. ramosa. Furthermore, Pcl7-Bt spores attached readily to susceptible host genotypes, but only slightly to resistant host genotypes. These findings indicated that the fusion protein was properly expressed and folded and demonstrated that indeed the C-terminus of Pcl7 mediates attachment in a host genotype-specific manner. These results provide strong evidence for the involvement of a CLP in the coevolution of Daphnia and P. ramosa and open new avenues for genetic epidemiological studies of host-parasite interactions.

A small bacteriophage protein determines the hierarchy over co-residential jumbo phage in Bacillus thuringiensis serovar israelensis

Bacillus thuringiensis serovar israelensis is the most widely used biopesticide against insects, including vectors of animal and human diseases. Among several extrachromosomal elements, this endospore-forming entomopathogen harbors two bacteriophages: a linear DNA replicon named GIL01 that does not integrate into the chromosome during lysogeny and a circular-jumbo prophage known as pBtic235. Here, we show that GIL01 hinders the induction of cohabiting prophage pBtic235. The GIL01-encoded small protein, gp7, which interacts with the host LexA repressor, is a global transcription regulator and represses the induction of pBtic235 after DNA damage to presumably allow GIL01 to multiply first. In a complex with host LexA in stressed cells, gp7 down-regulates the expression of more than 250 host and pBtic235 genes, many of which are involved in the cellular functions of genome maintenance, cell-wall transport, and membrane and protein stability. We show that gp7 homologs that are found exclusively in bacteriophages act in a similar fashion to enhance LexA's binding to DNA, while likely also affecting host gene expression. Our results provide evidence that GIL01 influences both its host and its co-resident bacteriophage.

Oral Immune Priming Treatment Alters Microbiome Composition in the Red Flour Beetle Tribolium castaneum

It is now well-established that the microbiome is relevant for many of an organism’s properties and that its composition reacts dynamically to various conditions. The microbiome interacts with host immunity and can play important roles in the defenses against pathogens. In invertebrates, immune priming, that is, improved survival upon secondary exposure to a previously encountered pathogen, can be dependent upon the presence of the gut microbiome. However, it is currently unknown whether the microbiome changes upon priming treatment. We here addressed this question in a well-established model for immune priming, the red flour beetle Tribolium castaneum exposed to the entomopathogenic bacterium Bacillus thuringiensis (Bt). After priming treatments, the microbiota composition of beetle larvae was assessed by deep sequencing of the V1-V2 region of the bacterial 16S rRNA gene. We compared the effect of two established routes of priming treatments in this system: injection priming with heat-killed Bt and oral priming via ingestion of filtered sterilized bacterial spore culture supernatants. For oral priming, we used several strains of Bt known to vary in their ability to induce priming. Our study revealed changes in microbiome composition following the oral priming treatment with two different strains of Bt, only one of which (Bt tenebrionis, Btt) is known to lead to improved survival. In contrast, injection priming treatment with the same bacterial strain did not result in microbiome changes. Combined with the previous results indicating that oral priming with Btt depends on the larval microbiome, this suggests that certain members of the microbiome could be involved in forming an oral priming response in the red flour beetle.

Characterization of strain-specific Bacillus cereus swimming motility and flagella by means of specific antibodies

One of the multiple factors determining the onset of the diarrhoeal disease caused by enteropathogenic Bacillus cereus is the ability of the bacteria to actively move towards the site of infection. This ability depends on flagella, but it also varies widely between different strains. To gain more insights into these strain-specific variations, polyclonal rabbit antisera as well as monoclonal antibodies (mAbs) were generated in this study, which detected recombinant and natural B. cereus flagellin proteins in Western blots as well as in enzyme immunoassays (EIAs). Based on mAb 1A11 and HRP-labelled rabbit serum, a highly specific sandwich EIA was developed. Overall, it could be shown that strain-specific swimming motility correlates with the presence of flagella/flagellin titres obtained in EIAs. Interestingly, mAb 1A11, recognizing an epitope in the N-terminal region of the flagellin protein, proved to inhibit bacterial swimming motility, while the rabbit serum rather decreased growth of selected B. cereus strains. Altogether, powerful tools enabling the in-depth characterization of the strain-specific variations in B. cereus swimming motility were developed.

Extracellular Vesicles in Human Milk

Milk supports the growth and development of infants. An increasing number of mostly recent studies have demonstrated that milk contains a hitherto undescribed component called extracellular vesicles (EVs). This presents questions regarding why milk contains EVs and what their function is. Recently, we showed that EVs in human milk expose tissue factor, the protein that triggers coagulation or blood clotting, and that milk-derived EVs promote coagulation. Because bovine milk, which also contains EVs, completely lacks this coagulant activity, important differences are present in the biological functions of human milk-derived EVs between species. In this review, we will summarize the current knowledge regarding the presence and biochemical composition of milk EVs, their function(s) and potential clinical applications such as in probiotics, and the unique problems that milk EVs encounter in vivo, including survival of the gastrointestinal conditions encountered in the newborn. The main focus of this review will be human milk-derived EVs, but when available, we will also include information regarding non-human milk for comparison.

Massive Integration of Planktonic Cells within a Developing Biofilm

During biofilm growth, the coexistence of planktonic and sessile cells can lead to dynamic exchanges between the two populations. We have monitored the fate of these populations in glass tube assays, where the Bacillus thuringiensis 407 strain produces a floating pellicle. Time-lapse spectrophotometric measurement methods revealed that the planktonic population grew until the pellicle started to be produced. Thereafter, the planktonic population decreased rapidly down to a value close to zero while the biofilm was in continuous growth, showing no dispersal until 120 h of culture. We found that this decrease was induced by the presence of the pellicle, but did not occur when oxygen availability was limited, suggesting that it was independent of cell death or cell sedimentation and that the entire planktonic population has integrated the biofilm. To follow the distribution of recruited planktonic cells within the pellicle, we tagged planktonic cells with GFP and sessile cells with mCherry. Fluorescence binocular microscopy observations revealed that planktonic cells, injected through a 24-h-aged pellicle, were found only in specific areas of the biofilm, where the density of sessile cells was low, showing that spatial heterogeneity can occur between recruited cells and sessile cells in a monospecies biofilm.

The Food Poisoning Toxins of Bacillus cereus

Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.

MogR Is a Ubiquitous Transcriptional Repressor Affecting Motility, Biofilm Formation and Virulence in Bacillus thuringiensis

Flagellar motility is considered an important virulence factor in different pathogenic bacteria. In Listeria monocytogenes the transcriptional repressor MogR regulates motility in a temperature-dependent manner, directly repressing flagellar- and chemotaxis genes. The only other bacteria known to carry a mogR homolog are members of the Bacillus cereus group, which includes motile species such as B. cereus and Bacillus thuringiensis as well as the non-motile species Bacillus anthracis, Bacillus mycoides and Bacillus pseudomycoides. Furthermore, the main motility locus in B. cereus group bacteria, carrying the genes for flagellar synthesis, appears to be more closely related to L. monocytogenes than to Bacillus subtilis, which belongs to a separate phylogenetic group of Bacilli and does not carry a mogR ortholog. Here, we show that in B. thuringiensis, MogR overexpression results in non-motile cells devoid of flagella. Global gene expression profiling showed that 110 genes were differentially regulated by MogR overexpression, including flagellar motility genes, but also genes associated with virulence, stress response and biofilm lifestyle. Accordingly, phenotypic assays showed that MogR also affects cytotoxicity and biofilm formation in B. thuringiensis. Overexpression of a MogR variant mutated in two amino acids within the putative DNA binding domain restored phenotypes to those of an empty vector control. In accordance, introduction of these mutations resulted in complete loss in MogR binding to its candidate flagellar locus target site in vitro. In contrast to L. monocytogenes, MogR appears to be regulated in a growth-phase dependent and temperature-independent manner in B. thuringiensis 407. Interestingly, mogR was found to be conserved also in non-motile B. cereus group species such as B. mycoides and B. pseudomycoides, which both carry major gene deletions in the flagellar motility locus and where in B. pseudomycoides mogR is the only gene retained. Furthermore, mogR is expressed in non-motile B. anthracis. Altogether this provides indications of an expanded set of functions for MogR in B. cereus group species, beyond motility regulation. In conclusion, MogR constitutes a novel B. thuringiensis pleiotropic transcriptional regulator, acting as a repressor of motility genes, and affecting the expression of a variety of additional genes involved in biofilm formation and virulence.

When Appearance Misleads: The Role of the Entomopathogen Surface in the Relationship with Its Host

Currently, potentially harmful insects are controlled mainly by chemical synthetic insecticides, but environmental emergencies strongly require less invasive control techniques. The use of biological insecticides in the form of entomopathogenic organisms is undoubtedly a fundamental resource for the biological control of insect pests in the future. These infectious agents and endogenous parasites generally act by profoundly altering the host's physiology to death, but their success is closely related to the neutralization of the target insect's immune response. In general, entomopathogen parasites, entomopathogenic bacteria, and fungi can counteract immune processes through the effects of secretion/excretion products that interfere with and damage the cells and molecules typical of innate immunity. However, these effects are observed in the later stages of infection, whereas the risk of being recognized and neutralized occurs very early after penetration and involves the pathogen surface components and molecular architecture; therefore, their role becomes crucial, particularly in the earliest pathogenesis. In this review, we analyze the evasion/interference strategies that entomopathogens such as the bacterium Bacillus thuringiensis, fungi, nematocomplexes, and wasps implement in the initial stages of infection, i.e., the phases during which body or cell surfaces play a key role in the interaction with the host receptors responsible for the immunological discrimination between self and non-self. In this regard, these organisms demonstrate evasive abilities ascribed to their body surface and cell wall; it appears that the key process of these mechanisms is the capability to modify the surface, converting it into an immunocompatible structure, or interaction that is more or less specific to host factors.

Rap Protein Paralogs of Bacillus thuringiensis: a Multifunctional and Redundant Regulatory Repertoire for the Control of Collective Functions

Quorum sensing (QS) is a mechanism of synthesis and detection of signaling molecules to regulate gene expression and coordinate behaviors in bacterial populations. In Bacillus subtilis, multiple paralog Rap-Phr QS systems (receptor-signaling peptides) are highly redundant and multifunctional, interconnecting the regulation of differentiation processes such as sporulation and competence. However, their functions in the Bacillus cereus group are largely unknown. We evaluated the functions of Rap proteins in Bacillus thuringiensis Bt8741, which codes for eight Rap-Phr systems; these were individually overexpressed to study their participation in sporulation, biofilm formation, spreading, and extracellular proteolytic activity. Our results show that four Rap-Phr systems (RapC, RapK, RapF, and RapLike) inhibit sporulation, two of which (RapK and RapF) probably dephosphorylate Spo0F from the Spo0A phosphorelay; these two Rap proteins also inhibit biofilm formation. Four systems (RapC, RacF1, RacF2, and RapLike) participate in spreading inhibition; finally, six systems (RapC, -F, -F2, -I, and -I1 and RapLike) decrease extracellular proteolytic activity. We foresee that functions performed by Rap proteins of Bt8741 could also be carried out by Rap homologs in other strains within the B. cereus group. These results indicate that Rap-Phr systems constitute a highly multifunctional and redundant regulatory repertoire that enables B. thuringiensis and other species from the B. cereus group to efficiently regulate collective functions during their life cycle in the face of changing environments.IMPORTANCE The Bacillus cereus group of bacteria includes species of high economic, clinical, biological warfare, and biotechnological interest, e.g., B. anthracis in bioterrorism, B. cereus in food intoxications, and B. thuringiensis in biocontrol. Knowledge about the ecology of these bacteria is hindered by our limited understanding of the regulatory circuits that control differentiation and specialization processes. Here, we uncover the participation of eight Rap quorum-sensing receptors in collective functions of B. thuringiensis These proteins are highly multifunctional and redundant in their functions, linking ecologically relevant processes such as sporulation, biofilm formation, spreading, extracellular proteolytic activity, and probably other functions in species from the B. cereus group.

The signaling peptide PapR is required for the activity of the quorum-sensor PlcRa in Bacillus thuringiensis

The transcriptional regulator PlcR, its cognate cell-cell signaling heptapeptide PapR₇, and the oligopeptide permease OppABCDF, required for PapR₇ import, form a quorum-sensing system that controls the expression of virulence factors in Bacillus cereus and Bacillus thuringiensis species. In B. cereus strain ATCC 14579, the transcriptional regulator PlcRa activates the expression of abrB2 gene, which encodes an AbrB-like transcriptional regulator involved in cysteine biosynthesis. PlcRa is a structural homolog of PlcR: in particular, its C-terminal TPR peptide-binding domain could be similarly arranged as in PlcR. The signaling peptide of PlcRa is not known. As PlcRa is a PlcR-like protein, the cognate PapR₇ peptide (ADLPFEF) is a relevant candidate to act as a signaling peptide for PlcRa activation. Also, the putative PapRa₇ peptide (CSIPYEY), encoded by the papRa gene adjacent to the plcRa gene, is a relevant candidate as addition of synthetic PapRa₇ induces a dose-dependent increase of abrB2 expression. To address the issue of peptide selectivity of PlcRa, the role of PapR and PapRa peptides in PlcRa activity was investigated in B. thuringiensis 407 strain, by genetic and functional complementation analyses. A transcriptional fusion between the promoter of abrB2 and lacZ was used to monitor the PlcRa activity in various genetic backgrounds. We demonstrated that PapR was necessary and sufficient for PlcRa activity. We showed that synthetic PapRs from pherogroups II, III and IV and synthetic PapRa₇ were able to trigger abrB2 expression, suggesting that PlcRa is less selective than PlcR. Lastly, the mode of binding of PlcRa was addressed using an in silico approach. Overall, we report a new role for PapR as a signaling peptide for PlcRa activity and show a functional link between PlcR and PlcRa regulons in B. thuringiensis.

Advanced Proteomics as a Powerful Tool for Studying Toxins of Human Bacterial Pathogens

Exotoxins contribute to the infectious processes of many bacterial pathogens, mainly by causing host tissue damages. The production of exotoxins varies according to the bacterial species. Recent advances in proteomics revealed that pathogenic bacteria are capable of simultaneously producing more than a dozen exotoxins. Interestingly, these toxins may be subject to post-transcriptional modifications in response to environmental conditions. In this review, we give an outline of different bacterial exotoxins and their mechanism of action. We also report how proteomics contributed to immense progress in the study of toxinogenic potential of pathogenic bacteria over the last two decades.

An immunoproteomic approach to identify antigenic proteins in Nocardia farcinica IFM 10152

Nocardia farcinica is the etiological agent of nocardiosis, leading to serious pulmonary or systemic infections. To uncover virulence factors and early diagnostic markers, secreted proteins of N. farcinica IFM 10152 were analyzed using an immunoproteome-based approach. A total of 5 proteins were identified by matrix-assisted laser desorption (MALDI-TOF-MS). Bioinformatic analyses showed that the identified proteins were involved in defense against the host innate immune system and required for pathogenesis. All proteins were expressed in E. coli and antigenicity was analyzed with Western blot. To our knowledge, these proteins with antigenicity were identified for the first time in N. farcinica and they may help elucidate the pathogenesis underlying Nocardia and provide potential future diagnostic markers.

Multifaceted toxin profile, an approach toward a better understanding of probiotic Bacillus cereus

Strains of the Bacillus cereus group have been widely used as probiotics for human beings, food animals, plants, and environmental remediation. Paradoxically, B. cereus is responsible for both gastrointestinal and nongastrointestinal syndromes and represents an important opportunistic food-borne pathogen. Toxicity assessment is a fundamental issue to evaluate safety of probiotics. Here, we summarize the state of our current knowledge about the toxins of B. cereus sensu lato to be considered for safety assessment of probiotic candidates. Surfactin-like emetic toxin (cereulide) and various enterotoxins including nonhemolytic enterotoxin, hemolysin BL, and cytotoxin K are responsible for food poisoning outbreaks characterized by emesis and diarrhea. In addition, other factors, such as hemolysin II, Certhrax, immune inhibitor A1, and sphingomyelinase, contribute to toxicity and overall virulence of B. cereus.

Structural characterization of a pathogenicity-related superoxide dismutase codified by a probably essential gene in Xanthomonas citri subsp. citri

Citrus canker is a plant disease caused by the bacteria Xanthomonas citri subsp. citri that affects all domestic varieties of citrus. Some annotated genes from the X. citri subsp. citri genome are assigned to an interesting class named "pathogenicity, virulence and adaptation". Amongst these is sodM, which encodes for the gene product XcSOD, one of four superoxide dismutase homologs predicted from the genome. SODs are widespread enzymes that play roles in the oxidative stress response, catalyzing the degradation of the deleterious superoxide radical. In Xanthomonas, SOD has been associated with pathogenesis as a counter measure against the plant defense response. In this work we initially present the 1.8 Å crystal structure of XcSOD, a manganese containing superoxide dismutase from Xanthomonas citri subsp. citri. The structure bears all the hallmarks of a dimeric member of the MnSOD family, including the conserved hydrogen-bonding network residues. Despite the apparent gene redundancy, several attempts to obtain a sodM deletion mutant were unsuccessful, suggesting the encoded protein to be essential for bacterial survival. This intriguing observation led us to extend our structural studies to the remaining three SOD homologs, for which comparative models were built. The models imply that X. citri subsp. citri produces an iron-containing SOD which is unlikely to be catalytically active along with two conventional Cu,ZnSODs. Although the latter are expected to possess catalytic activity, we propose they may not be able to replace XcSOD for reasons such as distinct subcellular compartmentalization or differential gene expression in pathogenicity-inducing conditions.

Clostridium acetobutylicum grows vegetatively in a biofilm rich in heteropolysaccharides and cytoplasmic proteins

BACKGROUND

Biofilms are cell communities wherein cells are embedded in a self-produced extracellular polymeric substances (EPS). The biofilm of Clostridium acetobutylicum confers the cells superior phenotypes and has been extensively exploited to produce a variety of liquid biofuels and bulk chemicals. However, little has been known about the physiology of C. acetobutylicum in biofilm as well as the composition and biosynthesis of the EPS. Thus, this study is focused on revealing the cell physiology and EPS composition of C. acetobutylicum biofilm.

RESULTS

Here, we revealed a novel lifestyle of C. acetobutylicum in biofilm: elimination of sporulation and vegetative growth. Extracellular polymeric substances and wire-like structures were also observed in the biofilm. Furthermore, for the first time, the biofilm polysaccharides and proteins were isolated and characterized. The biofilm contained three heteropolysaccharides. The major fraction consisted of predominantly glucose, mannose and aminoglucose. Also, a great variety of proteins including many non-classically secreted proteins moonlighting as adhesins were found considerably present in the biofilm, with GroEL, a S-layer protein and rubrerythrin being the most abundant ones.

CONCLUSIONS

This study evidenced that vegetative C. acetobutylicum cells rather than commonly assumed spore-forming cells were essentially the solvent-forming cells. The abundant non-classically secreted moonlighting proteins might be important for the biofilm formation. This study provides the first physiological and molecular insights into C. acetobutylicum biofilm which should be valuable for understanding and development of the biofilm-based processes.

Two New Secreted Proteases Generate a Casein-Derived Antimicrobial Peptide in Bacillus cereus Food Born Isolate Leading to Bacterial Competition in Milk

Milk and dairy products harbor a wide variety of bacterial species that compete for both limited resources and space. Under these competitive conditions, bacteria develop specialized mechanisms to protect themselves during niche colonization and nutrient acquisition processes. The bacterial antagonism mechanisms include the production of antimicrobial agents or molecules that facilitate competitor dispersal. In the present work, a bacterial strain designated RC6 was isolated from Ricotta and identified as Bacillus cereus. It generates antimicrobial peptide (AMP) when grown in the presence of casein. The AMP was active against several species of Bacillus and Listeria monocytogenes. MALDI-TOF analysis of the RP-HPLC purified fractions and amino acid sequencing revealed a molecular mass of 751 Da comprised of a 6-residue sequence, YPVEPF. BLAST analysis showed that the AMP corresponds to the fractions 114-119 of bovine β-casein and represents the product of a specific proteolysis. Analysis of the purified proteolytic fractions from the B. cereus RC6 culture supernatant indicated that the presence of at least two different endoproteases is crucial for the generation of the AMP. Indeed, we were able to identify two new candidate endoproteases by means of genome sequencing and functional assignment using a 3D structural model and molecular docking of misannotated hypothetical proteins. In this light, the capacity of B. cereus RC6 to generate antimicrobial peptides from casein, through the production of extracellular enzymes, presents a new model of antagonistic competition leading to niche colonization. Hence, as a dairy product contaminant, this strategy may enable proteolytic B. cereus RC6 niche specialization in milk matrices.

Plant Polyphenols Stimulate Adhesion to Intestinal Mucosa and Induce Proteome Changes in the Probiotic Lactobacillus acidophilus NCFM

SCOPE

Plant phenolics, known to exert beneficial effects on human health, were supplemented to cultures of the probiotic bacterium Lactobacillus acidophilus NCFM (NCFM) to assess their effect on its adhesive capacity and the abundancy of individual proteins.

METHODS AND RESULTS

The presence of resveratrol and ferulic acid during bacterial growth stimulated adhesion of NCFM to mucin and human intestinal HT-29 cells, while tannic acid improved adhesion only to HT-29 cells and caffeic acid had very modest effect overall. Some dosage dependence was found for the four phenolics supplemented at 100, 250, and 500 μg mL^-1 to the cultures. Notably, 500 μg mL^-1 ferulic acid only stimulated adhesion to mucin. Analyses of differential whole-cell as well as surface proteomes revealed relative abundancy changes for a total of 27 and 22 NCFM proteins, respectively. These changes include enzymes acting in metabolic pathways, such as glycolysis, nucleotide metabolism, and stress response, as well as known moonlighting or surface-associated proteins.

CONCLUSION

The five plant phenolics found in various foods stimulate the adhesive capacity of NCFM in diverse ways and elicit relative abundancy changes of specific proteins, providing molecular level insight into the mechanism of the putative beneficial effects of the polyphenols.

RNA-Seq Analysis of Antibiotic-Producing Bacillus subtilis SC-8 Reveals a Role for Small Peptides in Controlling PapR Signaling

Bacillus subtilis SC-8 (BSSC8) shows a narrow antimicrobial activity against the Bacillus cereus group. Previously, B. cereus-derived PapR as a signal peptide to stimulate PlcR, which plays a significant role in regulating the transcription of virulence factors, was assumed to stimulate antibiotic production in BSSC8. To better understand the functional role of PapR in the antibiotic production of BSSC8 and the interspecies interaction, the global transcriptomic profiling of BSSC8 was investigated using RNA-Seq in this study. Small peptides derived from B. cereus wild type (WTBC) and a papR-deleted mutant strain (MTBC) were individually supplied to BSSC8 cultures, and changes in global transcription levels were compared by RNA-Seq. In the presence of WTBC small peptides, more genes (80.9%) were significantly upregulated than in cells exposed to MTBC small peptides. Specifically, 48.8 and 83.4% of genes involved in glycolysis and the TCA cycle, respectively, showed changes in transcription levels in response to small peptides from both strains. Of the genes showing the alterations, 35.0% (glycolysis) and 60.0% (TCA cycle) of transcripts were significantly regulated only in response to WTBC-derived small peptides. Furthermore, the expression of biosynthetic genes encoding several known antibiotics in BSSC8 was further decreased in response to WTBC small peptides.

The CodY-dependent clhAB2 operon is involved in cell shape, chaining and autolysis in Bacillus cereus ATCC 14579

The Gram-positive pathogen Bacillus cereus is able to grow in chains of rod-shaped cells, but the regulation of chaining remains largely unknown. Here, we observe that glucose-grown cells of B. cereus ATCC 14579 form longer chains than those grown in the absence of glucose during the late exponential and transition growth phases, and identify that the clhAB₂ operon is required for this chain lengthening phenotype. The clhAB₂ operon is specific to the B. cereus group (i.e., B. thuringiensis, B. anthracis and B. cereus) and encodes two membrane proteins of unknown function, which are homologous to the Staphylococcus aureus CidA and CidB proteins involved in cell death control within glucose-grown cells. A deletion mutant (ΔclhAB₂) was constructed and our quantitative image analyses show that ΔclhAB₂ cells formed abnormal short chains regardless of the presence of glucose. We also found that glucose-grown cells of ΔclhAB₂ were significantly wider than wild-type cells (1.47 μm ±CI_95% 0.04 vs 1.19 μm ±CI_95% 0.03, respectively), suggesting an alteration of the bacterial cell wall. Remarkably, ΔclhAB₂ cells showed accelerated autolysis under autolysis-inducing conditions, compared to wild-type cells. Overall, our data suggest that the B. cereus clhAB₂ operon modulates peptidoglycan hydrolase activity, which is required for proper cell shape and chain length during cell growth, and down-regulates autolysin activity. Lastly, we studied the transcription of clhAB₂ using a lacZ transcriptional reporter in wild-type, ccpA and codY deletion-mutant strains. We found that the global transcriptional regulatory protein CodY is required for the basal level of clhAB₂ expression under all conditions tested, including the transition growth phase while CcpA, the major global carbon regulator, is needed for the high-level expression of clhAB₂ in glucose-grown cells.

Mucin- and carbohydrate-stimulated adhesion and subproteome changes of the probiotic bacterium Lactobacillus acidophilus NCFM

Adhesion to intestinal mucosa is a crucial property for probiotic bacteria. Adhesion is thought to increase host-bacterial interactions, thus potentially enabling health benefits to the host. Molecular events connected with adhesion and surface proteome changes were investigated for the probiotic Lactobacillus acidophilus NCFM cultured with established or emerging prebiotic carbohydrates as carbon source and in the presence of mucin, the glycoprotein of the epithelial mucus layer. Variation in adhesion to HT29-cells and mucin was associated with carbon source and mucin-induced subproteome abundancy differences. Specifically, while growth on fructooligosaccharides (FOS) only stimulated adhesion to intestinal HT-29 cells, cellobiose and polydextrose in addition increased adhesion to mucin. Adhesion to HT-29 cells increased by about 2-fold for bacteria grown on mucin-supplemented glucose. Comparative 2DE-MS surface proteome analysis showed different proteins in energy metabolism appearing on the surface, suggesting they exert moonlighting functions. Mucin-supplemented bacteria had relative abundance of pyruvate kinase and fructose-bisphosphate aldolase increased by about 2-fold while six spots with 3.2-2.1 fold reduced relative abundance comprised elongation factor G, phosphoglycerate kinase, BipAEFTU family GTP-binding protein, ribonucleoside triphosphate reductase, adenylosuccinate synthetase, 30S ribosomal protein S1, and manganese-dependent inorganic pyrophosphatase. Surface proteome of cellobiose- compared to glucose-grown L. acidophilus NCFM had phosphate starvation inducible protein stress-related, thermostable pullulanase, and elongation factor G increasing 4.4-2.4 fold, while GAPDH, elongation factor Ts, and pyruvate kinase were reduced by 2.0-1.5 fold in relative abundance. Addition of recombinant L. acidophilus NCFM elongation factor G and pyruvate kinase to a coated mucin layer significantly suppressed subsequent adhesion of the bacterium.

BIOLOGICAL SIGNIFICANCE

Human diet is important for intestinal health and food components, especially non-digestible carbohydrates can beneficially modify the microbiota. In the present study, effects of emerging and established prebiotic carbohydrates on the probiotic potential of Lactobacillus acidophilus NCFM were investigated by testing adhesion to a mucin layer and intestinal cells, and comparing this with changes in abundancy of surface proteins thought to be important for host interactions. Increased adhesion was observed following culturing of the bacterium with fructooligosaccharides, cellobiose or polydextrose, as well as mucin-supplemented glucose as carbon source. Enhanced adhesion ability can prolong bacterial residence in GIT yielding positive health effects. Higher relative abundance of certain surface proteins under various conditions (i.e. grown on cellobiose or mucin-supplemented glucose) suggested involvement of these proteins in adhesion, as confirmed by competition in case of two recombinantly produced moonlighting proteins. Combination of Lactobacillus acidophilus NCFM with different carbohydrates revealed potential bacterial determinants of synbiotic interactions, including stimulation of adhesion.

The naringenin-induced exoproteome of Rhizobium etli CE3

Flavonoids excreted by legume roots induce the expression of symbiotically essential nodulation (nod) genes in rhizobia, as well as that of specific protein export systems. In the bean microsymbiont Rhizobium etli CE3, nod genes are induced by the flavonoid naringenin. In this study, we identified 693 proteins in the exoproteome of strain CE3 grown in minimal medium with or without naringenin, with 101 and 100 exoproteins being exclusive to these conditions, respectively. Four hundred ninety-two (71%) of the extracellular proteins were found in both cultures. Of the total exoproteins identified, nearly 35% were also present in the intracellular proteome of R. etli bacteroids, 27% had N-terminal signal sequences and a significant number had previously demonstrated or possible novel roles in symbiosis, including bacterial cell surface modification, adhesins, proteins classified as MAMPs (microbe-associated molecular patterns), such as flagellin and EF-Tu, and several normally cytoplasmic proteins as Ndk and glycolytic enzymes, which are known to have extracellular "moonlighting" roles in bacteria that interact with eukaryotic cells. It is noteworthy that the transmembrane ß (1,2) glucan biosynthesis protein NdvB, an essential symbiotic protein in rhizobia, was found in the R. etli naringenin-induced exoproteome. In addition, potential binding sites for two nod-gene transcriptional regulators (NodD) occurred somewhat more frequently in the promoters of genes encoding naringenin-induced exoproteins in comparison to those ofexoproteins found in the control condition.

FlhF Is Required for Swarming Motility and Full Pathogenicity of Bacillus cereus

Besides sporulation, Bacillus cereus can undergo a differentiation process in which short swimmer cells become elongated and hyperflagellated swarmer cells that favor migration of the bacterial community on a surface. The functionally enigmatic flagellar protein FlhF, which is the third paralog of the signal recognition particle (SRP) GTPases Ffh and FtsY, is required for swarming in many bacteria. Previous data showed that FlhF is involved in the control of the number and positioning of flagella in B. cereus. In this study, in silico analysis of B. cereus FlhF revealed that this protein presents conserved domains that are typical of SRPs in many organisms and a peculiar N-terminal basic domain. By proteomic analysis, a significant effect of FlhF depletion on the amount of secreted proteins was found with some proteins increased (e.g., B component of the non-hemolytic enterotoxin, cereolysin O, enolase) and others reduced (e.g., flagellin, L₂ component of hemolysin BL, bacillolysin, sphingomyelinase, PC-PLC, PI-PLC, cytotoxin K) in the extracellular proteome of a ΔflhF mutant. Deprivation of FlhF also resulted in significant attenuation in the pathogenicity of this strain in an experimental model of infection in Galleria mellonella larvae. Our work highlights the multifunctional role of FlhF in B. cereus, being this protein involved in bacterial flagellation, swarming, protein secretion, and pathogenicity.

Differential proteome and cellular adhesion analyses of the probiotic bacterium Lactobacillus acidophilus NCFM grown on raffinose - an emerging prebiotic

Whole cell and surface proteomes were analyzed together with adhesive properties of the probiotic bacterium Lactobacillus acidophilus NCFM (NCFM) grown on the emerging prebiotic raffinose, exemplifying a synbiotic. Adhesion of NCFM to mucin and intestinal HT-29 cells increased three-fold after culture with raffinose versus glucose, as also visualized by scanning electron microscopy. Comparative proteomics using 2D-DIGE showed 43 unique proteins to change in relative abundance in whole cell lysates from NCFM grown on raffinose compared to glucose. Furthermore, 14 unique proteins in 18 spots of the surface subproteome underwent changes identified by differential 2DE, including elongation factor G, thermostable pullulanase, and phosphate starvation inducible stress-related protein increasing in a range of +2.1 - +4.7 fold. By contrast five known moonlighting proteins decreased in relative abundance by up to -2.4 fold. Enzymes involved in raffinose catabolism were elevated in the whole cell proteome; α-galactosidase (+13.9 fold); sucrose phosphorylase (+5.4 fold) together with metabolic enzymes from the Leloir pathway for galactose utilization and the glycolysis; β-galactosidase (+5.7 fold); galactose (+2.9/+3.1 fold) and fructose (+2.8 fold) kinases. The insights at the molecular and cellular levels contributed to the understanding of the interplay of a synbiotic composed of NCFM and raffinose with the host.

Cytotoxic Potential of Bacillus cereus Strains ATCC 11778 and 14579 Against Human Lung Epithelial Cells Under Microaerobic Growth Conditions

Bacillus cereus, a food poisoning bacterium closely related to Bacillus anthracis, secretes a multitude of virulence factors including enterotoxins, hemolysins, and phospholipases. However, the majority of the in vitro experiments evaluating the cytotoxic potential of B. cereus were carried out in the conditions of aeration, and the impact of the oxygen limitation in conditions encountered by the microbe in natural environment such as gastrointestinal tract remains poorly understood. This research reports comparative analysis of ATCC strains 11778 (BC1) and 14579 (BC2) in aerobic and microaerobic (static) cultures with regard to their toxicity for human lung epithelial cells. We showed that BC1 increased its toxicity upon oxygen limitation while BC2 was highly cytotoxic in both growth conditions. The combined effect of the pore-forming, cholesterol-dependent hemolysin, cereolysin O (CLO), and metabolic product(s) such as succinate produced in microaerobic conditions provided substantial contribution to the toxicity of BC1 but not BC2 which relied mainly on other toxins. This mechanism is shared between CB1 and B. anthracis. It involves the permeabilization of the cell membrane which facilitates transport of toxic bacterial metabolites into the cell. The toxicity of BC1 was potentiated in the presence of bovine serum albumin which appeared to serve as reservoir for bacteria-derived nitric oxide participating in the downstream production of reactive oxidizing species with the properties of peroxynitrite. In agreement with this the BC1 cultures demonstrated the increased oxidation of the indicator dye Amplex Red catalyzed by peroxidase as well as the increased toxicity in the presence of externally added ascorbic acid.

A novel metalloproteinase virulence factor is involved in Bacillus thuringiensis pathogenesis in nematodes and insects

The Gram-positive soil bacterium Bacillus thuringiensis has been developed as the leading microbial insecticide for years. The pathogenesis of B. thuringiensis requires common extracellular factors that depend on the PlcR regulon, which regulates a large number of virulence factors; however, the precise role of many of these proteins is not known. In this study, we describe the complete lifecycle of a nematicidal B. thuringiensis strain in the free living nematode Caenorhabditis elegans using in vitro and in vivo molecular techniques to follow host and bacterial effectors during the infection process. We then focus on the metalloproteinase ColB, a collagenase, which was found highly important for destruction of the intestine thereby facilitates the adaptation and colonization of B. thuringiensis in C. elegans. In vivo green fluorescent protein (GFP) reporter-gene studies showed that ColB expression is highly induced and regulated by the global activator PlcR. Finally, we demonstrated that ColB also takes part in B. thuringiensis virulence in an insect model following injection and oral infection. Indeed, addition of purified ColB accelerates the action of Cry toxin proteins in insects, too. These results give novel insights into host adaptation for B. thuringiensis and other B. cereus group bacteria and highlight the role of collagenase metalloproteases to synergize infection process.

From genome to toxicity: a combinatory approach highlights the complexity of enterotoxin production in Bacillus cereus

In recent years Bacillus cereus has gained increasing importance as a food poisoning pathogen. It is the eponymous member of the B. cereus sensu lato group that consists of eight closely related species showing impressive diversity of their pathogenicity. The high variability of cytotoxicity and the complex regulatory network of enterotoxin expression have complicated efforts to predict the toxic potential of new B. cereus isolates. In this study, comprehensive analyses of enterotoxin gene sequences, transcription, toxin secretion and cytotoxicity were performed. For the first time, these parameters were compared in a whole set of B. cereus strains representing isolates of different origin (food or food poisoning outbreaks) and of different toxic potential (enteropathogenic and apathogenic) to elucidate potential starting points of strain-specific differential toxicity. While toxin gene sequences were highly conserved and did not allow for differentiation between high and low toxicity strains, comparison of nheB and hblD enterotoxin gene transcription and Nhe and Hbl protein titers revealed not only strain-specific differences but also incongruence between toxin gene transcripts and toxin protein levels. With one exception all strains showed comparable capability of protein secretion and so far, no secretion patterns specific for high and low toxicity strains were identified. These results indicate that enterotoxin expression is more complex than expected, possibly involving the orchestrated interplay of different transcriptional regulator proteins, as well as posttranscriptional and posttranslational regulatory mechanisms plus additional influences of environmental conditions.

Molecular engineering of secretory machinery components for high-level secretion of proteins in Bacillus species

Secretory expression of valuable enzymes by Bacillus subtilis and its related species has attracted intensive work over the past three decades. Although many proteins have been expressed and secreted, the titers of some recombinant enzymes are still low to meet the needs of practical applications. Signal peptides that located at the N-terminal of nascent peptide chains play crucial roles in the secretion process. In this mini-review, we summarize recent progress in secretory expression of recombinant proteins in Bacillus species. In particular, we highlighted and discussed the advances in molecular engineering of secretory machinery components, construction of signal sequence libraries and identification of functional signal peptides with high-throughput screening strategy. The prospects of future research are also proposed.

Isolation and characterization of flagellar filaments from Bacillus cereus ATCC 14579

Isolated flagellar filaments from the type strain of Bacillus cereus, ATCC 14579, were shown to consist of 34, 32 and 31 kDa proteins in similar proportions as judged by band intensities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequences of these three proteins of strain ATCC 14579 were identical with the deduced sequences of three flagellin genes BC1657, BC1658 and BC1659 in the whole genome sequence. Strain ATCC 14579 was classified into serotype T2 by a flagellar serotyping scheme for B. cereus strains that are untypeable into known flagellar serotypes H1 to H23. Flagellar filaments from a reference strain of serotype T2 contained two protein bands at 34 and 32 kDa, but a single protein band at 39 kDa was detected in flagellar filaments of a reference strain of serotype H1. Two murine monoclonal antibodies, 1A5 and 2A5, which recognize both the 34 and 32 kDa flagellins and a single flagellin of 32 kDa, respectively, were specifically reactive with B. cereus strains ATCC 14579 and serotype T2 in whole-cell ELISA and bacterial motility inhibition tests. In immunoelectron microscopy with monoclonal antibodies 1A5 and 2A5, colloidal gold spheres were shown to localize almost evenly over the entire part of flagellar filaments. Since strain ATCC 14579, and presumably strain serotype T2, are unusual among B. cereus strains in possessing multiple genes that encode flagellin subunits, a possible unique mechanism may contribute to assembly of multiple flagellin subunits into the filament over its entire length.

SecDF as part of the Sec-translocase facilitates efficient secretion of Bacillus cereus toxins and cell wall-associated proteins

The aim of this study was to explore the role of SecDF in protein secretion in Bacillus cereus ATCC 14579 by in-depth characterization of a markerless secDF knock out mutant. Deletion of secDF resulted in pleiotropic effects characterized by a moderately slower growth rate, aberrant cell morphology, enhanced susceptibility to xenobiotics, reduced virulence and motility. Most toxins, including food poisoning-associated enterotoxins Nhe, Hbl, and cytotoxin K, as well as phospholipase C were less abundant in the secretome of the ΔsecDF mutant as determined by label-free mass spectrometry. Global transcriptome studies revealed profound transcriptional changes upon deletion of secDF indicating cell envelope stress. Interestingly, the addition of glucose enhanced the described phenotypes. This study shows that SecDF is an important part of the Sec-translocase mediating efficient secretion of virulence factors in the Gram-positive opportunistic pathogen B. cereus, and further supports the notion that B. cereus enterotoxins are secreted by the Sec-system.

Identification of stringent response-related and potential serological proteins released from Bacillus anthracis overexpressing the RelA/SpoT homolog, Rsh Bant

RelA and SpoT synthesize ppGpp, a key effector molecule that facilitates the adaptation of bacteria to nutrient starvation and other stresses, known as the stringent response. To investigate the role of Rsh Bant , a putative RelA/SpoT homolog (encoded by BAS4302) in Bacillus anthracis, we examined the alteration of the secretome profiles after the overexpression of a functional His-Rsh Bant protein in the B. anthracis strain Sterne at the stationary growth phase. In the ppGpp-deficient E. coli mutant strain CF1693, overexpression of Rsh Bant restored a ppGpp-dependent growth defect on minimal glucose media. The secretome profiles obtained using a two-dimensional electrophoresis (2-DE) analysis were altered by overexpression of Rsh Bant in B. anthracis. Among the 66 protein spots differentially expressed >1.5-fold, the 29 proteins were abundant for further identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Functional categorization of those proteins implicated their involvement in various biological activities. Taken together, our results imply that overexpression of a functional His-Rsh Bant can lead to the increased levels of intracellular ppGpp in B. anthracis, resulting in the significant changes in its secretome profiling. The stringent response-controlled proteins identified are likely useful as potential targets for serodiagnostic applications.

Selenium effects on the metabolism of a Se-metabolizingLactobacillus reuteri: analysis of envelope-enriched and extracellular proteomes

Fixation of selenium byLactobacillus reuteriLb2 BM DSM 16143 into secreted proteins as selenocysteine.

in silico identification of cross affinity towards Cry1Ac pesticidal protein with receptor enzyme in Bos taurus and sequence, structure analysis of crystal proteins for stability

Any novel protein introduced into the GM crops need to be evaluated for cross affinity on living organisms. Many researchers are currently focusing on the impact of Bacillus thuringiensis cotton on soil and microbial diversity by field experiments. In spite of this, in silico approach might be helpful to elucidate the impact of cry genes. The crystal a protein which was produced by Bt at the time of sporulation has been used as a biological pesticide to target the insectivorous pests like Cry1Ac for Helicoverpa armigera and Cry2Ab for Spodoptera sp. and Heliothis sp. Here, we present the comprehensive in silico analysis of Cry1Ac and Cry2Ab proteins with available in silico tools, databases and docking servers. Molecular docking of Cry1Ac with procarboxypeptidase from Helicoverpa armigera and Cry1Ac with Leucine aminopeptidase from Bos taurus has showed the 125^th amino acid position to be the preference site of Cry1Ac protein. The structures were compared with each other and it showed 5% of similarity. The cross affinity of this toxin that have confirmed the earlier reports of ill effects of Bt cotton consumed by cattle.

Exoproteomics: exploring the world around biological systems

The term 'exoproteome' describes the protein content that can be found in the extracellular proximity of a given biological system. These proteins arise from cellular secretion, other protein export mechanisms or cell lysis, but only the most stable proteins in this environment will remain in abundance. It has been shown that these proteins reflect the physiological state of the cells in a given condition and are indicators of how living systems interact with their environments. High-throughput proteomic approaches based on a shotgun strategy, and high-resolution mass spectrometers, have modified the authors' view of exoproteomes. In the present review, the authors describe how these new approaches should be exploited to obtain the maximum useful information from a sample, whatever its origin. The methodologies used for studying secretion from model cell lines derived from eukaryotic, multicellular organisms, virulence determinants of pathogens and environmental bacteria and their relationships with their habitats are illustrated with several examples. The implication of such data, in terms of proteogenomics and the discovery of novel protein functions, is discussed.

Complex formation between NheB and NheC is necessary to induce cytotoxic activity by the three-component Bacillus cereus Nhe enterotoxin

The nonhemolytic enterotoxin (Nhe) is known as a major pathogenicity factor for the diarrheal type of food poisoning caused by Bacillus cereus. The Nhe complex consists of NheA, NheB and NheC, all of them required to reach maximum cytotoxicity following a specific binding order on cell membranes. Here we show that complexes, formed between NheB and NheC under natural conditions before targeting the host cells, are essential for toxicity in Vero cells. To enable detection of NheC and its interaction with NheB, monoclonal antibodies against NheC were established and characterized. The antibodies allowed detection of recombinant NheC in a sandwich immunoassay at levels below 10 ng ml⁻¹, but no or only minor amounts of NheC were detectable in natural culture supernatants of B. cereus strains. When NheB- and NheC-specific monoclonal antibodies were combined in a sandwich immunoassay, complexes between NheB and NheC could be demonstrated. The level of these complexes was directly correlated with the relative concentrations of NheB and NheC. Toxicity, however, showed a bell-shaped dose-response curve with a plateau at ratios of NheB and NheC between 50:1 and 5:1. Both lower and higher ratios between NheB and NheC strongly reduced cytotoxicity. When the ratio approached an equimolar ratio, complex formation reached its maximum resulting in decreased binding of NheB to Vero cells. These data indicate that a defined level of NheB-NheC complexes as well as a sufficient amount of free NheB is necessary for efficient cell binding and toxicity. Altogether, the results of this study provide evidence that the interaction of NheB and NheC is a balanced process, necessary to induce, but also able to limit the toxic action of Nhe.

Microbial proteomics using mass spectrometry

Proteomic analyses involve a series of intricate, interdependent steps involving approaches and technical issues that must be fully coordinated to obtain the optimal amount of required information about the test subject. Fortunately, many of these steps are common to most test subjects, requiring only modifications to or, in some cases, substitution of some of the steps to ensure they are relevant to the desired objective of a study. This fortunate occurrence creates an essential core of proteomic approaches and techniques that are consistently available for most studies, regardless of test subject. In this chapter, an overview of some of these core approaches, techniques, and mass spectrometric instrumentation is given, while indicating how such steps are useful for and applied to bacterial investigations. To exemplify how such proteomic concepts and techniques are applicable to bacterial investigations, a practical, quantitative method useful for bacterial proteomic analysis is presented with a discussion of possibilities, pitfalls, and some emerging technology to provide a compilation of information from the diverse literature that is intermingled with experimental experience.

Proteomic analysis of Bacillus thuringiensis ΔphaC mutant BMB171/PHB(-1) reveals that the PHB synthetic pathway warrants normal carbon metabolism

A phaC knockout mutant from Bacillus thuringiensis (Bt) strain BMB171, named BMB171/PHB(-1), was constructed. A physiological and metabolic investigation and a proteomic analysis were conducted for both ΔphaC mutant and its parent strain. Grown in peptone medium with 5 gram glucose per liter as sole carbon source, BMB171/PHB(-1) produced various organic acids. Here the excreted pyruvate, citrate, lactate, acetate and glutamate were quantitatively analyzed. Deletion of phaC gene from the BMB171 strain resulted in 1) growth delay; 2) higher consumption of dioxigen but lower cell yield; 3) stagnation of pH movement; 4) overproduction of organic acids; 5) rapid descent of cell density in the stationary phase; and 6) a sporulation-deficient phenotype. Our proteomic study with qPCR reconfirmation reveals that the absence of PhaC led to a metabolic turmoil which showed repressed glycolysis, and over-expressed TCA cycle, various futile pathways and amino acid synthesis during vegetative growth. It is thus thought that B. thuringiensis BMB171 effectively regulated its carbon metabolism upon the presence of the functional PHB synthetic pathway. The presence of this pathway warrants a PHB-producing bacterium better surviving under different environmental conditions.

Proteomic analysis of Bacillus thuringiensis at different growth phases by using an automated online two-dimensional liquid chromatography-tandem mass spectrometry strategy

The proteome of a new Bacillus thuringiensis subsp. kurstaki strain, 4.0718, from the middle vegetative (T(1)), early sporulation (T(2)), and late sporulation (T(3)) phases was analyzed using an integrated liquid chromatography (LC)-based protein identification system. The system comprised two-dimensional (2D) LC coupled with nanoscale electrospray ionization (ESI) tandem mass spectrometry (MS/MS) on a high-resolution hybrid mass spectrometer with an automated data analysis system. After deletion of redundant proteins from the different batches and B. thuringiensis subspecies, 918, 703, and 778 proteins were identified in the respective three phases. Their molecular masses ranged from 4.6 Da to 477.4 Da, and their isoelectric points ranged from 4.01 to 11.84. Function clustering revealed that most of the proteins in the three phases were functional metabolic proteins, followed by proteins participating in cell processes. Small molecular and macromolecular metabolic proteins were further classified according to the Kyoto Encyclopedia of Genes and Genome and BioCyc metabolic pathway database. Three protoxins (Cry2Aa, Cry1Aa, and Cry1Ac) as well as a series of potential intracellular active factors were detected. Many significant proteins related to spore and crystal formation, including sporulation proteins, help proteins, chaperones, and so on, were identified. The expression patterns of two identified proteins, CotJc and glutamine synthetase, were validated by Western blot analysis, which further confirmed the MS results. This study is the first to use shotgun technology to research the proteome of B. thuringiensis. Valuable experimental data are provided regarding the methodology of analyzing the B. thuringiensis proteome (which can be used to produce insecticidal crystal proteins) and have been added to the related protein database.

Proteomic analysis of Bacillus thuringiensis strain 4.0718 at different growth phases

The growth process of Bacillus thuringiensis Bt4.0718 strain was studied using proteomic technologies. The proteins of Bt whole cells at three phases—middle vegetative, early sporulation, and late sporulation—were extracted with lysis buffer, followed with separation by 2-DE and identified by MALDI-TOF/TOF MS. Bioactive factors such as insecticidal crystal proteins (ICPs) including Cry1Ac(3), Cry2Aa, and BTRX28, immune inhibitor (InhA), and InhA precursor were identified. InhA started to express at the middle vegetative phase, suggesting its contribution to the survival of Bt in the host body. At the early sporulation phase, ICPs started their expression. CotJC, OppA, ORF1, and SpoIVA related to the formation of crystals and spores were identified, the expression characteristics of which ensured the stable formation of crystals and spores. This study provides an important foundation for further exploration of the stable expression of ICPs, the smooth formation of crystals, and the construction of recombinant strains.

Macroevolutionary Immunology: A Role for Immunity in the Diversification of Animal life

An emerging picture of the nature of immune systems across animal phyla reveals both conservatism of some features and the appearance among and within phyla of novel, lineage-specific defense solutions. The latter collectively represent a major and underappreciated form of animal diversity. Factors influencing this macroevolutionary (above the species level) pattern of novelty are considered and include adoption of different life styles, life histories, and body plans; a general advantage of being distinctive with respect to immune defenses; and the responses required to cope with parasites, many of which afflict hosts in a lineage-specific manner. This large-scale pattern of novelty implies that immunological phenomena can affect microevolutionary processes (at the population level within species) that can eventually lead to macroevolutionary events such as speciation, radiations, or extinctions. Immunologically based phenomena play a role in favoring intraspecific diversification, specialization and host specificity of parasites, and mechanisms are discussed whereby this could lead to parasite speciation. Host switching - the acquisition of new host species by parasites - is a major mechanism that drives parasite diversity and is frequently involved in disease emergence. It is also one that can be favored by reductions in immune competence of new hosts. Mechanisms involving immune phenomena favoring intraspecific diversification and speciation of host species are also discussed. A macroevolutionary perspective on immunology is invaluable in today's world, including the need to study a broader range of species with distinctive immune systems. Many of these species are faced with extinction, another macroevolutionary process influenced by immune phenomena.