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Fen peatlands are specific wetland ecosystems containing high soil organic carbon (SOC). There is a general lack of knowledge about the microbial communities that abound in these systems. We examined the microbial activity and community... more
Fen peatlands are specific wetland ecosystems containing high soil organic carbon (SOC). There is a general lack of knowledge about the microbial communities that abound in these systems. We examined the microbial activity and community structure in two fen soils differing in SOC content sampled from the Ljubljana Marsh under different seasonal conditions. Substrate-induced respiration and dehydrogenase activity were used
Research Interests: Diversity, Biomass, Microbial Population Biology, Biological Sciences, Seasonality, and 15 moreEnvironmental Sciences, Members, Community Structure, Reduction, Microbial Activity, Fen, Performance Comparison, Marsh, Organic Matter, Microbial Community Structure, Peat Soil, Environments, Microbial community, Nitrogen mineralization, and bacterial community
Negative controls play an important role in the regulation of differentiation in many organisms. Sporulation in Bacillus subtilis is also regulated by DNA-binding proteins which exert a repressive effect on genes which are essential for... more
Negative controls play an important role in the regulation of differentiation in many organisms. Sporulation in Bacillus subtilis is also regulated by DNA-binding proteins which exert a repressive effect on genes which are essential for this process. AbrB represses spo0H, coding for sigma H. One of the earliest events in the initiation of sporulation is the lifting of this repression so that more sigma H can be made. As part of an RNA polymerase holoenzyme, this positive transcription factor is responsible for the elevated synthesis of sufficient phosphorylated Spo0A to activate the expression of several stage II genes. Sin, another DNA-binding protein, represses the same genes, spoIIA, spoIIE and spoIIG, that are activated by Spo0A. Thus sporulation is controlled at the two earliest stages by at least two repressors. Sin and AbrB are repressors of other late growth functions but are essential for competence development. Sin is also a positive regulator for motility and autolysin production. These results suggest that AbrB and Sin act as developmental switches, enabling cells at the beginning of stationary growth to choose different developmental fates.
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Probiotic bacteria represent an alternative for controlling foodborne disease caused by Salmonella enterica , which constitutes a serious concern during food production due to its antibiotic resistance and resilience to environmental... more
Probiotic bacteria represent an alternative for controlling foodborne disease caused by Salmonella enterica , which constitutes a serious concern during food production due to its antibiotic resistance and resilience to environmental stress. Bacillus subtilis is gaining popularity as a probiotic, but its behavior in biofilms with pathogens such as Salmonella remains to be elucidated. Here, we show that the antagonism of B. subtilis is mediated by the polyketide bacillaene and that the production of bacillaene is a highly dynamic trait which depends on environmental factors such as nutrient availability and the presence of competitors.
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Research Interests: Biology and Metagenomics
Research Interests: Microbiology, Biology, Membrane Proteins, Macrophages, Medicine, and 15 moreBiological Sciences, Escherichia coli, Bacteria, Enterobacteriaceae, Neutrophils, Antimicrobial Cationic Peptides, Epithelium, Phagocytosis, Oxygen, Phagosome, Shigella, Cytoplasm, Blood Proteins, Intracellular, and Medical and Health Sciences
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Quorum sensing (QS) is a widespread bacterial communication system that controls important adaptive traits in a cell density-dependent manner. However, mechanisms by which QS-regulated traits are linked within the cell and mechanisms by... more
Quorum sensing (QS) is a widespread bacterial communication system that controls important adaptive traits in a cell density-dependent manner. However, mechanisms by which QS-regulated traits are linked within the cell and mechanisms by which these links affect adaptation are not well understood. In this study, Bacillus subtilis was used as a model bacterium to investigate the link between the ComQXPA QS system, DegQ, surfactin and protease production in planktonic and biofilm cultures. The work tests two alternative hypotheses predicting that hypersensitivity of the QS signal-deficient mutant ( comQ::kan ) to exogenously added ComX, resulting in increased surfactin production, is linked to an additional genetic locus, or alternatively, to overexpression of the ComX receptor ComP. Results are in agreement with the first hypothesis and show that the P srfAA hypersensitivity of the comQ::kan mutant is linked to a 168 strain-specific mutation in the P degQ region. Hence, the markerless...
Plant growth-promoting rhizobacteria (PGPR) represent a green solution to emerging food production challenges but the knowledge of their role in shaping phylogenetic and social relationships of bacterial rhizosphere community is lacking.... more
Plant growth-promoting rhizobacteria (PGPR) represent a green solution to emerging food production challenges but the knowledge of their role in shaping phylogenetic and social relationships of bacterial rhizosphere community is lacking. We here address this gap in knowledge by following effects of Bacillus velezensis SQR9, the commercially important PGP rhizobacterium, on rhizosphere community focusing on Bacillus species. Results show that SQR9 dramatically shifts phylogenetic and social relationships in the rhizosphere enriching moderately related and swarming compatible Bacillus species with decreased carbon resource niche overlap. By combining Bacillus isolates from the SQR9 treated rhizosphere with SQR9 into multispecies consortia we confirm in hydroponic systems and soil experiments that relatedness-based sociality and competition for carbon resources represent fundamental knowledge for the intelligent design of efficient PGP consortia. The work contributes toward sustainable...
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Biofilm communities have beneficial and harmful effects on human societies in natural, medical, and industrial environments. Bacillus subtilis is a biotechnologically important bacterium that serves as a model for studying biofilms.... more
Biofilm communities have beneficial and harmful effects on human societies in natural, medical, and industrial environments. Bacillus subtilis is a biotechnologically important bacterium that serves as a model for studying biofilms. Recent studies have shown that this species engages in kin discriminatory behavior during swarming, which may have implications for community assembly, thus being of fundamental importance.
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Campylobacter jejuni is a prevalent cause of foodborne infections worldwide, while Bacillus subtilis as a potential probiotic represents an alternative strategy to control this alimentary infection. However, only limited literature exists... more
Campylobacter jejuni is a prevalent cause of foodborne infections worldwide, while Bacillus subtilis as a potential probiotic represents an alternative strategy to control this alimentary infection. However, only limited literature exists on the specific mechanisms that shape interactions between B. subtilis and C. jejuni in biofilms.
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In aquatic ecosystems, the biomass, activity and composition of microorganisms are determined to a large extent by local and regional environmental conditions. While karst aquifers are an important source for drinking water, the ecology... more
In aquatic ecosystems, the biomass, activity and composition of microorganisms are determined to a large extent by local and regional environmental conditions. While karst aquifers are an important source for drinking water, the ecology of microbial communities in karst waters has hardly been studied. This study examined the regional variations and seasonal dynamics of microbial communities in pristine karst spring waters of Slovenia (Central Europe). Fifteen springs distributed across 5 eco-regions exhibiting a strong altitudinal gradient were sampled 4 times a year. Evaluation of the microbial communities included quantification of prokaryotic biomass via total cell counts and microbial activity estimated via measurements of electron transport system activity. The taxonomic structure of the bacterial communities was analysed by terminal restriction fragment length polymorphism fingerprinting. Biological measures were complemented by a set of physico-chemical parameters, including ...
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ABSTRACTBacillus spp. strains that are beneficial to plants are widely used in commercial biofertilizers and biocontrol agents for sustainable agriculture. Generally, functional Bacillus strains are applied as single strain communities... more
ABSTRACTBacillus spp. strains that are beneficial to plants are widely used in commercial biofertilizers and biocontrol agents for sustainable agriculture. Generally, functional Bacillus strains are applied as single strain communities since the principles of synthetic microbial consortia constructed with Bacillus strains remain largely unclear. Here, we demonstrated that the mutual compatibility directly affects the survival and function of two-member consortia composed of B. velezensis SQR9 and FZB42 in the rhizosphere. A mutation in the global regulator Spo0A of SQR9 markedly reduced the boundary phenotype with wild-type FZB42, and the combined use of the SQR9∆spo0A mutant and FZB42 improved biofilm formation, root colonization and the production of secondary metabolites that are beneficial to plants. We further confirmed the correlation between the swarm discrimination phenotype between the two consortia members and the effects that are beneficial to plants in a greenhouse exper...
Research Interests: Biology and Rhizosphere
Campylobacter jejuni is an intestinal commensal in animals (including broiler chickens) but also the most frequent cause of bacterial foodborne infection in humans. This pathogen forms biofilms which enhance survival of C. jejuni in food... more
Campylobacter jejuni is an intestinal commensal in animals (including broiler chickens) but also the most frequent cause of bacterial foodborne infection in humans. This pathogen forms biofilms which enhance survival of C. jejuni in food processing and thus threaten human health.
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Kin selection plays an important role in stabilizing population cooperation and maintaining the progeny benefits for bacteria in nature. However, to date, the role of flagellin in kin recognition in Bacillus has not been reported.
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In this study, we link pellicle development at the water–air interface with the vertical distribution and viability of the individual B. subtilis PS-216 cells throughout the water column. Real-time interfacial rheology and time-lapse... more
In this study, we link pellicle development at the water–air interface with the vertical distribution and viability of the individual B. subtilis PS-216 cells throughout the water column. Real-time interfacial rheology and time-lapse confocal laser scanning microscopy were combined to correlate mechanical properties with morphological changes (aggregation status, filament formation, pellicle thickness, spore formation) of the growing pellicle. Six key events were identified in B. subtilis pellicle formation that are accompanied by a major change in viscoelastic and morphology behaviour of the pellicle. The results imply that pellicle development is a multifaceted response to a changing environment induced by bacterial growth that causes population redistribution within the model system, reduction of the viable habitat to the water–air interface, cell development, and morphogenesis. The outcome is a build-up of mechanical stress supporting structure that eventually, due to nutrient d...
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Research background. In recent decades, laccases (p-diphenol-dioxygen oxidoreductases; EC 1.10.3.2) have attracted the attention of researchers due to their wide range of biotechnological and industrial applications. Laccases can oxidize... more
Research background. In recent decades, laccases (p-diphenol-dioxygen oxidoreductases; EC 1.10.3.2) have attracted the attention of researchers due to their wide range of biotechnological and industrial applications. Laccases can oxidize a variety of organic and inorganic compounds, making them suitable as biocatalysts in biotechnological processes. Even though the most traditionally used laccases in the industry are of fungal origin, bacterial laccases have shown an enormous potential given their ability to act on several substrates and in multiple conditions. The present study aims to characterize a plasmid-encoded laccase-like multicopper oxidase (LMCO) from Ochrobactrum sp. BF15, a bacterial strain previously isolated from polluted soil. Experimental approach. We used in silico profile hidden Markov models to identify novel laccase-like genes in Ochrobactrum sp. BF15. For laccase characterization, we performed heterologous expression in Escherichia coli, purification and activit...
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Sin is a Bacillus subtilis DNA-binding protein which is essential for competence, motility, and autolysin production but also, if expressed on a multicopy plasmid, is inhibitory to sporulation and alkaline protease synthesis. We have now... more
Sin is a Bacillus subtilis DNA-binding protein which is essential for competence, motility, and autolysin production but also, if expressed on a multicopy plasmid, is inhibitory to sporulation and alkaline protease synthesis. We have now examined the physiological role of Sin in sporulation and found that this protein specifically represses three stage II sporulation genes (spoIIA, spoIIE, and spoIIG) but not the earlier-acting stage 0 sporulation genes. sin loss-of-function mutations cause higher expression of stage II genes and result in a higher frequency of sporulation, in general. Sin binds to the upstream promoter region of spoIIA in vitro and may thus gate entry into sporulation by directly repressing the transcription of stage II genes. In vivo levels of Sin increase rather than decrease at the time of stage II gene induction, suggesting that posttranslational modification may play a role in downregulation of negative Sin function.
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ABSTRACTAccording to the Lotka-Volterra competition model, intraspecific competition in plant-associated microbial communities should be stronger than interspecific competition. However, there is limited information on whether microbial... more
ABSTRACTAccording to the Lotka-Volterra competition model, intraspecific competition in plant-associated microbial communities should be stronger than interspecific competition. However, there is limited information on whether microbial communities follow this pattern and how disturbance by a newcomer affects them. Given the increasing popularity of probiotics, filling this knowledge gap could help guide future coexistence research. Here, we show that inoculation with a known probiotic,B. velezensisSQR9 shifts species co-occurrence patterns by decreasing the diversity of more distant species and promoting the growth of more closely related species, especially within theBacilluscommunity. By testing the sociality ofBacillusrhizosphere isolates, we then demonstrated that SQR9 increases the frequency of cooperative interactions in theBacilluscommunity, which may contribute to the promotion of plant growth. Finally, we provide an ecosystem framework comprising the strain’s genetic relat...
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Bacillus velezensis is one of the most widely applied bacteria in biofertilizers in China and Europe. Additionally, the molecular mechanisms of plant growth promotion and disease suppression by representative model strains are well... more
Bacillus velezensis is one of the most widely applied bacteria in biofertilizers in China and Europe. Additionally, the molecular mechanisms of plant growth promotion and disease suppression by representative model strains are well established, such as B. velezensis SQR9 and FZB42.
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Bacillus is a ubiquitous microorganism and is one of the most commercially important species widely used in industry, agriculture and healthcare. Bacillus is relatively well understood at the single-cell level; however, molecular tools... more
Bacillus is a ubiquitous microorganism and is one of the most commercially important species widely used in industry, agriculture and healthcare. Bacillus is relatively well understood at the single-cell level; however, molecular tools that determine diversity and ecology of Bacillus community are limited, which limits our understanding of how the Bacillus community works. In the present study, we investigated the potential of the housekeeping gene gyrA as a molecular marker for determining the diversity of Bacillus species. The amplification efficiency for Bacillus species diversity could be greatly improved by primer design. Therefore, we designed a novel primer pair gyrA3 that can detect at least 92 Bacillus species and related species. For Bacillus amyloliquefaciens, Bacillus pumilus, and Bacillus megaterium, we observed that the high variability of the gyrA gene allows for more detailed clustering at the subspecies level that cannot be achieved by the 16S rRNA gene. Since gyrA ...
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SinR is a pleiotropic DNA binding protein that is essential for the late-growth processes of competence and motility in Bacillus subtilis and is also a repressor of others, e.g., sporulation and subtilisin synthesis. In this report, we... more
SinR is a pleiotropic DNA binding protein that is essential for the late-growth processes of competence and motility in Bacillus subtilis and is also a repressor of others, e.g., sporulation and subtilisin synthesis. In this report, we show that SinR, in addition to being an inhibitor of sporulation stage II gene expression, is a repressor of the key early sporulation gene spo0A. The sporulation-specific rise in spo0A expression at time zero is absent in a SinR-overproducing strain and is much higher than normal in strains with a disrupted sinR gene. This effect is direct, since SinR binds specifically to spo0A in vitro, in a region overlapping the -10 region of the sporulation-specific Ps promoter that is recognized by E-sigma H polymerase. Methyl interference and site-directed mutagenesis studies have identified guanine residues that are important for SinR recognition of this DNA sequence. Finally, we present evidence that SinR controls sporulation through several independent gene...
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As the incidence of Campylobacter jejuni and campylobacteriosis grows, so does the need for a better understanding and control of this pathogen. We studied the interactions of C. jejuni NCTC 11168 and a potential probiotic, Bacillus... more
As the incidence of Campylobacter jejuni and campylobacteriosis grows, so does the need for a better understanding and control of this pathogen. We studied the interactions of C. jejuni NCTC 11168 and a potential probiotic, Bacillus subtilis PS-216, in cocultures at different starting ratios and temperatures (20 °C, 37 °C, 42 °C), under different atmospheres (aerobic, microaerobic), and in different growth media (Mueller–Hinton, chicken litter medium, chicken intestinal-content medium). Under microaerobic conditions, B. subtilis effectively inhibited the growth of C. jejuni at 42 °C (log reduction, 4.19), even when C. jejuni counts surpassed B. subtilis by 1000-fold in the starting inoculum. This inhibition was weaker at 37 °C (log reduction, 1.63), while no impact on CFUs was noted at 20 °C, which is a temperature nonpermissive of C. jejuni growth. Under aerobic conditions, B. subtilis supported C. jejuni survival. B. subtilis PS-216 inhibited the growth of C. jejuni in sterile chi...
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ABSTRACTMicroorganisms in nature form multicellular groups called biofilms. In biofilms bacteria embedded in a matrix of extracellular polymeric substances (EPS) interact intensely, due to their proximity to each other. Most studies have... more
ABSTRACTMicroorganisms in nature form multicellular groups called biofilms. In biofilms bacteria embedded in a matrix of extracellular polymeric substances (EPS) interact intensely, due to their proximity to each other. Most studies have investigated genetically homogeneous biofilms, leaving a gap in knowledge on genetically heterogeneous biofilms. Recent insights show that a Gram-positive model bacterium, Bacillus subtilis, discriminates between strains of high (kin) and low (non-kin) phylogenetic relatedness, reflected in merging (kin) and boundaries (non-kin) between swarms. However, it is not clear how kinship between interacting strains affects their fitness, the genotype distribution, and the EPS sharing in floating biofilms (pellicles). To address this gap in knowledge we cultivate B. subtilis strains as mixtures of kin and non-kin strains in static cultures, allowing them to form pellicles. We show here that in non-kin pellicles only one strain’s fitness was reduced; at the ...
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The analysis of the living soil as well as plant rhizosphere has been greatly assisted by the application of modern environmental DNAor RNA-based methods (Van Elsas et al., 2007; de Bruijn, 2011a; 2011b). The main reason for this... more
The analysis of the living soil as well as plant rhizosphere has been greatly assisted by the application of modern environmental DNAor RNA-based methods (Van Elsas et al., 2007; de Bruijn, 2011a; 2011b). The main reason for this contention is that these methods theoretically allow a direct, snapshot-like, observation of the extant microbiota, thus overcoming the problems posed by the “great plate count anomaly” (Staley and Konopka, 1985). However, the statement that basically all extant microbiota can thus be visualized has been revealed to be contentious, as the method by which DNA/RNA is extracted from the (soil) sample was shown to greatly determine the “window” offered at this microbiota (Inceoglu et al., 2010a). Nevertheless, in the early days of this development, that is, the 1990s, soilor rhizosphere-extracted nucleic acids have been subjected to either direct polymerase chain reaction (PCR) or to PCR preceeded by reverse transcription, in order to subsequently perform denaturing gradient gel electrophoresis (DGGE) or produce terminal restriction fragment length polymorphism (T-RFLP) based profiles of the targeted microbial communities.
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Bacillus subtilis PS216, a strain isolated in Slovenia, has been sequenced. PS216 is transformable and forms robust biofilms, making it useful for the study of competence regulation in an undomesticated bacterium.
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Bacillus subtilis strains communicate through the comQXPA quorum sensing (QS) system, which regulates genes expressed during early stationary phase. A high polymorphism of comQXP ′ loci was found in closely related strains isolated from... more
Bacillus subtilis strains communicate through the comQXPA quorum sensing (QS) system, which regulates genes expressed during early stationary phase. A high polymorphism of comQXP ′ loci was found in closely related strains isolated from desert soil samples separated by distances ranging from meters to kilometers. The observed polymorphism comprised four communication groups (pherotypes), such that strains belonging to the same pherotype exchanged information efficiently but strains from different pherotypes failed to communicate. To determine whether the same level of polymorphism in the comQXP ′ QS system could be detected at microscale, B. subtilis isolates were obtained from two separate 1-cm 3 soil samples, which were progressively divided into smaller sections. Cross-activation studies using pherotype-responsive reporter strains indicated the same number of communication pherotypes at microscale as previously determined at macroscale. Sequencing of the housekeeping gene gyrA an...
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Kin discrimination, broadly defined as differential treatment of conspecifics according to their relatedness, could help biological systems direct cooperative behavior toward their relatives. Here we investigated the ability of the soil... more
Kin discrimination, broadly defined as differential treatment of conspecifics according to their relatedness, could help biological systems direct cooperative behavior toward their relatives. Here we investigated the ability of the soil bacterium Bacillus subtilis to discriminate kin from nonkin in the context of swarming, a cooperative multicellular behavior. We tested a collection of sympatric conspecifics from soil in pairwise combinations and found that despite their history of coexistence, the vast majority formed distinct boundaries when the swarms met. Some swarms did merge, and most interestingly, this behavior was only seen in the most highly related strain pairs. Overall the swarm interaction phenotype strongly correlated with phylogenetic relatedness, indicative of kin discrimination. Using a subset of strains, we examined cocolonization patterns on plant roots. Pairs of kin strains were able to cocolonize roots and formed a mixed-strain biofilm. In contrast, inoculating ...
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Quorum sensing (QS) is a form of cooperative social behaviour which relies on extracellular signalling molecules that elicit the QS response across many cells and controls the development of many cooperative traits including biofilm... more
Quorum sensing (QS) is a form of cooperative social behaviour which relies on extracellular signalling molecules that elicit the QS response across many cells and controls the development of many cooperative traits including biofilm formation. The main aim of this work is to review the published work on cooperative social behaviour of Bacillus subtilis and especially its QS system ComQXPA. This QS system involves four interacting components: the signal-processing enzyme ComQ, the ComX signal, the ComP receptor and the ComA transcriptional regulator. Phosphorylated ComA controls the transcription of many genes including those responsible for the production of surfactin and extracellular matrix, essential for biofilm formation. The ComQXPA QS shows a high degree of genetic polymorphism, which manifests itself in the separation of Bacillus subtilis strains into four different communication groups (pherotypes). The information exchange is possible between members of the same pherotype b...
SUMMARY Research background The occurrence and environmental toxicity of pharmaceuticals have recently attracted increasing attention. Diclofenac is a highly consumed non-steroidal anti-inflammatory drug, which is often detected in... more
SUMMARY Research background The occurrence and environmental toxicity of pharmaceuticals have recently attracted increasing attention. Diclofenac is a highly consumed non-steroidal anti-inflammatory drug, which is often detected in wastewaters, but investigations of its influence on bacteria are scarce. Experimental approach We investigated the influence of this pharmaceutical on bacterial community in activated sludge exposed to increasing concentrations of diclofenac in fed-batch reactors over 41 days. Nitrification activity of the activated sludge was measured and changes in bacterial community structure were followed using culture-independent molecular method (terminal restriction fragment length polymorphism, T-RFLP) and by the cultivation approach. Results and conclusions Nitrification activity was not detectably influenced by the addition of diclofenac, while the main change of the bacterial community structure was detected only at the end of incubation (after 41 days) when d...
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Bacillus subtilis is a soil bacterium that is competent for natural transformation. Genetically distinct B. subtilis swarms form a boundary upon encounter, resulting in killing of one of the strains. This process is mediated by a... more
Bacillus subtilis is a soil bacterium that is competent for natural transformation. Genetically distinct B. subtilis swarms form a boundary upon encounter, resulting in killing of one of the strains. This process is mediated by a fast-evolving kin discrimination (KD) system consisting of cellular attack and defence mechanisms. Here, we show that these swarm antagonisms promote transformation-mediated horizontal gene transfer between strains of low relatedness. Gene transfer between interacting non-kin strains is largely unidirectional, from killed cells of the donor strain to surviving cells of the recipient strain. It is associated with activation of a stress response mediated by sigma factor SigW in the donor cells, and induction of competence in the recipient strain. More closely related strains, which in theory would experience more efficient recombination due to increased sequence homology, do not upregulate transformation upon encounter. This result indicates that social inter...
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Genetic competence for the uptake and integration of extracellular DNA is a key process in horizontal gene transfer (HGT), one of the most powerful forces driving the evolution of bacteria. In several species, development of genetic... more
Genetic competence for the uptake and integration of extracellular DNA is a key process in horizontal gene transfer (HGT), one of the most powerful forces driving the evolution of bacteria. In several species, development of genetic competence is coupled with cell lysis. Using Bacillus subtilis as a model bacterium, we studied the role of surfactin, a powerful biosurfactant and antimicrobial lipopeptide, in genetic transformation. We showed that surfactin itself promotes cell lysis and DNA release, thereby promoting HGT. These results, therefore, provide evidence for a fundamental mechanism involved in HGT and significantly increase our understanding of the spreading of antibiotic resistance genes and diversification of microbial communities in the environment.
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Gram-positive bacteria use peptides as auto-inducing (AI) signals to regulate the production of extracellular enzymes (e.g., proteases). ComX is an AI peptide, mostly known for its role in the regulation of bacterial competence and... more
Gram-positive bacteria use peptides as auto-inducing (AI) signals to regulate the production of extracellular enzymes (e.g., proteases). ComX is an AI peptide, mostly known for its role in the regulation of bacterial competence and surfactant production in . These two traits are regulated accordingly to the bacterial population size, thus classifying ComX as a quorum sensing signal. ComX also indirectly regulates exoprotease production through the intermediate transcriptional regulator DegQ. We here use this peptide-based AI system (the ComQXPA system) as a model to address exoprotease regulation by ComX in biofilms. We also investigate the potential of ComX regulated proteases to degrade the ComX AI peptide. Results indicate that ComX indeed induces the expression of , the gene for the major serine protease subtilisin, and stimulates overall exoprotease production in biofilms of PS-216 and several other soil isolates. We also provide evidence that these exoproteases can degrade Com...
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PurposePeatlands have an important role in methane cycling in the natural environment. Methane emissions as a result of methanogenesis and methanotrophy in soil are affected by several environmental factors such as temperature, oxygen and... more
PurposePeatlands have an important role in methane cycling in the natural environment. Methane emissions as a result of methanogenesis and methanotrophy in soil are affected by several environmental factors such as temperature, oxygen and groundwater level. The objective of this study was to analyse methane cycling as a function of soil depth.Materials and methodsIn this study, methane cycling and soil organic matter mineralization were investigated in a drained fen grassland area of Ljubljana marsh, Slovenia that has been subjected to reclamation strategies for several centuries. Potential mineralization, methane production and methane oxidation rates were measured in slurry incubation experiments with soil samples from 10 sampling depths of a 1-m profile. In addition, the extent of iron reduction in the soil was determined.Results and discussionThe potential for methane production was low in the investigated soil profile, even in constantly flooded layers below the water table fluctuations. During anaerobic incubations, the highest accumulated concentrations and production rates of methane were observed in the upper 10-cm layer and the lowest in deeper soil layers, indicating that plant exudates are the main source of energy for heterotrophic soil microbes and that methanogenesis in deeper layers is limited by the availability of appropriate organic substrates. Methane oxidation was on the other hand active throughout the soil profile, suggesting that the potentially active methane oxidizing community is present despite low methane production. The highest abundance and activity of methanotrophs was detected in the water table fluctuation layers.ConclusionsTogether, these findings have implications for understanding the biogeochemical function of drained peat soils and emphasize the influence of drainage on quality of soil organic matter and consequently on methane production even in flooded soils.