Social Interactions and Biofilm Formation in Bacillus subtilis

Međustanična je komunikacija (engl. quorum sensing, QS) oblik kooperativnog socijalnog ponašanja bakterija što se oslanja na prepoznavanje izvanstaničnih signalnih molekula. Signalna se molekula veže na receptor i inducira promjenu transkripcije gena, odgovornih za stvaranje biofilma, proizvodnju izvanstaničnih enzima i druge kooperativne značajke populacije. Svrha je ovoga rada bila dati pregled objavljenih znanstvenih radova koji se bave kooperativnim socijalnim ponašanjem bakterije Bacillus subtilis, a naročito doprinosom komunikacijskog sustava ComQXPA. Sustav QS obuhvaća četiri komponente koje su u međusobnoj interakciji: izoprenil transferazu ComQ što procesira i modificira signal, peptid ComX koji ima ulogu signala, receptor ComP i transkripcijski regulator ComA. Fosforilirani ComA kontrolira transkripciju brojnih gena, uključujući i one odgovorne za proizvodnju surfaktina te izvanstaničnog matriksa, važnog za nastajanje biofilma. Sustav ComQXPA QS ima visok stupanj genetičkog polimorfizma, što je vidljivo iz činjenice da se sojevi Bacillus subtilis mogu podijeliti u četiri skupine. Sojevi jedne skupine (ferotipa) mogu razmjenjivati signale i informacije, dok to nije moguće između različitih ferotipova. Nedavno smo pokazali da je ovaj fenomen djelomično posljedica ekološke raznolikosti sojeva, ali su moguće i alternativne hipoteze, koje daju prednost socijalnoj evoluciji. Između ostalog, sustav ComQXPA kontrolira i proizvodnju izvanstaničnog matriksa, koji se sastoji od polisaharida, proteina i nukleinskih kiselina. U ovom je radu dan pregled trenutnih spoznaja o regulaciji, strukturi, kemijskom sastavu i funkciji izvanstaničnog matriksa. Usprkos mnogim važnim nedavnim otkrićima u području regulacije formiranja biofilma B. subtilis, molekularne interakcije među komponentama matriksa i njihov utjecaj na QS i stabilnost biofilma nisu još dobro poznati, pa se u ovom radu razmatraju i moguća rješenja ovih zanimljivih pitanja.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 but not across pherotypes. We have recently suggested that this phenomenon is at least in part driven by the ecological divergence of strains, but may also be induced by frequency-dependent selection. The ComQXPA QS system controls the production of extracellular matrix (ECM) components: polysaccharides, proteins and nucleic acids. We will address the present understanding of the ECM structure-function relationships in B. subtilis biofilms and review published results on regulation, composition and distribution of ECM components. Despite many important recent discoveries on regulation of B. subtilis biofilm development, we know little about the molecular interactions in the ECM and the role they play in the QS and stability of the biofilm. Future research needs to address these questions better

The ComX Quorum Sensing Peptide of Bacillus subtilis Affects Biofilm Formation Negatively and Sporulation Positively

Quorum sensing (QS) is often required for the formation of bacterial biofilms and is a popular target of biofilm control strategies. Previous studies implicate the ComQXPA quorum sensing system of Bacillus subtilis as a promoter of biofilm formation. Here, we report that ComX signaling peptide deficient mutants form thicker and more robust pellicle biofilms that contain chains of cells. We confirm that ComX positively affects the transcriptional activity of the P$_{epsA}$ promoter, which controls the synthesis of the major matrix polysaccharide. In contrast, ComX negatively controls the P$_{tapA}$ promoter, which drives the production of TasA, a fibrous matrix protein. Overall, the biomass of the mutant biofilm lacking ComX accumulates more monosaccharide and protein content than the wild type. We conclude that this QS phenotype might be due to extended investment into growth rather than spore development. Consistent with this, the ComX deficient mutant shows a delayed activation of the pre-spore specific promoter, P$_{spoIIQ}$, and a delayed, more synchronous commitment to sporulation. We conclude that ComX mediated early commitment to sporulation of the wild type slows down biofilm formation and modulates the coexistence of multiple biological states during the early stages of biofilm development

Ecology of Bacillaceae

Members of the family Bacillaceae are among the most robust bacteria on Earth, which is mainly due to their ability to form resistant endospores. This trait is believed to be the key factor determining the ecology of these bacteria. However, they also perform fundamental roles in soil ecology (i.e., the cycling of organic matter) and in plant health and growth stimulation (e.g., via suppression of plant pathogens and phosphate solubilization). In this review, we describe the high functional and genetic diversity that is found within the Bacillaceae (a family of low-G+C% Gram-positive spore-forming bacteria), their roles in ecology and in applied sciences related to agriculture. We then pose questions with respect to their ecological behavior, zooming in on the intricate social behavior that is becoming increasingly well characterized for some members of Bacillaceae. Such social behavior, which includes cell-to-cell signaling via quorum sensing or other mechanisms (e.g., the production of extracellular hydrolytic enzymes, toxins, antibiotics and/or surfactants) is a key determinant of their lifestyle and is also believed to drive diversification processes. It is only with a deeper understanding of cell-to-cell interactions that we will be able to understand the ecological and diversification processes of natural populations within the family Bacillaceae. Ultimately, the resulting improvements in understanding will benefit practical efforts to apply representatives of these bacteria in promoting plant growth as well as biological control of plant pathogens

Ecology of <i>Bacillaceae</i>

Members of the family Bacillaceae are among the most robust bacteria on Earth, which is mainly due to their ability to form resistant endospores. This trait is believed to be the key factor determining the ecology of these bacteria. However, they also perform fundamental roles in soil ecology (i.e., the cycling of organic matter) and in plant health and growth stimulation (e.g., via suppression of plant pathogens and phosphate solubilization). In this review, we describe the high functional and genetic diversity that is found within the Bacillaceae (a family of low-G+C% Gram-positive spore-forming bacteria), their roles in ecology and in applied sciences related to agriculture. We then pose questions with respect to their ecological behavior, zooming in on the intricate social behavior that is becoming increasingly well characterized for some members of Bacillaceae. Such social behavior, which includes cell-to-cell signaling via quorum sensing or other mechanisms (e.g., the production of extracellular hydrolytic enzymes, toxins, antibiotics and/or surfactants) is a key determinant of their lifestyle and is also believed to drive diversification processes. It is only with a deeper understanding of cell-to-cell interactions that we will be able to understand the ecological and diversification processes of natural populations within the family Bacillaceae. Ultimately, the resulting improvements in understanding will benefit practical efforts to apply representatives of these bacteria in promoting plant growth as well as biological control of plant pathogens

Ecology of Bacillaceae

Members of the family Bacillaceae are among the most robust bacteria on Earth, which is mainly due to their ability to form resistant endospores. This trait is believed to be the key factor determining the ecology of these bacteria. However, they also perform fundamental roles in soil ecology (i.e., the cycling of organic matter) and in plant health and growth stimulation (e.g., via suppression of plant pathogens and phosphate solubilization). In this review, we describe the high functional and genetic diversity that is found within the Bacillaceae (a family of low-G+C% Gram-positive spore-forming bacteria), their roles in ecology and in applied sciences related to agriculture. We then pose questions with respect to their ecological behavior, zooming in on the intricate social behavior that is becoming increasingly well characterized for some members of Bacillaceae. Such social behavior, which includes cell-to-cell signaling via quorum sensing or other mechanisms (e.g., the production of extracellular hydrolytic enzymes, toxins, antibiotics and/or surfactants) is a key determinant of their lifestyle and is also believed to drive diversification processes. It is only with a deeper understanding of cell-to-cell interactions that we will be able to understand the ecological and diversification processes of natural populations within the family Bacillaceae. Ultimately, the resulting improvements in understanding will benefit practical efforts to apply representatives of these bacteria in promoting plant growth as well as biological control of plant pathogens

Ecology of Bacillaceae

Members of the family Bacillaceae are among the most robust bacteria on Earth, which is mainly due to their ability to form resistant endospores. This trait is believed to be the key factor determining the ecology of these bacteria. However, they also perform fundamental roles in soil ecology (i.e., the cycling of organic matter) and in plant health and growth stimulation (e.g., via suppression of plant pathogens and phosphate solubilization). In this review, we describe the high functional and genetic diversity that is found within the Bacillaceae (a family of low-G+C% Gram-positive spore-forming bacteria), their roles in ecology and in applied sciences related to agriculture. We then pose questions with respect to their ecological behavior, zooming in on the intricate social behavior that is becoming increasingly well characterized for some members of Bacillaceae. Such social behavior, which includes cell-to-cell signaling via quorum sensing or other mechanisms (e.g., the production of extracellular hydrolytic enzymes, toxins, antibiotics and/or surfactants) is a key determinant of their lifestyle and is also believed to drive diversification processes. It is only with a deeper understanding of cell-to-cell interactions that we will be able to understand the ecological and diversification processes of natural populations within the family Bacillaceae. Ultimately, the resulting improvements in understanding will benefit practical efforts to apply representatives of these bacteria in promoting plant growth as well as biological control of plant pathogens