Projects / Programmes
Ecology of social interactions in Bacillus subtilis
Code |
Science |
Field |
Subfield |
4.03.00 |
Biotechnical sciences |
Plant production |
|
Code |
Science |
Field |
B230 |
Biomedical sciences |
Microbiology, bacteriology, virology, mycology |
Code |
Science |
Field |
4.01 |
Agricultural and Veterinary Sciences |
Agriculture, Forestry and Fisheries |
Bacterial social interactions, cell signaling, cooperativity, antagonism, fitness, communication types, Bacillus subtilis, biofilm, EPS, surfactin, soil, rhizosphere, biopesticide, plant pathogen, microbial diversity, ecosystem function
Researchers (17)
Organisations (2)
Abstract
Background: Bacteria use cell-cell signaling (social interactions) to control important cellular processes (e.g. synthesis of antibiotics, biofilm formation) in response to cell density. Signaling is mediated by small molecules, which accumulate in the extracellular environment. Upon reaching a critical concentration signaling molecules induce gene expression, resulting in coordinated adaptive responses of the population. In a Gram positive bacterium Bacillus subtilis, ,the ComQXPA communication system controls production of a lipopeptide antibiotic surfactin, extracellular matrix (EPS) production and many other adaptive processes. The first three genes of the communication locus are highly polymorphic, leading to the formation of four different communication groups. Communication is possible between strains within the same group, but not between strains belonging to different groups. Problem description: In B. subtilis, one of the most commonly used and well studied soil organisms; 4-5% of the genome is devoted to antibiotic synthesis, partly explaining its use as an excellent biocontrol agent. Liquid culture studies have demonstrated a strong dependence of biocontrol potential (e.g. surfactin synthesis) on the ComQXPA communication system. Little is known of cell-density control of processes, including ComQXPA-mediated communication in soil. It is likely that biocontrol efficiency is reduced in soil, using standard inoculation procedures, and that determination of bacterial communication control in soil will lead to rational optimization of biocontrol procedures. The ComQXPA system also provides an excellent model for initiating understanding of other cell-density systems in soil. The aim of the study: The project aims to determine the relationship between environment (soil or rhizosphere), microbial diversity (B. subtilis communication groups), social interactions (cell signaling) and ecosystem function (biocontrol). Soil and rhizosphere systems will be used to determine whether the cell-density control characterized in liquid medium is reproduced in complex heterogeneous environments. The influence of cell density of individual B. subtilis strains, and inoculation of multiple strains from the same and different communication groups, on surfactin production will be determined. The role of EPS production in influencing cell density signaling and viscoelastic properties of biofilms will be determined using EPS- mutants. Originality of the results: The proposed project is the first study to transfer knowledge of cell signaling mechanisms, obtained in liquid culture systems, to natural environments. Results will be novel and will show how habitat influences social interactions, which in turn influence an important ecosystem function. Results on fundamental aspects of the work will therefore be publishable in high-impact factor scientific journals. Methods: Our laboratories have environmental Bacillus strains of known communication type and will further develop molecular tools (PCR, Q-PCR, T-RFLP, specific primers) to monitor communication genes and surfactin gene expression, bacterial biosensors with fluorescent reporters to monitor cell communication at small scales and in EPS- mutants. Results potential and relevancy: The results will provide general information on the role of cell-density signaling mechanisms and social interactions in heterogeneous environments. This has relevance to the wide range of signal-based processes, occurring in soil, that control a wide range of important ecosystem functions. The use of B. subtilis, a key, commercially important, environmentally friendly, biocontrol agent, provides additional relevance, because of its action against plant pathogens and growth promotion of economically important crops. There is also significant potential for increased understanding to lead to optimization of biocontrol procedures, and to commercialization of this research.
Significance for science
Bacterial intercellular signaling is essential for coordination of survival strategies at the population level and understanding of this process is important for optimization of procedures applying bacteria as production organisms in industry, as probiotics for human health and husbandry or as biopesticides in agriculture. The project ‘Ecology of social interactions of Bacillus subtilis aimed to understand bacterial communication by focusing on the ComQXPA quorum sensing (QS) system. This QS system is especially interesting due to its high polymorphism, which increases the specificity of the response and prevents communication between strains of different communication types (pherotypes). Using in vitro and in situ models, we showed for the first time that pherotypes strongly correlate with ecotypes broadening our understanding of evolutionary forces contributing to diversification of pherotypes (Štefanič et al., Env. Microbiol., 2012). In addition we bring through a bioinformaics analysis a novel insight into the distribution of ComQXPA QS systems in sequenced bacterial genomes (Dogša et al ., PloS one, in press). We believe that this will encourage research of ComQXPA QS systems in other bacterial species. In co-authorship with an american laboratory, we sequenced the genome of our isolate PS216 (Durett et al., 2013), which makes it more interesting as a model organism for a wider scientific community, especially because this strains is also naturally competent and thus amenable for genetic manipulation. We also published two chapters in international books highlighting the ecology of Bacillacea and the role of B. subtilis in soil and rhizosphere. Frequent invitations and selection of our work as contributed talks, often selected among 1700 or more abstracts at international conferences, suggests a broad appeal and importance of the project results. Recently we also succeeded to highlight a role of bacterial communication as an interface between primary and secondary metabolism and for the first time demonstrated that the private signal synthesis is coupled to the response induced by the secreted signal. The results were published in one of the most respected scientific journals in the world (Oslizlo et al., PNAS, 2014). We expanded the knowledge on biofilms by contributing an in depth analysis of extra-cellular matrix (EPS) chemical composition and were the first (Dogša et al., 2013) linking the growth medium composition, matrix composition and biofilm strength. The results of the project were published in prestigious journals, often cited and indicated as important in several opinion articles. Therefore we believe that prject results importantly contributed to the development of science, especially as they bridge several scientific fields (gene regulation of Bacillus subtilis, social evolution, microbial ecology and structure-function studies of biologically active compounds). The scientific importance of the project is also reflected in increased interest of the best teams in the world (UCSD - USA, Harvard, Oxford, University of Copenhagen, University of Groningen, University of Aberdeen) to collaborate with us. Bacilllus is commercially highly important; therefore, our research has a far-reaching significance for the development of biotechnological applications and sustainable procedures foccusing on plant growth promotion and crop protection.
Significance for the country
The objectives of the project ‘Ecology of social interactions in Bacillus subtilis’ were closely related to basic questions at the forefront of natural sciences addressing molecular mechanisms of bacterial communication, ecology and social evolution. We aimed to understand bacterial communication and the mechanisms that maintain cooperation between microorganisms. We also focused on biofilms, their structure, physico-chemical properties and forces affecting signal diffusion in this high cell density structures. This topic is very interesting and has many significant applications for industry, agriculture and human and animal health. The aims of the project have been achieved and we consider the most important achievement of the project that our work was published in the most prestigious scientific journals and has been already well cited. The project provided the route to establish and maintain strong links with many prestigious institutions in the world such as UCSD –USA, Harvard –USA, PHRI –USA, Oxford -UK, Copenhagen Uni.- Denmark, Groningen Uni. - Netherlands, Aberdeen Uni. -UK, ICGBE -Trieste. Excellence is also confirmed by 1) the selection of our research to be presented at international congresses, 2) invitations to foreign universities and international doctoral commissions, 3) the invitation to IMM to be a partner and WP coordinator in the project TRANSMIT - Horizon 2020 (ETM project addresses microbial communication and multispecies biofilms with the aim to educate a new generation of professionals who will be able to apply knowledge of social microbiology in industry and agriculture). In 2013, we also organized a major international symposium on the ecology and genetics of bacteria (BAGECO - 12), which was presided and organized by prof. I. Mandič - Mulec. This conference brought to Ljubljana more than 300 delegates from all over the world including the most important experts in the field. Achievements of the project have been incorporated into undergraduate and graduate theoretical and practical courses at the University of Ljubljana. The project was linked to 4 undergraduate thesis, one master thesis and a doctoral dissertation of A. Oslizlo, who will defend her thesis this year. The project was also important to strengthen the working connections in Slovenia, through ongoing links with the group of M. Rupnik (NLZOH) and the group of I. Poberaj at FMF-UL.
Most important scientific results
Annual report
2010,
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2010,
2011,
2012,
final report,
complete report on dLib.si