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Xu S, Liu Z, Ren P, Liu Y, Xiao F, Li W. BmfR, a novel GntR family regulator, regulates biofilm formation in marine-derived, Bacillus methylotrophicus B-9987. Microbiol Res 2024; 287:127859. [PMID: 39098095 DOI: 10.1016/j.micres.2024.127859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2024] [Revised: 07/21/2024] [Accepted: 07/24/2024] [Indexed: 08/06/2024]
Abstract
Biofilms are common living states for microorganisms, allowing them to adapt to environmental changes. Numerous Bacillus strains can form complex biofilms that play crucial roles in biocontrol processes. However, our current understanding of the molecular mechanisms of biofilm formation in Bacillus is mainly based on studies of Bacillus subtilis. Knowledge regarding the biofilm formation of other Bacillus species remains limited. In this study, we identified a novel transcriptional regulator, BmfR, belonging to the GntR family, that regulates biofilm formation in marine-derived Bacillus methylotrophicus B-9987. We demonstrated that BmfR induces biofilm formation by activating the extracellular polysaccharide structural genes epsA-O and negatively regulating the matrix gene repressor, SinR; of note it positively affects the expression of the master regulator of sporulation, Spo0A. Furthermore, database mining for BmfR homologs has revealed their widespread distribution among many bacterial species, mainly Firmicutes and Proteobacteria. This study advances our understanding of the biofilm regulatory network of Bacillus strains, and provides a new target for exploiting and manipulating biofilm formation.
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Affiliation(s)
- Shanshan Xu
- Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China
| | - Zengzhi Liu
- Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China
| | - Pengfei Ren
- Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China
| | - Yang Liu
- Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China
| | - Fei Xiao
- Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China
| | - Wenli Li
- Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China; Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shannxi 712100, China.
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Seručnik M, Dogsa I, Zadravec LJ, Mandic-Mulec I, Žnidaršič-Plazl P. Development of a Microbioreactor for Bacillus subtilis Biofilm Cultivation. MICROMACHINES 2024; 15:1037. [PMID: 39203688 PMCID: PMC11356062 DOI: 10.3390/mi15081037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 08/08/2024] [Accepted: 08/09/2024] [Indexed: 09/03/2024]
Abstract
To improve our understanding of Bacillus subtilis growth and biofilm formation under different environmental conditions, two versions of a microfluidic reactor with two channels separated by a polydimethylsiloxane (PDMS) membrane were developed. The gas phase was introduced into the channel above the membrane, and oxygen transfer from the gas phase through the membrane was assessed by measuring the dissolved oxygen concentration in the liquid phase using a miniaturized optical sensor and oxygen-sensitive nanoparticles. B. subtilis biofilm formation was monitored in the growth channels of the microbioreactors, which were designed in two shapes: one with circular extensions and one without. The volumes of these microbioreactors were (17 ± 4) μL for the reactors without extensions and (28 ± 4) μL for those with extensions. The effect of microbioreactor geometry and aeration on B. subtilis biofilm growth was evaluated by digital image analysis. In both microbioreactor geometries, stable B. subtilis biofilm formation was achieved after 72 h of incubation at a growth medium flow rate of 1 μL/min. The amount of oxygen significantly influenced biofilm formation. When the culture was cultivated with a continuous air supply, biofilm surface coverage and biomass concentration were higher than in cultivations without aeration or with a 100% oxygen supply. The channel geometry with circular extensions did not lead to a higher total biomass in the microbioreactor compared to the geometry without extensions.
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Affiliation(s)
- Mojca Seručnik
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia; (M.S.); (L.J.Z.)
| | - Iztok Dogsa
- Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia; (I.D.); (I.M.-M.)
| | - Lan Julij Zadravec
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia; (M.S.); (L.J.Z.)
| | - Ines Mandic-Mulec
- Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia; (I.D.); (I.M.-M.)
- Chair of Micro Process Engineering and Technology—COMPETE, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Polona Žnidaršič-Plazl
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia; (M.S.); (L.J.Z.)
- Chair of Micro Process Engineering and Technology—COMPETE, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
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Dogsa I, Mandic-Mulec I. Multiscale spatial segregation analysis in digital images of biofilms. Biofilm 2023; 6:100157. [PMID: 37790733 PMCID: PMC10542597 DOI: 10.1016/j.bioflm.2023.100157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 09/15/2023] [Accepted: 09/19/2023] [Indexed: 10/05/2023] Open
Abstract
Quantifying the degree of spatial segregation of two bacterial strains in mixed biofilms is an important topic in microbiology. Spatial segregation is dependent on spatial scale as two strains may appear to be well mixed if observed from a distance, but a closer look can reveal strong separation. Typically, this information is encoded in a digital image that represents the binary system, e.g., a microscopy image of a two species biofilm. To decode spatial segregation information, we have developed quantitative measures for evaluating the degree of the spatial scale-dependent segregation of two bacterial strains in a digital image. The constructed algorithm is based on the new segregation measures and overcomes drawbacks of existing approaches for biofilm segregation analysis. The new approach is implemented in a freely available software and was successfully applied to biofilms of two strains and bacterial suspensions for detection of the different spatial scale-dependent segregation levels.
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Affiliation(s)
- Iztok Dogsa
- Chair of Microbiology, Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, EU, Slovenia
| | - Ines Mandic-Mulec
- Chair of Microbiology, Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, EU, Slovenia
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Podnar E, Erega A, Danevčič T, Kovačec E, Lories B, Steenackers H, Mandic-Mulec I. Nutrient Availability and Biofilm Polysaccharide Shape the Bacillaene-Dependent Antagonism of Bacillus subtilis against Salmonella Typhimurium. Microbiol Spectr 2022; 10:e0183622. [PMID: 36342318 PMCID: PMC9769773 DOI: 10.1128/spectrum.01836-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 10/18/2022] [Indexed: 11/09/2022] Open
Abstract
Salmonella enterica is one of the most common foodborne pathogens and, due to the spread of antibiotic resistance, new antimicrobial strategies are urgently needed to control it. In this study, we explored the probiotic potential of Bacillus subtilis PS-216 and elucidated the mechanisms that underlie the interactions between this soil isolate and the model pathogenic strain S. Typhimurium SL1344. The results reveal that B. subtilis PS-216 inhibits the growth and biofilm formation of S. Typhimurium through the production of the pks cluster-dependent polyketide bacillaene. The presence of S. Typhimurium enhanced the activity of the PpksC promoter that controls bacillaene production, suggesting that B. subtilis senses and responds to Salmonella. The level of Salmonella inhibition, overall PpksC activity, and PpksC induction by Salmonella were all higher in nutrient-rich conditions than in nutrient-depleted conditions. Although eliminating the extracellular polysaccharide production of B. subtilis via deletion of the epsA-O operon had no significant effect on inhibitory activity against Salmonella in nutrient-rich conditions, this deletion mutant showed an enhanced antagonism against Salmonella in nutrient-depleted conditions, revealing an intricate relationship between exopolysaccharide production, nutrient availability, and bacillaene synthesis. Overall, this work provides evidence on the regulatory role of nutrient availability, sensing of the competitor, and EpsA-O polysaccharide in the social outcome of bacillaene-dependent competition between B. subtilis and S. Typhimurium. IMPORTANCE 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. Moreover, the production of extracellular polysaccharides by B. subtilis further alters the influence of these factors. Hence, this work highlights the inhibitory effect of B. subtilis, which is condition-dependent, and the importance of evaluating probiotic strains under conditions relevant to the intended use.
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Affiliation(s)
- Eli Podnar
- Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Andi Erega
- Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Tjaša Danevčič
- Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Eva Kovačec
- Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Bram Lories
- Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Hans Steenackers
- Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Ines Mandic-Mulec
- Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
- Chair of Microprocess Engineering and Technology (COMPETE), University of Ljubljana, Ljubljana, Slovenia
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