Endospore Formation Research Articles

The small acid-soluble proteins of Clostridioides difficile regulate sporulation in a SpoIVB2-dependent manner.

Clostridioides difficile is a pathogen whose transmission relies on the formation of dormant endospores. Spores are highly resilient forms of bacteria that resist environmental and chemical insults. In recent work, we found that C. difficile SspA and SspB, two small acid-soluble proteins (SASPs), protect spores from UV damage and, interestingly, are necessary for the formation of mature spores. Here, we build upon this finding and show that C. difficile sspA and sspB are required for the formation of the spore cortex layer. Moreover, using an EMS mutagenesis selection strategy, we identified mutations that suppressed the defect in sporulation of C. difficile SASP mutants. Many of these strains contained mutations in CDR20291_0714 (spoIVB2) revealing a connection between the SpoIVB2 protease and the SASPs in the sporulation pathway. This work builds upon the hypothesis that the small acid-soluble proteins can regulate gene expression.

INDUCTION ENDOSPORE FORMATION OF Bacillus subtilis KM16 AS A PROBIOTIC CANDIDATE BY OPTIMIZATION OF THE GROWTH CONDITIONS

Probiotics are living microorganisms which have beneficial effects. One of the benefits is enhancing immunity. Therefore, probiotics are often supplemented into food, medical, and aquaculture products. B. subtilis KM16 as endospore-producing bacteria have been known to increase probiotic resistance to confront the unstable conditions of the digestive tract. Spore formation of Bacillus is supported by the optimal condition of growth medium and incubation periods. The sufficient availability of carbon, nitrogen, and mineral source in the growth medium, and environmental conditions can support the formation of optimal endospores. This research aimed to determine the suitable sugar composition of a medium and optimum incubation time suitable for endospores formation of B. subtilis KM16. Glucose and maltose were utilized as a carbon source in several concentration as a growth medium for B. subtilis KM 16. The incubation time was 48 and 72 hours. The viable number of vegetative cells was not significantly different for the type of sugar and incubation periods. Based on the glucose concentration, 0.2% glucose exhibited the uppermost number of cells, while 1% glucose concentration caused the decrease of vegetative cells. In this study, 0.2% glucose with 48 hours incubation period showed the highest percentage of sporulation frequencies, up to 48%, but it was not significantly different from the other glucose concentration. The medium that contains 0.2% glucose with 48 hours incubation period is the best medium for the utilization of B. subtilis KM16 cells and spores as probiotic candidates.

Docking interactions determine substrate specificity of members of a widespread family of protein phosphatases

How protein phosphatases achieve specificity for their substrates is a major outstanding question. PPM family serine/threonine phosphatases are widespread in bacteria and eukaryotes, where they dephosphorylate target proteins with a high degree of specificity. In bacteria, PPM phosphatases control diverse transcriptional responses by dephosphorylating anti-anti-sigma factors of the STAS domain family, exemplified by B. subtilis phosphatases SpoIIE, which controls cell-fate during endospore formation, and RsbU, which initiates the General Stress Response. Using a combination of forward genetics, biochemical reconstitution, and AlphaFold2 structure prediction, we identified a conserved, tripartite substrate docking interface comprised of three variable loops on the surface of the PPM phosphatase domains of SpoIIE and RsbU that recognize the three-dimensional structure of the substrate protein. Non-conserved amino acids in these loops facilitate the accommodation of the cognate substrate and prevent dephosphorylation of the non-cognate substrate. Together, single-amino acid substitutions in these three elements cause an over five-hundred fold change in specificity. Our data additionally suggest that substrate-docking interactions regulate phosphatase specificity through a conserved allosteric switch element that controls the catalytic efficiency of the phosphatase by positioning the metal cofactor and substrate. We hypothesize that this is a generalizable mechanistic model for PPM family phosphatase substrate specificity. Importantly, the substrate docking interface with the phosphatase is only partially overlapping with the much more extensive interface with the upstream kinase, suggesting the possibility that kinase and phosphatase specificity evolved independently.

The small acid-soluble proteins of Clostridioides difficile regulate sporulation in a SpoIVB2-dependent manner.

Clostridioides difficile is a pathogen whose transmission relies on the formation of dormant endospores. Spores are highly resilient forms of bacteria that resist environmental and chemical insults. In recent work, we found that C. difficile SspA and SspB, two small acid-soluble proteins (SASPs), protect spores from UV damage and, interestingly, are necessary for the formation of mature spores. Here, we build upon this finding and show that C. difficile sspA and sspB are required for the formation of the spore cortex layer. Moreover, using an EMS mutagenesis selection strategy, we identified mutations that suppressed the defect in sporulation of C. difficile SASP mutants. Many of these strains contained mutations in CDR20291_0714 (spoIVB2) revealing a connection between the SpoIVB2 protease and the SASPs in the sporulation pathway. This work builds upon the hypothesis that the small acid-soluble proteins can regulate gene expression.

Retraction of: Disruption of the gene (spooA) encoding sporulation transcription factor blocks endospore formation and enterotoxin production in enterotoxigenic Clostridium perfringens type A.

Retraction of: Disruption of the gene (spooA) encoding sporulation transcription factor blocks endospore formation and enterotoxin production in enterotoxigenic Clostridium perfringens type A.

Multiple independent losses of sporulation and peptidoglycan in the Mycoplasmatales and related orders of the class Bacilli.

Many peptidoglycan-deficient bacteria such as the Mycoplasmatales are known host-associated lineages, lacking the environmental resistance mechanisms and metabolic capabilities necessary for a free-living lifestyle. Several peptidoglycan-deficient and non-sporulating orders of interest are thought to be descended from Gram-positive sporulating Bacilli through reductive evolution. Here we annotate 2650 genomes belonging to the class Bacilli, according to the Genome Taxonomy Database, to predict the peptidoglycan and sporulation phenotypes of three novel orders, RFN20, RF39 and ML615J-28, known only through environmental sequence surveys. These lineages are interspersed between peptidoglycan-deficient non-sporulating orders including the Mycoplasmatales and Acholeplasmatales, and more typical Gram-positive orders such as the Erysipelotrichales and Staphylococcales. We use the extant genotypes to perform ancestral state reconstructions. The novel orders are predicted to have small genomes with minimal metabolic capabilities and to comprise a mix of peptidoglycan-deficient and/or non-sporulating species. In contrast to expectations based on cultured representatives, the order Erysipelotrichales lacks many of the genes involved in peptidoglycan and endospore formation. The reconstructed evolutionary history of these traits suggests multiple independent whole-genome reductions and loss of phenotype via intermediate transition states that continue into the present. We suggest that the evolutionary history of the reduced-genome lineages within the class Bacilli is one driven by multiple independent transitions to host-associated lifestyles, with the degree of reduction in environmental resistance and metabolic capabilities correlated with degree of host association.

Mechanism of deltamethrin biodegradation by Brevibacillus parabrevis BCP-09 with proteomic methods.

Ester-containing deltamethrin pesticides are widely used in farmland and have inevitable side effects on the biosphere and human health. Microbia have been used for efficient degradation of deltamethrin, but the related mechanism and enzyme characteristics have not been elucidated. In this study, a species Brevibacillus parabrevis BCP-09 could degrade up to 75 mg L−1 deltamethrin with a degradation efficiency of 95.41%. Proteomic and genomic methods were used to explore its degradation mechanism. Enzymes belonged to hydrolases, oxidases and aromatic compound degrading enzymes were expressed enhanced and might participate in the deltamethrin degradtion. RT-PCR experiment and enzyme activity analysis verified the degradation of deltamethrin by bacterial protein. Additionally, the formation of endospores can help strain BCP-09 resist the toxicity of deltamethrin and enhance its degradation. This study supplies a scientific evidence for the application of Brevibacillus parabrevis BCP-09 in the bioremediation of environmental pollution and enriches the resources of deltamethrin-biodegradable proteins.

Isolation of Weizmannia coagulansand probiotic characterisation of strains

Weizmannia coagulans is a potential bacterial candidate for probiotics because of their advantageous characteristics in endospore formation, antibacterial production, and other beneficial human health effects. In this study, we isolated W. coagulans strains from different sample types collected in Hanoi and examined them for probiotic characteristics. From 40 samples, 5 strains were isolated from cow faeces. All W. coagulans strains had non-haemolytic activity and were susceptible to seven tested antibiotics. Cell-free supernatants of W. coagulans strains cultured in MRS medium could inhibit some bacterial pathogens such as Enterococcus faecalis, Listeria monocytogenes, Vibrio vulnificus, and Aeromonas dhakensis. The strains showed antioxidant activity with scavenging DPPH rates ranging from 72 to 82%. Three strains were able to adhere to the HT-29 cell line with adhesion ratesranging from 46 to 62.59%. The spores and vegetative cells of the three strains also showed great stress tolerance (survival rates >90%) against simulated gastrointestinal fluid. In liquid media containing 0.1% pancreatin and 0.3% bile salt, spores of VTCC 12782 and VTCC 12779 could germinate at rates of 25 and 2%, respectively. With the most beneficial characteristics, W. coagulans VTCC 12782 is suggested as a potential candidate for the development of probiotic products in the future.

R/K selection of GC content in prokaryotes.

The guanine/cytosine (GC) content of prokaryotic genomes is species-specific, taking values from 16% to 77%. This diversity of selection for GC content remains contentious. We analyse the correlations between GC content and a range of phenotypic and genotypic data in thousands of prokaryotes. GC content integrates well with these traits into r/K selection theory when phenotypic plasticity is considered. High GC-content prokaryotes are r-strategists with cheaper descendants thanks to a lower average amino acid metabolic cost, colonize unstable environments thanks to flagella and a bacillus form and are generalists in terms of resource opportunism and their defence mechanisms. Low GC content prokaryotes are K-strategists specialized for stable environments that maintain homeostasis via a high-cost outer cell membrane and endospore formation as a response to nutrient deprivation, and attain a higher nutrient-to-biomass yield. The lower proteome cost of high GC content prokaryotes is driven by the association between GC-rich codons and cheaper amino acids in the genetic code, while the correlation between GC content and genome size may be partly due to functional diversity driven by r/K selection. In all, molecular diversity in the GC content of prokaryotes may be a consequence of ecological r/K selection.

Bacillus subtilis NrnB is expressed during sporulation and acts as a unique 3'-5' exonuclease.

All cells employ a combination of endo- and exoribonucleases to degrade long RNA polymers to fragments 2-5 nucleotides in length. These short RNA fragments are processed to monoribonucleotides by nanoRNases. Genetic depletion of nanoRNases has been shown to increase abundance of short RNAs. This deleteriously affects viability, virulence, and fitness, indicating that short RNAs are a metabolic burden. Previously, we provided evidence that NrnA is the housekeeping nanoRNase for Bacillus subtilis. Herein, we investigate the biological and biochemical functions of the evolutionarily related protein, B. subtilis NrnB (NrnBBs). These experiments show that NrnB is surprisingly different from NrnA. While NrnA acts at the 5' terminus of RNA substrates, NrnB acts at the 3' terminus. Additionally, NrnA is expressed constitutively under standard growth conditions, yet NrnB is selectively expressed during endospore formation. Furthermore, NrnA processes only short RNAs, while NrnB unexpectedly processes both short RNAs and longer RNAs. Indeed, inducible expression of NrnB can even complement the loss of the known global 3'-5' exoribonucleases, indicating that it acts as a general exonuclease. Together, these data demonstrate that NrnB proteins, which are widely found in Firmicutes, Epsilonproteobacteria and Archaea, are fundamentally different than NrnA proteins and may be used for specialized purposes.

Bacterial molecular machinery in the Martian cryosphere conditions.

The exploration of Mars is one of the main objectives of space missions since the red planet is considered to be, or was in the past, potentially habitable. Although the surface of Mars is now dry and arid, abundant research suggests that water covered Mars billions of years ago. Recently, the existence of liquid water in subglacial lakes has been postulated below the South pole of Mars. Until now, experiments have been carried out on the survival of microorganisms in Martian surface conditions, but it remains unknown how their adaptation mechanisms would be in the Martian cryosphere. In this work, two bacterial species (Bacillus subtilis and Curtobacterium flacumfaciens) were subjected to a simulated Martian environment during 24 h using a planetary chamber. Afterward, the molecular machinery of both species was studied to investigate how they had been modified. Proteomes, the entire set of proteins expressed by each bacterium under Earth (named standard) conditions and Martian conditions, were compared using proteomic techniques. To establish this evaluation, both the expression levels of each protein, and the variation in their distribution within the different functional categories were considered. The results showed that these bacterial species followed a different strategy. The Bacillus subtilis resistance approach consisted of improving its stress response, membrane bioenergetics, degradation of biomolecules; and to a lesser extent, increasing its mobility and the formation of biofilms or resistance endospores. On the contrary, enduring strategy of Curtobacterium flacumfaciens comprised of strengthening the cell envelope, trying to protect cells from the extracellular environment. These results are especially important due to their implications for planetary protection, missions to Mars and sample return since contamination by microorganisms would invalidate the results of these investigations.

An improved integrative GFP-based vector for genetic engineering of Parageobacillus thermoglucosidasius facilitates the identification of a key sporulation regulator

Parageobacillus thermoglucosidasius is a thermophilic Gram-positive bacterium, which is a promising host organism for sustainable bio-based production processes. However, to take full advantage of the potential of P. thermoglucosidasius, more efficient tools for genetic engineering are required. The present study describes an improved shuttle vector, which speeds up recombination-based genomic modification by incorporating a thermostable sfGFP variant into the vector backbone. This additional selection marker allows for easier identification of recombinants, thereby removing the need for several culturing steps. The novel GFP-based shuttle is therefore capable of facilitating faster metabolic engineering of P. thermoglucosidasius through genomic deletion, integration, or exchange. To demonstrate the efficiency of the new system, the GFP-based vector was utilised for deletion of the spo0A gene in P. thermoglucosidasius DSM2542. This gene is known to be a key regulator of sporulation in Bacillus subtilis, and it was therefore hypothesised that the deletion of spo0A in P. thermoglucosiadius would produce an analogous sporulation-inhibited phenotype. Subsequent analyses of cell morphology and culture heat resistance suggests that the P. thermoglucosidasius ∆spo0A strain is sporulation-deficient. This strain may be an excellent starting point for future cell factory engineering of P. thermoglucosidasius, as the formation of endospores is normally not a desired trait in large-scale production.

A Sporulation-Independent Way of Life for Bacillus thuringiensis in the Late Stages of an Infection.

The formation of endospores has been considered the unique survival and transmission mode of sporulating Firmicutes due to the exceptional resistance and persistence of this bacterial form. However, nonsporulated bacteria (Spo-) were reported at the early stages following the death of a host infected with Bacillus thuringiensis, an entomopathogenic sporulating bacterium. Here, we investigated the characteristics of the bacterial population in the late stages of an infection in the B. thuringiensis/Galleria mellonella infection model. Using fluorescent reporters and molecular markers coupled to flow cytometry, we demonstrated that the Spo- cells persist and constitute about half of the population 2 weeks post-infection (p.i.). Protein synthesis and growth recovery assays indicated that they are in a metabolically slowed-down state. These bacteria were extremely resistant to the insect cadaver environment, which did not support growth of in vitro-grown vegetative cells and spores. A transcriptomic analysis of this subpopulation at 7 days p.i. revealed a signature profile of this state, and the expression analysis of individual genes at the cell level showed that more bacteria mount an oxidative stress response as their survival time increases, in agreement with the increase of the free radical level in the host cadaver and in the number of reactive oxygen species (ROS)-producing bacteria. Altogether, these data show for the first time that nonsporulated bacteria are able to survive for a prolonged period of time in the context of an infection and indicate that they engage in a profound adaptation process that leads to their persistence in the host cadaver. IMPORTANCE Bacillus thuringiensis is an entomopathogenic bacterium widely used as a biopesticide. It belongs to the Bacillus cereus group, comprising the foodborne pathogen B. cereus sensu stricto and the anthrax agent Bacillus anthracis. Like other Firmicutes when they encounter harsh conditions, these Gram-positive bacteria can form dormant cells called spores. Due to its highly resistant nature, the spore was considered the unique mode of long-term survival, eclipsing any other form of persistence. Breaking this paradigm, we observed that B. thuringiensis was able to persist in its host cadaver in a nonsporulated form for at least 14 days. Our results show that these bacteria survived in the cadaver environment, which proved hostile for actively growing bacteria by engaging in a profound adaptation process. Studying this facet of the life cycle of a sporulating bacterium provides new fundamental knowledge and might lead to the development of strategies to combat sporulating pathogenic species.

Effect of Sublethal Concentrations of Zinc Oxide Nanoparticles on Bacillus cereus

Zinc oxide nanoparticles (ZnONPs), which are produced on a large scale, pose a potential threat to various environments because they can interact with the microbial populations found in them. Bacteria that are widespread in soil, water, and plant material include the Bacillus cereus group, which plays an important role in biodegradation and the nutrient cycle and is a major factor determining ecological balance. This group includes, among others, the foodborne pathogen B. cereus sensu stricto (herein referred to as B. cereus). The aim of this study was a comprehensive assessment of the effects of commercially available ZnONPs on B. cereus. The MIC (minimum inhibitory concentration) for B. cereus was 1.6 mg/mL, and the MBC (minimum bactericidal concentration) was 1.8 mg/mL. Growth of B. cereus was inhibited by a concentration of ZnONPs lower than or equal to MIC50. Concentrations from 0.2 to 0.8 mg/mL inhibited the growth of these bacteria in liquid media, induced symptoms of oxidative stress, and stimulated an environmental stress response in the form of biofilm and endospore formation. In addition, ZnONPs negatively affected the ability of the bacteria to break down the azo dye Evans Blue but enhanced the antimicrobial properties of phenolic compounds. Sublethal concentrations of ZnONPs generally decreased the activity of B. cereus cells, especially in the presence of phenolics, which indicates their potential toxicological impact, but at the same time they induced universal defence responses in these cells, which in the case of potential pathogens can hinder their removal.

Profiling Mycobacterium ulcerans: sporulation, survival strategy and response to environmental factors.

Mycobacterium ulcerans is the causative agent of Buruli ulcer - a necrotizing skin infection. As an environmental pathogen, it has developed stress response mechanisms for survival. Similar to endospore formation in M. marinum, it is likely that M. ulcerans employs sporulation mechanisms for its survival and transmission. In this review, we modeled possible transmission routes and patterns of M. ulcerans from the environment to its host. We provided insights into the evolution of M. ulcerans and its genomic profiles. We discuss reservoirs of M. ulcerans as an environmental pathogen and its environmental survival. We comprehensively discuss sporulation as a possible stress response mechanism and modelled endospore formation in M. ulcerans. At last, we highlighted sporulationassociated markers, which upon expression trigger endospore formation.

ANTIMICROBIAL ACTIVITY OF METABOLITES PRODUCED BY NOVEL COAGULASE-NEGATIVE STAPHYLOCOCCI (CNS) ISOLATED FROM FERMENTED DAIRY PRODUCTS IN MALANG, INDONESIA

Yogurt and kefir are well-known fermented dairy products that provide many benefits to human health. Microorganisms contained in yogurt and kefir play an important role to produce bioactive metabolites, including eradicating pathogens. This study presents the antimicrobial activity of 12 strains isolated from kefir and yogurt samples obtained in Malang, Indonesia. Strain K3 from kefir shows the highest antimicrobial activity with the diameter of the inhibitory zone was 8.11±0.07 mm against Escherichia coli and 8.20±0.17 mm against Staphylococcus aureus. Phenotypic characterization through Gram-staining, endospore-forming, motility, catalase, oxidase, and carbohydrate fermentation test, and genotypic identification through the 16S rRNA gene sequencing and phylogenetic analysis was performed to identify the species of isolate. Based on the result, K3 was characterized as non-motile Gram-negative bacilli bacteria, tested negative in endospore formation, catalase, and oxidase. According to the nucleotide sequence of 16S rRNA gene, the isolate was classified as Staphylococcus saprophyticus strain UTI-045 with 100% of similarity. Furthermore, the GC-MS analysis of the strain’s cell-free supernatant (CFS) reveals 3,6-Dioxa-2, 7-disilaoctane, 2,2,4,7,7-pentamethyl- (Rt=9.449 min); and Propanoic acid, 2-[(trimethylsilyl)oxy]-, trimethylsilyl ester (Rt=11.328 min) as the active metabolites.

Assessing Indigenous Soil Ureolytic Bacteria as Potential Agents for Soil Stabilization

Microbially induced carbonate precipitation by ureolysis is a biomineralization process that has been adapted by various microorganisms in different natural environments. This widespread natural phenomenon can be employed in numerous civil engineering and soil stabilization applications. In the present study, the potential of indigenous soil urease-producing bacteria as potential agents for soil stabilization methods was investigated. Assessment of the eight active urease-producing bacterial species isolated from the farm soil samples has demonstrated that all the isolates were Gram-positive rod-shaped bacteria with promising characteristics such as the formation of endospore which is essential for bacterial survival in harsh conditions within the soil environment. The pH profile and growth profile of the isolates were studied and urease activity was measured by the phenol hypochlorite assay method. Two isolates designated isolate O6w and isolate O3a were selected based on the highest urease activity recorded at 665 U/mL and 620 U/mL, respectively, and they were able to increase and sustain alkaline culture condition (pH 8.71 ± 0.01 and 8.55 ± 0.01) which was suitable for CaCO3 precipitation. The isolates were identified based on 16S ribosomal RNA sequencing to be Bacillus cereus (O6w) and Bacillus paramycoides (O3a). This current study suggested that indigenous soil ureolytic bacteria are potential raw material for the biotreatment of soils stability.

Antifungal activity and genomic characterization of the biocontrol agent Bacillus velezensis CMRP 4489

The development of bio-based products has increased in recent years, and species of the Bacillus genus have been widely used for product development due to their elevated production of antimicrobial molecules and resistance to extreme environmental conditions through endospore formation. In this context, the antifungal potential of Bacillus velezensis CMRP 4489 was investigated using in silico predictions of secondary metabolites in its genome and in vitro tests against the following phytopathogenic fungi: Sclerotinia sclerotiorum, Macrophomina phaseolina, and Botrytis cinerea. The in-silico predictions indicated that CMRP 4489 possesses several Biosynthetic Gene Clusters (BGCs) capable of producing molecules with antifungal properties and other non-identified BGCs. The in vitro assay results evidenced strong antifungal activity, inhibiting more than 60% of the tested fungi, and the isolate’s molecules were stable under diverse physicochemical conditions. The in vitro assay evidenced significant antifungal activity, deformation of the hyphal structure in SS, biofilm formation capacity, and swarming motility. In the colonization assay, we observed attachment, colonization, and net-shaped biofilm formation, with the strain transitioning from the seeds to nearby structures. Therefore, CMRP 4489 showed to be a potential biocontrol agent against various diseases with agronomic importance and can be used under adverse environmental conditions.

Phenotypic Characterization and Identification of Potential L-Asparaginase-Producing Thermohalophilic Bacteria from Wawolesea Hot Spring, North Konawe, Southeast Sulawesi, Indonesia.

<b>Background and Objective:</b> L-asparaginase-producing thermohalophilic bacteria have the potential of producing an enzyme tolerant to high heat and salt levels. This enzyme, L-asparaginase, can be used as a biological agent for the cancer therapy of acute lymphoblastic leukemia and melanosarcoma as it has a specific ability to inhibit the formation of nutrients for cancer cells. This enzyme is also used effectively in food industries operating at high temperatures due to its ability to reduce acrylamide, a trigger of cancer cells. This study sought to figure out the phenotypic characters of and identify potential L-asparaginase-producing thermohalophilic bacteria from Wawolesea Hot Spring, North Konawe, Southeast Sulawesi. <b>Materials and Methods:</b> The characterization conducted on potential L-asparaginase-producing thermohalophilic bacterial isolates consisted of the following: Colony morphological characterization, covering the shapes, edges, internal structures, elevations and colours of the colonies, cell morphological characterization, covering gram staining, endospore formation and motility, biochemical characterization, covering catalase, Methyl Red and Voges Proskauer (MR-VP), gelatin hydrolysis, citrate, indole and carbohydrate fermentation tests and physiological characterization, covering pH effect, salinity, oxygen demand and temperature effect tests. Bacterial isolate identification was carried out in two stages, namely phenetic identification based on the phenotypic characterization data determine through a preliminary identification and numeric-phenetic identification. <b>Results:</b> The characterization results showed that the bacterial isolates AAT 1.4, AAT 3.2 and CAT 3.4 were <i>bacillus</i>-shaped, Gram-positive, motile, catalase-positive and aerobic. Based on the numeric-phenetic analysis results, the isolates AAT 1.4 and CAT 3.4 had a 92.9% similarity to <i>Bacillus subtilis</i>, while isolate AAT 3.2 had a 92.9% similarity to <i>Brevibacillus limnophilus</i>. <b>Conclusion:</b> According to the numeric-phenetic analysis results, the isolates AAT 1.4 and CAT 3.4 belong to the species <i>Bacillus subtilis</i>, while isolate AAT 3.2 belongs to the species <i>Brevibacillus limnophilus</i>.

Chromosome remodelling by SMC/Condensin in B. subtilis is regulated by monomeric Soj/ParA during growth and sporulation

SMC complexes, loaded at ParB-parS sites, are key mediators of chromosome organization in bacteria. ParA/Soj proteins interact with ParB/Spo0J in a pathway involving adenosine triphosphate (ATP)-dependent dimerization and DNA binding, facilitating chromosome segregation in bacteria. In Bacillus subtilis, ParA/Soj also regulates DNA replication initiation and along with ParB/Spo0J is involved in cell cycle changes during endospore formation. The first morphological stage in sporulation is the formation of an elongated chromosome structure called an axial filament. Here, we show that a major redistribution of SMC complexes drives axial filament formation in a process regulated by ParA/Soj. Furthermore, and unexpectedly, this regulation is dependent on monomeric forms of ParA/Soj that cannot bind DNA or hydrolyze ATP. These results reveal additional roles for ParA/Soj proteins in the regulation of SMC dynamics in bacteria and yet further complexity in the web of interactions involving chromosome replication, segregation and organization, controlled by ParAB and SMC.