SpoVG is an important regulator of sporulation and affects biofilm formation by regulating Spo0A transcription in Bacillus cereus 0–9

Abstract

Background Bacillus cereus 0–9, a Gram-positive, endospore-forming bacterium isolated from healthy wheat roots in our previous research, is considered to be an effective biocontrol strain against several soil-borne plant diseases. SpoVG, a regulator that is broadly conserved among many Gram-positive bacteria, may help this organism coordinate environmental growth and virulence to survive. This study aimed to explore the multiple functions of SpoVG in B. cereus 0–9. Methods The gene knockout strains were constructed by homologous recombination, and the sporulation process of B. cereus 0–9 and its mutants were observed by fluorescence staining method. We further determined the spore yields and biofilm formation abilities of test strains. Transcriptional fusion strains were constructed by overlapping PCR technique, and the promoter activity of the target gene was detected by measuring its fluorescence intensity. The biofilm production and colonial morphology of B. cereus 0–9 and its mutants were determined to study the functions of the target genes, and the transcription level of the target gene was determined by qRT-PCR. Results According to observation of the sporulation process of B. cereus 0–9 in germination medium, SpoVG is crucial for regulating sporulation stage V of B. cereus 0–9, which is identical to that of Bacillus subtilis but differs from that of Bacillus anthracis. In addition, SpoVG could influence biofilm formation of B. cereus 0–9. The transcription levels of two genes closely related to biofilm-formation, sipW and calY, were downregulated in a ΔspoVG mutant. The role of SpoVG in regulating biofilm formation was further explored by deleting the genes abrB and sinR in the ΔspoVG mutant, respectively, generating the double mutant strains ΔspoVGΔabrB and ΔspoVGΔsinR. The phenotypes of these double mutants were congruent with those of the single abrB and sinR deletion strains, respectively, which showed increased biofilm formation. This indicated that spoVG was located upstream of abrB and sinR in the regulatory pathway of B. cereus biofilm formation. Further, the results of qRT-PCR and the luminescence intensity of transcriptional fusion strains indicated that spoVG gene deletion could inhibit the transcription of Spo0A. Conclusions SpoVG, an important regulator in the sporulation of B. cereus, is located upstream of Spo0A and participates in regulation of biofilm formation of B. cereus 0–9 through regulating the transcription level of spo0A. Sporulation and biofilm formation are crucial mechanisms by which bacteria respond to adverse conditions. SpoVG is therefore an important regulator of Spo0A and is crucial for both sporulation and biofilm formation of B. cereus 0–9. This study provides a new insight into the regulatory mechanism of environmental adaptation in bacteria and a foundation for future studies on biofilm formation of B. cereus.

The Study of Diversity in Sporulation among Closely Genetically Related <i>Bacillus cereus</i> Strains

“…2B) . FM 4-64 is also used to stain the membranes of sporulating cells of B. subtilis and B. cereus; however, it cannot stain the forespore at stage VI and later (Pogliano et al, 1999;Huang et al, 2021) . Hoechst 33342 facilitated the visualization of chromosomal DNA in B. cereus NBRC 3836, most of the cells observed were vegetative cells (Fig.…”

Bacillus cereus sensu lato biofilm formation and its ecological importance

“…For example, experiments using mutagenesis, heterologous expression, and transcription profiling indicated that B. cereus AR156 harbors a highly similar genetic circuit ( Bcspo0A - BcsinI - BcsinR ) [ 49 ]. A more recent study explored the multiple functions of SpoVG, another important sporulation regulator, in B. cereus 0–9 [ 50 ]. In B. subtilis , SpoVG is involved in sporulation via an unexplored mechanism, while studies on B. cereus 0–9 revealed that SpoVG controls biofilm formation by activating the transcription of Spo0A.…”

“…In B. subtilis , SpoVG is involved in sporulation via an unexplored mechanism, while studies on B. cereus 0–9 revealed that SpoVG controls biofilm formation by activating the transcription of Spo0A. Furthermore, SpoVG was also reported to influence both AbrB and SinI/SinR networks, and therefore biofilm development [ 50 ]. Thus, it was speculated that SpoVG is positioned upstream of Spo0A in the regulatory pathway, which expanded our knowledge of the spo0A - sinI - sinR genetic circuit in B. cereus .…”

The Transcription Factor SpoVG Is of Major Importance for Biofilm Formation of Staphylococcus epidermidis under In Vitro Conditions, but Dispensable for In Vivo Biofilm Formation

“…One putative mediator of σ B activity could be SpoVG (aka BarB in S. epidermidis ), a DNA/RNA-binding protein that is highly conserved in eubacteria [ 30 ]. SpoVG is a known regulator of virulence in a number of pathogenic firmicutes such as Bacillus cereus [ 31 ], Listeria monocytogenes [ 32 ], and S. aureus [ 33 , 34 , 35 ]. The regulatory protein is also reported to affect biofilm formation in B. cereus [ 31 ].…”

“…SpoVG is a known regulator of virulence in a number of pathogenic firmicutes such as Bacillus cereus [ 31 ], Listeria monocytogenes [ 32 ], and S. aureus [ 33 , 34 , 35 ]. The regulatory protein is also reported to affect biofilm formation in B. cereus [ 31 ]. Given that σ B controls the transcription of SpoVG in S. aureus [ 33 ] and that activity of SpoVG is enhanced by Stk1-mediated phosphorylation in the latter species [ 36 ], we wondered whether and how SpoVG might affect biofilm formation and ica transcription in S. epidermidis .…”