bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/310516

Bacillus cereus HS24 Suppresses Conidia Germination of Magnaporthe oryzae by Inhibiting the Ca2+ Signaling Pathway

Huang, W.·Liu, X.·Zhou, X.·Chen, Y.·Li, Y.·Liu, H.-x.
View original source ↗Export metadata ↓

Abstract

Rice yield is greatly reduced due to rice blast, a worldwide multi-cycle fungal disease caused by the ascomycete Magnaporthe oryzae. Previously, Bacillus cereus HS24 was isolated from rice growing area, which showed a strong bio-control effect on M. oryzae. In order to better exploit it as a bio-control agent, HS24 has been studied for its mechanism of controlling rice blast. Our results showed that conidial germination of M. oryzae was significantly inhibited by HS24 suspension, n and the inhibition rate reached to 97.83% at the concentration of 10 CFU/ml. The transcriptional level of CAMKII, PMC1 and CCH1, which are key genes involved in Ca2+ signaling pathway, were significantly decreased in HS24-treated conidia. The treatment of M. oryzae with Ca2+ signaling pathway inhibitors KN-93, Verapamil, and cyclopiazonic acid (CPA) significantly reduced conidial germination rate and inhibited germ tube elongation. This inhibition effect was found to be concentration-dependent, similar to the HS24 treatment. By quantifying free Ca2+ in M. oryzae conidia, a significant reduction of intracellular free Ca2+ concentration in HS24-treated conidia in comparison to sterile water-treated conidia was found. The addition of exogenous Ca2+ did not abolish the inhibitory effect of HS24 on the reduction of intracellular free Ca2+ concentration and conidial germination. In conclusion, B. cereus HS24 can inhibit conidial germination by suppressing Ca2+ signaling in M. oryzae, and thus offers a great potential as a bio-control agent in rice blast management.\n\nImportanceIn the bio-control of rice blast, most of researches focused on the inhibitory effect of bio-control agents on development of M. oryzae, including inhibition of conidia germination, germ tube deformity, mycelium growth inhibition, etc, while little work has elucidated the molecular mechanisms underlying the various phenotypic change in M. oryzae. In order to better exploit HS24 as a potential bio-control agent, we studied the molecular mechanisms underlying the suppression of B. cereus HS24 on M. oryzae Guy11, and draw the conclusion that HS24 may inhibit conidia germination and germ tube elongation through inhibiting the Ca2+ signaling pathway. In this study, we characterized the morphological and physiological changes of M. oryzae when interacting with B. cereus HS24, and further investgated the responses of M. oryzae Ca2+ signallig pathway to HS24 treatment. Thus we have provided one more piece for the B. cereus / M. oryzae supression puzzle at the molecular level.

Explore related subjects

microbiologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Huang, W., Liu, X., Zhou, X., Chen, Y., Li, Y., Liu, H.-x.. 2018-04-28. Bacillus cereus HS24 Suppresses Conidia Germination of Magnaporthe oryzae by Inhibiting the Ca2+ Signaling Pathway. https://doi.org/10.1101/310516

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

A closed genome of Streptococcus agalactiae ST347/II reveals a composite integrative element coupling nisin P biosynthesis to erm(B) and tet(O) in Dominican group B Streptococcus

Clindamycin is the alternative for intrapartum prophylaxis against group B Streptococcus in penicillin-allergic women, and whether it works depends on which lineages carry the resistance and on the mobile element that moves it. No Dominican group B Streptococcus genome has been closed. A Streptococcus agalactiae isolate from residual diagnostic material was sequenced twice on Oxford Nanopore, annotated, and screened against 83 genomes from a published Dominican maternal colonisation survey. The assembly is one circular chromosome of 2,066,859 bp with all seven rRNA operons resolved: ST347/CC19, serotype II, carrying erm(B), tet(O), mef(J) and msr(I). Two integrative conjugative elements were delimited: one of ~34 kb related to Tn5252 carrying erm(B) and tet(O), another of ~35 kb at a tRNA-Lys gene carrying mef(J) and msr(I). An eleven-gene class I lanthipeptide cluster lies 96 bp from the first element, on the same strand and with no annotated feature between them; its precursor encodes a 31-residue core identical to nisin P. The complete operon was found in 12 of the 83 genomes, 13 of 84 (15.5%) with the isolate. tet(O) was present in all 12 carriers and none of the 71 others (Fisher p = 1.03 x 10^-14), erm(B) in 12 of 12 against 3 of 71 (p = 4.70 x 10^-12). All eleven ST1 genomes lack both the operon and the nisin resistance protein; all 15 ST1010/IV genomes carry aac(6')-Ie/aph(2'')-Ia. Clindamycin resistance is therefore tightly associated with a lantibiotic-encoding element and contiguous with it in the one closed genome; in the drafts the relationship is statistical, and co-occurrence is not linkage. The ST1 absence predicts lineage-wide susceptibility, testable by deferred antagonism.

microbiology↗
bioRxiv2026

Factors affecting microbial community composition in Split Lake, MB, Canada

Split Lake is a large freshwater lake in northern Manitoba, Canada, that receives major inflows from the Nelson River, Burntwood River, and Grassy River. In 1976, during the Churchill River Diversion (CRD) project, most of the water in the Churchill River was diverted into the Nelson River via the Rat River, and the Burntwood River, creating a large inflow pressure in the lower Nelson area, including Split Lake. Decades after its implementation, the Churchill River Diversion still influences ecological and environmental processes in the area. In this study, metabarcoding of the 16S rRNA gene was employed to characterize the microbial community structure of the lake. Environmental factors (temperature, pH, turbidity, dissolved oxygen) and cyanotoxin levels were also assessed. The objectives of this study were to establish a baseline for microbiota across the lake and examine how environmental variables affect microbial population dynamics. The study was conducted in the summer of 2024, encompassing 14 sites on Split Lake and 2 sites on Assean Lake, an adjacent waterbody with minimal influence from hydroelectric infrastructure. Split Lake was found to harbor six distinct microbial clusters, with turbidity and dissolved oxygen levels correlating with different aquatic regimes within the lake. The predominant taxa in Split Lake included Actinobacteria hgcI clade and Cyanobium. Microcystin concentrations measured throughout the study were always below the Maximum Acceptable Concentration (MAC) set for Canadian federal drinking water standards.

microbiology↗
bioRxiv2026

Particle-Associated Prokaryotic Community Structures in the Bering and Chukchi Seas

Free-living and particle-associated bacteria play distinct roles in the cycling of organic matter, but how these lifestyles are partitioned in the highly productive, rapidly warming Bering and Chukchi Seas is largely unknown. During the Arctic Shelf Growth, Advection, Respiration and Deposition Rate Experiments (ASGARD) cruise in June 2017, a period of anomalously warm sea surface temperatures, we collected 78 samples at three depths (surface, middle, and bottom) at 12 process stations and sequentially filtered them onto 20 {micro}m, 3 {micro}m, and 0.2 {micro}m filters. Using 16S rRNA gene amplicon sequencing and hierarchical clustering of amplicon sequence variant (ASV) relative abundances, we resolved four sample clusters. Although pore size was not used to build the clusters, communities separated into a free-living cluster associated mainly with Anadyr Water (FL1; 0.2 {micro}m fraction) and three particle-associated clusters (PA1-PA3; 3 and 20 {micro}m fractions), several of which were enriched in Bacteroidia. Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia were present in all size fractions, with Gammaproteobacteria most biased toward the free-living fraction. Community structure did not differ with depth, consistent with the shallow, weakly stratified shelf, and distance-based redundancy analysis identified salinity as the sole significant environmental factor distinguishing communities. These results suggest that lifestyle and water-mass origin, rather than depth, structure size-fractionated bacterial communities on the Pacific Arctic shelf, and that freshening and changes in bloom dynamics could reshape particle-associated communities in this region.

microbiology↗