More Like this

1. The biocontrol potential of endophyte Bacillus velezensis to reduce post-harvest tomato infection caused by Rhizopus microsporus

   https://doi.org/10.1128/spectrum.01064-25  

   Kock, Alicia; Napo, Mmanoko; Viviers, Dionné; Akinmoladun, Oluwakemi V; Alayande, Kazeem A; Yusuf, Abdullahi; Uehling, Jessie; Pawlowska, Teresa E; Adeleke, Rasheed A (October 2025, Microbiology Spectrum)

   Hockett, Kevin Loren (Ed.)

   ABSTRACT Rhizopus microsporusis a necrotrophic post-harvest pathogen that causes significant economic losses in the agricultural sector. To explore alternatives to conventional management strategies for the mitigation of post-harvest infections, we investigated the potential of two previously identified endophyticBacillus velezensisstrains as biological control agents. Throughin vitroandin vivoexperiments, we examined the mechanisms of biocontrol displayed by twoB. velezensisstrains (KV10 and KV15) against threeR. microsporusstrains (W2-50, W2-51, and W2-58).In vitroassays assessed co-cultivability and the inhibitory effects ofB. velezensisagainstR. microsporus. The results demonstrated strain-specific antifungal activity with a reduction in fungal growth across treatments. Further analysis revealed that volatile organic compounds produced byB. velezensiscontributed to its antifungal properties. To evaluate the biocontrol efficacyin vivo, tomato fruits were inoculated withR. microsporusand subsequently treated withB. velezensis. The results support the strain-specific reduction in tomato spoilage, yielding various spoilage rates observed across treatments. Our findings highlight the potential ofB. velezensisas a promising biocontrol agent for the management ofR. microsporuspost-harvest infections in tomatoes. Further research is warranted to optimize the applicationof B. velezensisas a sustainable and environmentally friendly approach for controlling post-harvest diseases in tomatoes.IMPORTANCEOur study shows the significance of improving sustainable agriculture by offering an alternative to the use of chemical fungicides in post-harvest applications. Opportunistic fungal pathogens likeRhizopus microsporuscan have detrimental effects on post-harvest commodities like tomatoes. Post-harvest fungal infections are mainly controlled by chemical fungicides that pose health risks to humans and the environment. Utilizing biocontrol agents provides an environmentally safe alternative. Understanding the mechanisms of biocontrol employed by beneficial bacteria likeBacillus velezensison fungal pathogens gives insight into safer, more environmentally friendly alternatives to protect food crops. Our results suggest that targeted microbial solutions can mitigate post-harvest losses. 

   more » « less
2. Euprymna berryi as a comparative model host for Vibrio fischeri light organ symbiosis

   https://doi.org/10.1128/aem.00001-25  

   Imes, Avery M; Pavelsky, Morgan N; Badal, Klodia; Kamp, Derrick L; Briseño, John L; Sakmar, Taylor; Vogt, Miranda A; Nyholm, Spencer V; Heath-Heckman, Elizabeth_A C; Grasse, Bret; et al (July 2025, Applied and Environmental Microbiology)

   Rudi, Knut (Ed.)

   ABSTRACT Functional studies of host-microbe interactions benefit from natural model systems that enable the exploration of molecular mechanisms at the host-microbe interface. BioluminescentVibrio fischericolonize the light organ of the Hawaiian bobtail squid,Euprymna scolopes, and this binary model has enabled advances in understanding host-microbe communication, colonization specificity,in vivobiofilms, intraspecific competition, and quorum sensing. The hummingbird bobtail squid,Euprymna berryi,can be generationally bred and maintained in lab settings and has had multiple genes deleted by CRISPR approaches. The prospect of expanding the utility of the light organ model system by producing multigenerational host lines led us to determine the extent to which theE. berryilight organ symbiosis parallels known processes inE. scolopes. However, the nature of theE. berryilight organ, including its microbial constituency and specificity for microbial partners, has not been examined. In this report, we isolated bacteria fromE. berryianimals and tank water. Assays of bacterial behaviors required in the host, as well as host responses to bacterial colonization, illustrate largely parallel phenotypes inE. berryiandE. scolopeshatchlings. This study revealsE. berryito be a valuable comparative model to complement studies inE. scolopes.IMPORTANCEMicrobiome studies have been substantially advanced by model systems that enable functional interrogation of the roles of the partners and the molecular communication between those partners. TheEuprymna scolopes-Vibrio fischerisystem has contributed foundational knowledge, revealing key roles for bacterial quorum sensing broadly and in animal hosts, for bacteria in stimulating animal development, for bacterial motility in accessing host sites, and forin vivobiofilm formation in development and specificity of an animal’s microbiome.Euprymna berryiis a second bobtail squid host, and one that has recently been shown to be robust to laboratory husbandry and amenable to gene knockout. This study identifiesE. berryias a strong symbiosis model host due to features that are conserved with those ofE. scolopes, which will enable the extension of functional studies in bobtail squid symbioses. 

   more » « less
3. Four nudivirus core genes present in the genome of Venturia canescens are required for virus-like particle formation and prevention of encapsulation of parasitoid wasp eggs

   https://doi.org/10.1128/jvi.01305-25  

   Mao, Meng; Stouthamer, Corinne M; Lorenzi, Ange; Strand, Michael R; Burke, Gaelen R (November 2025, Journal of Virology)

   van_Oers, Monique M (Ed.)

   ABSTRACT Venturia canescensis a parasitoid wasp that harbors a domesticated endogenous virus (DEV) and parasitizes host insects likeEphestia kuehniella. TheV. canescensDEV evolved from an alphanudivirus and produces virus-like particles (VLPs) in females that protect wasp eggs from a host immune defense called encapsulation. In contrast, very few DEV genes required for VLP formation and function have been identified. In this study, we characterized fiveV. canescensDEV genes of unknown function that all nudiviruses encode. Three of these genes are single copy (OrNVorf18-like,OrNVorf61-like, andOrNVorf76-like), whileOrNVorf41-likehas expanded into a six-member family andOrNVorf47-likehas expanded into a three-member family. Sequence analysis indicated all of these genes retain essential motifs present in nudivirus homologs, while transmission electron microscopy (TEM) studies characterized the timing of VLP formation during the wasp pupal stage. RNA interference (RNAi) assays identifiedOrNVorf18-like,OrNVorf61-like,OrNVorf41-like-1,andOrNVorf41-like-2as genes that are required for normal VLP formation. Knockdown ofOrNVorf47-likefamily members did not affect VLP formation but did disable binding of VLPs toV. canescenseggs and protection against encapsulation. Disabled formation of VLPs in response to RNAi knockdown ofOrNVorf18-like,OrNVorf61-like,OrNVorf41-like-1,andOrNVorf41-like-2also resulted in wasp eggs being encapsulated. In contrast, knockdown ofOrNVorf76-likehad no effect on VLP assembly, egg binding, or encapsulation. Altogether, reported results significantly advance our understanding ofV. canescensVLP (VcVLP) formation and function. IMPORTANCEUnderstanding howV. canescenscoopted an alphanudivirus to produce VcVLPs is of interest to the study of virus evolution. Our results show that three nudivirus core genes have essential functions in VcVLP formation, while one is essential for the novel function of binding to wasp eggs and protection from encapsulation, which is the most important immune defense of insects against parasitoids. 

   more » « less
4. The virulence regulator bvgS controls nutrient-induced filamentation in Bordetella avium

   https://doi.org/10.1128/jb.00030-25  

   Perslow, Niklas G; Meadows-Graves, Serena J; Luallen, Robert J (September 2025, Journal of Bacteriology)

   Kendall, Melissa M (Ed.)

   ABSTRACT Bacteria can change morphology in response to stressors and changes in their environment, including infection of a host. We previously identified the bacterial species,Bordetella atropi, which uses nutrient-induced filamentation as a novel mechanism for cell-to-cell spreading in the intestinal epithelial cells of a nematode host. To further investigate the conservation of nutrient-induced filamentation in Bordetellae, we utilized the turkey-infecting speciesBordetella avium,which filamentsin vitrowhen switched from a standard growth media to an enriched media. We conducted a selection-based filamentation screen withB. aviumand isolated two independent non-filamentous mutants that failed to filament in highly enriched media. These mutants contained different alleles inbvgS,the sensor in the two-component master virulence regulator (BvgAS) conserved across theBordetellagenus. To investigate the role ofbvgSin nutrient-induced filamentation, we conducted transcriptomics and found that our allele ofbvgSresulted in loss of responsiveness to highly enriched media, especially in genes related to nutrient uptake and metabolism. The most dysregulated gene in thebvgSmutant encoded for succinyl-CoA:acetate CoA-transferase, and we were able to regulate filamentation with exogenous metabolites up and downstream of this enzyme. These data suggest thatbvgSregulates nutrient-induced filamentation by controlling metabolic capacity. Overall, we found that the virulence regulatorbvgScan control nutrient-induced filamentation inB. avium,suggesting there may be conservation in Bordetellae for utilizing this morphological change as a virulence phenotype.IMPORTANCEBordetella aviumis the causative agent of bordetellosis, an infectious disease affecting the respiratory system of birds, significantly increasing morbidity in poultry, ultimately leading to economic losses. It is long known that the pathogenesis ofB. aviumis governed by the two-component master virulence regulator, BvgAS. However, this regulon has never before been associated with nutrient-induced filamentation. In this study, we identify BvgS to be regulating nutrient-induced filamentation. We also report the first transcriptomics analysis of filamentousB. avium, showing the enzyme succinyl-CoA:acetate CoA-transferase may be involved in a metabolic shift in enriched nutrient conditions leading to filamentation. Our results suggest that virulence inB. aviumis a dynamic relationship, affected by nutrient availability, rather than a simple binary decision. 

   more » « less
5. The Agrobacterium fabrum efflux pump PecM is produced in response to the plant exudate 4-hydroxybenzaldehyde to avoid disruption of central metabolism

   https://doi.org/10.1128/jb.00150-25  

   Ghosh, Arpita; Grove, Anne (July 2025, Journal of Bacteriology)

   Becker, Anke (Ed.)

   ABSTRACT Agrobacterium fabrum is a phytopathogen that causes crown gall disease. In the rhizosphere, it encounters plant exudates, some of which are toxic, such as 4-hydroxybenzaldehyde (4HBA). Others, including 4-hydroxybenzoate (4HB), participate in the induction of virulence genes.A. fabrum encodes the transcription factor PecS, which has been reported to enhance bacterial fitness in the rhizosphere. The gene encoding PecS is divergent from pecM, which encodes an efflux pump. PecS represses both pecS and pecM, as evidenced by increased expression in the presence of the PecS ligand urate and by elevated pecM expression in a pecS disruption strain. We report here that the expression ofpecM is induced selectively by 4HBA. Expression of genes encoding enzymes involved in the degradation of 4HB is induced by both 4HBA and 4HB, as expected; however, overexpression ofpecM attenuates the induction by 4HBA, suggesting that 4HBA is a substrate for PecM. Consistent with this inference, untargeted metabolomics shows that 4HBA accumulates intracellularly whenpecM is disrupted. Analysis of PecS by thermal stability assay and DNase I footprinting suggests that 4HBA is not a ligand for PecS. Taken together, our data suggest that 4HBA is a substrate for PecM.IMPORTANCEPlant roots secrete a number of compounds that may be toxic to bacteria residing in the surrounding soil. One such bacterium is Agrobacterium fabrum, which infects plants and induces tumor formation. We show here that an A. fabrum strain in which the efflux pump PecM has been disrupted accumulates 4-hydroxybenzaldehyde, and that this plant root exudate induces the expression of pecM. Our data suggest that PecM and PecS, a transcription factor that regulates pecM expression, both function to promote A. fabrum fitness in the rhizosphere. As a competitive advantage in the rhizosphere is a prerequisite for subsequent plant infection, our data contribute to a more complete understanding of the A. fabrum infection process. 

   more » « less