Phaseolotoxin is an antimetabolite toxin produced by diverse pathovars of Pseudomonas syringae which affects various plants, causing diseases of economic importance. Phaseolotoxin contributes to the systemic dissemination of the pathogen in the plant, therefore it is recognized as a major virulence factor. Genetic traits such as the Pht cluster, appear defining to the toxigenic strains phaseolotoxin producers. Extensive research has contributed to our knowledge concerning the regulation of phaseolotoxin revealing a complex regulatory network that involves processes at the transcriptional and posttranscriptional levels, in which specific and global regulators participate. Even more, significant advances in understanding how specific signals, including host metabolites, nutrient sources, and physical parameters such as the temperature, can affect phaseolotoxin production have been made. A general overview of the phaseolotoxin regulation, focusing on the chemical and physical cues, and regulatory pathways involved in the expression of this major virulence factor will be given in the present work.

Phaseolotoxin is a major virulence factor of the bean pathogen bacterium P. savastanoi pv. phaseolicola. This toxin plays a key role in the development of the halo blight disease in bean plants. So far, the signal transduction pathways involved in the synthesis of phaseolotoxin have not been elucidated. The influence of regulation mechanisms related to the oxidative stress response, in particular the OxyR protein, it has been suggested to be involved in this process.. In this study we evaluated the role of OxyR in P. savastanoi pv. phaseolicola, mainly compared to the synthesis of phaseolotoxin and the virulence of this phytopathogen. Generation of the oxyR-mutant, pathogenicity and virulence tests, and analyses of gene expression by RT-PCR assays were performed. The results showed that OxyR exerts an effect on the synthesis of phaseolotoxin and positively influences the expression of the Pht and Pbo cluster genes. Likewise, OxyR influences the production of pyoverdine by the control of the expression of the genes encoding the PvdS sigma factor, involved in the synthesis of this pigment. This study is the first report on members of the OxyR regulon of P. savastanoi pv. phaseolicola NPS3121.

The Jackfruit bronzing disease represents a significant phytosanitary constraint affecting Artocarpus heterophyllus production. In this context, the exploration of plant‐associated microorganisms as a source of potential biological control agents aligns with sustainable agricultural strategies. This study is aimed at isolating, characterizing, and evaluating the in vitro antagonistic interactions, and antimicrobial potential of indigenous rhizospheric and endophytic bacteria with the potential to be developed as biocontrol agents for the control jackfruit bronzing causal agent Pantoea stewartii subsp. stewartii . A total of 138 bacterial isolates were obtained from rhizospheric soils and internal plant tissues, with a predominance of rhizospheric bacteria (78.3%). In vitro antagonism assays revealed that only rhizospheric isolates exhibited inhibitory activity against the phytopathogen, identifying 12 strains with consistent antagonistic capacity. These isolates were further characterized to elucidate the potential mechanisms involved in microbial antagonism. Functional analyses demonstrated that the antagonistic isolates possessed multiple extracellular enzymatic activities, predominantly lipase, followed by amylase and cellulase activities, whereas protease activity was absent. Additionally, selected isolates exhibited biosurfactant production, suggesting their role in pathogen inhibition. Antibiosis was confirmed through the production of diffusible antimicrobial compounds. Furthermore, molecular screening revealed the presence of nonribosomal peptide synthetase (NRPS) gene fragments in several strains, supporting their genetic potential to synthesize bioactive secondary metabolites. Phylogenetic identification based on 16S rDNA gene sequencing assigned the isolates to bacterial taxa known for their ecological versatility and functional attributes. Overall, this study provides evidence that rhizospheric bacteria associated with jackfruit harbor significant antagonistic and antimicrobial capabilities against jackfruit bronzing causal agent. These findings contribute to the understanding of microbial interactions and functional traits associated with plant microbiota. This study provides the first assessment of microorganisms associated with jackfruit.

Enterococcus species are opportunistic pathogens frequently associated with hospital-acquired infections and biofilm formation. Hospital wastewater may act as a selective environment favoring the persistence of strains carrying virulence-associated traits. In this study, isolates of Enterococcus faecalis and Enterococcus faecium obtained from hospital effluents were evaluated for biofilm formation, gelatinase activity, and the presence of virulence-associated genes. A total of 60 isolates were randomly selected from wastewater samples collected from three public hospitals in Tepic, Nayarit, Mexico. Biofilm formation and gelatinase activity were evaluated using microtiter plate and nutrient gelatin assays. The presence of the quorum-sensing operon fsrABC and the gelatinase gene gelE was analyzed by PCR, while transcripts were detected by RT-PCR. E. faecium isolates exhibited stronger biofilm formation compared to E. faecalis, and several isolates carried both fsrABC and gelE. Although transcripts of some fsr components were not detected in E. faecium, gelatinase activity and gelE transcripts were observed in representative strains. These findings suggest that hospital wastewater may serve as a reservoir of enterococci with virulence-associated characteristics.

Six bacterial isolates recovered from the rhizosphere ofmaize and avocado in Nayarit, Mexico, were evaluated forantagonistic activity against soilborne vascular pathogens,including Fusarium oxysporum, F. stilboides, and Verticilliumsp. Partial 16S rRNA gene sequencing (99–100 % identity)identified the isolates as B acillus amyloliquefaciens ZJ-1, B.amyloliquefaciens ZJ-3, B. subtilis ZJ-19, Serratia marcescensZJ-157, Enterobacter cancerogenus ZJ-167, and E. bugandensisZJ-168. Cell-free supernatants of bacterial culturessignificantly reduced radial growth of Verticillium sp. (p ≤0.05), with inhibition exceeding 40 % in the Bacillus isolatesand E. cancerogenus ZJ-167, and approximately 20 % in S.marcescens ZJ-157 and E. bugandensis. Moderate inhibitionof F. stilboides was observed only for E. bugandensis ZJ-168(17.08 ± 1.54 %). No significant reduction in radial growthwas detected for F. oxysporum; however, distinct morphologicalalterations of the mycelium were observed. Protease activitywas associated with Bacillus isolates exhibiting strongerinhibition of Verticillium sp. All strains produced siderophoresand volatile organic compounds that reduced fungal growth.These findings indicate that fungal inhibition is associatedwith multiple complementary antagonistic mechanisms.