Amongst serious biotic factors deteriorating crop yield, the most destructive pathogen of rice is Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial leaf blight (BLB) disease. This study involved targeted use of biogenic silver nanoparticles (AgNPs) to control BLB in order to cope with the disadvantages of chemical disease control. AgNPs were biologically synthesized from natively isolated Bacillus cereus strain SZT1, which was identified through 16S rRNA gene sequence analysis. Synthesis of AgNPs in bacterial culture supernatant was confirmed through UV-VIS spectroscopy. Fourier transform infrared spectroscopy (FTIR) confirmed that the existence of AgNPs was stabilized with proteins and alcoholic groups. X-ray diffraction (XRD) data revealed the crystalline nature and imaging with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), showing the spherical shape of AgNPs with particle sizes ranging from 18 to 39 nm. The silver presence in AgNPs was further confirmed by energy dispersive spectra. Biogenic AgNPs showed substantial antibacterial activity (24.21 ± 1.01 mm) for Xoo. In a pot experiment, AgNPs were found to be effective weapons for BLB by significantly increasing the plant biomass with a decreased cellular concentration of reactive oxygen species and increased concentration of antioxidant enzyme activity.

Plants host diverse but taxonomically structured communities of microorganisms, called microbiome, which colonize various parts of host plants. Plant-associated microbial communities have been shown to confer multiple beneficial advantages to their host plants, such as nutrient acquisition, growth promotion, pathogen resistance, and environmental stress tolerance. Systematic studies have provided new insights into the economically and ecologically important microbial communities as hubs of core microbiota and revealed their beneficial impacts on the host plants. Microbiome engineering, which can improve the functional capabilities of native microbial species under challenging agricultural ambiance, is an emerging biotechnological strategy to improve crop yield and resilience against variety of environmental constraints of both biotic and abiotic nature. This review highlights the importance of indigenous microbial communities in improving plant health under pathogen-induced stress. Moreover, the potential solutions leading towards commercialization of proficient bioformulations for sustainable and improved crop production are also described.

Burkholderia glumae and B. gladioli are seed-borne rice pathogens that cause bacterial panicle blight (BPB) disease, resulting in huge rice yield losses worldwide. However, the excessive use of chemical pesticides in agriculture has led to an increase in environmental toxicity. Microbe-mediated nanoparticles (NPs) have recently gained significant attention owing to their promising application in plant disease control. In the current study, we biologically synthesize zinc oxide nanoparticles (ZnONPs) from a native Bacillus cereus RNT6 strain, which was taxonomically identified using 16S rRNA gene analysis. The biosynthesis of ZnONPs in the reaction mixture was confirmed by using UV–Vis spectroscopy. Moreover, XRD, FTIR, SEM-EDS, and TEM analysis revealed the functional groups, crystalline nature, and spherical shape of ZnONPs with sizes ranging from 21 to 35 nm, respectively. Biogenic ZnONPs showed significant antibacterial activity at 50 µg mL⁻¹ against B. glumae and B. gladioli with a 2.83 cm and 2.18 cm zone of inhibition, respectively, while cell numbers (measured by OD₆₀₀) of the two pathogens in broth culture were reduced by 71.2% and 68.1%, respectively. The ultrastructure studies revealed the morphological damage in ZnONPs-treated B. glumae and B. gladioli cells as compared to the corresponding control. The results of this study revealed that ZnONPs could be considered as promising nanopesticides to control BPB disease in rice.

Microbes communicate with each other by using quorum sensing (QS) systems and modulate their collective ‘behavior’ for in-host colonization and virulence, biofilm formation, and environmental adaptation. The recent increase in genome data availability reveals the presence of several putative QS sensing circuits in microbial pathogens, but many of these have not been functionally characterized yet, despite their possible utility as drug targets. To increase the repertoire of functionally characterized QS systems in bacteria, we studied Rgg144/Shp144 and Rgg939/Shp939, two putative QS systems in the important human pathogen Streptococcus pneumoniae. We find that both of these QS circuits are induced by short hydrophobic peptides (Shp) upon sensing sugars found in the respiratory tract, such as galactose and mannose. Microarray analyses using cultures grown on mannose and galactose revealed that the expression of a large number of genes is controlled by these QS systems, especially those encoding for essential physiological functions and virulence-related genes such as the capsular locus. Moreover, the array data revealed evidence for cross-talk between these systems. Finally, these Rgg systems play a key role in colonization and virulence, as deletion mutants of these QS systems are attenuated in the mouse models of colonization and pneumonia.