Outer Membrane Vesicles as Mediators of Plant-Bacterial Interactions

Molecular insights into PGPR fluorescent Pseudomonads complex mediated intercellular and interkingdom signal transduction mechanisms in promoting plant's immunity

The growth-promoting and immune modulatory properties of different strains of plant growth promoting rhizobacteria (PGPR) fluorescent Pseudomonads complex (PFPC) can be explored to combat food security challenges. These PFPC prime plants through induced systemic resistance, fortify plants to overcome future pathogen-mediated vulnerability by eliciting robust systemic acquired resistance through regulation by nonexpressor of pathogenesis-related genes 1. Moreover, outer membrane vesicles released from Pseudomonas fluorescens also elicit a broad spectrum of immune responses, presenting a rapid viable alternative to whole cells. Thus, PFPC can help the host to maintain an equilibrium between growth and immunity, ultimately leads to increased crop yield.

Multiomics integration for the function of bacterial outer membrane vesicles in the larval settlement of marine sponges

Bacterial outer membrane vesicles (OMVs) contain a variety of chemical compounds and play significant roles in maintaining symbiotic relationships in a changing ocean, but little is known about their function, particularly in sponge larval development. During the growth of sponge Tedania sp., OMVs from Bacteroidetes species significantly promoted larval settlement, and Tenacibaculum mesophilum SP-7-OMVs were selected as a representative strain for further investigation. According to OMVs metabolomics, larval settlement might be connected to organic acids and derivatives. The multiomics analysis of the T. mesophilum genome, SP-7-OMVs metabolome, and larval transcriptome revealed 47 shared KEGG pathways. Among the number of candidate metabolites, arginine was chosen for its greater ability to increase the settlement rate and its role as the principal substrate for nitric oxide (NO) synthesis of sponge larvae. In summary, these results demonstrated that sponge-associated bacteria might utilize OMVs and their cargo to support host development and make up for host metabolic pathway deficiencies. This study enhances our fundamental knowledge of OMVs in interactions between metazoan hosts and microorganisms that are crucial in the coevolution of marine ecosystems and the complex marine environment.

Environmental and ecological importance of bacterial extracellular vesicles (BEVs)

Extracellular vesicles are unique structures released by the cells of all life forms. Bacterial extracellular vesicles (BEVs) were found in various ecosystems and natural habitats. They are associated with bacterial-bacterial interactions as well as host-bacterial interactions in the environment. Moreover, BEVs facilitate bacterial adaptation to a variety of environmental conditions. BEVs were found to be abundant in the environment, and therefore they can regulate a broad range of environmental processes. In the environment, BEVs can serve as tools for cell-to-cell interaction, secreting mechanism of unwanted materials, transportation, genetic materials exchange and storage, defense and protection, growth support, electron transfer, and cell-surface interplay regulation. Thus, BEVs have a great potential to be used in a variety of environmental applications such as serving as bioremediating reagents for environmental disaster mitigation as well as removing problematic biofilms and waste treatment. This research area needs to be investigated further to disclose the full environmental and ecological importance of BEVs as well as to investigate how to harness BEVs as effective tools in a variety of environmental applications.

New Perspectives on Crosstalks Between Bacterial Regulatory RNAs from Outer Membrane Vesicles and Eukaryotic Cells

Regulatory small RNAs (sRNAs) help the bacteria to survive harsh environmental conditions by posttranscriptional regulation of genes involved in various biological pathways including stress responses, homeostasis, and virulence. These sRNAs can be found carried by different membrane-bound vesicles like extracellular vesicles (EVs), membrane vesicles (MVs), or outer membrane vesicles (OMVs). OMVs provide myriad functions in bacterial cells including carrying a cargo of proteins, lipids, and nucleic acids including sRNAs. A few interesting studies have shown that these sRNAs can be transported to the host cell by membrane vesicles and can regulate the host immune system. Although there is evidence that sRNAs can be exported to host cells and sometimes can even cross the blood-brain barrier, the exact mechanism is still unknown. In this review, we investigated the new techniques implemented in various studies, to elucidate the crosstalks between bacterial cells and human immune systems by membrane vesicles carrying bacterial regulatory sRNAs.

Solanum lycopersicum heme-binding protein 2 as a potent antimicrobial weapon against plant pathogens

The rise in antibiotic-resistant bacteria caused by the excessive use of antibiotics has led to the urgent exploration of alternative antimicrobial solutions. Among these alternatives, antimicrobial proteins, and peptides (Apps) have garnered attention due to their wide-ranging antimicrobial effects. This study focuses on evaluating the antimicrobial properties of Solanum lycopersicum heme-binding protein 2 (SlHBP2), an apoplastic protein extracted from tomato plants treated with 1-Methyl tryptophan (1-MT), against Pseudomonas syringae pv. tomato DC3000 (Pst). Computational studies indicate that SlHBP2 is annotated as a SOUL heme-binding family protein. Remarkably, recombinant SlHBP2 demonstrated significant efficacy in inhibiting the growth of Pst within a concentration range of 3-25 μg/mL. Moreover, SlHBP2 exhibited potent antimicrobial effects against other microorganisms, including Xanthomonas vesicatoria (Xv), Clavibacter michiganensis subsp. michiganensis (Cmm), and Botrytis cinerea. To understand the mechanism of action employed by SlHBP2 against Pst, various techniques such as microscopy and fluorescence assays were employed. The results revealed that SlHBP2 disrupts the bacterial cell wall and causes leakage of intracellular contents. To summarize, the findings suggest that SlHBP2 has significant antimicrobial properties, making it a potential antimicrobial agent against a wide range of pathogens. Although further studies are warranted to explore the full potential of SlHBP2 and its suitability in various applications.

Extracellular Vesicles and Bacteriophages: New Directions in Environmental Biocolloid Research

There is a long-standing appreciation among environmental engineers and scientists regarding the importance of biologically derived colloidal particles and their environmental fate. This interest has been recently renewed in considering bacteriophages and extracellular vesicles, which are each poised to offer engineers unique insights into fundamental aspects of environmental microbiology and novel approaches for engineering applications, including advances in wastewater treatment and sustainable agricultural practices. Challenges persist due to our limited understanding of interactions between these nanoscale particles with unique surface properties and their local environments. This review considers these biological particles through the lens of colloid science with attention given to their environmental impact and surface properties. We discuss methods developed for the study of inert (nonbiological) particle-particle interactions and the potential to use these to advance our understanding of the environmental fate and transport of extracellular vesicles and bacteriophages.