Antirestriction proteins protect mobile genetic elements from the host’s restriction-modification systems. Here, we investigated the ability of ArdA and ArdB antirestriction proteins to regulate gene expression in an engineered E. coli K-12 MG1655-based biosensor strain. This biosensor strain harbors a lux-based reporter system controlled by the AllR-repressed promoter. Although structurally similar, DNA-mimic ArdA proteins interact with AllR differently. Recently described small sArdC and well-known ArdA from the conjugative plasmid R64 appear to bind AllR and open the promoter, while the other tested antirestriction proteins (small sArdN protein and various full-sized ArdA proteins from different sources) have no effect on gene expression under AllR-controlled promoter. Direct binding between ArdA and AllR was experimentally confirmed using pull-down assays with His-tagged ArdA. Our study opens up prospects for the specific use of antirestriction proteins for the regulation of gene expression. Surprisingly, ArdB, a non-DNA-mimic antirestriction protein used initially as a control, was also able to open the promoter, apparently through nonspecific interaction with DNA. We verified this effect with a distant ArdB homolog from a rhizobacterium, which was also able to open the promoter.

Introduction: Fusarium species are devastating wheat pathogens. Plant growth-promoting rhizobacteria (PGPR) offer an effective biocontrol alternative. This study investigated the capacity of a Bacillus and Paenibacillus consortium to induce systemic resistance in winter wheat. Methods: Winter wheat plants were treated with a ten-strain PGPR consortium, with or without Fusarium oxysporum and F. graminearum. Expression of five PR-gene families was quantified in roots and shoots at 7 and 14 days post-treatment via RT-qPCR. Morphometric parameters were tracked for 28 days. Results: The consortium elicited a potent defense response. In roots at 7 days, PR-1 and PR-6 expression surged 16-fold and 38-fold, respectively. Defense activation in shoots was delayed, peaking at 14 days. After 28 days, PGPR-treated plants exhibited an 8% increase in shoot length. Discussion: The results confirm that the bacterial strains effectively prime the wheat immune system, modulating early defense pathways and enhancing plant growth.

The bioluminescence of entomopathogenic bacteria of the genus Photorhabdus was considered to be constitutive. However, it has recently been shown that under heat shock conditions, lux-operon is activated in Photorhabdus temperata cells. In the present study, bioluminescence thermoactivation was investigated in two isolated strains, Photorhabdus hainanensis FV2401 and P. temperata FV2402. The luminescence of the more thermotolerant P. hainanensis cells was activated at higher temperatures than that of P. temperata. At the maximum induction temperatures of 37 °C for FV2401 and 34 °C for FV2402, higher bioluminescence activation was observed in FV2401, whereas the increase in lux-genes mRNA levels was approximately the same in both strains. In P. hainanensis, elevated temperatures also affected the expression of the hexA, madB, and csrB genes, which are indirectly involved in luminescence in Photorhabdus. The heat-activated lux-operon promoter in P. hainanensis and P. temperata was determined. This is a σ⁷⁰-dependent promoter that differs in its distance from the luxC start codon. When promoter variants with or without the 5′-UTR mRNA were transferred to the heterologous Escherichia coli system, heat activation of luminescence was retained in constructs containing only the promoter and was independent of σ³² and σ^E, whereas constructs with the 5′-UTR exhibited repression of luminescence following thermoactivation. The obtained data on the temperature-induced promoter of the lux-operon can broaden understanding of the ecological and biological functions of Photorhabdus bioluminescence under heat shock conditions and provide a basis for the development of novel biosensors.

A previous study demonstrated that quorum sensing (QS) genes from the psychrophilic bacterium Aliivibrio logei can be used in Escherichia coli to obtain bacterial cultures with controlled amounts of a target protein. However, the QS system may be induced non-uniformly across the cell population. In this study, we used an expression vector containing luxR/luxI regulatory genes from A. logei carrying sfGFP as a reporter gene. Reporter expression was regulated by the autoinducer 3OxoC6-HSL, activated at 22 °C, and terminated at 37 °C. Flow cytometry was used to assess the GFP fluorescence distribution at the single-cell level. The system provided dose-dependent unimodal expression lacking formation of distinct ON/OFF subpopulations, while the robust coefficient of variation decreased with increasing autoinducer concentration. The autoinducer synthase LuxI enabled autoinduction, but under the tested conditions, no substantial effect on expression homogeneity was detected. Raising the temperature to 37 °C effectively halted expression, allowing intermediate target protein values to be fixed at the single-cell level. Overall, the developed system represents a promising tool for biotechnological applications requiring precise and uniform control of expression.

1. Cereal crops form the basis of the diet of the population in many countries (Poutanen et al. 2022), with wheat being one of the top five most produced cereal grains. In Russia, wheat occupies ab...

In this study, the rhizosphere bacterial community of winter wheat was investigated. Paenibacillus and Bacillus strains, previously identified for their significant hydrolytic activity, demonstrated higher phosphate mobilization efficiency compared to a commercial product. Furthermore, these strains were capable of synthesizing siderophores and auxins known to promote plant growth. The obtained results open prospects for the development of novel biopreparations based on the isolated strains, with the potential for wide application in various branches of agriculture, from crop production to fodder production.