Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth and gene expression patterns and induced resistance to plant pathogens. These compounds may represent novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and abiotic stress and to improve yields. We investigated whether the acyl-homoserine lactone N-hexanoyl-L-homoserine lactone (C6-HSL) impacted winter wheat ( Triticum aestivum L.) seed germination, plant development and productivity, using two Ukrainian varieties, Volodarka and Yatran 60, in both in vitro experiments and field trials. In vitro germination experiments indicated that C6-HSL seed priming had a small but significant positive impact on germination levels (1.2x increase, p < 0.0001), coleoptile and radicle development (1.4x increase, p < 0.0001). Field trials over two growing seasons (2015–16 and 2016–17) also demonstrated significant improvements in biomass at the tillering stage (1.4x increase, p < 0.0001), and crop structure and productivity at maturity including grain yield (1.4–1.5x increase, p < 0.0007) and quality (1.3x increase in good grain, p < 0.0001). In some cases variety effects were observed (p ≤ 0.05) suggesting that the effect of C6-HSL seed priming might depend on plant genetics, and some benefits of priming were also evident in F1 plants grown from seeds collected the previous season (p ≤ 0.05). These field-scale findings suggest that bacterial acyl-homoserine lactones such as C6-HSL could be used to improve cereal crop growth and yield and reduce reliance on fungicides and fertilisers to combat pathogens and stress.

The choice of effective biocides used for routine hospital practice should consider the role of disinfectants in the maintenance and development of local resistome and how they might affect antibiotic resistance gene transfer within the hospital microbial population. Currently, there is little understanding of how different biocides contribute to eDNA release that may contribute to gene transfer and subsequent environmental retention. Here, we investigated how different biocides affect the release of eDNA from mature biofilms of two opportunistic model strains Pseudomonas aeruginosa ATCC 27853 (PA) and Staphylococcus aureus ATCC 25923 (SA) and contribute to the hospital resistome in the form of surface and water contaminants and dust particles. The effect of four groups of biocides, alcohols, hydrogen peroxide, quaternary ammonium compounds, and the polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl), was evaluated using PA and SA biofilms. Most biocides, except for PHMG-Cl and 70% ethanol, caused substantial eDNA release, and PHMG-Cl was found to block biofilm development when used at concentrations of 0.5% and 0.1%. This might be associated with the formation of DNA–PHMG-Cl complexes as PHMG-Cl is predicted to bind to AT base pairs by molecular docking assays. PHMG-Cl was found to bind high-molecular DNA and plasmid DNA and continued to inactivate DNA on surfaces even after 4 weeks. PHMG-Cl also effectively inactivated biofilm-associated antibiotic resistance gene eDNA released by a pan-drug-resistant Klebsiella strain, which demonstrates the potential of a polymeric biocide as a new surface-active agent to combat the spread of antibiotic resistance in hospital settings.

Staphylococcus aureus is one of the most dangerous pathogens commonly associated with high levels of morbidity and mortality. Sortase A is considered as a promising molecular target for the development of antistaphylococcal agents. Using hybrid virtual screening approach and FRET analysis, we have identified five compounds able to decrease the activity of sortase A by more than 50% at the concentration of 200 µM. The most promising compound was 2-(2-amino-3-chloro-benzoylamino)-benzoic acid which was able to inhibit S. aureus sortase A at the IC 50 value of 59.7 µM. This compound was selective toward sortase A compared to other four cysteine proteases – cathepsin L, cathepsin B, rhodesain, and the SARS-CoV2 main protease. Microscale thermophoresis experiments confirmed that this compound bound sortase A with K D value of 189 µM. Antibacterial and antibiofilm assays also confirmed high specificity of the hit compound against two standard and three wild-type, S. aureus hospital infection isolates. The effect of the compound on biofilms produced by two S. aureus ATCC strains was also observed suggesting that the compound reduced biofilm formation by changing the biofilm structure and thickness.

Ацилгомосеринлактоны (АГЛ)-класс молекул медиаторов, координирующих активность клеток в популяции грамотрицательных бактерий. АГЛ синхронизируют индивидуальные клеточные геномы, благодаря чему бактериальная популяция функционирует как многоклеточный организм. Они обеспечивают дистанционный сигналинг между бактериями-колонизаторами фитосферы, что позволяет популяции реагировать на внешний сигналинг и устанавливать симбиотические либо антагонистические отношения с растением-хозяином (A.R. Stacy с соавт., 2018; А. Shrestha с соавт., 2020). Ауторецепция количественных параметров бактериальной популяции называется «quorum sensing» (QS) (R.G. Abisado с соавт., 2018). QS-системы образуют сигнальные молекулы аутоиндукторы, легко проникающие из клеток в окружающую среду и обратно в клетку (M.B. Miller с соавт., 2001; B. Bassler, 2002). Системам QS принадлежит ключевая роль в регуляции метаболических и физиологических процессов, происходящих в бактериальной клетке (M. Frederix с соавт., 2011; M. Whiteley с соавт., 2017). Бактериальный сигналинг воспринимается эукариотами, которые образуют симбиоз с микробными сообществами (S.T. Schenk с соавт., 2015; Л.М. Бабенко с соавт., 2016, 2017). Рост и развитие растения, ассимиляция питательных веществ, стрессоустойчивость во многом определяются характером такого взаимодействия (H.P. Bais с соавт., 2006; R. Ortíz-Castro с соавт., 2009; S. Basu с соавт., 2017). Управлять бактериальным сигналингом растению позволяет система «quorum quenching» (QQ) (N. Calatrava-Morales с соавт., 2018), механизм действия которой состоит в подавлении растительными метаболитами синтеза АГЛ, конкуренции с АГЛ за связывание с рецепторными белками, репрессии QS-контролируемых генов (H. Zhu с соавт., 2008; R. Sarkar с соавт., 2015). Однако в настоящее время молекулярные механизмы, с помощью которых растения реагируют на бактериальный сигналинг, до конца не выяснены. Часть метаболитов АГЛ-сигналинга охарактеризованы, однако их роль в химическом взаимодействии партнеров в большинстве случаев требует дальнейшего изучения. Показано, что явление QS и его участники причастны к регуляции взаимодействий между про-и эукариотами, в том числе к формированию биопленок, синтезу фитогормонов, трансферу плазмид, продукции факторов вирулентности, биолюминесценции, споруляции, образованию клубеньков (Л.М. Бабенко с соавт., 2017). Различия в строении молекул обеспечивают распознавание бактериями собственных АГЛ и отделение чужеродных. Перенос АГЛ от бактерии к растению-хозяину осуществляется при помощи мембранных везикул (M. Toyofuku, 2019). В последние годы активно изучаются генетика, геномика, биохимия и сигнальное разнообразие молекул QS. Регулирование функций ризосферынаиболее динамичного сайта взаимодействия растения и ассоциированной с ним микрофлоры с участием АГЛ приобретает особое значение при разработке новых биотехнологических подходов, направленных на повышение урожайности и стрессоустойчивости аграрных культур. Одна из эффективных технологий повышения устойчивости к биотическим и абиотическим стрессам-предпосевна...

250 / 300 words) 28 Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth 29 and gene expression patterns and induced resistance to plant pathogens. These compounds may represent 30 novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and 31 abiotic stress and to improve yields. We investigated whether the acyl-homoserine lactone N-hexanoyl-L-32 homoserine lactone (C6-HSL) impacted winter wheat (Triticum aestivum L.) seed germination, plant 33 development and productivity, using two Ukrainian varieties, Volodarka and Yatran 60, in both in vitro 34 experiments and field trials. In vitro germination experiments indicated that C6-HSL seed priming had a small 35 but significant positive impact on germination levels (1.2x increase, p < 0.0001), coleoptile and radicle 36 development (1.4x increase, p < 0.0001). Field trials over two growing seasons (2015-16 and 2016-17) also 37 demonstrated significant improvements in biomass at the tillering stage (1.4x increase, p < 0.0001), and crop 38 structure and productivity at maturity including grain yield (1.4 -1.5x increase, p < 0.0007) and quality (1.3x 39 increase in good grain, p < 0.0001). In some cases variety effects were observed (p ≤ 0.05) suggesting that 40 the effect of C6-HSL seed priming might depend on plant genetics, and some benefits of priming were also 41 evident in F1 plants grown from seeds collected the previous season (p ≤ 0.05). These field-scale findings 42 suggest that bacterial acyl-homoserine lactones such as C6-HSL could be used to improve cereal crop growth 43 and yield and reduce reliance on fungicides and fertilisers to combat pathogens and stress. 44 Keywords: crop productivity, N-acyl-L-homoserine lactone, quorum sensing, plant-microbial interactions, 45 phyto-protection, phyto-stimulation, seed priming, winter wheat.46 47

Staphylococcus aureus (S. aureus) is a causative agent of many hospital- and community-acquired infections with the tendency to develop resistance to all known antibiotics. Therefore, the development of novel antistaphylococcal agents is of urgent need. Sortase A is considered a promising molecular target for the development of antistaphylococcal agents. The main aim of this study was to identify novel sortase A inhibitors. In order to find novel antistaphylococcal agents, we performed phenotypic screening of a library containing 15512 compounds against S. aureus ATCC43300. The molecular docking of hits was performed using the DOCK program and 10 compounds were selected for in vitro enzymatic activity inhibition assay. Two inhibitors were identified, N,N-diethyl-N′-(5-nitro-2-(quinazolin-2-yl)phenyl)propane-1,3-diamine (1) and acridin-9-yl-(1H-benzoimidazol-5-yl)-amine (2), which decrease sortase A activity with IC50 values of 160.3 µM and 207.01 µM, respectively. It was found that compounds 1 and 2 possess antibacterial activity toward 29 tested multidrug resistant S. aureus strains with MIC values ranging from 78.12 to 312.5 mg/L. These compounds can be used for further structural optimization and biological research.

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The establishment of O2 gradients in liquid columns by bacterial metabolic activity produces a spatially-structured environment. This produces a high-O2 region at the top that represents an un-occupied niche which could be colonised by biofilm-competent strains. We have used this to develop an experimental model system using soil-wash inocula and a serial-transfer approach to investigate changes in community-based biofilm-formation and productivity. This involved ten transfers of mixed-community or biofilm-only samples over a total of 10–60 days incubation. In all final-transfer communities the ability to form biofilms was retained, though in longer incubations the build-up of toxic metabolites limited productivity. Measurements of microcosm productivity, biofilm-strength and attachment levels were used to assess community-aggregated traits which showed changes at both the community and individual-strain levels. Final-transfer communities were stratified with strains demonstrating a plastic phenotype when migrating between the high and low-O2 regions. The majority of community productivity came from the O2-depleted region rather than the top of the liquid column. This model system illustrates the complexity we expect to see in natural biofilm-forming communities. The connection between biofilms and the liquid column seen here has important implications for how these structures form and respond to selective pressure.