Biodegradable plastics play a vital role in addressing global plastics disposal challenges. Poly-3-hydroxybutyrate (P3HB) is a biodegradable bacterial intracellular storage polymer with substantial usage potential in agriculture. Poly-3-hydroxybutyrate and its degradation products are non-toxic; however, previous studies suggest that P3HB biodegradation negatively affects plant growth because the microorganisms compete with plants for nutrients. One possible solution to this issue could be inoculating soil with a consortium of plant growth-promoting and N-fixing microorganisms. To test this hypothesis, we conducted a pot experiment using lettuce (Lactuca sativa L. var. capitata L.) grown in soil amended with two doses (1 % and 5 % w/w) of P3HB and microbial inoculant (MI). We tested five experimental variations: P3HB 1 %, P3HB 1 % + MI, P3HB 5 %, P3HB 5 % + MI, and MI, to assess the impact of added microorganisms on plant growth and P3HB biodegradation. The efficient P3HB degradation, which was directly dependent on the amount of bioplastics added, was coupled with the preferential utilization of P3HB as a carbon (C) source. Due to the increased demand for nutrients in P3HB-amended soil by microbial degraders, respiration and enzyme activities were enhanced. This indicated an increased mineralisation of C as well as nitrogen (N), sulphur (S), and phosphorus (P). Microbial inoculation introduced specific bacterial taxa that further improved degradation efficiency and nutrient turnover (N, S, and P) in P3HB-amended soil. Notably, soil acidification related to P3HB was not the primary factor affecting plant growth inhibition. However, despite plant growth-promoting rhizobacteria and N2-fixing microorganisms originating from MI, plant biomass yield remained limited, suggesting that these microorganisms were not entirely successful in mitigating the growth inhibition caused by P3HB.

• Klíčová slova
• Agricultural production, Bioplastics, PGPR, Plant growth inhibition, Plastic pollution, Soil nutrients,
• MeSH
• biodegradace * MeSH
• hydroxybutyráty * metabolismus   MeSH
• látky znečišťující půdu metabolismus   MeSH
• mikrobiální společenstva fyziologie   MeSH
• mikrobiota MeSH
• polyestery * metabolismus   MeSH
• polyhydroxybutyráty MeSH
• půda chemie   MeSH
• půdní mikrobiologie * MeSH
• salát (hlávkový) metabolismus   mikrobiologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• hydroxybutyráty * MeSH
• látky znečišťující půdu MeSH
• poly-beta-hydroxybutyrate MeSH Prohlížeč
• polyestery * MeSH
• polyhydroxybutyráty MeSH
• půda MeSH

BACKGROUND: The genome of Pseudomonas aeruginosa contains at least three genes encoding eukaryotic-type Ser/Thr protein kinases, one of which, ppkA, has been implicated in P. aeruginosa virulence. Together with the adjacent pppA phosphatase gene, they belong to the type VI secretion system (H1-T6SS) locus, which is important for bacterial pathogenesis. To determine the biological function of this protein pair, we prepared a pppA-ppkA double mutant and characterised its phenotype and transcriptomic profiles. RESULTS: Phenotypic studies revealed that the mutant grew slower than the wild-type strain in minimal media and exhibited reduced secretion of pyoverdine. In addition, the mutant had altered sensitivity to oxidative and hyperosmotic stress conditions. Consequently, mutant cells had an impaired ability to survive in murine macrophages and an attenuated virulence in the plant model of infection. Whole-genome transcriptome analysis revealed that pppA-ppkA deletion affects the expression of oxidative stress-responsive genes, stationary phase σ-factor RpoS-regulated genes, and quorum-sensing regulons. The transcriptome of the pppA-ppkA mutant was also analysed under conditions of oxidative stress and showed an impaired response to the stress, manifested by a weaker induction of stress adaptation genes as well as the genes of the SOS regulon. In addition, expression of either RpoS-regulated genes or quorum-sensing-dependent genes was also affected. Complementation analysis confirmed that the transcription levels of the differentially expressed genes were specifically restored when the pppA and ppkA genes were expressed ectopically. CONCLUSIONS: Our results suggest that in addition to its crucial role in controlling the activity of P. aeruginosa H1-T6SS at the post-translational level, the PppA-PpkA pair also affects the transcription of stress-responsive genes. Based on these data, it is likely that the reduced virulence of the mutant strain results from an impaired ability to survive in the host due to the limited response to stress conditions.

• MeSH
• bakteriální proteiny genetika   MeSH
• bakteriální RNA genetika   MeSH
• buněčné linie MeSH
• delece genu * MeSH
• fenotyp MeSH
• makrofágy mikrobiologie   MeSH
• mikrobiální viabilita MeSH
• myši MeSH
• oligopeptidy biosyntéza   MeSH
• oxidační stres * MeSH
• protein-serin-threoninkinasy genetika   MeSH
• Pseudomonas aeruginosa genetika   růst a vývoj   patogenita   MeSH
• regulace genové exprese u bakterií MeSH
• salát (hlávkový) mikrobiologie   MeSH
• sekvenční analýza hybridizací s uspořádaným souborem oligonukleotidů MeSH
• testy genetické komplementace MeSH
• transkriptom MeSH
• virulence MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• bakteriální RNA MeSH
• oligopeptidy MeSH
• ppkA protein, Pseudomonas aeruginosa MeSH Prohlížeč
• protein-serin-threoninkinasy MeSH
• pyoverdin MeSH Prohlížeč

Changes in primary metabolism of lettuce, Lactuca sativa L. (cv. Cobham Green), induced by compatible interaction with the biotrophic oomycete pathogen Bremia lactucae Regel (race BL 16), under two intensities of illumination in the presence and absence of exogenous cytokinins were studied by chlorophyll fluorescence imaging. Thirteen days post-inoculation leaf discs infected by B. lactucae exhibited impairments of photosynthesis associated with biotrophic infections, including: reductions in photosynthetic pigment contents and the maximum quantum yield of photosystem II photochemistry (F(V)/F(M)), inhibition of electron transport (Phi(PSII)) and increased non-photochemical chlorophyll fluorescence quenching (NPQ). Detected changes in photosynthetic parameters correlated with the leaf area colonized by the pathogen's intercellular hyphae. Applications of two cytokinins, benzylaminopurine and meta-topolin, previously shown to suppress B. lactucae sporulation if applied 24 h prior to inoculation at a concentration of 200 microM, retarded the pathogen's asexual reproduction with no apparent negative effects on the host's photosynthetic apparatus. However, long-lasting treatment of healthy tissues with this high concentration of exogenous cytokinin led to effects parallel to pathogenesis: reductions in photosynthetic pigment contents accompanied by inhibition of photosystem II photochemistry and electron transport. These effects of both prolonged exposure to cytokinins and the pathogenesis were weaker in discs exposed to the lower photosynthetic photon flux density. The role of cytokinins in plant-biotrophic pathogen interactions and their potential as disease control agents are discussed.

• MeSH
• benzylové sloučeniny farmakologie   MeSH
• chlorofyl chemie   metabolismus   MeSH
• chloroplasty metabolismus   ultrastruktura   MeSH
• cytokininy farmakologie   MeSH
• fluorescence MeSH
• fotosyntéza účinky léků   MeSH
• fotosystém II - proteinový komplex chemie   metabolismus   MeSH
• interakce hostitele a patogenu MeSH
• listy rostlin metabolismus   mikrobiologie   fyziologie   MeSH
• nemoci rostlin mikrobiologie   MeSH
• oomycety fyziologie   MeSH
• puriny farmakologie   MeSH
• regulátory růstu rostlin farmakologie   MeSH
• salát (hlávkový) metabolismus   mikrobiologie   fyziologie   MeSH
• transmisní elektronová mikroskopie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• benzylaminopurine MeSH Prohlížeč
• benzylové sloučeniny MeSH
• chlorofyl MeSH
• cytokininy MeSH
• fotosystém II - proteinový komplex MeSH
• puriny MeSH
• regulátory růstu rostlin MeSH

A plant's physiology is modified simultaneously with Oomycete pathogen penetration, starting with release and accumulation of reactive oxygen species (ROS). Localisation of superoxide, hydrogen peroxide, peroxidase and variation in their activity, and the isoenzyme profile of antioxidant enzymes peroxidase (1.11.1.7), catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) were studied in six genotypes of four Lactuca spp. (L. sativa, L. serriola, L. saligna and L. virosa) challenged with Bremia lactucae (race NL16). These factors were related to the differential expression of resistance during the course of 96h after inoculation (hai). Accumulation of hydrogen peroxide in infected cells together with enhanced activity of H(2)O(2)-scavenging enzymes in leaf extracts characterised resistant Lactuca spp. genotypes 6-12hai, and peaked at 48-96hai with expression of a hypersensitive reaction. Substantial changes of guaiacol peroxidase activity were detected only in the cytosolic enzyme; activities of the membrane-bound and the ion-bound enzymes were insignificant in the interactions of host genotypes and pathogen isolate examined. The most significant modifications of ROS metabolism were found in resistant L. virosa (NVRS 10.001 602), a genotype responding to pathogen ingress by a rapid and extensive hypersensitive reaction. Formation of the superoxide anion was not detected in either susceptible or resistant plants, and there was also no increase of superoxide dismutase activity or changes in its isozyme profile. The significance of precise balancing the intracellular level of hydrogen peroxide for variability of phenotypic expression of responses to B. lactucae infection in Lactuca spp. is discussed.

• MeSH
• antioxidancia metabolismus   MeSH
• druhová specificita MeSH
• fenotyp MeSH
• genotyp MeSH
• listy rostlin enzymologie   MeSH
• Peronospora metabolismus   MeSH
• peroxid vodíku chemie   metabolismus   farmakologie   MeSH
• peroxidasy metabolismus   MeSH
• protein - isoformy MeSH
• reaktivní formy kyslíku * MeSH
• rostliny metabolismus   MeSH
• salát (hlávkový) metabolismus   mikrobiologie   MeSH
• superoxiddismutasa metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antioxidancia MeSH
• peroxid vodíku MeSH
• peroxidasy MeSH
• protein - isoformy MeSH
• reaktivní formy kyslíku * MeSH
• superoxiddismutasa MeSH