Search

The commensal/pathogenic Escherichia coli affects humans and animals, being present in diverse environmental niches, possibly surviving due to its adaptation to transient plant hosts like crops, increasing the risk of foodborne diseases. E. coli interaction with the plant host remains unknown, particularly the impacts on photosynthesis. We hypothesize that E. coli influences the tomato transient host’s photosynthetic capacity. To validate this hypothesis, we exposed 57-day-old tomato plants (Solanum lycopersicum) to different inoculation conditions, namely, non-inoculated plants (negative control, C−); plants directly injected with E. coli SL6.1 (107 CFU/mL) (positive control, C+); plants irrigated one time with E. coli SL6.1 (107 CFU/mL); and plants chronically irrigated with E. coli SL6.1 (104 CFU/mL). No significant changes were observed in chlorophyll fluorescence, pigments’ contents, morphological aspects, and fruiting in all conditions. However, irrigated plants (chronically and one-time contaminated) had decreased stomatal conductance (gs, 31.07 and 34.42 mol m−2 s−1, respectively, vs. 53.43 and 48.08 mol m−2 s−1 in C− and C+, respectively), transpiration rate (E, 0.32 and 0.35 mol m−2 s−1 in chronically and one-time contaminated conditions vs. 0.57 and 0.48 mol m−2 s−1 in C− and C+, respectively), and a trend of increased intrinsic carboxylation (Ci, 384 and 361 ppm in chronically and one-time irrigated plants vs. 321 and 313 ppm in C− and C+, respectively). The one-time inoculated plants presented more severe effects than the remaining conditions, with lower net photosynthetic rate (PN, 0.93 vs. 3.94–5.96 μmol (CO2) m−2 s−1 in the other conditions), intrinsic water use efficiency (iWUE, 33.1 vs. 74.51–184.40 μmol (CO2)/mmol (H2O) in the chronically irrigated and the control plants), and intrinsic carboxylation efficiency (iCE, 0.003 vs. 0.012–0.022 μmol (CO2)/ppm in the remaining conditions). Our data support that some observed effects are similar to those associated with phytopathogenic bacteria. Lastly, we propose that the decrease in some parameters of gas exchange requires direct contact with the leaf/stomata, and is mainly observed for high concentrations of E. coli.

Backgorund The production of red fruits, such as blueberry, has been threatened by several stressors from severe periods of drought, nutrient scarcity, phytopathogens, and costs with fertilization programs with adverse consequences. Thus, there is an urgent need to increase this crop’s resilience whilst promoting sustainable agriculture. Plant growth-promoting microorganisms (PGPMs) constitute not only a solution to tackle water and nutrient deficits in soils, but also as a control against phytopathogens and as green compounds for agricultural practices. Methods In this study, a metagenomic approach of the local fungal and bacterial community of the rhizosphere of Vaccinium corymbosum plants was performed. At the same time, both epiphytic and endophytic microorganisms were isolated in order to disclose putative beneficial native organisms. Results Results showed a high relative abundance of Archaeorhizomyces and Serendipita genera in the ITS sequencing, and Bradyrhizobium genus in the 16S sequencing. Diversity analysis disclosed that the fungal community presented a higher inter-sample variability than the bacterial community, and beta-diversity analysis further corroborated this result. Trichoderma spp., Bacillus spp., and Mucor moelleri were isolated from the V. corymbosum plants. Discussion This work revealed a native microbial community capable of establishing mycorrhizal relationships, and with beneficial physiological traits for blueberry production. It was also possible to isolate several naturally-occurring microorganisms that are known to have plant growth-promoting activity and confer tolerance to hydric stress, a serious climate change threat. Future studies should be performed with these isolates to disclose their efficiency in conferring the needed resilience for this and several crops.

Industrial applications of titanium dioxide nanoparticles (TiO2 NPs) are wide, and their use in nano-fertilizing technology has been proposed in the last few years. Bioactivity evaluation of different TiO2 NPs formulations is therefore crucial, not only to select the most appropriate formulation but also to validate potential agro-applications. In the current work, we compared the bioactivity of the two most used TiO2 NPs formulations (anatase and rutile–anatase) on the photosynthesis of Lactuca sativa. Seeds were exposed to concentrations of 0, 10, and 50 mg L−1 of anatase (A) or rutile–anatase (RA). Germination rate was not affected by NPs, but root growth was stimulated mainly by RA50. Compared with control, RA showed positive effects on photophosphorylation-related parameters. A50 was more efficient in promoting the gas exchange phase (PN, Ci, gs, and E) and in stimulating the absorption of some nutrients. Expanding on the biochemical and physiological data, we show that RA50 stimulated several genes coding for proteins involved in the electron transport in thylakoids (psbA, petB, petA, psaA, psaC, ndhA, ndhD) and ATP synthesis (atpA, atpB). The transcript coding for the large subunit of RuBisCO (rbcL), was stimulated by lower concentration (RA10). This suggests that RuBisCO is highly sensitive to these NPs even at low doses. RA at low doses has been demonstrated to be the most promising NP. These discriminative effects of TiO2 NPs, based on their formulation and dose, may present advantages for their use in the precision nanoagroindustry.