Urban wastewater disinfection by iron chelates mediated solar photo-Fenton: Effects on seven pathogens and antibiotic resistance transfer potential.

The effects of solar photo-Fenton (SPF) process mediated by the iron chelate Fe3+ imminodisuccinic acid (Fe:IDS) on both the inactivation of seven relevant pathogens and the potential for antibiotic resistance transfer (degradation of antibiotic resistance genes (ARGs) and after treatment regrowth), in real secondary treated urban wastewater, were investigated for the first time. A comparison with results obtained by sunlight/H2O2 process and Fe3+ ethylenediaminedisuccinic acid (Fe:EDDS) SPF was also carried out. ARGs were quantified by polymerase chain reaction (PCR) in samples before and after (3 h) the treatment. The persistence of the selected pathogens and ARGs was also evaluated in regrowth tests (72 h) under environmentally mimicking conditions. Fe:IDS SPF resulted to be more effective (from 1.4 log removal for Staphylococcus spp. to 4.3 log removal for Escherichia coli) than Fe:EDDS SPF (from 0.8 log removal for Pseudomonas aeruginosa to 2.0 log removal for Total coliphages) and sunlight/H2O2 (from 1.2 log removal for Clostridium perfringens to 3.3 log removal for E. coli) processes for the seven pathogens investigated. Potential pathogens regrowth was also severely affected, as no substantial regrowth was observed, both in presence and absence of catalase. A similar trend was observed for ARGs removal too (until 0.001 fold change expression for qnrS after 3 h). However, a poor effect and a slight increase in fold change was observed after treatment especially for gyrA, mefA and intl1. Overall, the effect of the investigated processes on ARGs was found to be ARG dependent. Noteworthy, coliphages can regrow after sunlight/H2O2 treatment unlike SPF processes, increasing the risk of antibiotic resistance transfer by transduction mechanism. In conclusion, Fe:IDS SPF is an attractive solution for tertiary treatment of urban wastewater in small wastewater treatment plants as it can provide effective disinfection and a higher protection against antibiotic resistance transfer than the other investigated processes.

Development of Broad-Range Microbial Minimal Culture Medium for Lanthanide Studies.

Rare Earth Elements (REE), also known as Lanthanides (Ln3+), are a group of 17 elements showing peculiar physical and chemical properties. Unlike technological applications, very little is known about the physiological role and toxicity of Ln3+ on biological systems, in particular on microorganisms (e.g., bacteria), which represent the most abundant domains on our planet. Up to now, very limited studies have been conducted due to Ln3+ precipitation with some anions commonly present in the culture media. Therefore, the development of a minimal medium is essential to allow the study of Ln3+-microbial interactions, limiting considerably the precipitation of insoluble salts. In this regard, a new minimal culture medium capable of solubilizing large amounts of Ln3+ and allowing the growth of different microbial taxa was successfully developed. Assays have shown that the medium is capable of solubilizing Ln3+ up to 100 times more than other common culture media and allowing the growth of 63 bacteria and 5 fungi. The kinetic growth of one yeast and one Gram-positive bacterium has been defined, proving to support superior growth and biomass compared to other commonly used minimal media. Moreover, the sensitivity and uptake/absorption of a Bacillus stratosphericus strain were tested, highlighting its capability to tolerate concentrations up to 10 mM of either Cerium, Gadolinium or Lanthanum and accumulate different quantities of the three.

Counteracting action of Bacillus stratosphericus and Staphylococcus succinus strains against deleterious salt effects on Zea mays L.

The salinization of soil is the process of progressive accumulation of salts such as sulfates, sodium, or chlorides into the soil. The increased level of salt has significant effects on glycophyte plants, such as rice, maize, and wheat, which are staple foods for the world's population. Consequently, it is important to develop biotechnologies that improve crops and clean up the soil. Among other remediation methods, there is an environmentally friendly approach to ameliorate the cultivation of glycophyte plants in saline soil, namely, the use of microorganisms tolerant to salt with growth-promoting features. Plant growth-promoting rhizobacteria (PGPR) can improve plant growth by colonizing their roots and playing a vital role in helping plants to establish and grow in nutrient-deficient conditions. Our research aimed to test in vivo halotolerant PGPR, isolated and characterized in vitro in a previous study conducted in our laboratory, inoculating them on maize seedlings to improve their growth in the presence of sodium chloride. The bacterial inoculation was performed using the seed-coating method, and the produced effects were evaluated by morphometric analysis, quantization of ion contents (sodium, potassium), produced biomass, both for epigeal (shoot) and hypogeal (root) organs, and by measuring salt-induced oxidative damage. The results showed an increase in biomass and sodium tolerance and even a reduction of oxidative stress in seedlings pretreated with a PGPR bacterial consortium (Staphylococcus succinus + Bacillus stratosphericus) over the control. Moreover, we observed that salt reduces growth and alters root system traits of maize seedlings, while bacterial treatment improves plant growth and partially restores the root architecture system in saline stress conditions. Therefore, the PGPR seed-coating or seedling treatment could be an effective strategy to enhance sustainable agriculture in saline soils due to the protection of the plants from their inhibitory effect.