Inoculating functional bacteria improved the humification process by regulating microbial networks and key genera in straw composting by adding different nitrogen sources.

The aim of this study was to compare the effect of functional inoculant and different nitrogen sources on the relationship among lignocellulose, precursors, and humus as well as their interactions with bacterial genera in straw composting. Results showed that inoculation improved the heating process and retained more nitrate compared to control. Inoculation increased the degradation of lignocellulosic components by 26.9%-81.6% and the formation of humus by 15.7%-23.0%. Bioinformatics analysis showed that inoculation enriched key genera Chryseolinea in complex nitrogen source (pig manure) compost and Pusillimas, Luteimonas, and Flavobacteria in single nitrogen source (urea) compost, which were related to humus formation. Network analysis found that inoculation and urea addition improved the microbial synergistic effect and inoculation combined with pig manure had more complex modularity and interactions. Combining the functional bacterial inoculant with urea helped to enhance the degradation of lignocellulose and humification process during straw composting especially with single nitrogen source.

CpxA/R-Controlled Nitroreductase Expression as Target for Combinatorial Therapy against Uropathogens by Promoting Reactive Oxygen Species Generation.

The antibiotic resistances emerged in uropathogens lead to accumulative treatment failure and recurrent episodes of urinary tract infection (UTI), necessitating more innovative therapeutics to curb UTI before systematic infection. In the current study, the combination of amikacin and nitrofurantoin is found to synergistically eradicate Gram-negative uropathogens in vitro and in vivo. The mechanistic analysis demonstrates that the amikacin, as an aminoglycoside, induced bacterial envelope stress by introducing mistranslated proteins, thereby constitutively activating the cpxA/R two-component system (Cpx signaling). The activation of Cpx signaling stimulates the expression of bacterial major nitroreductases (nfsA/nfsB) through soxS/marA regulons. As a result, the CpxA/R-dependent nitroreductases overexpression generates considerable quantity of lethal reactive intermediates via nitroreduction and promotes the prodrug activation of nitrofurantoin. As such, these actions together disrupt the bacterial cellular redox balance with excessively-produced reactive oxygen species (ROS) as "Domino effect", accelerating the clearance of uropathogens. Although aminoglycosides are used as proof-of-principle to elucidate the mechanism, the synergy between nitrofurantoin is generally applicable to other Cpx stimuli. To summarize, this study highlights the potential of aminoglycoside-nitrofurantoin combination to replenish the arsenal against recurrent Gram-negative uropathogens and shed light on the Cpx signaling-controlled nitroreductase as a potential target to manipulate the antibiotic susceptibility.

Natural flavonoids disrupt bacterial iron homeostasis to potentiate colistin efficacy.

In the face of the alarming rise in global antimicrobial resistance, only a handful of novel antibiotics have been developed in recent decades, necessitating innovations in therapeutic strategies to fill the void of antibiotic discovery. Here, we established a screening platform mimicking the host milieu to select antibiotic adjuvants and found three catechol-type flavonoids-7,8-dihydroxyflavone, myricetin, and luteolin-prominently potentiating the efficacy of colistin. Further mechanistic analysis demonstrated that these flavonoids are able to disrupt bacterial iron homeostasis through converting ferric iron to ferrous form. The excessive intracellular ferrous iron modulated the membrane charge of bacteria via interfering the two-component system pmrA/pmrB, thereby promoting the colistin binding and subsequent membrane damage. The potentiation of these flavonoids was further confirmed in an in vivo infection model. Collectively, the current study provided three flavonoids as colistin adjuvant to replenish our arsenals for combating bacterial infections and shed the light on the bacterial iron signaling as a promising target for antibacterial therapies.