## 2 Results and Discussion
### Acertainment of Affected Bacterial Pathways
saccharolyticus_ were resumed after 12 h of incubation with bio-AgNPs, while Gram-negative species suffered more extensive alteration of their original molecular profiles [21]. The negative charges of lipopolysaccharide-crosscharides composing the outer membrane of Gram-negative bacteria probably exert attraction on the residual positive charges from nanoparticles. The thick layer of peptidoglycan, composed by crosslinked chains of polysaccharides, confers improved rigidity to the structure of bacterial cell, resulting in a greater obstacle for the penetration of AgNPs and creating lower availability of anchoring sites for nanoparticles [73]. Among Gram-negative bacteria, _E. coli_ configured as the one with less disturbed metabolism. Once the antimicrobial action of metal nanoparticles possibly relies on their simultaneous interaction with bacterial cell components, the inhibition of resistance mechanisms could be supposed [6]. However, bacterial resistance to nanosilver has been documented and may involve genetic and phenotypic alternations. A mechanism based in the production of flagellin protein in _E. coli_ 013, _P. aeruginosa_ CCM 3955 and _E. coli_ CCM 3954 repeatedly exposed to AgNPs effectively induced nanoparticles aggregation [74]. Another study observed that nanosilver led to selective adaptation of _Bacillus_ sp., causing these to dominate a local model microbiota where _E. coli_ was previously predominant; the mechanism is possibly elicited by _Bacillus_ sp. resistance to cellular conditions of oxidative stress [75]. Naive _E. coli_ strain was evolved in a AgNP environment and developed resistance probably linked to the occurrence of accumulating mutations retained in the treatment group [76]. The application of AgNPs in the soil and plant environment appeared to shift the pattern of antibiotic resistance genes. The noticed augmentation of relative abundance of efflux pumps genes indicates that AgNPs may contribute to the propagation of antibiotic resistance via co-selection mechanism [77]. On the other hand, AgNPs tested against multidrug-resistant _K. pneumoniae_ MGH78578 proved to be effective by causing a tridosan-like bactericidal action, accompanied by the inhibition of fatty acid biosynthesis and notable triggering of oxidative stress [78]--effects also pointed out by the present study. Mechanistic model of action of AgNPs on _P. mirabilis_ revealed that agent effectiveness was deeply related to the release of free radicals, what induced lethal activity by deprivation of nutrients and signal supply [79]. However, _P. mirabilis_ SCDR1 isolated from a diabetic ulcer presented resistance against commercial Nanosilver products. Pathogenesis analysis showed that this strain carries several mechanisms related to biofilm formation, mobility, active transport and other detoxification methods, which may induce the observed resistance [80]. A schematic representation of pathways potentially impacted by the presence of bio-AgNPs is shown in Figure 9. The scheme contains the volatile final products of each cellular process represented. It was denoted that interference on each of the bacterial paths is dependent on agent concentration. Overall, at lowest concentration there is a stimulation in the production of bioactive compounds, which probably play a role in supporting microorganism adjustment to the medium. Besides that, fermentation pathways appear enhanced, implying yet a partial inhibition of respiratory chain functions. The addition of the two greater levels of bio-AgNPs caused noticeable loss in the variety of assessed volatilomes. The noticed interruption in the biosynthesis of VSCs can be a reflex of nanoparticles binding to precursors molecules and the inhibition of carbon-sulfur lyase enzymes responsible for cleaving S-containing amino acids [81]. \(\beta\)-oxidation cycle can be interpreted as an option for the origination of energy in view of deficient respiration after AgNPs action [82].