responsible for the generation of ROS. These ROS so generated results in the

inactivation of bacteria (Table 11.1).

2. Adsorption: Adsorption also plays an intrinsic role in controlling the bactericidal

potential of NPs. The interaction of NPs with the bacterial milieu results in the

fragmentation of these particles into their native ionic forms. These ions so

formed tend to establish a bridging with the charged functional moieties (viz.,

COOH, PO³

4 ^{) situated on the palisade region of the bacterial cell. This phenom-}

enon of adsorbing the NPs in bacterial vasculature is called bio-sorption (Nataraj

et al. 2014). The bio-sorption process results in the lysis of cell wall and its

congruent membranes, thus creating a detrimental effect on the bacterial popula-

tion (Table 11.1).

Recently gradual interests of researchers have been focused on the ability of NPs

to interfere with the translation and transcription mechanism, thereby altering the

protein and nucleic acid synthesis phenomenology (Table 11.1). Su et al. in a study

investigated the chief key mechanism responsible for the bacterial denitrification by

CuO NPs (Su et al. 2015b). The detailed proteomic bio-informatic analysis revealed

an alteration in the intracellular protein expressions due to the interaction of these

metallic NPs with bacterial cellular components. The alteration in translational

machinery resulted in the disruption of nitrogen metabolism cycle along with the

inhibition of two other major cellular phenomena, viz., respiratory cycle (electron

transport chain) and substance transport (Su et al. 2015b).

In an incessant attempt, Su et al. utilized varied state of the art techniques to

investigate the effect of AgNPs on the translational and metabolomic profile of

E. coli. The outcome of the study revealed that the Ag ions released from the NPs

resulted in depressed enzymatic activity and inhibition of ribosomal subunit protein

expression and activity of certain other proteins (Su et al. 2015b). In a similar study,

Cui et al. utilized proteomic and metabolomic assays to ascertain the potency of Au

NPs in evoking an antibacterial activity in Gram-negative E. coli bacteria (Cui et al.

2012). The study demonstrated two facile modes of action by which the NPs were

able to incite a bactericidal activity in the model organism;

(a) Inhibition of bridging between ribosomal subunit and transfer ribose nucleic

acid (viz., tRNA) results in disturbed protein synthesis.

(b) Alteration in the cellular membrane potential leads to depressed ATPase enzy-

matic activity and reduced ATP production. This ultimately results in the gross

cessation of cellular activity.

The knowledge of the exact mechanism responsible for the bactericidal efficacy

of NPs becomes prerequisite. Whole genome analysis is one such technique, which

has equipped the present-day researcher with an ability to elucidate the antibacterial

efficacy (apoptosis) in real time. A perfect example of this approach has been

depicted in a study conducted by Su et al. (2015a). In their study, they utilized this

170

A. Parmar and S. Sharma