###### Abstract
Their toxicity and possible mechanisms were also reviewed. The results showed that the comprehension of the interaction between bacteria and GrNs has critical importance. [PERSON] et al. [26] showed that there was no antibacterial activity of CVD graphene films on conductive (Au, Cu) substrates for _E. coli_ and _S. aureus_. The conductive substrates do not affect the viability of _E. coli_ and _S. aureus_ bacteria in contact with CVD graphene films. [PERSON] et al. [27] wrote the review that summarizes the antibacterial activity of the graphene family and the latest advances that have been made on GrNs, covering the functionalization with metal oxides/ions nanoparticles; silver nanoparticles [28]; and other polymers, enzymes, and antibiotics. [PERSON] et al. [29] showed the graphene/titanium dioxide nanocomposite-coated cotton specimen to have insignificant toxicity and excellent antimicrobial activity. [PERSON] et al. [11] selected _E. coli_ and _S. aureus_ as model bacteria to investigate the bacterial toxicity of GO and rGO nanowalls. Results showed that bacteria interaction between the very sharp edges of the nanowalls causes cell membrane damage. Again, GO showed the most powerful antibacterial activity under similar concentrations and incubation time among all materials, by graphite, graphite oxide, and rGO [14]. Several studies showed that GO inhibited Gram-positive bacteria more effectively than Gram-negative bacteria, while some Gram-negative bacteria, such as _E. coli_, were resistant to GO [30]. The morphology of the cells plays a vital role in the bactericidal effect of GO. Gram-negative bacteria and Gram-positive bacteria have dissimilar cell wall structures and chemical compositions. The differences observed between Gram-negative bacteria and Gram-positive bacteria could be related to differences in the cell wall structure, cell physiology, metabolism, or degree of contact. Indeed, while peptidoglycan counts for 90% of the cell wall in Gram-positives, it counts only for 5-10% of the cell wall in Gram-negatives. In addition, unlike Gram-positive bacteria, Gram-negative bacteria have an outer lipid membrane [31]. [PERSON] et al. [32] showed that GO and rGO nanosheets significantly inhibited the _E. coli_ bacterial growth while showing minimal cytotoxicity. Some researchers [33; 34; 35] have studied metal ions/oxides of antimicrobial activities against bacterial, viral, and fungal pathogens with toxicity against some mammalian cells. [PERSON] et al. [36] investigated the size-dependency of GO antimicrobial activity using the Gram-negative bacteria _E. coli_. They concluded that smaller sheet sizes can increase the antimicrobial activity of the material. [PERSON] et al. [37] researched the performance of polyethylene (PE)/clay/silver nanocomposites against _E. coli_. They concluded that the obtained nanocomposites showed enhanced barrier properties and outstanding antimicrobial properties against bacteria, _E. coli_. [PERSON] et al. [38] showed that graphene induces the formation of pores that kill spherical and rod-shaped bacteria. [PERSON] [39] investigated the antibacterial properties of plasma-treated Cu nanoparticles against _P. aeruginosa_ and _S. aureus_. The results showed that the comprehension of the interaction between bacteria and GrNs has critical importance. Hence, the components impacting the interactions and mechanism involved in induced bacterial death should be clarified [27]. The Gr-based antibacterial tests have been generally applied mainly against _E. coli_ and _S. aureus_. Looking at the practical applications of CVD and PECVD-GrNs, it is seen that GrNs can be synthesized on different substrates; herein, we have synthesized two kinds of GrNs (graphene nanosheets and graphene nanowalls) onto G substrates. Additionally, monolayer graphene nanosheets have been synthesized onto Ni substrate. To analyze the responses to the GrNs on G and Ni substrates, both Gram-negative _E. coli_ and Gram-positive _S. aureus_ were used in this study.