## 1 Introduction
The results reported in the literature showed that the antibacterial activity of metal oxides against bacterial species was attributed to the releases of toxic metallic ions that can kill the bacteria as well as to the oxidative stress, damage of the cell membrane, inhibition of enzymes, lipid peroxidation, and proteolysis [40]. Metal oxides such as ZnO NPs have been widely used in different applications and received significant attention owing to their toxicity and potential risks to human health and the environment [41; 42; 43]. However, the exact mechanism for its antimicrobial properties is not yet fully understood. The development of ROS species, as well as electrostatic forces in ZnO, can disrupt the cell membrane and hence inhibit a large variety of bacteria [27; 44; 45]. Consequently, the synthesis of more complex structures using ZnO and Zn (OH)\({}_{\rm x}\) has been a topic of interest for improving their properties. In fact, zinc oxide (ZnO) is a white powder used in sunscreens, rubber products, and pains, while zinc hydroxide (Zn(OH)\({}_{2}\)) is a white precipitate used in chemical reactions to form salts and water. Above all, hybrid structures incorporating ZnO NPs and carbon are being heavily studied. For example, [PERSON] et al. successfully reported the synthesis of ZnO-rGO nanorods using zinc nitrate precursor, which resulted in a hybrid material that exhibited a high performance of photocatalytic zinc hydroxide, intercalated with amoxicillin trhihydrate, against Gram-positive bacteria _Staphylococcus aureus_, _Klebsiella pneumonia_, and Gram-negative _Escherichia coli_[52]. In this work, graphene oxide was effectively synthesized and coated with different concentrations of zinc hydroxide to prepare a GO/Zn (OH)\({}_{\rm x}\) hybrid composite using a simple precipitation method/titration. In fact, there was no physical coating of Zn (OH)\({}_{\rm x}\) on GO substrates, such as when using the sputter coating method or other processes. The coating of GO with different concentrations of Zn (OH)\({}_{\rm x}\) NPs was performed using the precipitation synthesis method used in the present work. The effect of Zn (OH)\({}_{\rm x}\) coating on the antibacterial properties of the GO/Zn(OH)\({}_{\rm x}\) composites against _hacillus megaterium_ and _E. coli_ bacteria was systematically investigated. It is anticipated that the Zn (OH)\({}_{\rm x}\) NPs/GO nanocomposite may show enhanced antibacterial activity compared to Zn (OH)\({}_{\rm x}\) NPs or to the pristine GO. The main reason for using these bacteria in the present study is to observe the difference in behavior between the two different bacteria using a Gram-positive _Bacillus_ species that produces spores that belong to the same genus of serious pathogens to humans and a Gram-negative _Enterobacteriaceae_/_Escherichia coli_ as a standard coliform pathogen. There is a structural difference in the cell wall of both bacteria tested. In fact, the focus of the current study is not only on the antibacterial activity of GO and GO/Zb(OH)\({}_{\rm x}\) nanocomposite but also on their morphology and structural characterization. One of the main focuses of the present manuscript is the synthesis of Zb(OH)\({}_{\rm x}\), which is novel. To the best of the authors' knowledge, there is not sufficient work reported on the antibacterial activity of GO/Zb(OH)\({}_{\rm x}\) nanocomposite against different bacterial species.