Metal nanoparticles are nanosized entities with dimensions of 1-100 nm that are increasingly in demand due to applications in diverse fields like electronics, sensing, environmental remediation, oil recovery and drug delivery. Metal nanoparticles possess large surface energy and properties different from bulk materials due to their small size, large surface area with free dangling bonds and higher reactivity. High cost and pernicious effects associated with the chemical and physical methods of nanoparticle synthesis are gradually paving the way for biological methods due to their eco-friendly nature. Considering the vast potentiality of microbes and plants as sources, biological synthesis can serve as a green technique for the synthesis of nanoparticles as an alternative to conventional methods. A number of reviews are available on green synthesis of nanoparticles but few have focused on covering the entire biological agents in this process. Therefore present paper describes the use of various living organisms like bacteria, fungi, algae, bryophytes and tracheophytes in the biological synthesis of metal nanoparticles, the mechanisms involved and the advantages associated therein.

Control of infections in the operation theater (OT) is of utmost importance. Microbiological surveillance is an effective tool for identifying and controlling infections. The purpose of this study was to investigate the prevalence rate of microorganisms in OTs, to identify the type of microorganisms, and to detect contamination of various surfaces and air of OT. OTs were properly cleaned with soap and water. All surfaces were disinfected, followed by fumigation with quaternary ammonium compounds. OTs were kept closed overnight. In the morning, they were opened, and samples were collected, taking all aseptic precautions. The settle plate method was used for air sampling, and the swab method was used for surface sampling. Samples were collected from four surfaces of OTs, i.e., floor, wall, table, and light, and samples of the OT air were also collected and immediately transported to the microbiology laboratory of the institution in sterile conditions. A total of 1640 swab samples were taken from eight OTs, out of which 487 (29.7%) were found positive for bacterial growth. Most of them were non-pathological microorganisms such as aerobic spore-forming Bacilli and Micrococcus. Among various OTs, septic OT showed the highest bacterial growth (82 positive cultures out of 200). In the surface sampling of various OTs, aerobic spore-forming Bacilli (221/487) was the most common isolate, followed by coagulase-negative Staphylococci (74/487), and Micrococcus (67/487). General surgery, septic, and emergency OTs had maximum air bioload (97, 93, and 91 colony-forming unit (CFU)/M³, respectively). In surface sampling of OTs, it was found that septic OT and general surgery OT were most contaminated where the patient load was high. Among all the surfaces, OT walls and tables were most contaminated with pathogenic microorganisms. The average air bioload of all OTs was ranged between 79 and 97 CFU/M³.