Microplastic associated Enterobacteriaceae biofilms in marine sewage plant outfalls

• Main Author: Bhikhoo, Raeesa
• Other Authors: Molale-Tom, L.G., Bezuidenhout, C.C., Mienie, C.M.S., 20318634 - Molale-Tom, Lesego Gertrude ( Supervisor), 12540110 - Bezuidenhout, Cornelius Carlos (Supervisor)
• Format: Thesis
• Language: English
• Published: North-West University (South Africa) 2023
• Subjects: Microplastics; Antibiotic-resistance; Biofilms; Enterobacteriaceae; Marine sewage plant outfalls; Sea ice
• Online Access: http://hdl.handle.net/10394/42271

MSc (Microbiology), North-West University, Potchefstroom Campus Microplastics are small (<5 mm) plastic debris and cause a virtually ubiquitous form of pollution in marine settings. They have been found in all compartments ranging from sea ice to sediments, beaches, and the open ocean. Microplastics are known to adsorb chemical pollutants but also provide a surface for biofilm formation by microorganisms. They originate from land-based sources including wastewater treatment outfalls. Policy, at least in the South African context, dictates that partially treated wastewater from coastal cities could be deposited into the ocean. Plastics, and microplastics in particular, represent a considerable proportion of this mixture and includes a consortium of microorganisms, specifically Enterobacteriaceae. These bacteria are ubiquitously associated with gut content of humans and other animals. Furthermore, they may be resistant to antibiotics. Such antibiotic resistant Enterobacteriaceae, may form biofilms on the microplastics and these could be dispersed into oceans. This study aimed to isolate Enterobacteriaceae species from virgin and environmental microplastics that originated from a wastewater treatment plant (WWTP) dispersing into the ocean through a marine sewage outfall. This was achieved by utilizing a simulation. Microcosms were set up by spiking seawater and artificial seawater with WWTP effluent and adding the plastic pieces. Scanning electron microscopy (SEM) was used to determine colonization on the microplastics. Selective media and incubation conditions were used to isolate Enterobacteriaceae. Pure isolates were tested against 16 antibiotics normally used in a clinical environment. Dominant species identified were Citrobacter sp., Escherichia sp., Enterobacter sp., Raoultella sp., Klebsiella sp. as well as Aeromonas sp., and Pseudomonas sp. It is disquieting that some of these species were isolated from all three compartments of the wastewater treatment train, potentially demonstrating their extreme ...