ADVANCED MATERIALS & PROCESSES | JANUARY/FEBRUARY 2024 24 What is sometimes called slime is a soft and slippery surface coating that often forms in areas experiencing heavy water use, such as kitchens and bathrooms. This can lead to poor hygiene as well as material deterioration including corrosion. Slime is similar to biofilm, which is mainly produced by bacteria adhering to a material’s surface and developing into a community of micro- organisms that produce a slimy matrix in which to thrive (Fig. 1). Bacteria are everywhere. One type known as planktonic bacteria float individually in various environments as they seek a nutrient source for survival. For most bacteria, the nutritional requirement for continued growth is a carbon compound. Because material surfaces are energetically unstable, they often adsorb trace amounts of carbon compounds. Therefore, microorganisms such as bacteria try to attach themselves to material surfaces to ingest the carbon source as nutrition. Material surfaces must cross energy barriers to connect, but socalled nanowires—such as the cilia of bacteria—make this relatively easy. As the number of adherent bacteria gradually increase, a phenomenon called quorum sensing, or interbacterial EVALUATING BIOFILMS ON MATERIAL SURFACES: A NEW INTERNATIONAL STANDARD A new ISO standard could help spur development of new surface treatments and innovative products that can help defend against harmful bacteria and biofilms. Hideyuki Kanematsu, FASM,* National Institute of Technology, Suzuka College, and Osaka University, Japan Tomokatsu Ota, Japan Food Research Laboratories, Osaka Naoki Nakatsugawa and Susumu Hiranuma, Society of International Sustaining Growth for Antimicrobial Articles, Tokyo Material Carbon compounds Conditioning lms Bacteria Material Attachment and growth Material Quorum sensing Material Excretion of polysaccharides from bacteria Bio lms form on materials Bio lm formation and growth Fig. 1 — Schematic illustration of biofilm formation and growth. *Member of ASM International Although early biofilms are composed of bacteria, environmental moisture, and polymers derived from bacteria, many biological studies have shown that biofilms provide a favorable environment for bacterial growth. Bacteria can share nutrients and drugs are ineffective in preventing this process. Biofilms continue to grow, but when nutrients are depleted, they collapse. Bacteria that had been slowly growing inside the biofilm now swim back into the environment as planktonic bacteria and reattach themselves to another material surface. This repeated process communication, occurs. Next, the concentration of a signal molecule called an autoinducer (a relatively low molecular weight chemical secreted by the bacteria) increases with the higher concentration of adhesive bacteria. This signal molecule reenters the bacterial cell and through several reactions stimulates certain parts of the DNA, resulting in the discharge of polysaccharides. Thus, areas with high concentrations of adherent bacteria are covered with a thin, wet, hetero- geneous film of water. This is the formation process of a biofilm.
RkJQdWJsaXNoZXIy MTYyMzk3NQ==