Sharpest images ever reveal the patchy face of living bacteria

The sharpest images ever of living bacteria have been recorded by UCL researchers, revealing the complex architecture of the protective layer that surrounds many bacteria and makes them harder to be killed by antibiotics. The study, published today in Proceedings of the National Academy of Sciences of the USA and done in collaboration with scientists at National Physical Laboratory, King's College London, University of Oxford and Princeton University, reveals that bacteria with protective outer layers - called Gram-negative bacteria - may have stronger and weaker spots on their surface. The team found that the protective outer membrane of the bacteria contains dense networks of protein building blocks alternated by patches that do not appear to contain proteins. Instead, these patches are enriched in molecules with sugary chains (glycolipids) that keep the outer membrane tight. This is an important finding because the tough outer membrane of Gram-negative bacteria prevents certain drugs and antibiotics from penetrating the cell: this outer membrane is part of the reason why antimicrobial resistance of such bacteria (including A. baumannii , P. aeruginosa , and enterobacteriaceae such as Salmonella and E. coli ) is now considered a greater threat than that of Gram-positive bacteria such as resistant S. aureus (well known as MRSA). "The outer membrane is a formidable barrier against antibiotics and is an important factor in making infectious bacteria resistant to medical treatment.