A team of University College London researchers has recorded the sharpest image ever of living bacteria. The breakthrough study has revealed the complex architecture of the protective layer that covers many bacteria and makes them more difficult to destroy with medicines and could have ramifications against resistance to antibiotics.
The findings, published in the Proceedings of the National Academy of Sciences, suggest that Gram-negative bacteria, which have protective outer layers, may have stronger and weaker regions on their surface. This is significant because Gram-negative bacteria's thick outer layer inhibits some medicines and antibiotics from accessing the cell.
The researchers have discovered that their protective outer membrane contains networks of protein building blocks interspersed with patches that do not appear to contain them -- instead, they are rich in molecules with sugary chains (glycolipids), which help to maintain the outer membrane tight.
“By studying live bacteria from the molecular to cellular scale, we can see how membrane proteins form a network that spans the entire surface of the bacteria, leaving small gaps for patches that contain no protein," explains corresponding author Professor Bart Hoogenboom at UCL and UCL Physics & Astronomy, in a press release. "This suggests that the barrier may not be equally hard to breach or stretch all over the bacterium, but may have stronger and weaker spots that can also be targeted by antibiotics."
Getting a good look into living bacteria
To gain a better understanding of this architecture, the researchers ran a tiny needle over living Escherichia coli (E. coli) bacteria, "feeling" their general structure. Because the needle's tip is only a few nanometres wide, it was feasible to see molecular structures at the bacterial surface.
The resultant images indicate that the bacteria's whole outer membrane is jammed with small pores generated by proteins that enable nutrients to enter while blocking others from entering. Although the outer membrane was known to contain a large number of proteins, its packed and immobile character had come as a surprise, and this was how the researchers were able to reveal the large number of areas that did not appear to contain proteins.
Based on these findings, the researchers think that they could explain the ways by which bacteria can maintain a tightly packed, protective barrier while still allowing rapid growth. With further research, this "sharpest" image could pave the way to widen our understanding of bacteria and find new ways of combating resistance to antibiotics.