From The Johns Hopkins News-Letter
Bacterial antibiotic resistance genes discovered
By Aleena Lakhanpal
Issue date: 11/5/09
Antibacterial soap, hand sanitizer and antibiotics are all substances that we use in an attempt to kill bacteria that might make us sick.Whether we are concerned about getting strep throat, bacterial meningitis or something else, these prevention methods can offer protection. However, some bacteria, such as those that cause Staph and MRSA infections, are becoming increasingly resistant to antibiotics. Since the 1930s, researchers have been aware that bacteria may be able to resist treatment because they can morph into the L-form, or bacteria lacking cell walls.
Until the 1980s, not much else could be known about the L-form, but now, researchers at the Bloomberg School of Public Health have used a wide variety of modern molecular tools to learn more about the origin and biological functions of the L-form bacteria.Ying Zhang, a professor of molecular microbiology and immunology at Bloomberg, is the senior author of the study, which was published in PLoS ONE last month. Not all bacteria can transform into the L-form, but those that can include Bacillus anthracis (anthrax), Treponema pallidum (syphilis), Mycobacterium tuberculosis (tuberculosis), Heliobacter pylori (stomach ulcers and cancer), Borrelia burgdorferi (Lyme disease) and Escherichia coli (food poisoning).
Zhang's team used E. coli to create a culture of L-form bacteria. Although it had been difficult to culture L-form bacteria before, Zhang and his team created a new method that more closely simulated the in vivo conditions in which these bacteria form. "The presence of antibiotic stress is cell wall inhibiting, like penicillin," Zhang said. To prevent the cells from bursting because of this increased stress, Zhang's team added sucrose to the cell media.This culture represented the mechanism that occurs in the body. "L forms are formed in response to stress," Zhang said. "They have a different mode of survival and replication from classical bacteria." The cell wall-deficient bacteria cluster together in the shape of a fried egg rather than the smooth, homogeneous appearance of wild-type bacteria cultures.